A method for synchronously removing lead, cadmium and arsenic in soil

Abstract

This invention relates to a method for simultaneously removing lead, cadmium, and arsenic from soil, belonging to the field of soil pollution remediation technology. This invention is the first to propose using lignin sulfonate in conjunction with an electrochemical process to efficiently treat heavy metal-contaminated soil, simultaneously achieving the efficient and simultaneous removal of pollutants such as Pb, Cd, and As. This invention uses heavy metal-contaminated soil as the treatment target. The soil to be treated is added to water and mixed with lignin sulfonate to form a slurry. Then, an iron-based anode and an inert-based cathode are used for electrolysis under stirring. During electrolysis, the voltage is controlled at 0.4-0.6V; the amount of lignin sulfonate added is 0.1-1% of the mass of the soil to be treated. This invention features a simple and controllable process, high efficiency, excellent simultaneous removal effect, and is easy to promote and apply.

Description

Technical Field

[0001] This invention relates to a method for simultaneously removing lead, cadmium, and arsenic from soil, belonging to the field of soil pollution remediation technology. Background Technology

[0002] Soil pollution is a global environmental hazard caused by factors such as industrial development, tailings mining, overuse of agricultural pesticides, and improper waste disposal. The "2014 China Soil Pollution Survey Report" found that lead (Pb), cadmium (Cd), and arsenic (As) pollution accounted for 70% of all heavy metal pollution exceeding standards nationwide. Heavy metal pollution in soil (Pb, Cd, and As) not only degrades water and food quality but also reduces the availability of agricultural land, potentially posing significant problems for humans and ecosystems. Therefore, developing efficient and simultaneous remediation technologies is crucial for addressing Pb, Cd, and As pollution in soil.

[0003] Multi-component heavy metal pollution in soil poses a significant and widespread threat to ecosystems. Complex interactions exist among various heavy metals in soil, and the different chemical properties of different heavy metals present obstacles to the efficient and simultaneous remediation of multi-metal pollution. Taking Pb, Cd, and As pollution in soil as examples, Pb and Cd mainly exist as cations, while As mainly exists as oxygen-containing anions. The forms of Pb, Cd, and As change with soil pH. Higher pH values ​​result in stronger electrostatic adsorption of Pb and Cd, leading to higher concentrations of Pb in the soil. 2+ and Cd 2+ This will cause precipitation, which will also lead to a decrease in the exchangeable Pb and Cd content in the soil. The decrease in soil pH will cause Cd and Pb to dissociate and be released back into the soil. For As, the negative charge in the soil (from anions or OH-) - The concentration of ions increases with increasing soil pH, thus repelling equally negatively charged oxygen-containing anions. Therefore, these negatively charged ions compete with ions for adsorption sites associated with As, leading to As desorption and increased As mobility within the soil. Different oxygen environments also significantly affect the availability and forms of Pb, Cd, and As. In oxygen-limited environments, soil pH tends to rise, reducing the availability of Cd and Pb. However, the availability of low-toxicity pentavalent As (H₂AsO₄) remains relatively high. - and HAsO4 2- Trivalent As (H3AsO3 and H2AsO3) are mainly found in aerobic soils and are highly toxic. - These three heavy metals are generally found under anaerobic conditions. Therefore, these significant differences pose a challenge to simultaneously addressing pollution caused by these three heavy metals.

[0004] Currently, soil heavy metal remediation technologies mainly include physical, chemical, and bioremediation methods. While these strategies are generally applicable, they also have their limitations. First, there is a need to further improve remediation efficiency to meet the growing demand for rapid remediation. Second, due to the different properties of individual metals, treating multiple types of heavy metals in contaminated soil requires a combination of technologies. Finally, some soil remediation processes require the large-scale use of chemicals, which can lead to secondary pollution. In recent years, electrochemical technology has become a rapid and efficient method for removing heavy metals from aqueous solutions and soil due to its compact equipment structure, simple operation, and cost-effectiveness. Electrochemical treatment can mineralize metal ions in contaminated soil through various processes such as electrolysis, electroadsorption, and electrodeposition. For example, Qiu et al. used an electrochemical treatment method to remove Cu and Zn from contaminated soil through electrochemical adsorption and deposition. In addition, Cui and his collaborators developed an electrochemical remediation method based on the concept of asymmetric alternating current electrochemistry, simultaneously achieving the removal of various heavy metals (Cu, Pb, Cd) from soil pollutants. However, current electrochemical processes are mainly used for the simultaneous treatment of pollutants existing in the form of single cations or anions, and there are few reports on the simultaneous treatment of pollutants with opposite chemical properties such as Pb, Cd, and As. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes for the first time to utilize lignin sulfonate in conjunction with an electrochemical process to efficiently treat heavy metal contaminated soil, and simultaneously achieve the efficient and simultaneous removal of pollutants such as Pb, Cd, and As.

