LU501140B1

LU501140B1 - A method for treating water by using CQDs - Ni-Co LDH - diatomite composite

Info

Publication number: LU501140B1
Application number: LU501140A
Authority: LU
Inventors: Yi Wang; Nan Dai; Xingjian Dai; Weiling Liao; Kailin Li; Yuxin Zhang; Li Feng; Jiehang Ding
Original assignee: Chongqing Academy Of Eco Env Science; Univ Chongqing
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-06-30

Abstract

The present invention discloses a method for treating water by using CQDs - Ni-Co LDH - diatomite composite. CQDs - Ni-Co LDH - diatomite composite prepared by the present invention exhibits a good performance of removing MO and MB and adsorbing heavy metals, and a good performance of adsorbing and inhibiting colibacillus and staphylococcus aureus. CQDs - Ni-Co LDH - diatomite composite prepared by the present invention is an innovative material in structure to realize multi-functional applications of material, which is more suitable for actual needs. With simple preparation method, it is very suitable for industrialized production.

Description

A method for treating water by using CQDs - Ni-Co LDH - diatomite composite HUS01140

FIELD OF THE INVENTION

[0001] The present invention belongs to the technical field of water treatment, in particular to a method for treating water by using CQDs - Ni-Co LDH - diatomite composite.

BACKGROUND OF THE RELATED ART

[0002] Environmental pollution is one of the three major social problems in the world today, and the excessive discharge of dyes and heavy metals into water has aroused strong social concern.

[0003] Organic dyes are frequently used in the dyeing of textile, printing and dyeing, leather, papermaking and other industries, producing a large amount of dye-containing wastewater. According to statistics, the world’s annual output of textile dyes is more than 400,000 tons, and about 10% to 20% of the dyes are discharged as wastewater into rivers, lakes, seas and groundwater during the printing and dyeing process. The dyes in the wastewater can absorb light, reduce transparency of water body, affect the growth of aquatic organisms and microorganisms, which are not conducive to self-purification of the water body, and easily cause visual pollution.

[0004] Raw material is an indispensable basic factor in the industrial production. In the leather industry, raw material is an important production factor. The quality of raw material affects the quality of leather products to a certain extent. From the raw material to the finished product, it must go through the process of chromium blending. The chromium blending can bring the raw material the better flexibility, intensity and hardness, and can activate original trivalent chromium and hexavalent chromium factors. With the change of external factors, the content of hexavalent chromium will increase, even exceed specified standard, so that the product cannot enter the market. The hexavalent chromium is a swallowable/inhalable poison, which can lead to skin allergy. It is more likely to cause hereditary genetic defects, even cancer by inhalation, and is harmful to the environment. The hexavalent chromium is easily absorbed by 1 the human body, and can invade the human body through digestion, respiratory tract, skin and 10501160 mucosa. Inhaling different concentrations of chromic anhydride in air can cause hoarseness, nasal mucosal atrophy, and even severer symptoms, such as nasal septum perforation and bronchiectasis. Invasion through the digestive tract can cause vomiting and abdominal pain. Dermatitis and eczema can occur when the chromic anhydride invades human body through the skin. The biggest harm is the risk of carcinogenesis in long-term or short-term exposure or inhalation. The hexavalent chromium remaining in the leather can also be absorbed through skin and respiratory tract, causing damage to gastric tract, liver, kidney and organs, nausea, gastrointestinal irritation, gastric ulcer, cramp and even death. Excessive (more than 10ppm) hexavalent chromium is lethal to aquatic organisms. After animals drink wastewater containing the hexavalent chromium, the hexavalent chromium will be absorbed by cells in many tissues and organs in the body. In addition, colibacillus and staphylococcus aureus exist in wastewater widely, and are highly adaptable to the environment. Since the cell structure and functional organization are similar to a vast majority of microorganisms, animals and microorganisms can cause poisoning after drinking the wastewater.

