Adsorbent for efficiently removing cadmium and arsenic, and preparation method and application thereof

Abstract

The application discloses an adsorbent for efficiently removing cadmium and arsenic, and a preparation method and application thereof. The biomass raw material pyrolysis product with high exchangeable calcium content is impregnated with a K2FeO4 solution, and after heating and stirring until stable, the stable product is dried and ozone-activated to obtain the adsorbent for efficiently removing cadmium and arsenic. The adsorbent for efficiently removing cadmium and arsenic has high ash content, high alkalinity and many surface active sites, and can effectively adsorb and fix heavy metals in a heavy metal contaminated water body. The adsorbent can simultaneously effectively adsorb Cd(II) and As(III) in the water body. In a composite contaminated water body, the adsorption amount of Cd(II) and As(III) can reach 426.93 mg / g and 78.55 mg / g respectively, and the adsorbent can simultaneously effectively treat various heavy metal contaminated water bodies, and has a wide application prospect in heavy metal pollution treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, and relates to an adsorbent that can simultaneously and efficiently remove cadmium and arsenic ions from the environment. Specifically, it relates to an adsorbent that can efficiently remove cadmium and arsenic, its preparation method, and its application. Background Technology

[0002] Industrial production activities such as mining and metallurgy often involve the emission of excessive amounts of heavy metals such as cadmium and arsenic. This not only causes serious harm to the environment but can also accumulate in the human body through various pathways, thereby endangering human health. Cadmium and arsenic are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC) and rank seventh and first, respectively, on the U.S. List of Priority Hazardous Substances (ATSDR, 2017) posing the greatest potential threat to human health. They can cause diseases such as cirrhosis, kidney failure, and cardiovascular disease. Furthermore, studies have shown that more than 150 million people worldwide drink water contaminated with cadmium and arsenic, particularly in Latin America and Southeast / South Asia. In the environment, cadmium exists as a cation, Cd(II), while arsenic exists as an anion, As(III) or As(V). Their opposite ionic properties make the removal of cadmium and arsenic combined pollution a formidable challenge for society today. Therefore, developing efficient and low-cost methods for preparing remediation materials for removing cadmium and arsenic has become an urgent priority.

[0003] Biochar is a widely used material for heavy metal remediation. Previous studies have shown that calcium-rich biochar has good adsorption capacity for cationic heavy metals such as Cd(II), but its adsorption capacity for anionic heavy metals such as As(III) is weak due to the negative charge on its surface. Iron hydroxyl oxides have a high affinity for anionic heavy metals such as As(III) and As(V), because the metal oxide surface has abundant hydroxyl groups, which form complexes with arsenite or arsenate. However, due to the surface energy generated by strong magnetic forces or van der Waals forces, these complexes tend to aggregate, affecting their adsorption capacity for arsenic heavy metal pollution. Furthermore, the oxidizing properties of ozone can effectively increase the content of oxygen-containing functional groups on the surface of biochar. Therefore, developing a biochar material that is simple to prepare, has abundant raw material sources, and exhibits strong adsorption performance for both cationic and anionic heavy metals has significant application value in the remediation of environmental heavy metal ion pollution. Summary of the Invention

[0004] To overcome the aforementioned shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing an adsorbent for the efficient removal of cadmium and arsenic. This preparation method is simple, uses few chemicals, and poses no risk of secondary pollution. The raw material used in this method is crayfish shells, which are abundant, inexpensive, and readily available.

[0005] Another object of the present invention is an adsorbent for the efficient removal of cadmium and arsenic.

[0006] Another object of the present invention is the application of the above-mentioned highly efficient adsorbent for removing cadmium and arsenic.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a highly efficient adsorbent for removing cadmium and arsenic includes the following steps:

[0009] (1) Collect biomass raw materials and sequentially wash, dry, crush, grind and sieve them to obtain biomass raw material powder;

[0010] (2) The obtained powder was subjected to oxygen-limited pyrolysis to obtain adsorbent A;

[0011] (3) Take adsorbent A and add it to iron salt solution for mixing. Heat and stir until a stable mixture is obtained, then dry it, grind and sieve it to obtain a stable powder.

