CN112452300B

CN112452300B - Organic phosphorus composite material and preparation method and application thereof

Info

Publication number: CN112452300B
Application number: CN202010958445.6A
Authority: CN
Inventors: 杜辉辉; 聂宁; 徐丰; 杨潇泓; 蔡彤�; 铁柏清; 雷鸣; 刘孝利; 魏祥东
Original assignee: Hunan Agricultural University
Current assignee: Hunan Agricultural University
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2023-03-14
Anticipated expiration: 2040-09-14
Also published as: CN112452300A

Abstract

The invention belongs to the technical field of heavy metal adsorption, and particularly relates to a method for efficiently adsorbing heavy metal Cd ²⁺ A preparation method and application of the organophosphorus-hydroxy aluminum composite adsorption material. The raw materials are aluminum salt and phytic acid, and the preparation method specifically comprises the following steps: 1) Dissolving aluminum salt in water, adding phytic acid powder under the stirring condition to obtain an aluminum salt-phytic acid mixed solution, and stirring the mixed solution for about 1h, wherein the molar ratio of P to Al in the mixed solution is 0.01 to 0.1; 2) And (3) adjusting the pH of the mixed suspension to about 6.5 by using a dilute sodium hydroxide solution, stabilizing the mixed suspension to 0.5h, centrifuging, filtering, and freeze-drying to obtain the organophosphorus supported hydroxy aluminum composite material. Through water body adsorption reaction, the composite material is used for Cd ²⁺ The maximum adsorption capacity of the material reaches 205mg/g, and a stable inner ring complex is formed on the surface of the material. The material has low cost of raw materials and simple synthesis process, and has wide prospect in the field of treating Cd polluted wastewater.

Description

Organic phosphorus composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of heavy metal adsorption, particularly belongs to the technical field of water body heavy metal removal and treatment, and particularly relates to a method for efficiently adsorbing heavy metal Cd ²⁺ The organic phosphorus-hydroxyl aluminum composite adsorbing material and the preparation method and the application thereof.

Background

Cadmium is a highly toxic heavy metal, and the situation of cadmium pollution in China is more severe along with the development of industry and agriculture, unreasonable use of pesticides and fertilizers and the like. Cadmium is not easy to degrade in the environment, has strong mobility, is an unnecessary element for animals and plants, has certain volatility, can cause teratogenesis, carcinogenesis and mutation, and can be continuously accumulated in human beings and animals and plants through air and food chains until serious harm is generated. The existing methods for repairing cadmium pollution in the environment commonly comprise adsorption, ion exchange, membrane filtration, biological methods and the like, wherein the adsorption method is widely applied due to wide material sources, economy, high efficiency and less secondary pollution. The development of new adsorbents that are efficient, clean, low cost, and easy to prepare is the hot direction in the field of water treatment and purification.

Currently, active minerals, biochar, resistant microorganisms and the like are mostly adopted as adsorbents, but the materials generally have some defects: for example, the preparation condition of the biochar is complex and the cost is high; the microbial culture is complex and the survivability is low; mineral materials have low adsorption efficiency, etc., and thus are not suitable for large-scale application. The iron/manganese/aluminum hydroxyl compound is prepared by an alkali precipitation method, is simple to operate, has a loose and porous surface, a large specific surface area and rich hydroxyl groups, and can effectively remove heavy metals through physical and chemical reactions such as electrostatic adsorption, complexation and precipitation. Particularly, the iron/manganese/aluminum hydroxide is organically modified, so that functional groups on the surface of the adsorbent can be enriched, and the adsorption capacity of the adsorbent on heavy metal pollutants is improved. Phosphate compounds can generate strong chelation with heavy metals, so that the phosphate compounds are mostly used for preparing heavy metal adsorbing materials, but at present, people mainly focus on inorganic phosphorus, and research on organic phosphorus is less. The organic phosphorus in the soil accounts for 30-65% of the total phosphorus, the organic phosphorus in the soil with high organic matters is up to 90%, and various organic phosphorus such as phytic acid and the like can be formed in the body after being absorbed by crops, so the raw material is a low-cost and easily-obtained material.

