CN107987290B

CN107987290B - Nano lignocellulose/montmorillonite composite material and preparation and application thereof

Info

Publication number: CN107987290B
Application number: CN201711178542.8A
Authority: CN
Inventors: 张晓涛; 安宇宏; 李丽丽; 王喜明; 王哲; 王丽
Original assignee: Inner Mongolia Agricultural University
Current assignee: Inner Mongolia Agricultural University
Priority date: 2017-11-23
Filing date: 2017-11-23
Publication date: 2020-07-17
Anticipated expiration: 2037-11-23
Also published as: CN107987290A

Abstract

The invention provides a nano lignocellulose/montmorillonite composite material and preparation and application thereof, wherein the composite material is an intercalation-exfoliation type nano composite material, the composite material is formed by compounding nano lignocellulose and montmorillonite, and the nano lignocellulose intercalation enters between the sheets of the montmorillonite; the mass ratio of the nano lignocellulose to the montmorillonite is 1: 1-10. The nano lignocellulose/montmorillonite composite adsorbing material provided by the application is used as a novel heavy metal ion wastewater adsorbent with low cost, good biocompatibility and high efficiency, has multiple advantages of simple preparation method, good reproducibility, environmental friendliness and the like, and has obvious affinity and adsorption selectivity for heavy metal ions in wastewater.

Description

Nano lignocellulose/montmorillonite composite material and preparation and application thereof

Technical Field

The invention relates to a nano lignocellulose/montmorillonite composite material and preparation and application thereof, belonging to the technical field of composite materials.

Background

The water body is one of important natural resources on which human beings live and is an important component of the human ecological environment. Due to the influence of human industrial activities, there are increasing pollutants entering the environment of water bodies, which cause many problems for the environment and human health. Heavy metal pollution is one of the most harmful water pollution problems at present. Heavy metals enter water bodies in various forms such as mining, metal smelting, metal processing, chemical production wastewater, household garbage, pesticide and fertilizer application, geological erosion and weathering and the like, and the heavy metal ions have the characteristics of high toxicity, difficulty in metabolism, easiness in biological enrichment and the like, so that the heavy metal ions not only pollute the water environment, but also seriously threaten the health and survival of various living bodies including human beings. Therefore, the heavy metal pollution problem of the water body cannot be ignored.

There are many methods for removing heavy metal ions, and there are oxidation-reduction method, electrolysis method, ion exchange method, chemical precipitation method and biological method, but these methods have the disadvantages of large investment, high operation cost, complex operation management and easy generation of secondary pollution. At present, most of the adsorption method is adopted in practical application, and the adsorption method is always favored by people because the materials are cheap and easy to obtain, the cost is low, and the removal effect is good. Research in this respect by researchers in recent years has mainly focused on finding new, inexpensive and efficient adsorbent materials that are more suitable.

The polymer-inorganic clay nano composite material is a system obtained by carrying out composite assembly on a polymer serving as an organic phase and inorganic clay. Because the inorganic clay nano-scale lamellar structure has the surface effect, the quantum size effect, the macroscopic quantum tunneling effect and the like, and the polymer has the advantages of small density, high strength, corrosion resistance, easiness in processing and the like, the polymer-inorganic clay nano-composite material not only has the common characteristics of common composite materials, but also can comprehensively exert the synergistic effect of various components, which is the excellent performance that any single material does not have, and is endowed by the synergistic effect of the composite materials, so that the polymer-inorganic clay nano-composite material often shows a plurality of excellent characteristics different from the conventional polymer composite materials.

The method efficiently develops and utilizes renewable and recyclable biomass resources, and is an effective way for solving the current industrialized sustainable development bottleneck. The development and development of a novel adsorbent which is low in cost, nontoxic, efficient and practical has profound significance for human ecological environment and full utilization of the existing natural resources. Lignocellulose is an organic polymer obtained by chemical treatment of a wood material, and has the advantages of rich source, low cost and the like. During the chemical treatment, lignin and most of hemicellulose are decomposed, cellulose with high inertia is reserved, an organic high molecular polymer which takes the cellulose as a skeleton and the hemicellulose and the lignin as filling or bonding substances is formed, the organic high molecular polymer has a spatial three-dimensional network porous structure, and the specific surface area is up to 1.1m²(g), the adsorption performance is good. The nano lignocellulose is a rigid rod-shaped structure with the diameter of 1-100nm and the length of dozens to hundreds of nanometers, and can be dispersed in water to form a lignocellulose crystal of stable suspension. Compared with common lignocellulose, the nano lignocellulose has the characteristics of high purity, high crystallinity, high Young modulus, high strength, high polymerization degree, superfine structure, nano particles and the like, the molecular surface of the nano lignocellulose contains a large number of hydrophilic hydroxyl groups, the nano lignocellulose is easy to chemically modify and has different surface chemical properties, the dispersibility of the nano lignocellulose in a hydrophobic matrix material can be improved through surface modification, a convenient channel is provided for diffusion of heavy metal ions, and the application range of the nano lignocellulose is expanded. Montmorillonite is a layered silicate clay mineral with expansibility of 2:1, the basic structural unit of the montmorillonite is a nano-scale lamellar structure formed by sandwiching a layer of silicon-oxygen octahedron between two silicon-oxygen tetrahedrons and depending on shared oxygen atoms, the lamellar spacing of the montmorillonite is about 1-2nm, and the montmorillonite has certain interlayer cation exchange capacity, nano-size effect, surface effect and strong interaction between the interface of nano particles and a matrix, and shows good adsorption performance.

In recent years, the development of science and technology is changing day by day, new materials are continuously changed, and the composite material has the special properties which are not possessed by the raw materials because the composite material keeps the respective properties of the raw materials, and is one of the hot problems of the current research. At present, the most active development is to use the intercalation of layered inorganic materials to prepare polymer/inorganic clay nanocomposites. The nano composite material is a material with at least one phase in the dispersion phase of the composite, and the one-dimensional dimension of the at least one phase is within 100 nm. Generally, the interface area between the dispersed phase and the matrix phase of the nano composite material is large, a solution intercalation compounding method can be adopted to perform alkaline treatment on inorganic clay so as to increase the compatibility of the inorganic clay and a polymer, then the inorganic clay and the polymer solution are mixed, a polymer long chain enters between nano-scale lamella through diffusion, inorganic clay lamella layers are uniformly dispersed into lignocellulose macromolecules, the interface combination of the dispersed phase of organic nanoparticles and the matrix is the effect of mechanical hinge and a secondary valence bond, and after the nanoparticles are subjected to solvent treatment, the surfaces of the inorganic matrix and the organic nanoparticles are promoted to be completely infiltrated, so that the stress between the interfaces can be relaxed and reduced. Thus, the properties of the dispersed phase and the matrix are fully combined, which is beneficial to controlling the size and the distribution of the nanometer particle size and obviously improving various performances of the nanometer composite material.

Therefore, providing a nano lignocellulose/montmorillonite composite material and preparation and application thereof have become technical problems to be solved urgently in the field.

Disclosure of Invention

In order to solve the above disadvantages and shortcomings, the present invention is directed to a method for preparing nano lignocellulose.

The invention also aims to provide the nano lignocellulose prepared by the preparation method of the nano lignocellulose.

The invention also aims to provide a nano lignocellulose/montmorillonite composite material.

The invention also aims to provide a preparation method of the nano lignocellulose/montmorillonite composite material.

The invention also aims to provide application of the nano lignocellulose/montmorillonite composite material as a heavy metal ion adsorbent in adsorbing heavy metal ions contained in wastewater.

In order to achieve the above object, the present invention provides a method for preparing nano lignocellulose, which comprises the following steps:

placing lignocellulose in NaOH aqueous solution, and fully stirring the lignocellulose until the lignocellulose forms suspension;

and carrying out centralized ultrasonic treatment on the suspension to obtain the nano lignocellulose.

According to the specific embodiment of the invention, in the preparation method of the nano lignocellulose, preferably, the ultrasonic power is 600-1200W, the ultrasonic temperature is 7-35 ℃, and the ultrasonic time is 60-240 min;

more preferably, the ultrasonic power is 1080W, the ultrasonic temperature is 10 ℃, and the ultrasonic time is 150 min.

According to a specific embodiment of the present invention, in the method for preparing nano lignocellulose, preferably, the ratio of the mass of the lignocellulose to the volume of the NaOH aqueous solution is 1:400 to 1:750 in units of g and m L, respectively, more preferably 1:500 in units of g and m L, respectively.

According to a specific embodiment of the present invention, in the method for preparing nano lignocellulose, preferably, the concentration is 0 to 30 wt% calculated by the total weight of the aqueous NaOH solution as 100%;

more preferably, the concentration of the aqueous NaOH solution is 5-30 wt%;

further preferably, the concentration of the aqueous NaOH solution is 20 wt%.

Wherein, when the concentration of the NaOH aqueous solution is 0, the lignocellulose is put into pure water.

The alkali used in the invention can play a swelling role, and can simultaneously assist the action of ultrasonic waves to destroy hydrogen bonds among long chains of components such as lignin, cellulose, hemicellulose and the like and other intermolecular actions in a lignocellulose high polymer structure due to the cracking of the alkali into free radicals under the high-power ultrasonic environment, so that the aims of dispersing entangled and aggregated lignocellulose, partially hydrolyzing and even destroying amorphous regions of the components, and disordering the ordered arrangement of the crystalline regions to weaken and break the molecular chain strength to form a rigid rod-shaped structure with the diameter of 15-100nm and the length of dozens to hundreds of nanometers are fulfilled.

According to the specific embodiment of the present invention, in the method for preparing nano lignocellulose, preferably, the centralized ultrasonic treatment is implemented by using a SM-1200D ultrasonic cell crusher;

in the specific embodiment of the invention, the amplitude transformer phi used by the SM-1200D ultrasonic cell crusher is 20mm, the ultrasonic generation time is 1.0s, and the ultrasonic gap is 2.0 s. Wherein, the SM-1200D ultrasonic cell crusher is conventional equipment in the field.

The ultrasonic cell crusher used in the invention is a device which utilizes strong ultrasound to make longitudinal mechanical vibration in liquid, and the longitudinal vibration wave generates cavitation effect through a titanium alloy amplitude transformer immersed in a sample solution to excite the biological particles in an ultrasonic medium to vibrate violently, so as to achieve the purpose of crushing cells. The working principle is that the piezoelectric effect of the piezoelectric ceramic plate is utilized to convert an ultrasonic frequency alternating power supply output by an ultrasonic generator into mechanical energy of longitudinal vibration, the energy-gathering and amplitude-changing effects of an amplitude-changing rod are utilized to inject the mechanical vibration energy into liquid in the form of shock waves from the tail end of the amplitude-changing rod, so that a sample generates a cavitation explosion effect, the ultrasonic treatment effects of cell disruption, emulsification and the like are achieved, and the ultrasonic device is 'centralized' ultrasonic. Specifically, the amplitude transformer can directly enter a sodium hydroxide solution of the lignocellulose for centralized ultrasonic action, and simultaneously, the outside also carries out continuous ultrasonic action, so that the whole system can simultaneously carry out internal and external ultrasonic action, and the nano lignocellulose with good effect can be obtained.

The invention also provides the nano lignocellulose prepared by the preparation method of the nano lignocellulose.