[0005] The adsorption method is considered to be the most effective wastewater treatment technology due to its high efficiency, low cost, simple operation and environmental friendliness. Activated carbon, metal oxides, zeolites, clays, etc. are often used as adsorbents. However, most of them are expensive, have low adsorption capacity, and have complex preparation processes. After the adsorption treatment is completed, the methods, such as centrifugation, filtration, precipitation, etc., are generally used to separate the adsorbent from the treated water, but the entire separation process is complicated, and the incomplete separation will cause secondary pollution of water quality. Therefore, the preparation of an adsorption material with good adsorption performance, environmental friendliness and low cost, and easy separation from the treated water has become a technical issue that people pay more attention to. Compared with traditional adsorbents, the magnetic nano adsorbents have the advantages of small particle size, large specific surface area, good adsorption performance and easy recovery. 2

[0006] Layered Double Hydroxide (LDH) is an inorganic layered compound with a two- 10501160 dimensional structure. The general formula of the layered material is [M2+ 1-xM3+ x (OH) 2]x+[An-]x/n-yH2O, where M2+, M3+, An- respectively represent divalent metal cation, trivalent metal cation and interlayer anion. Due to the large amount of exchangeable anions in positive charge layer and interlayer space, LDH exhibits superior ion exchange and adsorption capacity, and its advantages such as high specific surface area, good stability, low cost, and controllable structure bring it broad application prospects in the water treatment field. However, some prepared LDHs are easily soluble in water, and instead become sources of heavy metal pollutants; the appropriate type of LDH shall be selected. Nano LDH also has a strong tendency to agglomerate, resulting in a decrease in its surface area and active sites. Due to the unique layered structure of LDH, the repulsion of ions makes it difficult to adsorb cationic dyes, which greatly limits its scope of application. In addition, although LDH as a magnetic material has potential broad application prospects and research value, there are relatively few studies on its magnetic properties.

[0007] Finding cheap and efficient functional nano carriers is still the direction of many scientific efforts. So far, there have been many studies by using substrates to support LDH nano materials to enhance their applications in printing and dyeing wastewater, such as montmorillonite, starch, carbon fiber, porous carbon, etc. CQDs is a kind of carbon-based zero- dimensional material with a carbon skeleton structure, usually in a dispersed form, in a spherical shape, and with 5nm average particle size of carbon nanoparticles. CQDs not only has superior fluorescence properties similar to those of semiconductor quantum dots, but also have excellent optical properties, good water solubility, low toxicity, environmental friendliness, wide source of raw materials, low cost, good biocompatibility, etc.. Similarly, CQDs also has the defect of easy agglomeration, which is difficult to be recycled in practical applications.

[0008] The diatomite (DE) is a natural porous material with a complex three-dimensional structure. It is a typical natural siliceous material containing a large amount of amorphous silicon dioxide, and can be used as a good biological template. The diatomite provides a large amount of silicon hydroxyl groups inside and on the surface, which can free H+ in the water 3 and make the diatomite negatively charged, and removes a certain amount of pollutants in 10501160 cationic dye wastewater through electrostatic attraction. Moreover, the diatomite has the advantages of large pore size, large specific surface area, stable biochemical properties, etc. Therefore, the diatomite is an efficient and environmentally friendly environment treatment material.

[0009] It can be seen that, zero-dimensional material, two-dimensional material and three- dimensional material have been widely introduced into water pollution control. For the function of nano material, due to the structural characteristics of the body material, the body material has a small specific surface area, low structure utilization, and single functionality. Therefore, most materials cannot achieve a multi-functional application environment, leading to their defects in practical applications.

[0010] Therefore, the preparation of a higher-performance composite can not only improve the material performance, but also is expected to greatly improve the performance by further modifying the body material, and achieve practical applications in multiple scenarios, which is of great significance. Therefore, zero-dimensional @ two-dimensional @ three-dimensional composite is an innovative material in structure to realize multi-functional applications of material, which is more suitable for actual needs.