[0012] (4) The stable powder is activated by ozone, cooled, ground and sieved to obtain adsorbent B, which is the highly efficient adsorbent for removing cadmium and arsenic.

[0013] Preferably, in step (1), the biomass raw material is any one or more combinations of rice straw, cow bone meal, chicken manure, clam shells, eggshells, oyster shells, giant African snail shells, and crayfish shells.

[0014] More preferably, in step (1), the biomass raw material is crayfish shells. The oxygen-limited pyrolysis products of crayfish shells have a higher exchangeable calcium content.

[0015] Preferably, in step (1), drying refers to drying until the moisture content is below 5%. If the moisture content of the raw material is too high, the drying temperature should be increased or the drying time should be extended appropriately.

[0016] More preferably, in step (1), the drying temperature is set to 50-120°C and the drying time is set to 36-72h.

[0017] In a further preferred embodiment, in step (1), the drying temperature is set to 70°C and the drying time is set to 48h.

[0018] Preferably, in step (1), the sieving process refers to passing the material through a sieve with a diameter of 0.15 mm or less.

[0019] More preferably, in step (1), the sieving process refers to passing the material through a sieve with a diameter of 0.25 mm or less.

[0020] Preferably, in step (2), the oxygen-limited pyrolysis is set as follows: the obtained powder is placed in a muffle furnace, nitrogen gas is introduced for 10 to 40 minutes, and then the temperature is increased to 300 to 700°C at a heating rate of 5 to 10°C / min. The powder is then carbonized at a constant temperature for 1 to 4 hours, cooled to room temperature, and then removed.

[0021] More preferably, in step (2), the oxygen-limited pyrolysis is set as follows: the obtained powder is placed in a muffle furnace, nitrogen is introduced for 10 min, and then the temperature is increased to 500°C at a heating rate of 10°C / min, carbonized at a constant temperature for 2 h, and then cooled to room temperature before being taken out.

[0022] Preferably, in step (3), the iron salt solution is a K2FeO4 solution.

[0023] Preferably, in step (3), the mass ratio of iron ions to adsorbent A in the iron salt solution is 0.5 to 3.0:1.

[0024] More preferably, in step (3), the mass ratio of iron ions to adsorbent A in the iron salt solution is 1.5 to 1.8:1.

[0025] Preferably, in step (3), heating and stirring refers to magnetic stirring at a temperature of 60-100℃ for 4-12 hours.

[0026] More preferably, in step (3), heating and stirring refers to magnetic stirring at a temperature of 80°C for 6 hours.

[0027] Preferably, in step (3), the drying temperature is set to 50-120°C and the drying time is set to 36-72h.

[0028] More preferably, in step (3), the drying temperature is set to 105°C and the drying time is set to 48h.

[0029] Preferably, in step (3), the sieving process refers to passing the powder through a 0.15 mm sieve. The resulting powder has a particle size of less than 0.15 mm.

[0030] Preferably, in step (4), the ozone activation is set as follows: place the stable powder in a muffle furnace, introduce ozone at a flow rate of 20-100 mL / min, then heat it to 80-280°C at a heating rate of 5-10°C / min, activate it at a constant temperature for 1-4 hours, cool it to room temperature and then take it out.

[0031] More preferably, in step (4), the ozone activation is set as follows: the stable powder is placed in a muffle furnace, ozone is introduced at a flow rate of 60 mL / min, and then the temperature is increased to 100°C at a heating rate of 5°C / min, activated at a constant temperature for 1 hour, and then cooled to room temperature before being taken out.

[0032] Preferably, in step (4), the grinding and sieving process refers to grinding the powder and passing it through a 0.15mm sieve. The resulting powder has a particle size of less than 0.15mm.

[0033] An adsorbent for the efficient removal of cadmium and arsenic is prepared by the above method.

[0034] A method for treating water bodies polluted by heavy metals includes the following steps: adding the above-mentioned highly efficient adsorbent for removing cadmium and arsenic to water bodies containing heavy metal cadmium and / or arsenic ions, allowing for sufficient contact and reaction to remove cadmium and / or arsenic ions from the water. Experiments have shown that this highly efficient adsorbent for removing cadmium and arsenic can rapidly and efficiently remove Cd(II) and As(III) from water bodies, achieving good treatment results.