Huihui, huang adsorbed Cd on amorphous aluminum hydroxide-bacterial composites ²⁺ However, it has been found that bacteria-modified amorphous aluminum hydroxide materials are sensitive to Cd in neutral and alkaline environments ²⁺ The adsorption-promoting effect of (a) is not significant. When the petrel and the like find that the aluminum hydroxide-polyacrylamide composite material is used for treating Cd at the temperature of 10 ℃, 30 ℃ and 50 DEG C ²⁺ Maximum adsorption amount q of _max Are 44.43mg/g, 50.11mg/g and 54.81mg/g, respectively. Cheng Jiao et al found that the adsorption material of phytic acid composite sepiolite was at p when the adsorbent concentration was 18g/L at 30 deg.CH3.8 has the best adsorption performance on Cd ²⁺ The maximum adsorption amount of (2) was 2.67mg/g. It is not difficult to find that these materials are paired with Cd ²⁺ The adsorption has certain limitation, so the research researches and researches develop a novel high-efficiency adsorption Cd ²⁺ The organic phosphorus-loaded hydroxyl aluminum composite material.

Reference documents:

1、Du HH,Huang,QY,Yang RJ,Tie BQ,Lei M Cd sequestration by bacteria–aluminum hydroxide composites[J].CHEMOSPHERE,2018,198,75-82.

2. manta esculenta, liu Renyuan, chen Zhenling the adsorption research of cadmium ions by the nano aluminum hydroxide-polyacrylamide composite flocculant [ J ] ion exchange and adsorption, 2016,32 (04): 324-332.

3. Cheng Jiao, zeng Guihua, shumei, he Aicui, liu Ying phytic acid sepiolite composite heavy metal adsorbent for Cd ²⁺ Study of adsorption [ J]Anhui agricultural science, 2013,41 (24): 10087-10088.

Disclosure of Invention

The invention aims to provide an organophosphorus composite material capable of efficiently adsorbing Cd ²⁺ Meanwhile, the preparation is simple, and secondary pollution can not be caused.

An organophosphorus composite material has a structural formula as follows:

the preparation method of the organophosphorus composite material comprises the following steps:

s1, adding organic phosphorus into aluminum salt, uniformly mixing, adjusting the pH value, centrifuging and filtering to obtain a precipitate;

s2, freeze-drying the precipitate to obtain the organic phosphorus composite material.

Preferably, the aluminum salt is a water-soluble aluminum salt.

Only water-soluble aluminum salts can be dissolved in water to adjust the hydrolysis equilibrium and then the aluminum salts are converted into amorphous aluminum hydroxide to prepare the organophosphorus composite materials required by the present invention.

Preferably, the water-soluble aluminum salt is one or more of aluminum chloride, aluminum chloride hydrate, aluminum nitrate hydrate, aluminum sulfate and aluminum sulfate hydrate.

Further preferably, the aluminum salt is aluminum nitrate hydrate.

The aluminum nitrate has small density and good solubility, and is easily dissolved in water, ethanol, acetone and nitric acid. Nitrate ions are easy to remove, the interference on the composite material is small, and aluminum nitrate nonahydrate is the most stable form in aluminum nitrate.

Preferably, the mixing is performed by stirring and mixing a magnetic stirrer at the rotating speed of 150-500 rpm.

Preferably, the organophosphorus is phytic acid.

The phytic acid is organic phosphate which is most abundant in most soil and sediments, contains a large amount of phosphate groups, is a rare metal polydentate chelating agent, and researches show that the phytic acid can improve Cd in heavy metal polluted soil ²⁺ The leaching rate and the leaching amount. And the phytic acid is low in cost, easy to obtain and abundant in natural environment.

Preferably, the molar ratio of P to Al in the organophosphorus composite material is 1 (10-100).

The phytic acid has large molecular weight, the excessively high molar ratio of P to Al increases the application amount of the composite material in practical application, further increases the cost, and the hydroxy aluminum has a certain upper limit of adsorption on the phytic acid; if the molar ratio of P to Al is too low, the modification of the aluminum hydroxide is not obvious.

Further preferably, the organic-inorganic composite material simulates the organic-inorganic composite ratio of minerals in natural environment, and the molar ratio of P to Al in the organic-phosphorus composite material is 0.1 in terms of practical application of the repairing agent.

Preferably, the step S1 adjusts the pH value to 6.5 ± 0.2, and the pH is adjusted by using a dilute alkali solution.