[0006] The present invention discloses a method for simultaneously removing Pb, Cd, and As from soil, comprising the following steps: taking soil contaminated with heavy metals as the treatment target, adding the treatment target to water and adding lignin sulfonate, stirring evenly to form a slurry, then using an iron material as the anode and an inert material as the cathode, electrolysis is carried out under stirring. During electrolysis, the voltage is controlled at 0.4-0.6V, preferably 0.45-0.55V, and more preferably 0.49-0.51V.

[0007] As a preferred embodiment, the present invention provides a method for simultaneously removing Pb, Cd and As from soil, using soil contaminated with heavy metals as the treatment target, and using a mass ratio of treatment target to water of 1:8-20, more preferably 1:9-15; the treatment target is added to the aqueous solution and stirred.

[0008] Outdoor soil is air-dried and pulverized at room temperature, then carefully combined to remove any stones or plant roots. The soil is then sieved through a 20-mesh sieve, and the undersize material is used for processing according to this invention.

[0009] In industrial applications, the material passing through a 20-100 mesh sieve, with the undersize material from the 20-mesh sieve and the oversize material from the 100-mesh sieve being the processing objects of this invention.

[0010] Preferably, in this invention, a method for simultaneously removing Pb, Cd, and As from soil involves adding lignin sulfonate at a concentration of 0.1-1% of the mass of the pollutant. More preferably, it is 0.4-0.7%, and even more preferably, 0.49-0.51%. In this invention, selecting an appropriate amount of lignin sulfonate can activate metastable Pb and Cd in contaminated soil into the solution, facilitating precipitation during the electrochemical process. It can also improve the removal rates of Pb, Cd, and As. However, excessive dosage can lead to resource waste and secondary pollution caused by soil foaming; insufficient dosage can result in inadequate effectiveness or low efficiency.

[0011] As a further preferred option, the lignin sulfonate is selected from at least one of calcium lignin sulfonate, potassium lignin sulfonate, and sodium lignin sulfonate.

[0012] The present invention controls the pH of the slurry to be 7-8 because most Pb, Cd and As contaminated soils are generally neutral or weakly alkaline. If the pH is too high, the removal rate of As will decrease; if the pH of the slurry is too low, the removal rate of Pb and Cd will decrease.

[0013] The inert material used as the cathode in this invention is selected from at least one of titanium, graphite, and stainless steel.

[0014] During electrolysis, the rotation speed is controlled at 50-150 rpm.

[0015] During electrolysis, the electrode spacing is 35-45 mm.

[0016] When performing electrolysis in this invention, the preferred processing time is 100-150 minutes.

[0017] When performing electrolysis in this invention, the electrolytic cell is preferably a circular cell.

[0018] Within 2 hours, this invention achieves a 100% removal rate of water-soluble Pb and a removal rate of at least 72% of available Pb in soil; a 100% removal rate of water-soluble Cd and a removal rate of at least 32% of available Cd; a 100% removal rate of water-soluble As and a removal rate of at least 78% of available As; and Pb, Cd, and As are removed simultaneously.

[0019] After optimization, within 2 hours, the removal rate of water-soluble Pb in the soil was 100%, and the removal rate of available Pb was 75%. The removal rate of water-soluble Cd was 100%, and the removal rate of available Cd was as high as 35%. At the same time, the removal rate of water-soluble As was 100%, and the removal rate of available As was as high as 80%.

[0020] Principles and advantages

[0021] This invention proposes a lignin surfactant-assisted electrochemical treatment method to achieve simultaneous and efficient immobilization and removal of As, Cd, and Pb from contaminated soil, such as... Figure 1 As shown in the diagram, in this method, calcium lignin sulfonate (CL), as an anionic surfactant, reacts with metastable Pb and Cd to generate lignin-metal chelate compounds through chelation. The CL surfactant can help desorb and disperse Pb and Cd pollutants from the soil through complexation and ion exchange. Furthermore, an electrochemical device consisting of an iron plate (Fe anode) and a titanium plate (Ti anode) was assembled for pollution remediation. During this process, Fe(II) ions generated at the anode react with Pb, Cd, and As to form precipitates.