[0035] Preferably, the amount of the highly efficient adsorbent for removing cadmium and arsenic in the water is 0.1 to 2 g / L; more preferably, it is 1 g / L.

[0036] Preferably, the initial pH value of the water body is 2.0 to 8.0; more preferably 4.0 to 6.0; and even more preferably 5.0 to 6.0.

[0037] Preferably, the initial concentration of cadmium ions in the water is 0.1–2500 mg / L; more preferably, it is 0.1–2000 mg / L.

[0038] Preferably, the initial concentration of arsenic ions in the water is 0.1–1000 mg / L; more preferably, it is 0.1–300 mg / L.

[0039] When the water contains cadmium and arsenic ions, the initial concentration of cadmium ions is 0.1–300 mg / L and the initial concentration of arsenic ions is 0.1–200 mg / L; more preferably, the initial concentration of cadmium ions is 0.1–100 mg / L and the initial concentration of arsenic ions is 0.1–200 mg / L.

[0040] Preferably, the conditions for the full contact reaction are set as follows: temperature 10-40°C, time 1-24h, and rotation speed 150r / min.

[0041] The technical principle of this invention: Crayfish shell biochar possesses a porous structure and a high exchangeable calcium content, enabling it to adsorb cationic heavy metals such as cadmium through ion exchange. However, its adsorption efficiency for anionic heavy metals such as arsenic is relatively low. Iron oxides are effective in adsorbing arsenic ions, but they tend to aggregate, affecting their ability to adsorb heavy metal pollution. Ozone activation effectively increases the oxygen-containing functional groups of the biochar. This invention utilizes the porous structure and high exchangeable calcium content of crayfish shell biochar. Potassium ferrate and ozone activation oxidation corrode the crayfish shell biochar, dispersing the iron oxides and activating the internal calcium ions to increase the oxygen-containing functional groups on its surface, further enhancing its cadmium adsorption capacity. Simultaneously, the porous structure of the crayfish shell biochar allows iron oxides to adhere to its surface and pores, increasing its affinity for arsenic and thus enhancing its arsenic adsorption capacity.

[0042] The present invention has the following advantages and effects compared with the prior art:

[0043] (1) The adsorbent for the efficient removal of cadmium and arsenic of the present invention has low preparation cost and simple process, providing a new way for the resource utilization of crayfish shells. Specifically, the preparation process is simple, requires few chemical reagents, and uses inexpensive and readily available raw materials, which has broad application prospects in the treatment of heavy metal polluted water bodies.

[0044] (2) The highly efficient adsorbent for removing cadmium and arsenic of the present invention can efficiently and rapidly adsorb heavy metals cadmium and arsenic in water. Specifically, under the condition of an initial Cd(II) concentration of 1000 mg / L, the highly efficient adsorbent for removing cadmium and arsenic reaches equilibrium within 60 min at the beginning of the reaction, with a maximum adsorption capacity of 545.67 mg / g; while under the condition of an initial As(III) concentration of 50 mg / L, it reaches adsorption equilibrium within 120 min, with a maximum adsorption capacity of 22.36 mg / g. Furthermore, the maximum Langmuir adsorption capacities of the highly efficient adsorbent for removing cadmium and arsenic of the present invention for Cd(II) and As(III) are 677.86 mg / g and 46.83 mg / g, respectively.

[0045] (3) The highly efficient adsorbent for removing cadmium and arsenic of the present invention can simultaneously and effectively adsorb heavy metals cadmium and arsenic in water. Specifically, in water containing 5-2000 mg / L Cd(II) and 100-1000 mg / L As(III), the highly efficient adsorbent for removing cadmium and arsenic retains an adsorption capacity of 397.55-426.93 mg / g for Cd(II); in water containing 1-200 mg / L As(III) and 10-100 mg / L Cd(II), the highly efficient adsorbent carbon for removing cadmium and arsenic can adsorb up to 78.55 mg / g for As(III). Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the physical object prepared by the method of the present invention.