The pH value needs to be controlled to be 6.5 +/-0.2, aluminum ions begin to generate precipitates at about pH 5, complete conversion is further ensured, alkali does not need to be added when the pH value is controlled to be about 6.5, and excessive alkali is easy to convert aluminum hydroxide into meta-aluminate.

Further preferably, the alkali solution may be a NaOH solution or a KOH solution.

Preferably, the pH value is adjusted in the step S1, then the pH value is stabilized for 0.5h, and the pH value is finely adjusted and centrifuged.

The invention also provides the organic phosphorus composite material for adsorbing heavy metal Cd ²⁺ The specific method comprises the following steps:

an organic phosphorus composite material is added into a centrifugal tube, the organic phosphorus composite material and heavy metal cadmium are tested according to the proportion of 100mg (0-4) mg, and the pH value is controlled to be 6.5 +/-0.05. The sample is shaken for 24h in a constant temperature shaking table (25 ℃), filtered and then measured for Cd by ICP (inductively coupled plasma mass spectrometry) ²⁺ Concentration according to Cd before and after adsorption ²⁺ The difference in concentration calculates the amount of adsorption. The theoretical adsorption capacity of the organic phosphorus composite material can reach 205mg/g, and the organic phosphorus composite material has a good heavy metal adsorption effect.

The invention is further illustrated below:

the invention selects pure hydroxyl aluminum and phytic acid as raw materials to prepare the composite material. The aluminum hydroxyl compound widely exists in aquatic and geological environments, has large surface area and rich hydroxyl functional groups, can effectively adsorb metals, phytic acid is organic phosphate with the most abundant content in most of soil and sediments, contains a large amount of phosphate groups, is a rare metal multidentate chelating agent, and researches show that the phytic acid can improve Cd in heavy metal polluted soil ²⁺ The leaching rate and the leaching amount. The aluminium (hydr) oxide adsorbs H of phytic acid across the surface relative to other iron/manganese hydroxy compounds ₂ The O and-OH groups are coordinately exchanged with the phosphate group. Thus, the adsorption process releases OH-while adsorption promotes deprotonation of the phosphate group. The infrared spectrum shows that phytic acid is adsorbed on aluminum hydroxide to form Al-O-P bonds. The pure hydroxyl aluminum has higher active site density, better binding capacity to phytic acid and adsorption capacity of 1.70mol/kg (34.3 mu mol/m) ² ) While the amounts of the gibbsite and the bayerite which adsorb phytic acid are respectively only 0.52 mu mol/m ² And 0.4. Mu. Mol/m ² . Chemical analysis of the solution, infrared spectrum characterization and quantum chemical theory calculation show that the phytic acid is adsorbed on the surface of the aluminum hydroxide through 3 phosphate groups.

The invention adopts the alkali precipitation method for preparation, and the operation is simple. The composite material can obviously adsorb Cd ²⁺ On the one hand, the addition of the phytic acid increases the negative charge on the surface of the aluminum hydroxide, thereby enhancing the Cd pairing effect ²⁺ On the other hand, the hydroxyl functional group on the surface of the pure hydroxyl aluminum and the multiple phosphate group of phytic acid on the surface of the pure hydroxyl aluminum and Cd ²⁺ Complexing to form Al-IHP-Cd ternary complex, thereby increasing the content of Cd ²⁺ The amount of adsorption of (3).

The invention has the following advantages:

1. the method is simple to prepare, is carried out at normal temperature and normal pressure, and has no special condition

2. The phytic acid is an organic phosphorus material which is low in cost and easy to obtain, and is commonly and largely existed in natural environment.

3. The raw materials of the invention are formed by mineral-organic complexes which widely exist in natural environment and simulate soil environment, the physicochemical property of the matrix is slightly changed, and secondary pollution is not easy to cause.

4. The phytic acid is loaded on the surface of the aluminum hydroxide, so that the physical and chemical properties of the phytic acid are improved, and the adsorption performance of the phytic acid on cadmium is improved.

5. In the phytic acid-hydroxyl aluminum-cadmium ternary system, cd not only reacts with-OH of hydroxyl aluminum, but also reacts with phosphate group-PO of phytic acid ₄ Reacting to generate Al-IHP-Cd stable coordination compound for Cd ²⁺ The maximum adsorption amount of the adsorbent is up to 205mg/g (20 wt.%), which is far larger than other types of adsorbents.