According to a specific embodiment of the present invention, preferably, the nano lignocellulose is a nano rod-like structure with an aspect ratio of 20:1 to 3: 1.

The invention also provides a nano lignocellulose/montmorillonite composite material, wherein the composite material is an intercalation-exfoliation type nano composite material, the composite material is formed by compounding nano lignocellulose and montmorillonite, and the nano lignocellulose intercalation enters between the montmorillonite layers;

the mass ratio of the nano lignocellulose to the montmorillonite is 1: 1-10.

According to a specific embodiment of the present invention, in the nano lignocellulose/montmorillonite composite material, preferably, the mass ratio of the nano lignocellulose to the montmorillonite is 1: 1.

According to a specific embodiment of the present invention, preferably, the nano lignocellulose/montmorillonite composite material has a BET specific surface area of 407.02-597.15m²The specific surface area of L angmuir is 598.60-780.14m²Per g, total pore volume of 0.691-1.175cm³Per g, the pore volume of the micropores is 0.198-0.273cm³The average pore diameter of the micropores is 0.427-0.719nm, and the pore volume of the mesopores is 0.472-0.656cm³(ii)/g, the average pore diameter of the mesopores is 102.40-212.37nm, and the average pore diameter is 2.086-19.375 nm.

The invention also provides a preparation method of the nano lignocellulose/montmorillonite composite material, which comprises the following steps:

dissolving nano lignocellulose in NaOH aqueous solution to obtain nano lignocellulose turbid liquid;

adding montmorillonite into water to obtain montmorillonite suspension;

slowly dripping the suspension of the nano lignocellulose into the suspension of the montmorillonite, uniformly mixing, heating to react, and obtaining the nano lignocellulose/montmorillonite composite material after the reaction is finished.

According to a specific embodiment of the present invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, preferably, the ratio of the mass of the nano lignocellulose to the volume of the NaOH aqueous solution is 1:150-1:350, and the units are g and m L respectively, more preferably 1:250, and the units are g and m L respectively.

According to a specific embodiment of the present invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, preferably, the concentration thereof is 3-15 wt% based on the total weight of the NaOH aqueous solution being 100%; more preferably 12.5 wt%.

According to a specific embodiment of the present invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, preferably, the ratio of the mass of the montmorillonite to the volume of water is 1:20-1:45, and the unit is g and m L respectively, more preferably 1:30, and the unit is g and m L respectively.

According to the specific embodiment of the invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, preferably, the reaction temperature is 30-80 ℃, and the reaction time is 2-7 h;

more preferably, the reaction temperature is 50 ℃ and the reaction time is 4 h.

According to the specific embodiment of the invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, after the nano lignocellulose is dissolved in the NaOH aqueous solution, the system can be heated and continuously stirred to obtain the suspension of the nano lignocellulose; in the specific embodiment of the present invention, the system may be heated to 60 ℃ and continuously stirred for 30min to obtain the suspension of nano lignocellulose.

According to the specific embodiment of the invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, montmorillonite is added into water, and then the system is stirred for 30min at room temperature to obtain montmorillonite suspension.

According to a specific embodiment of the present invention, in the preparation method of the nano lignocellulose/montmorillonite composite material, after the reaction is finished, the method further comprises: and carrying out suction filtration on the obtained product, washing the product to be neutral by distilled water, drying, grinding and other operations to finally obtain the nano lignocellulose/montmorillonite composite material.

Wherein, this application does not make specific requirements to the temperature and the time of stoving, and the temperature and the time of stoving can rationally be set up according to the operation needs to the technical staff in the field, as long as guarantee can realize the purpose of stoving, in this application embodiment, the stoving is 85 ℃ vacuum drying 240 min.

In addition, the screen mesh number for grinding can be reasonably selected by the skilled person according to the size of the nano lignocellulose/montmorillonite composite material required by field operation.

The invention also provides application of the nano lignocellulose/montmorillonite composite material as a heavy metal ion adsorbent in adsorbing heavy metal ions contained in wastewater.

According to a particular embodiment of the invention, in said application, preferably, said heavy metal ions comprise zn (ii), mn (ii), ni (ii) and cu (ii).

In the preparation process of the conventional lignocellulose/montmorillonite nano composite material, because the common lignocellulose is used, the length of the fiber is mostly longer, so that the wood fiber is difficult to be intercalated into and uniformly dispersed in a montmorillonite matrix, and the interface compatibility of the wood fiber and the montmorillonite matrix is also poor; firstly, carrying out ultrasonic treatment on lignocellulose uniformly dispersed in NaOH alkaline ultrasonic medium under high-power and low-temperature conditions by using an SM-1200D ultrasonic cell crusher to crush the molecular structure of the lignocellulose and break molecular chains to obtain a nano rod-like structure with a certain length-diameter ratio, namely nano lignocellulose; then the nano lignocellulose is intercalated into a nano-level montmorillonite lamellar structure, so that basic units of the nano-level montmorillonite lamellar are mutually peeled and uniformly dispersed in a nano-level lignocellulose matrix, the intercalation compounding of the nano-lignocellulose and the nano-level montmorillonite lamellar material on a nano scale is realized, and a novel nano-lignocellulose/montmorillonite nano composite material (intercalation-exfoliated composite material) is constructed; finally, the composite material is used for treating heavy metal ions Zn (II), Mn (II), Ni (II) and Cu (II) simulated wastewater.

The inner Mongolia autonomous region is an important metallurgical industry base in China, and the mineral resources of iron ores, nonferrous metals and rare metals are rich, so that the heavy chemical industry is relatively developed. However, the whole area discharges a large amount of pollutants containing heavy metals in relation to heavy wastewater production every year, and the pollutants form serious threats to the healthy survival of residents and aquatic organisms and the development of local industrial economy, so that how to play the advantages of the area as a wide resource production and processing base, continuously develop the mining, selection, smelting and processing industries of mineral resources, prevent and control the emission reduction of the total amount of heavy metal wastewater pollutants is one of major environmental problems which are urgently needed to be solved in the area at present, and the task is huge.

Lignocellulose is the most abundant natural polymer material with biodegradability in nature. Under the situation of rapid resource consumption and environmental deterioration in the world, the emphasis on developing renewable lignocellulose resources has important strategic significance. The nano lignocellulose provided by the application is a renewable nano material prepared by utilizing a high-power low-temperature ultrasonic cell crusher to act on lignocellulose uniformly dispersed in a NaOH alkaline ultrasonic medium, the nano lignocellulose has a high length-diameter ratio and a reticular cross-linked and entangled linear structure, the polymerization degree among molecular chains is very low, solvent molecules easily enter an amorphous area and a partial crystalline area of the nano lignocellulose, and the nano lignocellulose can be stably dispersed in a solvent system for a long time to form a quasi-alternate dispersion system to form a stable nano lignocellulose homogeneous solution, so that the defects of practical use of common lignocellulose are overcome, and various performances are optimized to a great extent. In addition, because the size is in the nanometer scale range, the particle size is generally between 15 and 100nm, and compared with the properties of common lignocellulose, the composite material has great advantages, such as huge specific surface area, higher Young modulus, super-strong adsorption capacity and extremely high reactivity. In conclusion, the nano lignocellulose not only has the basic structure and the performance of the lignocellulose, but also has the typical properties of nano particles, so that the natural renewable resource has wider application prospect.

Montmorillonite has wide sources and low price, has the advantages of mechanical stability, high porosity, various surfaces and structures, high ion exchange and adsorptivity and the like, but has the defects of fine granularity, easy pulverization and dispersion when meeting water, difficult desorption and regeneration and the like in the process of treating heavy metal wastewater, and the practical application is limited to a certain extent; lignocellulose is a renewable storable natural resource with high biological quantity and low economic coefficient, and a considerable part of lignocellulose is utilized at a low value, thereby not only wasting resources, but also causing secondary pollution to the environment. Therefore, the invention firstly carries out ultrasonic treatment on the lignocellulose uniformly dispersed in NaOH alkaline ultrasonic medium under the condition of high power and low temperature to prepare nano lignocellulose, and then carries out intercalation composite reaction with montmorillonite, the nano-scale lamellar structure of the montmorillonite is opened, and the nano lignocellulose is uniformly dispersed in the nano-scale lamellar structure to form the novel intercalation-exfoliation nano composite adsorption material. The nano lignocellulose/montmorillonite composite material not only has the advantages of the respective structures and properties of two raw materials, but also has excellent and unique nano particle effect, and has the excellent characteristics of light weight, degradability, biocompatibility, reproducibility and the like of a biological material, shows huge development space in the application of a high-performance composite material, is used for wastewater treatment, realizes the effect of treating wastes by wastes, achieves the effect of combining three effects of society, economy and environment, and has profound significance.

In conclusion, the nano lignocellulose/montmorillonite nano composite material provided by the application overcomes the defects of poor hydrophilicity, mechanical property and chemical stability of montmorillonite, overcomes the defects of easy aggregation, difficult separation, quality loss and the like of nano lignocellulose particles, enhances the chemical compatibility between interfaces of nano lignocellulose and montmorillonite, and has the nano quantum size effect and the macroscopic quantum tunnel effect in the structure, thereby enhancing various performances of the composite material to a great extent, improving the adsorption effect of the composite material on heavy metal ions in wastewater, widening the respective application range of two raw materials, and having original innovativeness in the field of developing natural high polymer/inorganic clay nano adsorption materials.

In addition, the nano lignocellulose/montmorillonite composite adsorbing material provided by the application is used as a novel high-efficiency heavy metal ion wastewater adsorbent with low cost and good biocompatibility, has the advantages of simple preparation method, good reproducibility, environmental friendliness and the like, has obvious affinity and adsorption selectivity for heavy metal ions in wastewater, is a new starting point for high value-added utilization of lignocellulose, and is widely applicable to enrichment and separation of heavy metal pollutants in industrial wastewater.