[0047] Figure 2 This is a graph showing the results of the exchangeable calcium content determination of the adsorbent in Example 1.

[0048] Figure 3 These are scanning electron microscope (SEM) images of adsorbent A and adsorbent B in Example 1; where (a) is adsorbent A and (b) is adsorbent B.

[0049] Figure 4 This is a diagram showing the response surface methodology optimization design results of adsorbent B adsorbing Cd(II) in Example 2.

[0050] Figure 5 This is a diagram showing the response surface methodology optimization design results of adsorbent B adsorbing As(III) in Example 2.

[0051] Figure 6 This is a graph showing the results of the study on the effect of different reaction times on the adsorption of Cd(II) and As(III) in Example 3.

[0052] Figure 7 This is a graph showing the results of the study on the effect of different initial concentrations on the adsorption of Cd(II) and As(III) in Example 4.

[0053] Figure 8 This is a graph showing the results of the study on the effect of the coexistence of Cd(II) and As(III) on the adsorption effect in Example 5. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto. For process parameters not specifically specified, conventional techniques shall be followed.

[0055] A physical schematic diagram of the implementation of the method of the present invention is shown below. Figure 1 As shown.

[0056] Example 1: Preparation of an adsorbent material for efficient removal of cadmium and arsenic

[0057] Collected rice straw, clam shells, eggshells, oyster shells, giant African snail shells, and crayfish shells were cleaned with deionized water. The cleaned rice straw, clam shells, eggshells, oyster shells, giant African snail shells, and crayfish shells, along with collected cow bone meal and chicken manure, were placed separately in an oven (70℃, 48h) to dry. The dried materials were then ground and sieved to obtain rice straw powder (<0.25mm), cow bone meal powder (<0.15mm), chicken manure powder (<0.15mm), clam shell powder (<0.15mm), eggshell powder (<0.15mm), and oyster shell powder. Powder (<0.15 mm), giant African snail shell powder (<0.15 mm), and crayfish shell powder (<0.15 mm) were placed in a muffle furnace. Nitrogen gas was first introduced for 10 min, and then the temperature was increased to 300℃, 500℃, and 700℃ respectively at a heating rate of 10℃ / min. Under oxygen-limited conditions, the carbonization was carried out at a constant temperature for 2 h. After cooling to room temperature, rice straw biochar, bovine bone meal biochar, chicken manure biochar, clam shell biochar, eggshell biochar, oyster shell biochar, giant African snail shell biochar, and crayfish shell biochar were obtained.

[0058] The obtained biochar was placed in 50 mL centrifuge tubes, and 1 mol / L ammonium acetate solution (pH 7.0) was added at a solid-liquid ratio (w / v, g / mL) of 1:20. The mixture was stirred thoroughly, and the tubes were centrifuged at 4000 rpm for 5 min. The supernatant was collected, and this process was repeated 2-3 times. After adjusting the volume, the calcium ion content in the supernatant was measured, and adsorbent A with the highest calcium exchange content was selected. Figure 2 It can be seen that adsorbent A is crayfish shell biochar obtained by pyrolysis at 500℃ under lower oxygen for 2 hours.

[0059] Adsorbent A and K2FeO4 solution were mixed at a mass ratio of iron ions to adsorbent of 1.5:1 and magnetically stirred at 80℃ for 6 hours. The stabilized product was then placed in an oven and dried at 105℃ for 48 hours. After drying, the product was cooled, ground, and sieved (0.15 mm) to obtain a powder. The powder was placed in a muffle furnace, and ozone was introduced at a flow rate of 60 mL / min. The temperature was then increased to 100℃ at a rate of 5℃ / min and activated at this temperature for 1 hour. After cooling to room temperature, the product was ground and sieved (0.15 mm) to obtain adsorbent B, which is a highly efficient adsorbent for removing cadmium and arsenic.