[0022] (1) Calcium lignosulfonate (CL) acts as an anionic surfactant, which activates metastable Cd and Pb in polluted soil to a stable state in solution, thus helping to repair Cd and Pb in the electrochemical process.

[0023] (2) Electrochemical treatment method was used to rapidly remediate mixed anodic and cationic contaminants (Pb, Cd and As). Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the present invention;

[0025] Figure 2 This is a schematic diagram illustrating the changes in composition.

[0026] Figure 3 This is a rendering of Example 1;

[0027] Figure 4 This is a rendering of Example 2;

[0028] Figure 5 This is a rendering of Example 3;

[0029] Figure 6 This is a rendering of Example 4;

[0030] Figure 7 This is a rendering of Example 5;

[0031] Figure 8 This is a rendering of Example 6;

[0032] Figure 9 This is a comparison image of Example 1;

[0033] Figure 10 This is the effect diagram for Comparative Example 2;

[0034] Figure 11 This is the effect diagram for Comparative Example 3;

[0035] Figure 12 This is the effect diagram for comparison example 4.

[0036] from Figure 1 The principle of this invention can be seen from this.

[0037] Figure 2 In the images, (a), (b), and (c) represent the original unremediated arsenic, lead, and cadmium-contaminated soil and the arsenic, lead, and cadmium-contaminated soil remediated by an anionic surfactant-enhanced ferroelectric field, respectively. The remediated soils were left to air dry for 90 days. In the original soil, the proportions of lead in the weakly acid-extractable, reducible, oxidizable, and residual states were 18.9%, 76%, 4%, and 1.1%, respectively. After remediation with the ferroelectric field, these proportions changed to 6%, 84%, 8%, and 2%, respectively, with the proportion of lead in the weakly acid-extractable state decreasing by 12.9% and the proportion in the residual state increasing by 0.9%. Similarly, in the original soil, the proportions of cadmium in the weakly acid-extractable, reducible, oxidizable, and residual states were 79%, 18%, 2.4%, and 0.6%, respectively. After remediation with the ferroelectric field, these proportions changed to 78%, 12%, 9%, and 1%, respectively, with the main change being from the reducible to the oxidizable state. In the original soil, the proportions of non-specific adsorption, specific adsorption, amorphous iron-manganese or iron-aluminum oxides, crystalline iron-manganese or iron-aluminum oxides, and residual arsenic were 5.2%, 12.3%, 48.3%, 24%, and 10.2%, respectively. After remediation with a ferroelectric field, these proportions became 0.7%, 6.2%, 44.1%, 26%, and 23%, respectively. The total proportion of non-specific and specific adsorption decreased from 18.5% to 6.9%, while the proportions of amorphous iron-manganese or iron-aluminum oxides and crystalline iron-manganese or iron-aluminum oxides increased, and the residual proportion also increased from 10.2% to 23%. In summary, the data indicate that the effective hazard of arsenic, lead, and cadmium in the soil has been significantly reduced.

[0038] from Figure 3-8 The effects of Examples 1-6 can be seen respectively.

[0039] from Figure 9-12 The effects of comparisons 1-4 can be seen. (Comparison) Figure 3-8 and Figure 9-12 It can be seen that the present invention has achieved remarkable results. Detailed Implementation