Drawings

FIG. 1 is a graph of a standard Zn (II) curve used in the examples of the present invention;

FIG. 2 is a graph of a standard Mn (II) curve used in the examples of the present invention;

FIG. 3 is a graph of a standard curve for Ni (II) used in the examples of the present invention;

FIG. 4 is a graph of a Cu (II) standard curve used in an example of the present invention;

FIG. 5 is a graph showing the relationship between the impact of the composite material prepared under different ultrasonic power conditions on the Zn (II) adsorption amount in example 5 of the present invention;

FIG. 6 is a graph showing the relationship between the effect of the composite material prepared under different ultrasonic power conditions on the adsorption amount of Mn (II) in example 5 of the present invention;

FIG. 7 is a graph showing the relationship between the effect of the composite material prepared under different ultrasonic power conditions on the adsorption amount of Ni (II) in example 5 of the present invention;

FIG. 8 is a graph showing the relationship between the effect of the composite material prepared under different temperature conditions in example 6 of the present invention on the Zn (II) adsorption amount;

FIG. 9 is a graph showing the relationship between the effect of the composite material prepared under different temperature conditions in example 6 of the present invention on the adsorption amount of Mn (II);

FIG. 10 is a graph showing the relationship between the effect of the composite material prepared under different temperature conditions in example 6 of the present invention on the adsorption amount of Ni (II);

FIG. 11 is a graph showing the relationship between the effect of the composite material prepared at different ultrasonic times on the Zn (II) adsorption amount in example 7 of the present invention;

FIG. 12 is a graph showing the relationship between the effect of the composite material prepared at different ultrasonic times on the adsorption amount of Mn (II) in example 7 of the present invention;

FIG. 13 is a graph showing the relationship between the effect of the composite material prepared at different ultrasonic times on the adsorption amount of Ni (II) in example 7 of the present invention;

FIG. 14 is a graph showing the relationship between the effect of the composite material prepared by using different NaOH concentrations as ultrasonic media on the adsorption amount of Zn (II) in example 8 of the present invention;

FIG. 15 is a graph showing the relationship between the effect of composite materials prepared by different concentrations of NaOH on the adsorption amount of Mn (II) in example 8 of the present invention;

FIG. 16 is a graph showing the relationship between the effect of composite materials prepared by different concentrations of NaOH in ultrasonic medium on the adsorption amount of Ni (II) in example 8 of the present invention;

FIG. 17 is a graph showing the relationship between the effect of the composite material prepared under different doping ratios of nano-lignocellulose and montmorillonite on the Zn (II) adsorption in example 9 of the present invention;

FIG. 18 is a graph showing the relationship between the effect of the composite material prepared under different doping ratios of nano-lignocellulose and montmorillonite on the adsorption amount of Mn (II);

FIG. 19 is a graph showing the relationship between the effect of the composite material prepared under different doping ratios of nano-lignocellulose and montmorillonite on the adsorption amount of Ni (II) in example 9 of the present invention;

FIG. 20 is a graph showing the relationship between the effect of the composite material prepared under different NaOH concentrations on the Zn (II) adsorption in the intercalation complexation reaction in example 10 of the present invention;

FIG. 21 is a graph showing the relationship between the effect of the composite material prepared under different NaOH concentrations on the adsorption amount of Mn (II) in the intercalation complexation reaction in example 10 of the present invention;

FIG. 22 is a graph showing the relationship between the effect of the composite material prepared under different NaOH concentrations on the adsorption amount of Ni (II) in the intercalation complexation reaction in example 10 of the present invention;

FIG. 23 is a graph showing the relationship between the effects of composite materials prepared at different reaction temperatures on the Zn (II) adsorption in the intercalation composite reaction of example 11;

FIG. 24 is a graph showing the relationship between the effect of composite materials prepared at different reaction temperatures on the adsorption amount of Mn (II) in the intercalation recombination reaction of example 11;

FIG. 25 is a graph showing the relationship between the effect of composite materials prepared at different reaction temperatures on the adsorption amount of Ni (II) in the intercalation recombination reaction in example 11 of the present invention;

FIG. 26 is a graph showing the relationship between the effect of the composite material prepared at different reaction times on the Zn (II) adsorption in the intercalation composite reaction of example 12;

FIG. 27 is a graph showing the relationship between the effect of the composite material prepared at different reaction times on the adsorption amount of Mn (II) in the intercalation recombination reaction in example 12 of the present invention;

FIG. 28 is a graph showing the relationship between the effect of the composite material prepared at different reaction times on the adsorption amount of Ni (II) in the intercalation recombination reaction in example 12 of the present invention;

FIG. 29 is FTIR spectra of lignocellulose (a) as raw material used in example 1, nano-lignocellulose (b) prepared in example 1, montmorillonite (c) as raw material used in example 2 and nano-lignocellulose/montmorillonite composite material (d) prepared in example 2;

FIG. 30 is an XRD diffraction pattern of the raw material montmorillonite used in example 6 of the present invention, the nano-lignocellulose/montmorillonite composite material prepared in example 6 at different ultrasonic temperatures;

FIG. 31A is an SEM photograph of the lignocellulose as the raw material used in example 1 of the present invention;

FIG. 31B is an SEM spectrum (50.0 μm) of nano-grade lignocellulose prepared in example 1 of the invention;

FIG. 31C is an SEM spectrum (2.00 μm) of nano-grade lignocellulose prepared in example 1 of the invention;

FIG. 31D is an SEM photograph of montmorillonite as the raw material used in example 2 of the present invention;

FIG. 31E is an SEM spectrum of the nano-sized lignocellulose/montmorillonite composite material prepared in example 2 of the present invention;

FIG. 32A is a TEM spectrum of a raw material montmorillonite used in example 2 of the present invention;

fig. 32B is a TEM spectrum of the nano-sized lignocellulose/montmorillonite composite material prepared in example 2 of the present invention.

Detailed Description

In order to clearly understand the technical features, objects and advantages of the present invention, the following detailed description of the technical solutions of the present invention will be made with reference to the following specific examples, which should not be construed as limiting the implementable scope of the present invention.

Example 1

The embodiment provides a preparation method of nano lignocellulose, which comprises the following steps:

weighing 0.5000g of lignocellulose, placing the lignocellulose in a 250m aqueous solution of NaOH with the mass fraction of L percent, fully stirring the lignocellulose with a glass rod until the lignocellulose forms suspension, then carrying out ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher (China electric Co., Ltd., China), wherein the amplitude transformer phi is 20mm, the ultrasonic temperature is 10 ℃, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic power is 1080W, the ultrasonic time is 150min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

Example 2

The embodiment provides a preparation method of a nano lignocellulose/montmorillonite composite material, which comprises the following steps:

1. weighing 0.5000g of the nano lignocellulose subnatant obtained in the embodiment 1, dissolving the subnatant in 75m L NaOH aqueous solution with the mass fraction of 12.5%, and stirring the solution for 30min at the temperature of 60 ℃ to form nano lignocellulose suspension;

2. weighing 0.5000g of montmorillonite, dissolving in 15m L distilled water, and stirring at room temperature for 30min to obtain montmorillonite suspension;

3. slowly dripping the nano lignocellulose suspension in the step 1 into the montmorillonite suspension in the step 2 under the condition of continuous stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by distilled water, drying the product in vacuum at 85 ℃ for 240min, grinding the dried product and sieving by a 200-mesh sieve to obtain the nano lignocellulose/montmorillonite composite material.

Infrared spectroscopy was performed on the raw material lignocellulose used in example 1, the nano lignocellulose prepared in example 1, the raw material montmorillonite used in example 2, and the nano lignocellulose/montmorillonite composite material prepared in example 2, wherein FTIR spectra of the above substances are shown in fig. 29.

As can be seen from FIG. 29, there is 3350cm of lignocellulose^-1Near has absorption peak corresponding to the stretching vibration of alcoholic hydroxyl, because the lignocellulose has a plurality of-OH stretching vibration absorption peaks which are mutually superposed to form a wider absorption peak (a), the nano lignocellulose obtained after the ultrasonic alkali method is shifted to a low wave number of 3348cm^-1(b)。2990cm^-1Nearby corresponds to methylene (-CH)₂C-H symmetric stretching vibration absorption peak (a) of- (III) -) which shifts to a low wave number of 2986cm after nanocrystallization reaction^-1And (c) at (b). 1432cm in lignocellulose (a)^-1The near saturated C-H bending vibration peak is subjected to ultrasonic nanocrystallization and then moves to 1430cm in the low wave number direction^-1；1162cm^-1At 1088cm from the C-C skeleton stretching vibration absorption peak^-1The C-O stretching vibration peak of the lignocellulose alcohol and the C-O stretching vibration absorption peak of the intramolecular ether thereof are located at 891cm^-1Corresponding to the lignocellulose anomeric carbon (C)₁) Compared with FTIR spectrogram of nano lignocellulose (b), the absorption peak of stretching vibration has a high wave number of 1166cm^-1、1092cm^-1、898cm^-1The direction is moved. In addition, NaOH easily exposes the end active group of the lignocellulose in the process of preparing the nano lignocellulose by alkali ultrasonic method, so 1740cm^-1A new C ═ O stretching vibration absorption peak (b) appears in the vicinity, but this peak (a) is not found in lignocellulose. From the above analysis, it can be seen that the characteristic peaks of the obtained nano lignocellulose have no obvious change compared with the raw material, which indicates that the nano lignocellulose still has the basic chemical structure of the lignocellulose, and on the other hand, indicates that the specificity of the nano lignocellulose is derived from the size effect thereof.

After the nano lignocellulose is compounded with the montmorillonite, the montmorillonite (c) is 3634cm^-1the-OH stretching vibration absorption peak disappears (d), which indicates that the montmorillonite has removed the hydroxyl. The nano lignocellulose (b) is 3348cm^-1The C-OH stretching vibration absorption peak and montmorillonite (C) are in 3430cm^-1At H₂the-OH bending vibration absorption peaks of O are weakened and are 3438cm in the high wave number direction^-1Moving (d) shows that C-OH in the nano lignocellulose molecule and-OH in the montmorillonite molecule are subjected to coordination complexAnd (4) carrying out a synthesis reaction. The nano lignocellulose (b) is at 2986cm^-1Of (a) CH₂and-CH₃The asymmetric stretching vibration absorption peak is weakened and moves to a high wave number of 2992cm^-1(d)；1740cm^-1C ═ O expansion and contraction vibration absorption peak at (d) disappeared; 1430cm^-1The C-H bending vibration peak disappears (d); 1166cm^-1The attenuation of the C-C skeleton stretching vibration absorption peak is shifted to 1168cm^-1A (d); 1092cm^-1The peak of C-O stretching vibration and C-O-C stretching vibration of lignocellulose alcohol is shifted to 1038cm^-1A (d); 898cm^-1Processing lignocellulose C₂—C₁—C₆The stretching vibration absorption peak of (2) is weakened and shifted to a low wavenumber of 894cm^-1(d) In that respect Montmorillonite (c) is 1644cm^-1C ═ O stretching vibration absorption peak and H in the vicinity₂The O-H bending vibration absorption peak of O is enhanced and the wave number is 1646cm^-1A directional movement (d); 1040cm^-1The absorption peak of the strong Si-O stretching vibration is weakened (d); 791cm^-1The Al-O stretching vibration absorption peak disappears (d); 694cm^-1The surface of the nearby bending vibration absorption peak has Al₂O₃And Fe₂O₃The peak is almost completely disappeared in the spectrum of the nano lignocellulose/montmorillonite composite material (d). As explained above, the nano lignocellulose molecules are intercalated and dispersed into the interlayer of montmorillonite nano-scale sheets, and C-OH and C-O, C-H, CH on the nano lignocellulose occur in the interlayer region₂And C-O-C and other active groups coordinate or complex with-OH, Si-O, Al-O and other groups in the montmorillonite structure and cations between layers to form the nano lignocellulose/montmorillonite intercalation stripping type nano composite material.

SEM analysis was performed on the raw material lignocellulose used in example 1, the nano lignocellulose prepared in example 1, the raw material montmorillonite used in example 2, and the nano lignocellulose/montmorillonite composite material prepared in example 2, respectively, wherein an SEM spectrum of the raw material lignocellulose used in example 1 is shown in fig. 31A; the SEM spectrogram (50.0 μm) of the nano lignocellulose prepared in example 1 is shown in FIG. 31B; the SEM spectrogram (2.00 mu m) of the nano lignocellulose prepared in example 1 is shown in FIG. 31C; the SEM spectrogram of the raw material montmorillonite used in example 2 is shown in FIG. 31D; the SEM spectrum of the nano lignocellulose/montmorillonite composite material prepared in example 2 is shown in fig. 31E.