[0060] The SEM image of the highly efficient cadmium and arsenic removal adsorbent in this embodiment is shown below. Figure 3 As shown. By Figure 3 It can be seen that adsorbent A has a porous structure and a smooth surface. After being impregnated with iron salt and activated by calcination, the porous structure of adsorbent B is corroded, and iron oxide particles are loaded on its surface.

[0061] Example 2: Optimization of adsorption conditions for efficient removal of cadmium and arsenic

[0062] The optimization solution was obtained using the Central Composite Design (CCD) model in the Response Surface Methodology (RSM). Adsorption capacity and adsorption rate were used as response values. Three factors affecting the adsorption effect were selected for the experimental design. The pH value of the reaction medium (X1), the mass concentration of adsorbent B (dosage, X2), and the mass ratio of iron ions to adsorbent A (Fe:biochar, X3) were used as experimental variables in the CCD model. The levels of X1, X2, and X3 were coded using +α, +1, 0, -1, and -α (α = 1.6812). A three-factor, five-level CCD experiment was designed to determine the optimal scheme for adsorbent B to adsorb cadmium or arsenic.

[0063] from Figure 4 It can be seen that with the increase of the mass concentration of adsorbent B, the adsorption capacity of adsorbent B for Cd(II) decreases, but the removal rate increases. Conversely, with the increase of pH and the mass ratio of iron ions to adsorbent A, both the adsorption capacity and removal rate show a trend of first increasing and then decreasing. Considering accessibility, the optimal adsorption conditions for adsorbent B to adsorb Cd(II) are pH 5.41, mass concentration 0.92 g / L, and the mass ratio of iron ions to adsorbent A 1.69:1. Under these conditions, the accessibility is highest, the adsorption capacity is 436.98 mg / g, and the removal rate reaches 83.70%.

[0064] from Figure 5 It can be seen that with the increase of the mass concentration of adsorbent B, the adsorption capacity of adsorbent B for As(III) decreases, but the removal rate increases. Conversely, with the increase of pH and the mass ratio of iron ions to adsorbent A, both the adsorption capacity and removal rate show a trend of first increasing and then decreasing. The optimal adsorption conditions for adsorbent B to adsorb As(III) are pH 5.48, mass concentration 1.11 g / L, and mass ratio of iron ions to adsorbent A 1.74:1. Under these conditions, the highest adsorption density is 0.767, and the adsorption capacity is 15.38 mg / g.

[0065] The optimal conditions for adsorbent B to adsorb cadmium or arsenic in this embodiment are shown in Table 1.

[0066] This embodiment illustrates that adsorbent B can achieve optimal adsorption of cadmium or arsenic under certain conditions, and has the potential to adsorb both cadmium and arsenic simultaneously, providing a reference for its practical application in the treatment of cadmium and / or arsenic-polluted water bodies.

[0067] Table 1 Optimal adsorption conditions optimized by response surface methodology

[0068]

[0069] Example 3: Effect of different reaction times on the adsorption of Cd(II) and As(III)

[0070] 20 mg of adsorbent A and B were added to 20 mL solutions of pH 5.0 containing 300, 500, and 1000 mg / L Cd(II), respectively. Samples were taken and filtered at different time points (1, 3, 5, 10, 15, 20, 40, 60, 90, 120, 180, 240, 360, 720, and 1440 min) under shaking at 25 °C and 150 r / min, and the Cd(II) concentration in the filtrate was determined. 20 mg of adsorbent A and B were added to 20 mL solutions of pH 6.0 containing 10, 20 and 50 mg / L As(III), respectively. Samples were taken and filtered at different time points (1, 3, 5, 10, 15, 20, 40, 60, 90, 120, 180, 240, 360, 720 and 1440 min) under shaking at 25 °C and 150 r / min, and the As(III) concentration in the filtrate was determined.