[0011] As far as we know, the studies on modifying diatomite based on Ni-Fe LDH by using hydrothermal synthesis method, removing anionic and cationic dyes and heavy metals and inhibiting bacteria by using CQDs as nano adsorbent have not been seen in the reports. The nano composites have shown a great potential for practical applications in terms of rapid removal of pollutants and excellent magnetic rapid recovery performance.

[0012] In order to solve the above problems, the present invention is proposed.

SUMMARY OF THE INVENTION

[0013] The present invention provides a method for treating water by using CQDs - Ni-Co LDH - diatomite composite. The preparation of the composite includes the following steps:

[0014] 1. Preparation of the Ni-Fe LDH -diatomite nano material by using hydrothermal method 4

Disperse 80mg pure diatomite into a 100mL beaker, and add 65mL deionized water. Add Ni 10501160 (NOs) 2-6H20, Fe (NOs) 2-6H20), urea, and then add trisodium citrate, and stir it for 30 minutes. Transfer the resulting mixture into PTFE-lined stainless steel autoclave, and react at 180°C for 24h. Cool it to room temperature, collect samples, centrifuge and wash with deionized water and alcohol for many times, and finally dry the resulting Ni-Fe LDH - diatomite DE at 60°C for 12h.

[0015] 2. Synthesis of CQDs: Weigh 0.1862g ascorbic acid, add 50mL water to dissolve it in a beaker, add 5.00 mL ethylenediamine after magnetic stirring for 10min, place it in a round- bottom flask, reflux at 363 K for 3h, cool it to room temperature and filter it, obtain transparent yellow supernatant, keep a constant volume of 250mL with water, with a concentration of 2.54 x 10-2 mol/L(calculated by carbon);

[0016] 3. Synthesis of CQDs -Ni-Fe LDH -diatomite composite Mix 100mg Ni-Fe LDH - diatomite powder into 10uL CQDs dispersion liquid (containing 1.67mg CQDs, defined as 1 equivalent [1eq, equivalent] ) . Take 100mg prepared Ni-Fe LDH -diatomite powder and mechanically grind it for 5 minutes, and then add 50uL deionized water and 1 eq (2 eq, 5 eq) CQDs dropwise, and continue grinding for 20 minutes to obtain CQDs -Ni-Fe LDH -diatomite composite (2 eq, 5 eq) composite.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, can be applied to simultaneously remove anionic and cationic dyes represented by Methylene Blue (MB) and Methyl Orange (MO), adsorb heavy metals (hexavalent chromium) and inhibit two types of bacteria (colibacillus and staphylococcus aureus). In both single-phase and two-phase solutions, it can exhibit a good performance of removing MO and MB and adsorbing heavy metals, and a good performance of adsorbing and inhibiting colibacillus and staphylococcus aureus.

[0019] (2) By combining biological template function of the three-dimensional natural diatomite, adsorption function of cations, high-performance removal function of anion dyes and hexavalent chromium by the two-dimensional Ni-Co LDH, and antibacterial function of 5 emerging zero-dimensional CQDs, the CQDs - Ni-Co LDH - diatomite composite prepared by 10501160 the present invention has realized the multi-functional application environment of the material and greatly improved the performance.

[0020] (3) CQDs - Ni-Co LDH - diatomite composite prepared by the present invention is an innovative material in structure to realize multi-functional applications of material, which is more suitable for actual needs.

[0021] (4) CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, with simple preparation method, is suitable for industrialized production.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Fig. 1 is a XRD diagram of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, reflecting crystal structure and chemical composition of the composite.

[0023] Fig. 2 is a XPS diagram of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, reflecting chemical composition and chemical valence of the composite.

[0024] Fig. 3 is a SEM diagram of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, reflecting morphologic structure of the composite.

[0025] Fig. 4 is a thermogravimetric diagram of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention, reflecting thermal stability of the composite.

[0026] Fig. 5 shows adsorption kinetics of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention to different initial concentrations of MB and MO, and Langmuir and Freundlich model fittings at different temperatures, reflecting the performance of the composite to adsorb anionic and cationic dyes.