The nano lignocellulose treated by ultrasonic treatment under high-power and low-temperature conditions in the NaOH alkaline ultrasonic medium is irregular short-line-shaped, mostly rod-shaped, the particle size range is approximately 15-100nm, part of the structure is composed of a small amount of sub-original fine fibers with smaller diameters, and stronger surface adhesion force is formed among the linear fibers to generate agglomeration, which is related to that a large amount of hydroxyl groups are exposed on the surface of nano lignocellulose molecules caused by ultrasonic treatment in the NaOH alkaline medium (figure 31B). The aggregation state of nano lignocellulose, so-called supramolecular structure (fig. 31B), is a system formed by the cross-bonding of crystalline regions and amorphous regions, and is characterized in that molecular chains in a part of aggregation state regions are regularly oriented, the density is high, and the surface is in a rough and loose state. At higher magnification (fig. 31C), it can be clearly seen that the nano lignocellulose crystal lattice presents a typical net-like nanostructure morphology, further illustrating that nano lignocellulose can be obtained by ultrasonic treatment in alkaline medium. The nanometer lignocellulose obtained by the invention has opened entangled and agglomerated lignocellulose molecules, each long-chain molecule is clear and visible, the nanometer lignocellulose presents irregular rigid short-line and rod-shaped structures with higher length-diameter ratio and reticular cross-linking entanglement, and the polymerization degree between molecular chains is very low. In high magnification (fig. 31C) it can be seen that the size is in the nanoscale range, the particle size is typically between 15-100nm, and compared to common lignocellulose (fig. 31A), it has both the basic structure and properties of lignocellulose and the typical properties of nanoparticles.

The surface of the montmorillonite is uniform and compact, the surface has a layered structure and a large number of pore structures, if the appearance of a single particle is observed, most of the montmorillonite can be analyzed and identified to be an appearance contour, the whole montmorillonite is a thick and large lump consisting of lamellar, the edge presents curl and wrinkle, and the montmorillonite has certain expansibility and a large specific surface area (fig. 31D). The surface of the nano lignocellulose/montmorillonite composite material has an irregular layered structure, a part of edge curls and a disordered fragment morphology structure (figure 31E), and compared with montmorillonite, the surface of the nano lignocellulose/montmorillonite composite material is looser, rougher and uneven, which indicates that the nano lignocellulose destroys the crystal structure of the montmorillonite, and the nano lignocellulose is successfully intercalated and dispersed into the nano-scale montmorillonite layers, so that the crystal-type substances and the amorphous-type substances in the inner hole pores form a random network structure, which is convenient for the solution to permeate into the structure of the nano composite material, and is beneficial to the adsorption of heavy metal ions.

TEM analysis was performed on the raw material montmorillonite used in example 2 and the nano lignocellulose/montmorillonite composite material prepared in example 2, wherein TEM spectra of the raw material montmorillonite and the nano lignocellulose/montmorillonite composite material are shown in fig. 32A and fig. 32B, respectively.

As can be seen from fig. 32A and 32B, for some polymer/inorganic clay nanocomposites having completely disappeared characteristic diffraction peaks on the XRD spectrum, what is observed with TEM is not the polymer/inorganic clay nanocomposite but a macrocomposite thereof. It can be seen that only combining the two characterization methods of XRD and TEM is an effective method to demonstrate the structure of the nanocomposite. As can be seen from FIG. 32A, most of the montmorillonite lamellar crystals have been exfoliated into 1-2 layers, and a few are 4-5 layers of lamellar crystals, the lamellar length is within the range of 100-200nm, the thickness of the grain layer is about 50nm, the lamellar spacing is increased, but the exfoliation of the lamellar is not reached, and the montmorillonite can be considered as a nano-material in one dimension; as can be seen from fig. 32B, the shaded portion is a montmorillonite lamellar structure, wherein the black short rod-shaped region is nano-lignocellulose, and the transverse diameter is distributed between 5nm and 30nm, further indicating that the montmorillonite nano-lamellar is effectively exfoliated, and a large number of nano-lignocellulose molecules reach nano-uniform dispersion and are intercalated between the lamellar; meanwhile, it can be clearly seen from fig. 32B that the exfoliated type and the intercalated type coexist between montmorillonite layers, that is, the intercalated-exfoliated composite material prepared by the present invention has montmorillonite dispersed in the nano lignocellulose matrix. It can be seen that even in the nanocomposite material in which the characteristic diffraction peak is completely disappeared in XRD analysis, montmorillonite is still present in both exfoliated and intercalated forms together in the nano lignocellulose matrix.

The characterization results of FTIR, XRD, SEM and TEM spectrograms all show that the nano lignocellulose/montmorillonite composite material provided by this example has an intercalation-exfoliation structure in which nano lignocellulose is intercalated into the interlayer of montmorillonite.

In addition, the relevant performance parameters of the nano lignocellulose/montmorillonite composite material prepared in example 2 and the montmorillonite raw material used in example 2 are shown in the following table 1.

TABLE 1

As can be seen from table 1, compared with montmorillonite, the nano lignocellulose/montmorillonite composite material provided by the present application has a large specific surface area, a high mesopore-micropore volume ratio, and a small average micropore and mesopore diameter, and these structural features of the composite material are beneficial to the adsorption effect of the nano cellulose/montmorillonite nanocomposite material on heavy metal ions.

Example 3

The embodiment provides an application of the nano lignocellulose/montmorillonite composite material obtained in the embodiment 2 in heavy metal ion adsorption, which specifically comprises the following steps:

1. taking 0.0500g of the nano lignocellulose/montmorillonite composite material prepared in the example 2, placing the nano lignocellulose/montmorillonite composite material into a water solution containing Zn (II) for carrying out adsorption capacity test, setting the temperature, placing the nano lignocellulose/montmorillonite composite material into a constant temperature oscillator (6000r/min), wherein the concentration of the Zn (II) in the solution is 1000 mg/L, the pH value is 2.6, the adsorption temperature is 65 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

2. Taking 0.0500g of the nano lignocellulose/montmorillonite composite material prepared in the embodiment 2, placing the nano lignocellulose/montmorillonite composite material into an aqueous solution containing Mn (II) for carrying out adsorption capacity test, setting the temperature, placing the nano lignocellulose/montmorillonite composite material into a constant temperature oscillator (6000r/min), wherein the concentration of Mn (II) in the solution is 1000 mg/L, the pH value is 6.3, the adsorption temperature is 50 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

3. Taking 0.0500g of the nano lignocellulose/montmorillonite composite material prepared in the embodiment 2, placing the nano lignocellulose/montmorillonite composite material into an aqueous solution containing Ni (II) for carrying out adsorption capacity test, setting the temperature, placing the nano lignocellulose/montmorillonite composite material into a constant temperature oscillator (6000r/min), wherein the concentration of the Ni (II) in the solution is 1000 mg/L, the pH value is 6.8, the adsorption temperature is 70 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

4. Taking 0.0500g of the nano lignocellulose/montmorillonite composite material prepared in the embodiment 2, placing the nano lignocellulose/montmorillonite composite material into a water solution containing Cu (II) for carrying out adsorption capacity test, setting the temperature, placing the nano lignocellulose/montmorillonite composite material into a constant temperature oscillator (6000r/min), wherein the concentration of the Cu (II) in the solution is 1000 mg/L, the pH value is 4.9, the adsorption temperature is 50 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

Example 4

The present embodiment provides a method for manufacturing standard working curves of zn (ii), (iii), (iv), (:

1. standard working curve of Zn (II)

And (3) zinc ion standard solution, namely accurately weighing 1.2520g of standard zinc oxide solid into a 1L volumetric flask, adding 10m of L concentrated sulfuric acid, using distilled water to fix the volume to a scale mark, shaking up, wherein the concentration of the standard solution is (1 g/L), and diluting when the standard solution is used subsequently.

The xylenol orange solution is prepared by accurately weighing 0.1500g xylenol orange in a 100m L volumetric flask, adding distilled water to a constant volume to reach a scale mark, and shaking up.

Accurately measuring 36m L glacial acetic acid in a 100m L volumetric flask to fix the volume, shaking up, weighing 200g of anhydrous sodium acetate solid, dissolving in water, heating, stirring, dissolving, transferring to a 1L volumetric flask, adding 26m L of the solution, cooling, fixing the volume to a scale mark, and shaking up.

The preparation of zinc ion standard curve is that 10m L zinc ion standard solution is put into a 1L volumetric flask (C is 10 mg/L0), distilled water is added to fix the volume to the scale mark, shaking is carried out, 2.5m L1, 5m L2, 7.5m L3, 10m L4, 12.5m L5, 15m L6, 17.5m L, 20m L, 22.5m L and 25m L zinc ion solution are respectively extracted from the solution and put into 10 50m L volumetric flasks, 10m L acetic acid-sodium acetate buffer solution and 2.5m L xylenol orange solution are sequentially added to the scale mark, shaking is carried out, standing is carried out for 10 minutes, the absorbance is measured by using a 1cm cuvette at 570nm and taking water as a reference, the concentration C (mg/L) of Zn (II) is used as the horizontal coordinate, the absorbance (Abs) is used to prepare the standard curve, and Zn (II) is drawn as the standard curve, and the standard curve is shown in the 1 equation.

2. Standard working curve of Mn (II)

And (3) accurately weighing 3.6386g of manganese chloride solid into a 1L volumetric flask, adding distilled water to a constant volume to a scale mark, shaking up, and diluting when the standard solution is used subsequently, wherein the concentration of the standard solution is (1 g/L).

Transferring 10m L concentrated nitric acid into a 100m L volumetric flask, adding distilled water to a constant volume to a scale mark, shaking uniformly, accurately weighing 2.0000g potassium periodate solid, and dissolving in the 100m L nitric acid solution.

And (3) potassium pyrophosphate-sodium acetate buffer dissolution, namely accurately weighing 23g of potassium pyrophosphate solid and 8.2g of anhydrous sodium acetate solid, dissolving in water, heating, stirring, dissolving, transferring to a 100m L volumetric flask, cooling, fixing the volume to a scale mark, and shaking up.

Preparing a manganese ion standard curve, namely taking 4m L manganese ion standard solution in a 1L volumetric flask (C is 4 mg/L0), adding distilled water to fix the volume to a scale mark, shaking up, extracting 2.5m L1, 5m L2, 7.5m L3, 10m L4, 12.5m L5, 15m L6, 17.5m L, 20m L, 22.5m L and 25m L manganese chloride solution from the manganese ion standard solution, respectively placing the manganese chloride solution in 10 50m L volumetric flasks, sequentially adding 10m L potassium pyrophosphate-sodium acetate buffer solution and 3m L potassium periodate solution, adding distilled water to the scale mark, shaking up, placing for 20 minutes, measuring the absorbance at 525nm by using a 1cm cuvette and taking water as a reference, taking the concentration C (mg/L) of Mn (II) as a horizontal coordinate, taking the absorbance (Abs) as a vertical coordinate, drawing up a standard curve (II), and drawing up a standard curve (shown in a Mn standard curve equation 2) as a graph.