[0040] Pb and Cd contaminated soil samples (Sample A) were collected from an abandoned factory in Changde, China. Contaminated soil sample B was collected from another abandoned factory in Changde, China. For the preparation of Pb, Cd, and As contaminated soil samples, Sample A and Sample B were mixed at a mass ratio of 3:1. The samples were air-dried and pulverized at room temperature, then carefully combined to remove any stones or plant roots. The soil was then filtered through a 20-100 mesh sieve and stored for later use. The pH of the soil was tested using a soil-to-water mass ratio of 1:10. The total concentrations of Pb, Cd, and As in the contaminated soil were determined after digestion in a mixed solution of HNO3-HCl-HF using the K. Kameda method. The available contents of Pb, Cd, and Mn in the soil (denoted as E-Pb, E-Pb, and E-Mn, respectively) were determined using previously reported methods (see: Yang, Zhihui, et al. "Iron-doped hydroxyapatite for the simultaneous remediation of lead-, cadmium- and arsenic-co-contaminated soil." Environmental Pollution 312(2022):119953.). The method for determining the water-soluble As content (denoted as W-As) has also been documented in our previous studies (see: Jiang, Zhi, et al. "Cooperative effect of slow-release ferrous and phosphate for simultaneous stabilization of As, Cd, and Pb in soil." Journal of Hazardous Materials 452(2023):131232.). The effective Mn content (denoted as E-Mn) was determined using the reported method (see: Xiang, Hongrui, et al. Natural pyrite-assisted mechanochemical recovery of insoluble manganese from electrolytic manganese residue: kinetics and mechanisms. ACS ES&TEngineering 3.10(2023):1661-1673.).The elemental contents in the soil were determined using a graphite furnace atomic absorption spectrometer (AAS, 240Z, Agilent Technologies Ltd., Malaysia) for Pb and Cd, and an atomic fluorescence spectrophotometer (AFS, HGF-V2, Beijing Haiguang Instruments Co., Ltd., China) for As. A summary of the heavy metal contents in the soil is shown in Table 1.

[0041] Table 1 Heavy metal content in soil

[0042]

[0043] Determination of As, Pb, and Cd content

[0044] (1) Determination of available As, Pb and Cd content: The weighed soil sample was added to DTPA extraction solution (to extract Pb and Cd) at a solid-liquid ratio of 1:5 g / mL or to NaHCO3 solution (to extract As) at a solid-liquid ratio of 1:10 g / mL. The sample was shaken at 180 r / min for two hours at room temperature (25℃±2℃), allowed to stand and filtered, and the As, Pb and Cd content in the filtrate was determined.

[0045] (2) Determination of water-soluble As, Pb and Cd content: Weigh 1.000g of soil sample into a 50mL centrifuge tube, add 10mL of deionized water, shake at 180r / min for two hours at room temperature (25℃±2℃), let stand and filter, and determine the As, Pb and Cd content in the filtrate.

[0046] (3) Determination of total As: Weigh 0.500g of soil sample into a 50mL stoppered colorimetric tube, add 10mL of aqua regia (1+1), digest in a boiling water bath for two hours, shaking the colorimetric tube several times during the process, cool, dilute to the mark, shake well, let stand and filter, and then measure.

[0047] (4) Determination of total Pb and Cd: Weigh 0.500g of soil sample into a polytetrafluoroethylene digestion vessel, add 6mL HCl, 2mL HNO3 and 2mL HF, place it on a microwave digestion instrument, select the soil digestion program, after digestion, take out the inner digestion vessel and place it on an acid removal instrument, add 1mL of perchloric acid to each tube, set the temperature to 160℃, when there is no obvious solid in the vessel and the liquid becomes 1-2mL of yellow viscous liquid, stop the acid removal, pour the liquid in the digestion vessel into a volumetric flask and make up to volume, and also introduce the digestion vessel rinsing solution into the volumetric flask, and set a blank group at the same time.

[0048] The As content in the filtrate was determined using an atomic fluorescence spectrophotometer (AFS), and the Pb and Cd contents in the filtrate were determined using a flame atomic absorption spectrophotometer (AAS).

[0049] Speciation extraction of As, Pb, and Cd

[0050] The chemical sequential extraction method proposed by Wenzel et al. was used to study the changes in As speciation in soil before and after the addition of materials. As in the soil was classified into five speciations, and the specific speciations and extraction steps are shown in Table 2. An improved BCR sequential extraction method was used to study the changes in Pb and Cd speciation in soil before and after the addition of materials; the specific speciations and extraction steps are shown in Table 3.

[0051] Table 2 Extraction of arsenic speciation in soil

[0052]

[0053]

[0054] Table 3 Extraction of cadmium and lead speciation in soil

[0055]

[0056] Example 1

[0057] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:1. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0058] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%; available Pb: 74%; water-soluble Cd: 100%; available Cd: 33%; water-soluble As: 100%; available As: 78%.

[0059] Example 2

[0060] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:0.8. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0061] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%; available Pb: 73%; water-soluble Cd: 100%; available Cd: 32%; water-soluble As: 100%; available As: 79%.

[0062] Example 3

[0063] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:0.6. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0064] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%; available Pb: 72%; water-soluble Cd: 100%; available Cd: 32%; water-soluble As: 100%; available As: 79%.

[0065] Example 4

[0066] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:0.4. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0067] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%; available Pb: 73%; water-soluble Cd: 100%; available Cd: 31%; water-soluble As: 100%; available As: 80%.