The complex provided by the invention can also be applied to other heavy metals (Pb) with similar properties in water body ²⁺ 、Cu ²⁺ 、Ni ²⁺ 、Zn ² ⁺ ) And (4) removing by adsorption.

Drawings

FIG. 1 is a TEM spectrum of pure aluminum hydroxide (AAH), low concentration organophosphorus supported aluminum hydroxide composite material (AAH-OP _ low), and high concentration organophosphorus supported aluminum hydroxide composite material (AAH-OP _ high) in the examples of the present invention.

FIG. 2 shows XRD patterns of pure aluminum hydroxide (AAH), low concentration organic phosphorus-supported aluminum hydroxide composite (AAH-OP _ low), and high concentration organic phosphorus-supported aluminum hydroxide composite (AAH-OP _ high) in examples.

FIG. 3 is an FTIR spectra of pure aluminum hydroxide (AAH), low concentration organophosphorus supported aluminum hydroxide composite (AAH-OP _ low), and high concentration organophosphorus supported aluminum hydroxide composite (AAH-OP _ high) in examples.

FIG. 4 is a schematic structural diagram of phytic acid loaded with aluminum hydroxide

FIG. 5 shows the adsorption performance of pure aluminum hydroxide (AAH), low-concentration organic phosphorus-loaded aluminum hydroxide composite material (AAH-OP _ low), and high-concentration organic phosphorus-loaded aluminum hydroxide composite material (AAH-OP _ high) on Cd ²⁺ Adsorption isotherm of (1).

FIG. 6 shows Cd adsorption of pure aluminum hydroxide (AAH) and organophosphorus supported aluminum hydroxide composite material in adsorption performance test ²⁺ Comparison of NMR spectra before and after.

FIG. 7 shows Cd adsorption by pure aluminum hydroxide (AAH) and organophosphorus supported aluminum hydroxide composite material in adsorption performance test ²⁺ Comparison of FTIR spectra before and after.

FIG. 8 shows the high concentration organic phosphorus loaded hydroxyl aluminum composite material (AAH-OP _ high) to Cd ²⁺ pH adsorption experimental profile of (a).

Detailed Description

The invention is further described below with reference to specific preferred embodiments, without thereby limiting the scope of protection of the invention.

Example 1

The preparation of the organophosphorus-loaded hydroxy aluminum composite material with two concentrations takes pure hydroxy aluminum as a reference, and the surface appearance, functional group potential and spatial structure of the composite material are explored. The method comprises the following steps:

the synthesis steps of the organophosphorus supported hydroxyl aluminum composite material are as follows: accurately weigh 0.05mol of aluminum nitrate nonahydrate (Al (NO) ₃ ) ₃ ·9H ₂ O) is dissolved in 500mL of deionized water, stirred and dissolved by a magnetic stirrer, 0.33g of phytic acid and 3.3g of phytic acid are respectively added into any two parts of the deionized water for reaction for 1 hour, 1mol/L of NaOH solution is slowly added into the solution, the pH value of the solution is adjusted to 6.5, the stirring is stopped after the solution is stabilized for 0.5 hour, the synthesized organophosphorus loaded hydroxyl aluminum complex suspension is centrifuged to remove supernatant, the step is repeated for 3 times, and the preparation is finished after freeze drying.

Zeta potential of the surface of the adsorbent was determined by a Zeta potential analyzer (Zetaplus 90, brookhaven) by dispersing each adsorbent in 0.1mol/L KNO before testing ₃ The solution, 3 replicates of each adsorbent were set up, the pH adjusted to 6.5, and equilibrated in a 25 ℃ constant temperature shaker for 24h. As a result, as shown in Table 1, the addition of phytic acid changed the mineral surface potential from positive to negative, and the higher the molar ratio of P to Al in the composite material, the greater the degree of decrease. The reduction of the electronegativity of the surface makes the adsorbent pair Cd ²⁺ The electrostatic attraction of (a) is increased, thereby promoting the adsorption thereof.