3. Standard working curve of Ni (II)

Ni (II) with dimethylglyoxime [ H ] in ammoniacal solution₃CC(NOH)C(NOH)CH₃]Abbreviated as (H)₂Dm) to form the pink complex nickel dimethylglyoxime [ Ni (HDm)₂]The complex is insoluble in water and readily soluble in chloroform (CHCl)₃) Nickel dimethylglyoxime [ Ni (HDm) ]₂]At K_maxMolar absorptiveness at 360nm is 3400. In the presence of an alkaline medium and an oxidizing agent, [ Ni (HDm)₂]Can give birth toInto a brownish red water-soluble [ Ni (HDm) ]₃]^2-The measurement can be carried out spectrophotometrically. The compound is at lambda_maxMolar absorption coefficient at 470nm 15000.

0.4m L, 0.6m L0, 0.8m L, 1.0m L and 1.2m L diluted standard Ni (II) solution (0.1mg/m L) are respectively added into 5 50m L volumetric flasks, 1m L dimethylglyoxime (1%) ethanol solution, 2m L saturated bromine water and 5m L concentrated ammonia water are respectively added into the flasks and diluted to scale by distilled water and mixed uniformly, a blank sample is taken as a reference solution at 470nm of a 1m L cuvette, the absorbance of the blank sample is measured by an ultraviolet spectrophotometer, and the obtained data are subjected to regression fitting to draw a standard working curve, which is shown in figure 3.

4. Standard working curve of Cu (II)

0.5g/m L of citric acid, 0.1 percent of ammonia water solution (ammonia water: water is 1:1 volume ratio), and 0.1 percent of bicycloacetophenone phthalein dihuang solution (1g of solid sample is weighed, added with 100m L ethanol in a 200m L beaker, warmed to 60 ℃, dissolved and transferred to a 1000m L volumetric flask, and distilled water is added to the volume to be calibrated.

1m L, 1.2m L0, 1.4m L, 1.6m L and 2m L Cu (II) standard solutions (10ug/m L), 2m L citric acid solution, 4m L ammonia water solution and 10m L dicycloacetophenone phthalein dihydrated brown solution (BCO) are accurately added into a 50m L volumetric flask, the mixture is shaken evenly and diluted to a scale for 10min (the instrument is preheated for 10min), 1m L cuvette is selected for colorimetry, a blank sample is used as a reference solution at 610nm, the absorbance of the blank sample is measured by an ultraviolet spectrophotometer, and the obtained data is subjected to regression fitting to draw a standard working curve, which is shown in figure 4.

Example 5

In this embodiment, the influence of different ultrasonic powers used in the preparation process of nano lignocellulose on the adsorption amounts of zn (ii), mn (ii), and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

1) respectively weighing 0.5000g of lignocellulose, placing the lignocellulose in six parts of 250m aqueous solution of NaOH with the mass fraction of L% and fully stirring the lignocellulose with a glass rod until the lignocellulose forms suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, wherein the amplitude of the ultrasonic rod is phi 20mm, the ultrasonic temperature is 10 ℃, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic power is 600W, 720W, 840W, 960W, 1080W and 1200W respectively, the ultrasonic time is 150min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

2) Weighing 0.5000g of each of the six parts of nano lignocellulose subnatants, respectively dissolving in 75m of aqueous solution of sodium hydroxide (NaOH) L with the mass fraction of 12.5%, and stirring for 30min at 60 ℃ to form nano lignocellulose suspension.

3) 0.5000g of montmorillonite is weighed and dissolved in 15m L distilled water, and stirred for 30min at room temperature to obtain montmorillonite suspension.

4) And (3) slowly and respectively dripping the six parts of nano lignocellulose suspension liquid in the step 2) into the montmorillonite suspension liquid in the step 3) under the condition of continuously stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by distilled water, carrying out vacuum drying for 240min at 85 ℃, grinding and sieving by a 200-mesh sieve to obtain six parts of nano lignocellulose/montmorillonite composite material.

5) Taking six parts of the nano lignocellulose/montmorillonite composite material in the step 4), 0.0500g of each nano lignocellulose/montmorillonite composite material, respectively putting the six parts of nano lignocellulose/montmorillonite composite material into water solution containing Zn (II) for carrying out adsorption capacity test, wherein the concentration of Zn (II) in the solution is 1000 mg/L, the pH value is 2.6, the adsorption temperature is 65 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

6) Taking six parts of the nano lignocellulose/montmorillonite composite material in the step 4), respectively putting 0.0500g of the nano lignocellulose/montmorillonite composite material into aqueous solution containing Mn (II) for adsorption capacity test, wherein the concentration of Mn (II) in the solution is 1000 mg/L, the pH value is 6.3, the adsorption temperature is 50 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

7) Taking 0.0500g of the six parts of the nano lignocellulose/montmorillonite composite material in the step 4), placing the six parts of the nano lignocellulose/montmorillonite composite material in an aqueous solution containing Ni (II) for carrying out adsorption capacity test, setting the temperature, placing the solution in a constant temperature oscillator (6000r/min), wherein the concentration of the Ni (II) in the solution is 1000 mg/L, the pH value is 6.8, the adsorption temperature is 70 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

Wherein, the relation curve chart of the influence of the composite material prepared under different ultrasonic power conditions on the adsorption quantity of Zn (II) is shown in FIG. 5; the graph of the relationship of the influence of the composite material prepared under different ultrasonic power conditions on the adsorption amount of Mn (II) is shown in FIG. 6; the graph of the relationship between the effect of the composite materials prepared under different ultrasonic power conditions on the adsorption amount of Ni (II) is shown in FIG. 7.

As can be seen from fig. 5-7, with the increase of the ultrasonic power, the adsorption amount of the nano lignocellulose/montmorillonite composite material to zn (ii), mn (ii), and ni (ii) ions rapidly increases, when the ultrasonic power is 1080W, the adsorption amount of the nano lignocellulose/montmorillonite composite material to zn (ii), mn (ii), and ni (ii) ions reaches the maximum, and if the ultrasonic power is continuously increased, the adsorption amount shows a decreasing trend. This is because: when the lignocellulose is treated by ultrasonic, the micro jet flow generated by ultrasonic cavitation generates strong impact, shearing and crushing actions on the lignocellulose, so that hydrogen bonds and van der waals force in a molecular structure of the clustered and entangled lignocellulose are opened to form a structure with smaller microscopic particle size, long chain molecules in each component are destroyed and broken, the polymerization degree between the long chain molecules is obviously reduced, the specific surface area is increased, a large number of active functional groups at the tail end of a high molecular chain and the breaking points of a plurality of molecular chains are exposed outside to generate stronger hydrophilic performance and chemical reaction activity, and the micro jet flow is more easily dispersed among nano-scale layers of montmorillonite in the form of small-sized linear nano-particles when being subjected to composite reaction with the montmorillonite. Specifically, under the action of high ultrasonic power, the generated elastic mechanical waves with extremely strong penetration capacity and huge ultrasonic energy enable medium particles to enter a high-frequency vibration state, and the medium particles are continuously compressed and stretched to be periodically and alternately changed, a series of secondary chain reactions are initiated under the action of strong stress and sound pressure, meanwhile, the liquid medium is torn to be a plurality of small cavities, namely 'cavitation', by the strong tensile stress, the transient cavitation of high-power ultrasonic waves generates a large number of micro-jets and 'cavity effects' to play strong impact, shearing and crushing roles on lignocellulose, the cavitation is different from ordinary mechanical stirring, the speed of material transfer can be directly and rapidly accelerated, and inherent crystal lattice structures such as hydrogen bonds, intermolecular forces, crystalline regions, amorphous regions and the like in molecular structures among lignocellulose molecules and long chain molecules are further destroyed, the regularity of arrangement among molecules is reduced, the degree of order and the degree of polymerization are reduced, the degree of crystallinity is reduced, the specific surface area is increased, a large number of active functional groups at the tail end of a high-molecular long chain and the fracture points of a plurality of molecular chains are exposed outside, and stronger hydrophilic performance and chemical reaction activity are generated, so that the nanocrystallization dispersion degree of the lignocellulose molecules is obviously enhanced.

When the ultrasonic power is 1080W, the adsorption quantity of the nano composite adsorbent to Zn (II), Mn (II) and Ni (II) reaches the maximum value. Continue to increase ultrasonic power, because of producing obvious vortex heat in the solution, the intensification is rapid in the ultrasonic crusher container, the heat has the partial weakening to offset to the effect of hot vortex to ultrasonic wave, and simultaneously, overheated air makes the interior solution molecular motion aggravation of container, moisture scatters and disappears sooner, the amplitude transformer intensifies, the resistance increase, be unfavorable for going on of ultrasonic conduction effect, and simultaneously, because of higher ultrasonic power can make the chemical bond in the nanometer lignocellulose structure break, lead to nanometer lignocellulose to take place degradation reaction, influence nanometer composite's adsorption capacity. Therefore, 1080W is preferably selected as the ultrasonic power in the invention by comprehensively considering the treatment effect, the dispersion degree and other factors of the lignocellulose.

Example 6

In this embodiment, the influence of the ultrasonic temperature in the preparation process of the nano lignocellulose on the adsorption amounts of the prepared nano lignocellulose/montmorillonite composite material zn (ii), mn (ii), and ni (ii) is examined, and the method specifically includes the following steps:

1) respectively weighing 0.5000g of lignocellulose, placing the lignocellulose in six parts of 250m L mass percent NaOH aqueous solution, fully stirring the lignocellulose with a glass rod until the lignocellulose forms suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, carrying out centrifugal separation on the lignocellulose with the amplitude-variable rod phi of 20mm, the ultrasonic power of 1080W, the ultrasonic generation time of 1.0s, the ultrasonic gap of 2.0s, the ultrasonic temperature of 7 ℃, 10 ℃, 17 ℃, 23 ℃, 30 ℃ and 35 ℃ respectively and the ultrasonic time of 150min, and taking the lower layer liquid for later use.

4) Slowly dripping the six parts of nano lignocellulose suspension liquid obtained in the step 2) into the montmorillonite suspension liquid obtained in the step 3) under continuous stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, performing suction filtration, washing a product to be neutral by distilled water, performing vacuum drying for 240min at 85 ℃, grinding and sieving by a 200-mesh sieve to obtain six parts of nano lignocellulose/montmorillonite composite material.

Wherein, the relation curve chart of the influence of the composite materials prepared under different temperature conditions on the adsorption quantity of Zn (II) is shown in FIG. 8; the graph of the relationship of the influence of the composite materials prepared under different temperature conditions on the adsorption amount of Mn (II) is shown in FIG. 9; the graph of the relationship between the effects of the composite materials prepared under different temperature conditions on the adsorption amount of Ni (II) is shown in FIG. 10.

As can be seen from fig. 8-10, the adsorption amounts of the nano-lignocellulose/montmorillonite composite material to zn (ii), mn (ii), and ni (ii) ions gradually increase with the increase of the ultrasonic temperature, and when the ultrasonic temperature is 10 ℃, the adsorption amounts of the nano-composite material to zn (ii), mn (ii), and ni (ii) ions reach maximum values, and when the ultrasonic temperature is continuously increased, the adsorption amounts show a decreasing trend. Therefore, in the present application, the ultrasonic temperature is preferably 10 ℃.

XRD diffraction analysis is respectively carried out on the raw material montmorillonite used in the example 6 and the nano lignocellulose/montmorillonite composite material prepared in the example 6 under different ultrasonic temperature conditions, wherein XRD diffraction spectrums of the substances are shown in figure 30.