[0071] Depend on Figure 6It can be seen that adsorbent B has a significantly greater adsorption capacity for Cd(II) and As(III) than adsorbent A. Furthermore, in the initial stage of the reaction, the adsorption capacity increases rapidly with increasing reaction time, then tends towards equilibrium. When the initial concentration of Cd(II) is 300 mg / L, adsorbent B rapidly reaches adsorption equilibrium within 60 min, with a removal rate exceeding 99%; while adsorbent A reaches equilibrium at 120 min, with a removal rate of only about 31%. When the initial concentration of Cd(II) is 500 and 1000 mg / L, adsorbent B still achieves a removal rate of over 80% for Cd(II), with an adsorption capacity of 370.89–545.67 mg / g, significantly better than adsorbent A (removal rate around 20%). For As(III), adsorbents A and B reach adsorption equilibrium within 180 min and 120 min, respectively. At three different initial concentrations (10, 20, and 50 mg / L), adsorbent A adsorbed 1.12–2.31 mg / g of As(III), with removal rates all below 10%. Adsorbent B, however, exhibited superior As(III) adsorption capacity. At an initial As(III) concentration of 10 mg / L, adsorbent B achieved an adsorption capacity of 7.07 mg / g within 120 min, with a removal rate exceeding 67.06%. When the initial As(III) concentrations were increased to 20 and 50 mg / L, the equilibrium adsorption capacities reached 12.46 and 23.63 mg / g, respectively, with removal rates remaining above 55% and 49%, respectively. These results indicate that adsorbent B can rapidly and extensively adsorb Cd(II) and As(III) from water. At 1000 mg / L Cd(II) or 20 mg / L As(III), the adsorption equilibrium time was less than 2 h, with removal rates exceeding 80% and 55%, respectively.

[0072] This embodiment illustrates that the adsorbent B, which efficiently removes cadmium and arsenic, has a faster adsorption rate and the highest adsorption rate for Cd(II) and As(III) in water, providing a technical guarantee for its rapid and efficient treatment of heavy metal pollution in water bodies.

[0073] Example 4: Effect of different initial concentrations on the adsorption of Cd(II) and As(III)

[0074] 20 mg of adsorbent A and B were added to 20 mL of pH 5.0 solution containing different initial Cd(II) concentrations (5, 10, 20, 50, 100, 150, 200, 300, 500, 700, 1000, 1500 and 2000 mg / L), respectively. After shaking at 150 r / min for 24 h at 10, 25 and 40 °C, samples were taken and filtered, and the concentration of Cd(II) in the filtrate was determined. 20 mg of adsorbent A and B were added to 20 mL of pH 6.0 solutions containing different initial As(III) concentrations (1, 3, 5, 7, 10, 15, 20, 30, 50, 70, 100, 150 and 200 mg / L), respectively. After shaking at 150 r / min for 24 h at 10, 25 and 40 °C, samples were taken and filtered, and the concentration of As(III) in the filtrate was determined.

[0075] from Figure 7 It can be seen that adsorbent B has a significantly greater adsorption capacity for Cd(II) than adsorbent A. When the initial Cd(II) concentration is between 5 and 150 mg / L, the adsorption capacity of the adsorbents increases significantly. When the initial Cd(II) concentration is greater than 200 mg / L, the increase in adsorption capacity of adsorbent A slows down, while the increase in adsorption capacity of adsorbent B continues to increase rapidly, only slowing down when the initial Cd(II) concentration is greater than 500 mg / L. When the initial Cd(II) concentration is 2000 mg / L, the adsorption capacities of adsorbents A and B for Cd(II) are 128.28–199.70 and 479.88–497.76 mg / g, respectively, and the adsorption capacity shows a slight decreasing trend with increasing temperature. Furthermore, the adsorption process of the adsorbents was fitted using the Langmuir isotherm model. The results showed that the maximum Langmuir adsorption capacity of adsorbent B for Cd(II) was 616.33 mg / g, significantly greater than that of adsorbent A (126.01 mg / g). Regarding the adsorption of As(III), adsorbent A exhibited a relatively small overall adsorption capacity, only 2.25–3.02 mg / g, while adsorbent B showed superior adsorption efficiency. When the initial As(III) concentration was between 1 and 70 mg / L, the adsorption capacity of adsorbent B for As(III) increased rapidly, gradually leveling off only when the concentration exceeded 100 mg / L. At 200 mg / L, the adsorption capacity ranged from 23.71 to 34.41 mg / g. The maximum Langmuir adsorption capacities of adsorbent A and adsorbent B for As(III), obtained from the Langmuir isotherm model fitting, were 2.71 mg / g and 46.83 mg / g, respectively. Compared with the maximum Langmuir adsorption capacity of adsorbents involved in other studies (Table 2), the adsorbent B prepared in this invention has a superior adsorption effect on Cd(II) and As(III) in water.