TABLE 1 three adsorbents at pH 6.5, 0.1mol/L KNO ₃ Zeta potential table under condition

After the composite sample is subjected to vacuum freeze drying treatment, the composite sample is ground into fine powder by an agate mortar, the surface morphology of the fine powder is analyzed and determined by a Tecnai G2F 20S-TWIN transmission electron microscope (TEM, feI company in America), the result is shown in figure 1, the synthesized pure aluminum hydroxide is irregular nano-particles, loose in texture and belongs to Amorphous Aluminum Hydroxide (AAH), and the influence of the addition of phytic acid on the surface morphology of the pure aluminum hydroxide is not obvious when the composite is prepared.

The crystal structure of the composite sample was determined by analysis with a Bruker D8 ADVANCE powder diffractometer (XRD, bruker, germany). As shown in figure 2, the addition of phytic acid can alleviate the tendency of the crystallinity of pure aluminum hydroxide to increase, and the phytic acid on AAH is in the transition stage from surface complexation to surface precipitation.

The FTIR pattern was measured by NICOLET 5700 Fourier Infrared spectrometer (ATR-FTIR, thermomanian instruments and instruments Co., USA), and the result is shown in FIG. 3, according to the ATR-FTIR pattern, the chemical environment of Al-O-H changed after loading phytic acid, wherein the FTIR spectrum change of AAH-OP _ high is more obvious, and at 946cm ^-1 The peak at Al-OH is blue-shifted at 883cm ^-1 、1065cm ^-1 、1176cm ^-1 、1724cm ^-1 A new peak appeared. 1065cm ^-1 、1176cm ^-1 The symmetrical and asymmetrical stretching vibration of the P-O-Al corresponding to the phytic acid adsorbed on the surface of the AAH. 1724cm ^-1 The peak is C-C in phytic acid, 883cm ^-1 The peak may be generated by P-OH stretching vibration, 2428cm ^-1 The peak intensity was reduced and was presumed to be the absorption peak of Al-OH in the pure aluminum hydroxide impurity having a high degree of crystallinity. At pH 6 to 7, the four phosphate groups in phytic acid are protonated, so that no more than four phosphate groups undergo surface complexation with AAH, mainly three phosphate groups at positions 1, 3, 5. Therefore, the specific structural formula of the organophosphorus-loaded hydroxyl aluminum composite material provided by the invention is shown in figure 4.

Example 2

Adsorption Performance test one

Organophosphorus-loaded hydroxy aluminum composite material pair Cd ²⁺ Isothermal adsorption experiment of (1), pure hydroxyl aluminum adsorbs Cd ²⁺ As a reference, the maximum adsorption amount of the adsorbent was tested under the conditions of 25 ℃ and pH 6.5.

The experiment was performed in a 50mL centrifuge tube, and the complex prepared in example 1 was used as an adsorbent, and a certain volume of adsorbent and Cd was added to the centrifuge tube ²⁺ Mother liquor with 0.1mol/L KNO ₃ Constant volume is carried out until the volume is equal and the final adsorbent concentration is controlled to be 0.1g/L, cd ²⁺ The concentration is 0-40 mg/L, and the pH value of the system is adjusted to 6.5. Three replicates were set for each concentration and were compared without adsorbent. Placing the centrifugal tube in a constant temperature oscillator at 25 ℃ for reaction for 24h, centrifuging at 5000g for 15min, filtering supernate in the centrifugal tube through a 0.45 mu m nylon filter membrane, and measuring Cd in filtrate by ICP (inductively coupled plasma mass spectrometry) ²⁺ And (4) concentration. The measurement data were fitted with a Langmuir model.

TABLE 2 isothermal adsorption line fitting parameters for examples of cadmium

Note that: k represents an adsorption affinity constant (L/g), Q _max Representing that the maximum adsorption capacity (mg/g) is the Cd adsorbed by unit mass obtained by fitting a Langmuir model ²⁺ By mass of

According to FIG. 5 and Table 2, the pairs of AAH, AAH-OP _ low, AAH-OP _ high for Cd ²⁺ The adsorption behavior ofMonolayer adsorption can be well fitted by using a Langmuir model to the Cd ²⁺ The adsorption capacity of (A) is ranked as AAH-OP _ high>AAH-OP_low>AAH, wherein the maximum adsorption capacity of AAH-OP _ high is 205mg/g, and the addition of high-concentration phytic acid can improve the adsorption capacity to Cd ²⁺ The adsorption performance of (3).