FIG. 30 is a phase structure analysis of montmorillonite used in example 6 and six kinds of nano-lignocellulose/montmorillonite composites prepared in example 6 in the range of 2-18 degrees, wherein the curves in FIG. 30 are, from top to bottom, XRD curves of montmorillonite, nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 35 degrees C.), nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 30 degrees C.), nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 8 degrees C.), nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 17 degrees C.), nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 23 degrees C.), and nano-lignocellulose/montmorillonite composites (ultrasonic temperature is 10 degrees C.). As can be seen from FIG. 30, the montmorillonite has an obvious characteristic diffraction peak at 5.92 °, indicating that the montmorillonite has a relatively complete crystal structure and typical nanomaterial structural characteristics. After intercalation composite reaction with the nano lignocellulose, the characteristic diffraction peak of the montmorillonite at 5.92 ℃ shows the trend that the diffraction peak is reduced to disappear (35-10 ℃) firstly and then is slightly increased (10-8 ℃) along with the reduction of the ultrasonic temperature. When the ultrasonic temperature is 10 ℃, the characteristic diffraction peak of montmorillonite in the structure of the nano lignocellulose/montmorillonite composite material at 5.92 ℃ almost disappears, which shows that molecular chains of nano lignocellulose are well inserted into the nano-scale lamellar structure of montmorillonite and are dispersed in the lamellar, and the nano lignocellulose/montmorillonite composite adsorption material forms a more uniform stripping type nano structure.

Example 7

In this embodiment, the influence of the ultrasonic time in the preparation process of the nano lignocellulose on the adsorption amounts of zn (ii), mn (ii), and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

1) respectively weighing 0.5000g of lignocellulose, placing the lignocellulose in six parts of NaOH aqueous solution with the mass fraction of 20% of 250m L, fully stirring the lignocellulose with a glass rod until the lignocellulose forms suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, wherein the amplitude transformer phi is 20mm, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic temperature is 10 ℃, the ultrasonic power is 1080W, the ultrasonic time is 60min, 90min, 120min, 150min, 180min and 240min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

Wherein, the relation curve chart of the influence of the composite materials prepared under different ultrasonic time on the adsorption quantity of Zn (II) is shown in FIG. 11; the graph of the relationship of the influence of the composite materials prepared under different ultrasonic times on the adsorption amount of Mn (II) is shown in FIG. 12; the graph of the relationship between the effect of the composite materials prepared under different ultrasonic times on the adsorption amount of Ni (II) is shown in FIG. 13.

As can be seen from FIGS. 11-13, the adsorption amounts of Zn (II), Mn (II) and Ni (II) of the nano lignocellulose/montmorillonite composite material tend to increase and then decrease with the increase of the ultrasonic time. The reason is that when the lignocellulose is treated by ultrasonic, the liquid is torn by strong tensile stress to form a plurality of small cavities, namely, cavitations, which are filled with gas or even vacuum, small bubbles formed by cavitation can move continuously, grow and are broken suddenly along with the vibration of surrounding media, and when the small bubbles are broken, the surrounding liquid instantly rushes into the bubbles to generate high temperature, high pressure, shock waves and micro-jet, so that strong mutual collision and shearing action is generated among molecules, the lignocellulose can generate chemical bond breakage, aqueous phase combustion, thermal decomposition reaction and the like in the cavitation bubbles, the mass transfer and heat transfer process between two phase interfaces is accelerated, the stirring and the phase interface renewal among heterogeneous interfaces are promoted, and the reticular entangled and aggregated lignocellulose molecules are opened. When the ultrasonic time is 150min, the adsorption capacity of the composite material to Zn (II), Mn (II) and Ni (II) reaches the maximum value. Along with the continuous increase of the ultrasonic time, the heat of the liquid in the container is accumulated, the temperature of the lignocellulose and the amplitude transformer is rapidly increased, the resistance of the amplitude transformer is increased, the heat is difficult to rapidly release, the ultrasonic eddy effect is weakened, the dispersion and shearing effect on the lignocellulose aggregated among molecules is correspondingly weakened, and the formation of the nano lignocellulose with small particle size is not facilitated. Considering comprehensive factors, the ultrasonic time is preferably selected to be 150 min.

Example 8

In this embodiment, the influence of the concentration of NaOH in the ultrasonic medium in the preparation process of nano lignocellulose on the adsorption amounts of zn (ii), mn (ii), and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

1) respectively weighing 0.5000g of lignocellulose, respectively placing the lignocellulose in seven parts of 250m aqueous solution of L mass percent of 0%, 5%, 10%, 15%, 20%, 25% and 30% NaOH, fully stirring the lignocellulose by using a glass rod until suspension is formed, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, wherein the amplitude of the amplitude transformer is phi 20mm, the ultrasonic temperature is 10 ℃, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic power is 1080W, after the ultrasonic time is 150min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

2) Weighing seven parts of nano lignocellulose underlayer solution, respectively dissolving 0.5000g of the seven parts of nano lignocellulose underlayer solution in 75m of aqueous solution of NaOH with the mass fraction of L being 12.5%, and stirring for 30min at 60 ℃ to form suspension.

3) Respectively weighing 0.5000g of montmorillonite, dissolving in 15m L distilled water, and stirring at room temperature for 30min to obtain montmorillonite suspension.

4) And (3) slowly dripping the seven parts of nano lignocellulose suspension liquid obtained in the step 2) into the montmorillonite suspension liquid obtained in the step 3) under the condition of continuous stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by using distilled water, drying for 240min in vacuum at 85 ℃, grinding and sieving by using a 200-mesh sieve to obtain seven parts of nano lignocellulose/montmorillonite composite material.

5) Taking seven parts of the nano lignocellulose/montmorillonite composite material in the step 4), 0.0500g of each nano lignocellulose/montmorillonite composite material, respectively putting the seven parts of nano lignocellulose/montmorillonite composite material into water solution containing Zn (II) for carrying out adsorption capacity test, wherein the concentration of Zn (II) in the solution is 1000 mg/L, the pH value is 2.6, the adsorption temperature is 65 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

6) And taking seven parts of the nano lignocellulose/montmorillonite composite material in the step 4), respectively putting 0.0500g of the nano lignocellulose/montmorillonite composite material into aqueous solution containing Mn (II) for adsorption capacity test, wherein the concentration of Mn (II) in the solution is 1000 mg/L, the pH value is 6.3, the adsorption temperature is 50 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

7) Taking 0.0500g of seven parts of nano lignocellulose/montmorillonite composite material in the step 4), placing the seven parts of nano lignocellulose/montmorillonite composite material in the step 4) into an aqueous solution containing Ni (II) for carrying out adsorption capacity test, setting the temperature, placing the aqueous solution in a constant temperature oscillator (6000r/min), wherein the concentration of the Ni (II) in the solution is 1000 mg/L, the pH value is 6.8, the adsorption temperature is 70 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

Wherein, a relation curve chart of the influence of the composite materials prepared by different ultrasonic medium NaOH concentrations on the Zn (II) adsorption amount is shown in FIG. 14; the graph of the relationship of the effect of the composite materials prepared by different ultrasonic medium NaOH concentrations on the adsorption amount of Mn (II) is shown in FIG. 15; the graph of the relationship between the effect of the composite materials prepared by different ultrasonic medium NaOH concentrations on the adsorption amount of Ni (II) is shown in FIG. 16.

Because the amplitude transformer of the SM-1200D ultrasonic cell crusher is made of metal materials and is easy to react with an acidic reagent, only water and NaOH are selected to be used as ultrasonic media in the experiment. As can be seen from fig. 14, 15 and 16, when the concentration of NaOH in the ultrasonic medium is 0-20% by mass, the adsorption amounts of zn (ii), mn (ii) and ni (ii) of the nano lignocellulose/montmorillonite composite material all show a tendency of increasing with the increase of the concentration of NaOH, and when the concentration of NaOH in mass% is 20%, the adsorption amount of the nano composite material reaches a maximum value. Subsequently, when the concentration of NaOH is higher than 20% by mass, the adsorption amount of the nanocomposite decreases correspondingly with the increase of the concentration of NaOH. This is because, when lignocellulose is treated by ultrasonic waves, ultrasonic waves propagate in a solution medium and interact with each other, so that the alkaline ultrasonic medium NaOH solution is subjected to physical and chemical changes, thereby generating a series of ultrasonic effects. Because the temperature of the ultrasonic cavitation area is extremely high, a liquid shell area can be formed at the interface of bubbles and NaOH solution in the area, NaOH solution molecules are cracked into free radicals, certain chemical reactions are accelerated, the reaction activation energy is reduced, the emulsification of NaOH and the shearing and dispersing action of lignocellulose are promoted (under high temperature and high pressure, strong shock waves and micro-jet flows generated when the free radicals and cavitation bubbles are broken generate mechanical damage and tangential force action on surrounding liquid substances, the swelling action of the lignocellulose is accelerated, hydrogen bond structures, van der Waals force and other intermolecular forces in the lignocellulose molecules, which are agglomerated and entangled together, and among long molecular chains are opened, the morphological structure and the fine structure of the lignocellulose are changed greatly, more high-activity hydroxyl groups are exposed outside, and hemicellulose and low-polymerization cellulose skeletons are dissolved, increase the accessibility and the reactivity of the lignocellulose and simultaneously cooperate with the high-power ultrasonic wave action to effectively form the nano lignocellulose). Along with the increase of the concentration of NaOH, the viscosity of a liquid medium is increased, the ultrasonic pressure required by ultrasonic cavitation is increased, hydrogen bonds among lignocellulose molecules and an amorphous area are further destroyed, the regularity of molecular arrangement is reduced, the degree of order is reduced, the degree of crystallinity is reduced, the degree of molecular nanocrystallization dispersion is obviously enhanced, and the adsorption effect of the formed nanocomposite on heavy metal ions is enhanced; when the concentration of the ultrasonic medium NaOH is 20%, the adsorption capacity reaches the maximum value; with the continuous increase of the concentration of NaOH in the ultrasonic medium, under the simultaneous action of the acoustic cavitation effect and the high-concentration alkali liquor, the lignocellulose can be subjected to various degradations, so that the generation of esterified substances and etherified substances, the self viscosity and other performances are reduced, the effective dispersion of the aggregation state of the lignocellulose and the breakage of hydrogen bonds in an amorphous area and a crystalline area are greatly reduced, and the NaOH solution is limited from entering the structure of the lignocellulose; meanwhile, a large number of micro bubbles generated by ultrasonic cavitation are difficult to be orderly arranged outside the crystal nucleus of the lignocellulose particles, so that the size and the distribution of the nano particle size are uneven, and the adsorption capacity of the prepared novel nano composite material to Zn (II), Mn (II) and Ni (II) is correspondingly reduced. Considering the factors comprehensively, the concentration of NaOH is preferably selected to be 20%.

Example 9

In this embodiment, the influence of the doping ratio of the nano lignocellulose and the montmorillonite on the adsorption amounts of the prepared nano lignocellulose/montmorillonite composite material zn (ii), mn (ii), and ni (ii) is examined, and the method specifically includes the following steps:

1) weighing 0.5000g of lignocellulose, placing the lignocellulose in 250m of aqueous solution of NaOH with the mass fraction of L percent, fully stirring the lignocellulose with a glass rod until the lignocellulose forms suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, carrying out centrifugal separation after an amplitude transformer phi of 20mm, an ultrasonic temperature of 10 ℃, an ultrasonic generation time of 1.0s, an ultrasonic gap of 2.0s, an ultrasonic power of 1080W and an ultrasonic time of 150min, and taking a lower layer liquid for later use.