[0027] Fig. 6 shows time-varying relationship of the removal efficiency for CQDs - Ni-Co LDH - diatomite composite prepared by the present invention to remove different initial concentrations of hexavalent chromium, reflecting the good efficiency for removing hexavalent chromium.

[0028] Fig. 7 is a control experiment effect diagram of CQDs - Ni-Co LDH - diatomite composite prepared by the present invention for inhibiting staphylococcus aureus and colibacillu. 6

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS LUS01140

[0029] Embodiment 1

[0030] 1. Preparation of the Ni-Fe LDH -diatomite nano material by using hydrothermal method Disperse 80mg pure diatomite into a 100mL beaker, and add 65mL deionized water. Add Ni (NOs) 2-6H:0, Fe (NOs) 2:6H,0, urea, and then add trisodium citrate, and stir it for 30 minutes. Transfer the resulting mixture into PTFE-lined stainless steel autoclave, and react at 180°C for 24h. Cool it to room temperature, collect samples, centrifuge and wash with deionized water and alcohol for many times, and finally dry the resulting Ni-Fe LDH - diatomite DE at 60°C for 12h.

[0031] 2. Synthesis of CQDs: Weigh 0.1862g ascorbic acid, add 50mL water to dissolve it in a beaker, add 5.00 mL ethylenediamine after magnetic stirring for 10min, place it in a round- bottom flask, reflux at 363 K for 3h, cool it to room temperature and filter it, obtain transparent yellow supernatant, keep a constant volume of 250mL with water, with a concentration of 2.54 x 10-2 mol/L(calculated by carbon);

[0032] 3. Synthesis of CQDs -Ni-Fe LDH -diatomite composite Mix 100mg Ni-Fe LDH - diatomite powder into 10uL CQDs dispersion liquid (containing 1.67mg CQDs, defined as 1 equivalent [1eq, equivalent] ) . Take 100mg prepared Ni-Fe LDH -diatomite powder and mechanically grind it for 5 minutes, and then add 50pL deionized water and 1 eq (2 eq, 5 eq) CQDs dropwise, and continue grinding for 20 minutes to obtain CQDs -Ni-Fe LDH -diatomite composite (2 eq, 5 eq) composite.

[0033] The characterization result of XRD diagram of CQDs -Ni-Fe LDH -diatomite composite obtained by using X-ray diffraction instrument, shown in Fig. 1, reflects crystal structure and chemical composition of the composite.

[0034] The characterization result of XPS diagram of CQDs -Ni-Fe LDH -diatomite composite,shown in Fig. 2, reflects chemical composition and chemical valence of the composite.

[0035] The characterization result of SEM diagram of CQDs - Ni-Co LDH - diatomite composite, shown in Fig. 3, reflects morphologic structure of the composite. 7

[0036] The characterization result of thermogravimetric diagram of CQDs - Ni-Co LDH - 7501140 diatomite composite, shown in Fig. 4, reflects thermal stability of the composite.

[0037] The characterization result of adsorption kinetics of CQDs - Ni-Co LDH - diatomite composite to different initial concentrations of MB and MO, and Langmuir and Freundlich model fittings at different temperatures, shown in Fig. 5, reflects the performance of the composite to adsorb anionic and cationic dyes.

[0038] The characterization result of time-varying relationship of the removal efficiency forCQDs - Ni-Co LDH - diatomite composite to remove different initial concentrations of hexavalent chromium, shown in Fig. 6, reflects the good efficiency for removing hexavalent chromium.

[0039] The characterization result of control experiment effect of CQDs - Ni-Co LDH - diatomite composite for inhibiting staphylococcus aureus and colibacillu,shown in Fig. 7, reflects the good performance of adsorbing and inhibiting colibacillus and staphylococcus aureus.