Measured with a Bruker 600 Mega-Cavity solid Nuclear magnetic resonance spectrometer (NMR, bruker, germany) ¹ And H NMR spectrum, and analyzing functional group and structure information. According to FIG. 6AAH-OP _ high ¹ H NMR spectrum, the chemical environment of H in P-O-H in phytic acid is very similar to that of H in Al-O-H in gibbsite. Adsorption of Cd with AAH ²⁺ Compared with the change of the characteristic peak of H before and after the adsorption of Cd by AAH-OP _ high ²⁺ The peak area change amplitude of the front and rear H characteristic peaks becomes smaller. This indicates Cd ²⁺ Mainly has complexation with-OH contained in the phosphate group of phytic acid, and only a small part of Cd ²⁺ The complex still occurs with the-OH of AAH.

Adsorption of Cd by adsorbent ²⁺ The samples were vacuum freeze-dried, ground into fine powder with an agate mortar, and subjected to FTIR chart measurement using a NICOLET 5700 Fourier Infrared spectrometer (ATR-FTIR, thermomanian instruments Co., U.S.A.). As can be seen from FIG. 7, cd ²⁺ Not only reacts with-OH of AAH, but also reacts with-OH of phosphate group of phytic acid, and the addition of the phytic acid improves the adsorption of Cd by hydroxyl aluminum ²⁺ The ability of the cell to perform.

Adsorption Performance test 2

Organophosphorus-loaded hydroxy aluminum composite material pair Cd ²⁺ The pH adsorption experiment of (1) tests that the adsorbent is used for adsorbing Cd at the temperature of 25 ℃ and the pH value of 4-8 ²⁺ The effect of adsorption.

The experiments were all performed in 50mL centrifuge tubes. Preparing a series of Cd ²⁺ Selecting high-concentration organic phosphorus-loaded hydroxyl aluminum composite material (AAH-OP _ high) as an adsorbent with the addition of 1.0g/L of the adsorbent, and adding 0.1mol/L of KNO ₃ The solution is subjected to constant volume to 30mL, the pH value of the solution is adjusted by using 1mol/L NaOH and 1mol/L HCl, the solution is shaken for 24 hours at the constant temperature of 25 ℃ by a constant temperature shaking machine, and then the solution is centrifuged for 15min. The supernatant in the centrifuge tube was filtered through a 0.45 μm nylon membrane and then through ICP (electric plasma)Inductively coupled plasma mass spectrometry) to analyze residual Cd in the supernatant ²⁺ And (4) concentration.

For Cd in the range of pH 4-8 with the composite material according to FIG. 8 ²⁺ The adsorption capacity of the composite material is increased along with the increase of pH, and the graph shows that the composite material can adsorb Cd under neutral to alkaline environments ²⁺ Has excellent adsorption performance.

Comparative example 1

pH adsorption of complex of aluminum hydroxide and bacteria to cadmium

With Cd (NO) ₃ ) ₃ ·4H ₂ Preparing cadmium mother liquor from O and Cd in reaction system ²⁺ The concentration was 0.1mM, the concentration of the adsorbent (amorphous aluminum hydroxide, aluminum hydroxide-bacteria complex in various proportions) was 1g/L, and KNO was used at 0.1mol/L ₃ The solution was made up to 30mL and no adsorbent was added to the control. 1mol/L NaOH and 1mol/L HNO are used ₃ Adjusting the pH value of the suspension to 4-7, oscillating for 24 hours at the constant temperature of 25 ℃ by using a constant temperature oscillator to wait for adsorption equilibrium, and then centrifuging. Filtering the supernatant with 0.45 μm nylon membrane, and analyzing the residual Cd in the supernatant by atomic absorption spectrometry ²⁺ And (4) concentration.

Each adsorbent pair Cd ²⁺ The adsorption quantity of (2) is increased along with the increase of pH, and when the pH is less than 6, the Cd pair of the complex ²⁺ The adsorption performance of the aluminum hydroxide is better than that of pure aluminum hydroxide, the adsorption performance of the aluminum hydroxide material is not obviously improved by the modification of bacteria on the aluminum hydroxide material at the pH value of 6-7, and the adsorption quantity is about 7.9mg/g.

