Composite thallium removal agent for treating thallium-containing wastewater, preparation method and application thereof

Abstract

The invention discloses a composite thallium removal agent for treating thallium-containing wastewater, a preparation method thereof and an application thereof. The composite thallium removal agent comprises the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite. The composite thallium removal agent of the invention can quickly convert thallium ions into large-particle thallium composite precipitates through the mutual cooperation of various effective components, so as to facilitate the efficient purification of thallium-containing wastewater, and has the advantages of low treatment cost, good thallium removal effect and green environmental protection. It is a novel thallium removal agent with excellent thallium removal performance, which can be widely used to treat thallium-containing wastewater of various water qualities, and can realize deep treatment. In particular, through the combined action of processes such as "polyaluminium ferric sulfate + composite thallium removal agent + flocculant", not only high-quality thallium-containing filter residues can be obtained, and the resource recovery and utilization of thallium can be realized, but also the water body can be effectively purified, so that the thallium content in the filtrate is less than 5μg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering, and in particular relates to a composite thallium removal agent for treating thallium-containing wastewater, and a preparation method and application thereof. Background Art

[0002] A large amount of thallium enters the water environment, causing serious environmental pollution problems. At the same time, due to its neurotoxicity, thallium can enter the human body through drinking water and the food chain. It can replace potassium in the enzymatic reaction process of the human body and has a strong affinity with enzymes, which is toxic to the liver and kidneys, and can be fatal in severe cases. Therefore, the harm caused by thallium to the water environment and humans has attracted widespread attention and the environmental protection department has attached great importance to it.

[0003] At present, the main treatment technologies for thallium-containing wastewater include adsorption, membrane, biological and chemical precipitation. In the adsorption method, porous adsorbents and ion exchange resins can be used to adsorb thallium ions in wastewater, but the adsorption method is only applicable to wastewater with an initial concentration of less than 10 μg / L, and has certain requirements for the salt content of the influent, and its adaptability is poor. The membrane method mainly uses nanofiltration membranes and reverse osmosis membranes. Although nanofiltration membranes are not very effective for thallium removal, they are not suitable for wastewater with an initial concentration of less than 10 μg / L. 3+ It has an interception effect, but it has an impact on Tl + The interception effect is poor; although the reverse osmosis membrane can 3+ Ion, Tl + Ions are separated from water, but the pore size of the reverse osmosis membrane is very small, so the water quality requirements for the inlet water are high, and the maximum salinity value that can be tolerated is 3% to 5%. Therefore, it is necessary to effectively remove the dissolved salts, colloids, microorganisms, organic matter, etc. in the wastewater first; in particular, the membrane method also has the defects of high investment cost and high operating cost, which is not conducive to large-scale utilization. The biological method uses the metabolism of microorganisms to absorb the thallium element in the wastewater, and removes the thallium in the wastewater through mud-water separation technology, but the thallium in the wastewater has very strong biological toxicity and will seriously inhibit the growth of microorganisms. Therefore, the heavy metal tolerance and impact resistance of microorganisms are easily affected by thallium, especially for high-concentration thallium wastewater, the adaptability of microorganisms is even worse.