[0076] Table 2 Comparison of Langmuir adsorption capacity for different adsorbents

[0077]

[0078] Table 4 References:

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[0099] This embodiment demonstrates that adsorbent B has a strong adsorption capacity for Cd(II) and As(III) in water, with Langmuir adsorption capacities as high as 616.33 and 46.83 mg / g, respectively, which are 4.89 times and 17.28 times that of adsorbent A, and can effectively treat heavy metal wastewater with different levels of pollution.

[0100] Example 5: Effect of coexistence of Cd(II) and As(III) on adsorption efficiency

[0101] 20 mg of adsorbent A and B were added to 20 mL of pH 5.0 solution containing different initial Cd(II) concentrations (5, 10, 20, 50, 100, 150, 200, 300, 500, 700, 1000, 1500 and 2000 mg / L) and different initial As(III) concentrations (0, 300, 500 and 1000 mg / L). After shaking at 150 r / min for 24 h at 25 °C, samples were taken and filtered, and the concentration of Cd(II) in the filtrate was determined. 20 mg of adsorbent A and B were added to 20 mL of pH 6.0 solution containing different initial As(III) concentrations (1, 3, 5, 7, 10, 15, 20, 30, 50, 70, 100, 150 and 200 mg / L) and different initial Cd(II) concentrations (0, 10, 50 and 100 mg / L). After shaking at 150 r / min for 24 h at 25 °C, samples were taken and filtered, and the concentration of As(III) in the filtrate was determined.

[0102] Depend on Figure 8 It can be seen that when Cd(II) and As(III) coexist, the adsorption capacity of adsorbent B for both Cd(II) and As(III) is significantly greater than that of adsorbent A. Although the adsorption capacity of adsorbents A and B for Cd(II) decreased at the three As(III) concentrations, from 21.68% to 25.60% and from 12.76% to 18.67%, respectively, adsorbent B still maintained a higher adsorption capacity for Cd(II) than adsorbent A, with an adsorption capacity of 397.55–426.93 mg / g, which is 4.08–4.46 times that of adsorbent A. Furthermore, when the Cd(II) concentration is below 300 mg / L, the adsorption of Cd(II) by adsorbent B is almost unaffected by As(III). Different concentrations of Cd(II) increased the adsorption capacity of adsorbents A and B for As(III) by 76.00–327.11% and 10.55–124.56%, respectively, with the increasing concentration of Cd(II) leading to a greater increase in adsorption capacity. At a Cd(II) concentration of 10 mg / L, the increase in adsorption capacity for As(III) was relatively small, ranging from 1.71 to 3.69 mg / g. However, when the Cd(II) concentration was 100 mg / L, the adsorption capacities of adsorbents A and B for As(III) reached 9.61 mg / g and 78.55 mg / g, respectively.

[0103] This embodiment demonstrates that adsorbent B still has excellent adsorption capacity in water bodies polluted by both Cd(II) and As(III), with maximum adsorption capacities of 426.93 mg / g for Cd(II) and 78.55 mg / g for As(III), and can effectively treat water bodies polluted by multiple heavy metals simultaneously.

[0104] The above are the preferred embodiments of the present invention. Those skilled in the art can make various modifications and optimizations without departing from the scope of the inventive concept. All such modifications and optimizations are included within the scope defined by the claims of the present invention and do not depart from the spirit and practical application of the present invention.