Comparative example 2

Aluminum hydroxide-polyacrylamide p-Cd ²⁺ Adsorption isotherm of

Adding 220mg of aluminum hydroxide-polyacrylamide solution into a conical flask containing 400mL of cadmium solution in the cadmium stock solution (1.000 g/L), placing the conical flask in a rotary table concentrator for reaction for 4 hours, wherein the rotating speed of the table concentrator is 180r/min. Then the solution is centrifugally separated, and the supernatant is taken to measure Cd by adopting an atomic absorption spectrophotometer ²⁺ And (4) concentration.

In the temperature range of research, the Langmuir isothermal adsorption model better conforms to the aluminum hydroxide-polyacrylamide pair Cd ²⁺ Adsorption isotherm data of (a). This indicates Cd ²⁺ In the presence of aluminum hydroxideThe polyacrylamide surface forms a single-layer adsorption layer. Aluminum hydroxide-polyacrylamide p-Cd at 10 deg.C, 30 deg.C and 50 deg.C ²⁺ Maximum adsorption amount q of _max Are 44.43mg/g, 50.11mg/g and 54.81mg/g, respectively.

Comparative example 3

Phytic acid sepiolite composite heavy metal adsorbent for Cd ²⁺ Study on adsorption

Preparing phytic acid-sepiolite composite adsorbing material by taking phytic acid and sepiolite as raw materials, wherein the temperature is 30 ℃, the adsorbent concentration is 18g/L, and Cd is ²⁺ Adjusting the pH to 1-6 at a concentration of 100mg/L, and carrying out a pH adsorption experiment; the temperature is 30 ℃, the concentration of the adsorbent is 18g/L, and the pH value is 3.8, so that the influence of the concentration of the heavy metal on the adsorption performance is discussed;

research results show that the phytic acid sepiolite composite heavy metal adsorbent has the best adsorption performance at the pH =3.8 when the concentration of the adsorbent is 18g/L at the temperature of 30 ℃, and the maximum adsorption quantity is 2.67mg/g.

From the performance test and the comparison case, the organophosphorus loaded hydroxyl aluminum pair Cd ²⁺ Has good adsorption effect which is higher than the normal adsorption capacity (50 mg/g) of the prior art, the addition of high-concentration organic phosphorus can obviously enhance the adsorption performance, and the adsorption effect on Cd is improved ²⁺ The maximum adsorption capacity of the adsorbent can reach more than 205mg/g, which is four times higher than the normal adsorption capacity of the prior art. The invention has simple preparation, low cost, higher adsorption capacity than other inventions and higher industrial and agricultural popularization value.

The above description is only for the preferred embodiment of the present application and should not be taken as limiting the present application in any way, and although the present application has been disclosed in the preferred embodiment, it is not intended to limit the present application, and those skilled in the art should understand that they can make various changes and modifications within the technical scope of the present application without departing from the scope of the present application, and therefore all the changes and modifications can be made within the technical scope of the present application.

Claims

1. The application of the organic phosphorus composite material in heavy metal adsorption is characterized in that the structural formula of the organic phosphorus composite material is as follows:

。

2. the use according to claim 1, wherein the organophosphorus composite material is prepared by a method comprising the following steps:

s1, adding organic phosphorus into an aluminum salt solution, uniformly mixing, adjusting the pH value, centrifuging and filtering to obtain a precipitate;

s2, freeze-drying the precipitate to obtain an organic phosphorus composite material;

the organic phosphorus is phytic acid;

the aluminum salt is water-soluble aluminum salt; the molar ratio of P to Al in the organophosphorus composite material is 1 (10 to 100); and S1, adjusting the pH value to 6.5 +/-0.2, and adjusting the pH value by using a dilute NaOH solution.

3. The use according to claim 2, wherein the water-soluble aluminum salt is one or more of aluminum chloride, aluminum chloride hydrate, aluminum nitrate hydrate, aluminum sulfate and aluminum sulfate hydrate.

4. Use according to claim 2, characterized in that the water-soluble aluminium salt is aluminium nitrate hydrate.

5. Use according to claim 2, wherein the molar ratio of P to Al in the organophosphorus composite material is 1.

6. Use according to claim 2, wherein step S1 is carried out by adjusting the pH to a value of 0.5h, during which the pH is finely adjusted, followed by centrifugation.