[0004] Compared with the above methods, the chemical precipitation method has the advantages of simple process, convenient operation, low cost, and suitability for large-scale use. It plays an important role in achieving harmless and resourceful treatment of thallium-containing wastewater. However, the existing chemical precipitation method is mainly the sulfide precipitation method, which is based on the principle of converting Tl + It reacts with sulfide to form Tl2S precipitation, thereby removing thallium from the wastewater. The ion product of Tl2S insoluble matter is 5.0×10 -21Theoretically, the maximum thallium concentration in the wastewater is reduced to about 45μg / L, which cannot reach the current emission limit of thallium <5μg / L; at the same time, Tl2S precipitation will decompose into toxic and harmful gas hydrogen sulfide under acidic conditions, and there is a certain risk of secondary pollution. In addition, some researchers have proposed a method for removing thallium ions from wastewater using a specific catalytic oxidation technology. The method first adjusts the pH value of the thallium-containing wastewater to 10-14, adds an oxidant and a catalyst, and oxidizes the monovalent thallium in the wastewater into trivalent thallium through a catalytic oxidation reaction, and forms thallium hydroxide under alkaline conditions, and forms thallium oxide particles after dehydration. Then, under the action of a coagulant, the thallium oxide particles are condensed and the solid-liquid separation is performed to effectively remove the thallium ions in the wastewater. The defects are: (a1) The treatment cycle is long, and the catalytic oxidation time alone is as long as 30 minutes, accounting for more than two-thirds of the total treatment time; (a2) The alkaline conditions are required to be high, and the pH value of the system needs to be maintained at 10-14 during the whole process; (a3) ​​The oxidant and catalyst used are used in large quantities and are expensive, resulting in very high wastewater treatment costs; (a4) The thallium ion content in the filtrate is still high, and the content of other metal ions in the filtrate is still high, which cannot meet the emission standards. Furthermore, researchers have proposed a thallium removal composition and a method for treating thallium-containing wastewater. The effective components of the thallium removal composition are alkaline agents and sulfides. The sulfides include sodium sulfide, sodium hydrosulfide and ferrous sulfide. The alkaline agent and the sulfide can be used in combination without the need to remove thallium. + Oxidation to Tl 3+Under the premise of effective removal of thallium from wastewater, the removal rate is as high as 99%. However, the above-mentioned thallium removal composition and the process for treating thallium-containing wastewater still need to be improved in the following aspects: (b1) The thallium removal effect is poor. With alkaline agents and sulfides as the main components of the precipitant, the ion products of the formed Tl (OH) 3 precipitates, Tl2S precipitates, and Tl2S3 precipitates are all high, which leads to the thallium concentration in the filtrate obtained after the thallium-containing wastewater is treated with alkaline agents and sulfides. It is still as high as 9μg / L, exceeding 5μg / L, which not only fails to meet the thallium emission standards, but also is not conducive to improving the recovery rate of thallium. (b2) There is a risk of secondary pollution. The formed Tl2S precipitates and Tl2S3 precipitates will also release harmful and smelly gases such as hydrogen sulfide under acidic conditions, which is easy to bring secondary pollution risks and is not conducive to subsequent resource utilization. (b3) The treatment process is complicated and the treatment efficiency is low. The combined process of two precipitations and two flocculations is adopted. The process is complicated and the operation is difficult. The treatment time is as long as 19min-60min. In particular, the precipitation time is as long as 30min and the flocculation time is as long as 40min. (b4) The dosage of reagents is large and the cost is high. The adjustment system is strongly alkaline, and a large amount of alkaline reagents are required, which leads to a very large dosage of reagents and a very high cost. In particular, the optimal pH value of the system is above 10, which will further increase the dosage of alkaline reagents, making the cost of reagents higher. (b5) The pH value of the obtained filtrate is strongly alkaline, which will increase the difficulty of subsequent treatment, or a large amount of acidic reagents need to be used to reduce the pH value of the wastewater, which will further increase the difficulty and cost of treatment. Therefore, it is urgent to obtain a composite thallium removal agent with low cost, good thallium removal effect, and green environmental protection, as well as a method for completely purifying thallium-containing wastewater and realizing the resource utilization of thallium-containing wastewater. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a composite thallium removal agent for treating thallium-containing wastewater, which has low cost, good thallium removal effect and is green and environmentally friendly, and a preparation method and application thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A composite thallium remover for treating thallium-containing wastewater comprises the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite; the mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite is 10-14: 5-8: 4-7: 2-4.5: 0.5-3: 1-3.

[0008] The above-mentioned composite thallium removal agent is further improved in that the composite thallium removal agent also includes water, the mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water is 12:6.5:5.5:3.1:1.9:1:100, and the sodium selenite is sodium selenite pentahydrate.

[0009] As a general technical concept, the present invention also provides a method for preparing a composite thallium removal agent for treating thallium-containing wastewater, comprising the following steps: mixing magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water to obtain a composite thallium removal agent; the mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water is 10-14:5-8:4-7:2-4.5:0.5-3:1-3:100.