[0068] Example 5

[0069] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:0.2. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0070] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%, available Pb: 74%; water-soluble Cd: 100%, available Cd: 32%; water-soluble As: 100%, available As: 79%.

[0071] Example 6

[0072] Using the soil in Table 1 as the treatment object, the mass ratio of treatment object to water is 1:10, and the mass ratio of treatment object to calcium lignosulfonate is 100:0.5. The treatment object is added to water and calcium lignosulfonate is added and stirred evenly to make a slurry. The pH of the slurry is controlled at 8.5. Stir for 1 hour before electrolysis.

[0073] Electrolysis was performed using a dual-electrode electrolysis apparatus. During electrolysis, Fe foil served as the anode and Ti foil as the cathode, with an electrode spacing of 40 mm. 100 g of slurry was introduced into a 300 mL circular electrolytic cell, and the stirring speed was maintained at 100 rpm throughout the electrolysis process. The voltage was 0.5 V, and the treatment time was 120 min. After 120 min, the removal rates were as follows: water-soluble Pb: 100%; available Pb: 75%; water-soluble Cd: 100%; available Cd: 35%; water-soluble As: 100%; available As: 80%.

[0074] Comparative Example 1

[0075] The raw materials and other conditions were the same as in Example 1, except that calcium lignosulfonate was not added. After electrolysis for 120 min, the removal rate of water-soluble Pb was 100%, the removal rate of available Pb was 50%, the removal rate of water-soluble Cd was 100%, the removal rate of available Cd was 10%, the removal rate of water-soluble As was 100%, and the removal rate of available As was 75%.

[0076] Comparative Example 2

[0077] The raw materials and other conditions were the same as in Example 1, except that: the treatment target was calcium lignosulfonate at a ratio of 100:0.05. After 120 min, the removal rate of water-soluble Pb was 100%, the removal rate of available Pb was 65%, the removal rate of water-soluble Cd was 100%, the removal rate of available Cd was 20%, the removal rate of water-soluble As was 100%, and the removal rate of available As was 76%.

[0078] Comparative Example 3

[0079] The raw materials and other conditions were the same as in Example 1, except that: the treatment target was calcium lignosulfonate at a ratio of 1:0.2. After 120 min, the removal rate of water-soluble Pb was 100%, the removal rate of available Pb was 75%, the removal rate of water-soluble Cd was 100%, the removal rate of available Cd was 29%, the removal rate of water-soluble As was 100%, and the removal rate of available As was 79%.

[0080] Comparative Example 4

[0081] The raw materials and other conditions were the same as in Example 1, except that calcium stearate was used instead of calcium lignosulfonate of equal mass. After 120 min, the removal rate of water-soluble Pb was 100%, the removal rate of available Pb was 75%, the removal rate of water-soluble Cd was 100%, the removal rate of available Cd was 32%, the removal rate of water-soluble As was 100%, and the removal rate of available As was 75%.

Claims

1. A method for simultaneously removing Pb, Cd, and As from soil, characterized in that, The process includes the following steps: Using heavy metal-contaminated soil as the treatment target, the soil is added to water and mixed with lignin sulfonate to form a slurry. Then, an iron anode and an inert cathode are used for electrolysis under stirring. During electrolysis, the voltage is controlled at 0.49-0.51V. The amount of lignin sulfonate added is 0.49-0.51% of the mass of the soil being treated. The mass ratio of the object to be treated to water is 1:9-15; add the object to be treated to the aqueous solution and stir. Control the pH of the slurry to 7-8; The inert material used as the cathode is selected from at least one of titanium, graphite, and stainless steel; During electrolysis, the rotation speed is controlled at 50-150 rpm; During electrolysis, the electrode spacing is 35-45 mm; The electrolysis process takes 100-150 minutes. During electrolysis, the electrolytic cell is a circular cell; Within 2 hours, the removal rates of water-soluble Pb in the soil were 100% and the removal rates of available Pb were greater than or equal to 72%; the removal rates of water-soluble Cd were 100% and the removal rates of available Cd were greater than or equal to 32%; the removal rates of water-soluble As were 100% and the removal rates of available As were greater than or equal to 78%; and Pb, Cd and As were removed simultaneously; the lignin sulfonate was selected from at least one of calcium lignin sulfonate, potassium lignin sulfonate, and sodium lignin sulfonate.

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