Claims

1. A method for treating a heavy metal contaminated water body, characterized in that: The method comprises the following steps: The adsorbent for efficiently removing cadmium and arsenic is prepared by the method comprising the following steps: (1) Collecting biomass raw materials and sequentially performing cleaning, drying, crushing, grinding and sieving to obtain powder of the biomass raw materials; (2) Taking the obtained powder to perform limited oxygen pyrolysis to obtain adsorbent A; (3) Taking the adsorbent A and adding it into an iron salt solution to perform mixing, heating and stirring until a stable mixed solution is obtained, and then performing drying, grinding and sieving to obtain a stable powder; (4) Performing ozone activation on the stable powder, and then performing grinding and sieving after cooling to obtain adsorbent B, which is the adsorbent for efficiently removing cadmium and arsenic; In the step (1), the biomass raw materials are crayfish shells; In the step (3), the iron salt solution is a K2FeO4 solution.

2. The method for treating heavy metal contaminated water bodies according to claim 1, characterized in that: In the step (1), the temperature for drying is set to 50-120 DEG C, and the time is set to 36-72 h; In the step (1), the sieving refers to passing through a sieve with a size of less than or equal to 0.15 mm; In the step (2), the limited oxygen pyrolysis is set as follows: the obtained powder is placed in a muffle furnace, nitrogen is first introduced for 10-40 min, and then the temperature is raised to 300-700 DEG C at a temperature raising speed of 5-10 DEG C / min, and the temperature is kept constant for carbonization for 1-4 h, and then the powder is taken out after cooling to room temperature.

3. The method for treating heavy metal contaminated water bodies according to claim 2, characterized in that: In the step (1), the temperature for drying is set to 70 DEG C, and the time is set to 48 h; In the step (2), the limited oxygen pyrolysis is set as follows: the obtained powder is placed in a muffle furnace, nitrogen is first introduced for 10 min, and then the temperature is raised to 500 DEG C at a temperature raising speed of 10 DEG C / min, and the temperature is kept constant for carbonization for 2 h, and then the powder is taken out after cooling to room temperature.

4. The method for treating heavy metal contaminated water bodies according to claim 1, characterized in that: In the step (3), the mass ratio of iron ions in the iron salt solution to the adsorbent A is 0.5-3.0:1; In the step (3), the heating and stirring refers to magnetic stirring at a temperature of 60-100 DEG C for 4-12 h; In the step (3), the temperature for drying is set to 50-120 DEG C, and the time is set to 36-72 h; In the step (4), the ozone activation is set as follows: the stable powder is placed in a muffle furnace, ozone is introduced at a flow rate of 20-100 mL / min, and then the temperature is raised to 80-280 DEG C at a temperature raising speed of 5-10 DEG C / min, and the temperature is kept constant for activation for 1-4 h, and then the powder is taken out after cooling to room temperature.

5. The method for treating heavy metal contaminated water bodies according to claim 4, characterized in that: In the step (3), the mass ratio of iron ions in the iron salt to the adsorbent A is 1.5-1.8:1; In the step (3), the heating and stirring refers to magnetic stirring at a 80 DEG C for 6 h; In step (3), the drying temperature is set to 105℃ and the drying time is set to 48 h; In step (3), sieving refers to passing the material through a 0.15mm sieve. In step (4), the ozone activation is set as follows: place the stable powder in a muffle furnace, introduce ozone at a flow rate of 60 mL / min, then heat it to 100℃ at a heating rate of 5℃ / min, activate it at a constant temperature for 1h, cool it to room temperature and then take it out. In step (4), sieving refers to passing the material through a 0.15mm sieve.

6. The method for treating heavy metal-polluted water bodies according to claim 1, characterized in that: The dosage of the highly efficient adsorbent for removing cadmium and arsenic in water is 0.1–2 g / L. The initial pH value of the water body is 2.0 to 8.0; The initial concentration of cadmium ions in the water body is 0.1–2500 mg / L; The initial concentration of arsenic ions in the water body is 0.1–1000 mg / L.

7. The method for treating heavy metal-polluted water bodies according to claim 1, characterized in that: The dosage of the highly efficient cadmium and arsenic removal adsorbent in water is 1 g / L; The initial pH value of the water body is 5.0 to 6.0; The initial concentration of cadmium ions was 0.1–300 mg / L, and the initial concentration of arsenic ions was 0.1–200 mg / L. The conditions for the fully contacted reaction are set as follows: temperature 10-40℃, time 1-24h, and rotation speed 150r / min.

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