2) Weighing the seven parts of nano lignocellulose underlayer solution, wherein the seven parts of nano lignocellulose underlayer solution respectively comprise 0.2500g, 0.5000g, 1.0000g, 2.0000g, 3.0000g, 4.0000g and 5.0000g, dissolving the seven parts of nano lignocellulose underlayer solution in NaOH aqueous solution with the mass fraction of 75m L percent of 12.5 percent respectively, and stirring the mixture for 30min at the temperature of 60 ℃ to form suspension.

4) And (3) respectively and slowly dripping the seven parts of nano lignocellulose suspension liquid in the step 2) into the montmorillonite suspension liquid in the step 3) under continuous stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by using distilled water, carrying out vacuum drying for 240min at 85 ℃, grinding and sieving by using a 200-mesh sieve to obtain seven parts of nano lignocellulose/montmorillonite composite material.

6) And taking seven parts of the nano lignocellulose/montmorillonite composite material in the step 4), respectively putting 0.0500g of the nano lignocellulose/montmorillonite composite material into aqueous solution containing Mn (II) for carrying out adsorption capacity test, wherein the concentration of Mn (II) in the solution is 1000 mg/L, the pH value is 6.3, the adsorption temperature is 50 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

Wherein, the relation curve chart of the influence of the composite material prepared under the conditions of different nano lignocellulose and montmorillonite doping ratios on the Zn (II) adsorption amount is shown in figure 17; a relation curve chart of the influence of the composite material prepared under different nano lignocellulose and montmorillonite doping ratio conditions on the adsorption quantity of Mn (II) is shown in figure 18; the graph of the relationship of the impact of the composite material prepared under different nano lignocellulose and montmorillonite doping ratio conditions on the adsorption amount of Ni (II) is shown in FIG. 19.

From fig. 17-19, it can be seen that when the doping ratio of the nano lignocellulose to the montmorillonite is 1:1, the adsorption amounts of the nano composite material to zn (ii), mn (ii), and ni (ii) reach the maximum. The reason is that the hydraulic radius of the nano lignocellulose is constant under a certain condition, the probability of collision and winding between long chain molecules of the nano lignocellulose is increased along with the increase of the content of the nano lignocellulose, and the acting force between nano lignocellulose molecules is also enhanced. If the content of the nano lignocellulose in the system is low, the strength of intermolecular force is weak, and only a small amount of nano lignocellulose molecules can enter between the nano-scale sheet layers of the montmorillonite in an intercalated manner, so that the adsorption of the nano composite material on heavy metal ions is not facilitated; when the doping ratio of the nano lignocellulose to the montmorillonite is 1:1, the intercalation and the exfoliation reactions of the nano lignocellulose and the montmorillonite are basically balanced, and the adsorption quantity of Zn (II), Mn (II) and Ni (II) reaches the maximum value; if the content of the nano lignocellulose is high, a large number of active functional groups at the tail of the nano lignocellulose molecule and cross-linking points among broken ends of the molecular chain are increased, so that the acting strength and energy among the molecules are not enough to overcome the activation energy generated by the reaction, the smooth proceeding of the intercalation composite reaction is not facilitated, and the adsorption quantity of heavy metal ions is reduced. Therefore, the doping ratio of the nano lignocellulose to the montmorillonite is preferably 1: 1.

Example 10

In this embodiment, the influence of the concentration of NaOH in the intercalation recombination reaction on the adsorption amounts of zn (ii), mn (ii), and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

2) Weighing 0.5000g of the six parts of nano lignocellulose subnatants, respectively dissolving in 75m L mass percent of NaOH aqueous solution with the mass percent of 3 percent, 5 percent, 8 percent, 10 percent, 12.5 percent and 15 percent respectively, and stirring for 30min at 60 ℃ to form suspension.

4) Slowly dripping the six parts of nano lignocellulose suspension liquid obtained in the step 2) into the montmorillonite suspension liquid obtained in the step 3) under the condition of continuous stirring, stirring and mixing, heating to 50 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by distilled water, carrying out vacuum drying for 240min at 85 ℃, grinding and sieving by a 200-mesh sieve to obtain six parts of nano lignocellulose/montmorillonite composite material.

Wherein, in the intercalation composite reaction, the relation curve chart of the influence of the composite material prepared under the condition of different NaOH concentrations on the adsorption quantity of Zn (II) is shown in figure 20; in the intercalation recombination reaction, the relation curve diagram of the influence of the composite material prepared under the condition of different NaOH concentrations on the adsorption quantity of Mn (II) is shown in FIG. 21; the graph of the relationship of the effect of the composite material prepared under the condition of different NaOH concentrations on the adsorption amount of Ni (II) in the intercalation recombination reaction is shown in FIG. 22.

As can be seen from FIGS. 20-22, when the mass concentration of the NaOH aqueous solution is 0-12.5%, the adsorption amounts of the nano lignocellulose/montmorillonite composite material to Zn (II), Mn (II) and Ni (II) all show a trend of increasing with the increase of the NaOH concentration; when the concentration of NaOH is 12.5%, the adsorption capacity reaches the maximum value; when the NaOH mass concentration is higher than 12.5%, the adsorption amount of the nanocomposite decreases as the NaOH concentration increases. The reason is that the purpose of using NaOH aqueous solution as ultrasonic medium is that during ultrasonic treatment, alkaline NaOH aqueous solution can simultaneously contribute to swelling effect on lignocellulose, so as to destroy hydrogen bond structure in lignocellulose molecule and between molecules,the morphological structure and the fine structure of the lignocellulose are greatly changed, more high-activity hydroxyl groups are exposed outside, hemicellulose and a cellulose skeleton with low polymerization degree are dissolved, the accessibility and the reaction performance of the lignocellulose are improved, the nano lignocellulose is more effectively formed under the action of high-power ultrasonic waves, the nano lignocellulose is favorably intercalated and compounded and uniformly dispersed to enter between nano-scale sheet layers of montmorillonite, and the adsorption capacity of the nano composite material on Zn (II), Mn (II) and Ni (II) is enhanced. When the concentration of NaOH is too low, NaOH only easily plays a swelling role on the nano lignocellulose and is difficult to form nano lignocellulose sodium salt and derivatives thereof; if the concentration of NaOH is too high, the concentration of NaOH is increased by Na⁺The hydration degree of the nano lignocellulose is smaller, the swelling degree of the nano lignocellulose is reduced, so that the reactive amorphous and partial crystalline regions are reduced, the alkali-nano lignocellulose and the derivatives thereof are not favorably formed, the nano lignocellulose and the montmorillonite are not favorably subjected to intercalation reaction, and the adsorption quantity of the nano composite material is correspondingly reduced. Therefore, the mass concentration of NaOH is preferably 12.5%.

Example 11

In this embodiment, the effect of the intercalation recombination reaction temperature on the adsorption amounts of zn (ii), mn (ii) and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

1) weighing 0.5000g of lignocellulose, placing the lignocellulose in a NaOH aqueous solution with the mass fraction of 250m L of 20%, fully stirring the lignocellulose with a glass rod until the lignocellulose forms a suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, wherein the amplitude transformer phi is 20mm, the ultrasonic temperature is 10 ℃, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic power is 1080W, after the ultrasonic time is 150min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

2) 0.5000g of each nano lignocellulose subnatant is weighed, dissolved in 75m of NaOH aqueous solution with the mass fraction of L being 12.5 percent respectively, and stirred for 30min at 60 ℃ to form suspension.

4) And (2) under continuous stirring, slowly dripping six parts of nano lignocellulose suspension liquid obtained in the step 2) into the montmorillonite suspension liquid obtained in the step 3, stirring and mixing, respectively heating to 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, stirring and reacting for 4 hours, carrying out suction filtration, washing a product to be neutral by using distilled water, carrying out vacuum drying for 240min at 85 ℃, and grinding and sieving by using a 200-mesh sieve to obtain six parts of nano lignocellulose/montmorillonite composite material.

Wherein, in the intercalation composite reaction, the relation curve chart of the influence of the composite materials prepared at different reaction temperatures on the adsorption quantity of Zn (II) is shown in fig. 23; in the intercalation recombination reaction, the graph of the relationship of the influence of the composite material prepared at different reaction temperatures on the adsorption amount of Mn (II) is shown in FIG. 24; the graph of the relationship of the effect of the composite materials prepared at different reaction temperatures on the adsorption amount of Ni (II) in the intercalation composite reaction is shown in FIG. 25.

It can be seen from FIGS. 23-25 that the adsorption amounts of the nano-lignocellulose/montmorillonite composite material to Zn (II), Mn (II) and Ni (II) all showed a rapid increase tendency with the increase of the temperature of the intercalation recombination reaction, but the adsorption amount of the nano-composite material decreased with the increase of the temperature when the temperature exceeded 50 ℃. The reason is that when the reaction temperature is lower, the viscosity of the system is higher, the activity of the nano lignocellulose molecules is weaker, and the strong hydrogen bond action among the long polymer chains limits the nano lignocellulose molecules to be dispersed and intercalated into the montmorillonite nano-scale sheet layer; with the increase of the intercalation reaction temperature, the activity of nano lignocellulose molecules is enhanced, the hydrogen bonding effect between molecular chains is relatively weakened, the nano lignocellulose is more easily inserted between montmorillonite layers, the intercalation composite reaction effect is optimal when the reaction temperature is 50 ℃, and the corresponding adsorption quantity value is maximized; however, if the reaction temperature is continuously increased, the adsorption amount of the nano lignocellulose on the NaOH aqueous solution is reduced, the swelling degree of the alkali liquor is reduced, the hydrolysis reaction of the alkali-nano lignocellulose is increased, the reducing end of the nano lignocellulose is easy to generate thermokalite action under the high-temperature condition, so that the reducing end of the nano lignocellulose falls off and is degraded, the reaction activity is obviously reduced, the continuous proceeding of the intercalation composite reaction between the nano lignocellulose and the montmorillonite is not facilitated, and the adsorption amounts of Zn (II), Mn (II) and Ni (II) are correspondingly reduced. Therefore, the intercalation temperature is preferably 50 ℃.

Example 12

In this embodiment, the influence of the intercalation recombination reaction time on the adsorption amounts of zn (ii), mn (ii), and ni (ii) of the prepared nano lignocellulose/montmorillonite composite material is examined, and the method specifically includes the following steps:

1) weighing 0.5000g of lignocellulose, placing the lignocellulose in a NaOH aqueous solution with the mass fraction of 250m L of 20%, fully stirring the lignocellulose with a glass rod until the lignocellulose forms a suspension, then carrying out centralized ultrasonic treatment on the lignocellulose uniformly dispersed in an alkaline ultrasonic medium by using an SM-1200D ultrasonic cell crusher, wherein the amplitude of the ultrasonic rod is phi 20mm, the ultrasonic temperature is 10 ℃, the ultrasonic generation time is 1.0s, the ultrasonic gap is 2.0s, the ultrasonic power is 1080W, after the ultrasonic time is 150min, carrying out centrifugal separation, and taking the lower layer liquid for later use.