[0040] The above XRD and SEM are excerpts from the original classical data. According to the above characterization results, the morphology of CQDs - Ni-Co LDH - diatomite composite is formed by two-dimensional nano sheets grown on the diatomite, CQDs cannot be seen in SEM diagram due to too small particle size, XRD and XPS also fully prove that the chemical compositions of nano materials are diatomite, Ni-Co LDH and CQDs .

[0041] The experimental results prove that, CQDs - Ni-Co LDH - diatomite composite prepared by the present invention has the characteristic structure of the three materials, and the biological template of diatomite effectively disperses Ni-Co LDH and CQDs to avoid the agglomeration of nano materials.

[0042] The experimental results prove that, CQDs - Ni-Co LDH - diatomite composite prepared by the present invention inherits the capability of Ni-Co LDH for removing anion dyes (MO), the capability of diatomite for removing cationic dyes (MB), and the capability of CQDs for inhibiting bacteria.

[0043] In the single-component removal system, the maximum adsorption capacities of CQDs - Ni-Co LDH - diatomite for MB and MO are respectively 133.05 and 73.81 mg/g; therefore, it 8 has a strong inhibitory effect on staphylococcus aureus and colibacillus, and its antibacterial effect on staphylococcus aureus is stronger than that on colibacillus.

Moreover, the composite, with good recyclability, can be recycled by simple magnet. 9

Claims

_ CLAIMS 00000

1. A method for treating water by using CQDs - Ni-Co LDH - diatomite composite, 10501160 characterized in that, the composite is of three-dimensional structure, wherein the zero-dimensional material is CQDs, the two-dimensional material is Ni-Co LDH, and the three-dimensional material is diatomite.

2. The method according to claim 1, characterized in that, the preparation method of the CQDs - Ni-Co LDH - diatomite composite comprises the following steps: A. Preparation of the Ni-Fe LDH -diatomite nano material by using hydrothermal method: Disperse 80mg pure diatomite into a 100mL beaker, and add 65mL deionized water. Add Ni (NOs) 2-6H:0, Fe (NOs) 2-6H20, urea, and then add trisodium citrate, stir it for 30 minutes; transfer the resulting mixture into PTFE-lined stainless steel autoclave, react at 180°C for 24h; cool it to room temperature, collect samples, centrifuge and wash with deionized water and alcohol for many times, and finally dry the resulting Ni-Fe LDH - diatomite DE at 60°C for 12h; B. Synthesis of CQDs: Weigh 0.1862g ascorbic acid, add 50mL water to dissolve it in a beaker, add 5.00 mL ethylenediamine after magnetic stirring for 10min, place it in a round-bottom flask, reflux at 363 K for 3h, cool it to room temperature and filter it, obtain transparent yellow supernatant, keep a constant volume of 250mL with water, with a concentration of 2.54 x 10-2 mol/L(calculated by carbon); C. Synthesis of CQDs -Ni-Fe LDH -diatomite composite: Mix 100mg Ni-Fe LDH -diatomite powder into 10uL CQDs dispersion liquid (containing

1.67mg CQDs, defined as 1 equivalent [1eq, equivalent] ) ; take 100mg prepared Ni-Fe LDH -diatomite powder and mechanically grind it for 5 minutes, and then add 50pL deionized water and 1 eq (2 eq, 5 eq) CQDs dropwise, and continue grinding for 20 minutes, to obtain CQDs -Ni-Fe LDH -diatomite composite (2 eq, 5 eq) composite.

3. The use of the CQDs - Ni-Co LDH - diatomite composite set forth in claim 1 or 2 for removing anionic and cationic dyes represented by Methylene Blue (MB) and Methyl Orange (MO).

10

_ CLAIMS 00000

4. The use of the CQDs - Ni-Co LDH - diatomite composite set forth in claim 1 or 2 for 10501160 adsorbing heavy metal pollutants.

5. The use of the CQDs - Ni-Co LDH - diatomite composite set forth in claim1 or 2 for inhibiting staphylococcus aureus and colibacillus. 11