2) 0.5000g of the nano lignocellulose subnatant is weighed and dissolved in 75m of NaOH aqueous solution with the mass fraction of L being 12.5 percent respectively, and the mixture is stirred for 30min at 60 ℃ to form suspension.

4) And (2) under the condition of continuously stirring, slowly dropwise adding the six parts of nano lignocellulose suspension liquid obtained in the step 2) into the montmorillonite suspension liquid obtained in the step 3, stirring and mixing, heating to 50 ℃, respectively stirring and reacting for 2h, 3h, 4h, 5h, 6h and 7h, carrying out suction filtration, washing a product to be neutral by using distilled water, carrying out vacuum drying for 240min at 85 ℃, and grinding and sieving by using a 200-mesh sieve to obtain six parts of nano lignocellulose/montmorillonite composite material.

7) Taking 0.0500g of the six parts of the nano lignocellulose/montmorillonite composite material in the step 4), placing the six parts of the nano lignocellulose/montmorillonite composite material in the water solution containing Ni (II) for adsorption capacity test, setting the temperature, placing the water solution at constant temperature for oscillation (6000r/min), wherein the concentration of the Ni (II) in the water solution is 1000 mg/L, the pH value is 6.8, the adsorption temperature is 70 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption capacity.

Wherein, in the intercalation composite reaction, the relation curve chart of the influence of the composite materials prepared under different reaction time on the adsorption quantity of Zn (II) is shown in FIG. 26; the graph of the relationship of the influence of the composite materials prepared under different reaction times on the adsorption amount of Mn (II) in the intercalation composite reaction is shown in FIG. 27; fig. 28 shows a graph of the relationship between the effect of the composite material prepared under different reaction times on the adsorption amount of ni (ii) in the intercalation recombination reaction.

It can be seen from fig. 26-28 that, as the intercalation reaction time is prolonged, the adsorption amounts of the nano lignocellulose/montmorillonite composite material to zn (ii), mn (ii) and ni (ii) first show a rapid increase trend, and when the intercalation reaction time is 4 hours, the adsorption amounts reach the maximum, and the reaction time is continuously increased, and the adsorption amounts begin to decrease. The reason is that, considering the sequence of swelling action between the 12.5% NaOH aqueous solution and the nano-lignocellulose, the alkaline NaOH aqueous solution is firstly contacted with the outer layer of nano-lignin, and the surface acidic alcoholic hydroxyl and NaOH which are originally in a saturated equilibrium state are hydrolyzed to separate the nano-lignin; then NaOH and nano hemicellulose generate stripping and hydrolysis effects, and the hemicellulose is stripped and decomposed; and finally, the NaOH aqueous solution and the nano-cellulose form alkali-nano-cellulose, macromolecules of the alkali-nano-cellulose are decomposed into a large number of small molecules, monomer glucose molecules are separated to achieve a relatively stable state, and the purity, accessibility and reaction activity of the nano-lignocellulose are obviously improved, so that the intercalation composite reaction is favorably carried out. Therefore, when the reaction time is short, the swelling effect of the NaOH aqueous solution is incomplete, and the accessibility and the reactivity of the nano lignocellulose are low; along with the prolonging of the reaction time, the swelling effect of NaOH is gradually completed, and the reaction speed of the intercalation between the nano lignocellulose and the montmorillonite molecules is increased; when the intercalation composite reaction time is 4 hours, the reaction that the nano lignocellulose long-chain molecules are intercalated and dispersed into the montmorillonite layers is basically balanced, and the adsorption quantity of the nano composite material is maximized; when the intercalation reaction time is continuously increased, the composite reaction is gradually changed from an intercalation type to a peeling type, and cross-linking entanglement and aggregation can also occur among part of the long-chain molecules of the nano lignocellulose, so that the uniform dispersion of the long-chain molecules in the montmorillonite lamellar structure is weakened, and the adsorption quantity of the nano lignocellulose/montmorillonite is correspondingly reduced. Thus, a suitable intercalation time of 4h was determined.

Comparative example

The comparative example examines the influence of simple physical mixed materials of lignocellulose, nano lignocellulose, montmorillonite, nano lignocellulose/montmorillonite composite material and nano lignocellulose and montmorillonite on the adsorption capacity of Zn (II), Mn (II), Ni (II) and Cu (II), and specifically comprises the following steps:

weighing 0.05000g of five adsorbing materials, namely lignocellulose (the raw material used in example 1), nano lignocellulose (the raw material used in example 1), montmorillonite (the raw material used in example 2), a simple physical mixture (mass ratio is 1:1) of nano lignocellulose and montmorillonite and the nano lignocellulose/montmorillonite composite material prepared in example 2, respectively putting the materials into a solution containing Zn (II), Mn (II), Ni (II) and Cu (II) ions for adsorption capacity test, wherein the concentration of Zn (II) in the solution is 1000 mg/L, the pH value is 2.6, the adsorption temperature is 65 ℃, the adsorption time is 120min, measuring the absorbance, and calculating the adsorption amount;

the concentration of Mn (II) in the solution is 1000 mg/L, the pH value is 6.3, the adsorption temperature is 50 ℃, the adsorption time is 120min, the absorbance is measured, and the adsorption quantity is calculated;

the concentration of Ni (II) in the solution is 1000 mg/L, the pH value is 6.8, the adsorption temperature is 70 ℃, the adsorption time is 120min, the absorbance is measured, and the adsorption quantity is calculated;

the concentration of Cu (II) in the solution was 1000 mg/L, the pH was 4.9, the adsorption temperature was 50 ℃, the adsorption time was 120min, the absorbance was measured, and the adsorption amount was calculated.

Comparative data on the adsorption capacities of the five different adsorbents described in this comparative example for Zn (II), Mn (II), Ni (II), and Cu (II) in solution are shown in Table 2.

TABLE 2

As can be seen from the data in Table 2, the adsorption performance of the nano lignocellulose/montmorillonite composite material prepared by the solution intercalation composite reaction is superior to that of the simple physical mixture (mass ratio is 1:1) of the lignocellulose, the nano lignocellulose, the montmorillonite and the nano lignocellulose and the montmorillonite, and the adsorption capacity of the nano lignocellulose/montmorillonite composite material provided by the invention on the Zn (II), the Mn (II), the Ni (II) and the Cu (II) in the solution is remarkably improved, compared with the adsorption of the Zn (II), the Mn (II), the Ni (II) and the Cu (II) in the solution, which shows that the nano lignocellulose/montmorillonite composite material provided by the invention serving as a heavy metal ion adsorbent has quite remarkable adsorption capacity on the Zn (II), the montmorillonite and the Zn (II) in wastewater when the nano lignocellulose/montmorillonite composite material is used as a heavy metal ion adsorbent, and the simple physical mixture of the two components, Mn (II), Ni (II) and Cu (II) ions have obviously excellent adsorption performance.

Claims

1. A preparation method of nano lignocellulose comprises the following steps:

placing lignocellulose in NaOH aqueous solution, and fully stirring the lignocellulose until the lignocellulose forms suspension; the concentration of the NaOH aqueous solution is 0-30 wt% calculated by taking the total weight of the NaOH aqueous solution as 100%;

the ratio of the mass of the lignocellulose to the volume of the NaOH aqueous solution is 1:400-1:750, and the units are g and m L respectively;

performing centralized ultrasonic treatment on the suspension to obtain the nano lignocellulose; the ultrasonic power is 600-1200W, the ultrasonic temperature is 7-35 ℃, and the ultrasonic time is 60-240 min.

2. The preparation method according to claim 1, wherein the ultrasonic power is 1080W, the ultrasonic temperature is 10 ℃, and the ultrasonic time is 150 min.

3. The method of claim 1, wherein the concentration of the aqueous NaOH solution is 5 to 30 wt%.

4. The method according to claim 3, wherein the concentration of the aqueous NaOH solution is 20 wt%.

5. The method of claim 1, wherein the ratio of the mass of the lignocellulose to the volume of the aqueous NaOH solution is 1:500 in g and m L, respectively.

6. The method of any one of claims 1-5, wherein the concentrated sonication is performed using a SM-1200D ultrasonic cell disruptor.

7. The nano lignocellulose produced by the method for producing nano lignocellulose according to any one of claims 1 to 6.

8. The nano lignocellulose according to claim 7, wherein the nano lignocellulose is a nano rod-like structure with an aspect ratio of 20:1 to 3: 1.

9. A nano lignocellulose/montmorillonite composite material, which is characterized in that the composite material is an intercalation-exfoliation type nano composite material, the composite material is formed by compounding the nano lignocellulose of claim 7 or 8 and montmorillonite, and the nano lignocellulose is intercalated between the montmorillonite layers;

the mass ratio of the nano lignocellulose to the montmorillonite is 1: 1-10.

10. The nano lignocellulose/montmorillonite composite material as recited in claim 9, wherein the mass ratio of nano lignocellulose to montmorillonite is 1: 1.

11. The nano lignocellulose/montmorillonite composite material as claimed in claim 9, wherein the BET specific surface area of the nano lignocellulose/montmorillonite composite material is 407.02-597.15m²The specific surface area of L angmuir is 598.60-780.14m²Per g, total pore volume of 0.691-1.175cm³Per g, the pore volume of the micropores is 0.198-0.273cm³The average pore diameter of the micropores is 0.427-0.719nm, and the pore volume of the mesopores is 0.472-0.656cm³(ii)/g, the average pore diameter of the mesopores is 102.40-212.37nm, and the average pore diameter is 2.086-19.375 nm.

12. A process for preparing the nano lignocellulose/montmorillonite composite material as described in any one of claims 9-11, which comprises the following steps:

the ratio of the mass of the nano lignocellulose to the volume of the NaOH aqueous solution is 1:150-1:350, and the units are g and m L respectively;

the total weight of the NaOH aqueous solution is 100 percent, and the concentration of the NaOH aqueous solution is 3 to 15 weight percent;

adding montmorillonite into water to obtain montmorillonite suspension;

slowly dripping the suspension of the nano lignocellulose into the suspension of the montmorillonite, uniformly mixing, heating to react, and obtaining the nano lignocellulose/montmorillonite composite material after the reaction is finished;

the reaction temperature is 30-80 ℃, and the reaction time is 2-7 h.

13. The method of claim 12, wherein the ratio of the mass of the nano lignocellulose to the volume of the aqueous NaOH solution is 1:250 in g and m L, respectively.

14. The method of claim 12, wherein the ratio of the mass of the montmorillonite to the volume of water is 1:20 to 1:45 in units of g and m L, respectively.

15. The method of claim 14, wherein the ratio of the mass of the montmorillonite to the volume of water is 1:30 in g and m L, respectively.

16. The method of claim 12, wherein the concentration of the aqueous NaOH solution is 12.5 wt% based on 100% of the total weight of the aqueous NaOH solution.

17. The method according to claim 12, wherein the reaction temperature is 50 ℃ and the reaction time is 4 hours.

18. Use of the nano lignocellulose/montmorillonite composite material as defined in any one of claims 9-11 as a heavy metal ion adsorbent in adsorption of heavy metal ions contained in wastewater.

19. The use of claim 18, wherein the heavy metal ions comprise zn (ii), mn (ii), ni (ii), and cu (ii).