[0010] As a general technical concept, the present invention also provides an application of the above-mentioned composite thallium removal agent in treating thallium-containing wastewater.

[0011] The above application, further improved, comprises the following steps:

[0012] S1, mixing polyaluminium ferric sulfate and thallium-containing wastewater, stirring to obtain a mixed solution A;

[0013] S2, adjusting the pH value of the mixed solution A obtained in step S1 to 8-9 to obtain a mixed solution B;

[0014] S3, adding a composite thallium removal agent to the mixed solution B obtained in step S2 to carry out a precipitation reaction to obtain a mixed solution C;

[0015] S4. Add a flocculant to the mixed solution C obtained in step S3 for flocculation treatment, let it stand, and filter to complete the treatment of the thallium-containing wastewater.

[0016] The above application is further improved, in step S1, the polyaluminum ferric sulfate is added to the thallium-containing wastewater in the form of a polyaluminum ferric sulfate solution, the volume ratio of the polyaluminum ferric sulfate solution to the thallium-containing wastewater is 0.1-0.3:100, and the mass percentage concentration of the polyaluminum ferric sulfate solution is 25%-35%;

[0017] In step S3, the volume ratio of the composite thallium removal agent to the thallium-containing wastewater is 0.5-1.5:100;

[0018] In step S4, the volume ratio of the flocculant to the thallium-containing wastewater is 0.1-0.3:100, the flocculant is a polyacrylamide solution, and the mass percentage concentration of the polyacrylamide solution is 0.1%.

[0019] The above application is further improved in that the volume ratio of the polyaluminum ferric sulfate solution to the thallium-containing wastewater is 0.3:100; the volume ratio of the composite thallium removal agent to the thallium-containing wastewater is 1-1.5:100.

[0020] The above application is further improved in that the concentration of thallium in the thallium-containing wastewater is ≤100 mg / L.

[0021] The above application is further improved, in step S1, the stirring time is 3min to 10min;

[0022] In step S2, calcium oxide is used to adjust the pH value of the mixed solution A obtained in step S1;

[0023] In step S3, the precipitation reaction time is 8 min to 15 min;

[0024] In step S4, the flocculation treatment time is 5 min to 10 min, and the standing time is 30 min to 60 min.

[0025] The above application is further improved in that step S4 further includes the following processing: collecting filter residues produced during the filtering process and recovering thallium from the filter residues.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) In view of the defects and shortcomings of existing thallium removal agents, such as poor thallium removal effect, low thallium removal efficiency, high thallium removal cost, and secondary pollution, the present invention creatively provides a composite thallium removal agent for treating thallium-containing wastewater, which uses magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, and sodium selenite as raw material components, and compound them into a composite thallium removal agent with good flocculation effect and good precipitation effect according to a mass ratio of 10-14:5-8:4-7:2-4.5:0.5-3:1-3. When the composite thallium removal agent is used to treat thallium-containing wastewater, on the one hand, under the action of sodium selenite, thallium ions in the wastewater can be quickly converted into thallium composite precipitates. Due to the thallium composite precipitates, The ion product is very low, and is much lower than the ion product of Tl2S insoluble matter, so it is conducive to separating the composite precipitate from the wastewater. On the other hand, under the synergistic effect of magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate and sodium citrate, the composite thallium removal agent has a very excellent flocculation effect, and can also promote the conversion of thallium ions into thallium composite precipitates, and can promote the particle size of thallium composite precipitates to become larger, forming large-particle precipitation. It can be seen that the composite thallium removal agent of the present invention can quickly convert thallium ions into large-particle thallium composite precipitates through the mutual cooperation of each effective ingredient, so as to effectively remove the thallium ions in the wastewater, and facilitate the efficient purification of thallium-containing wastewater. More importantly, the composite thallium removal agent of the present invention has low requirements for the water quality of wastewater, and does not require strong alkaline conditions, so it can be applied to thallium-containing wastewater of different water qualities, and is more convenient to use, which is conducive to reducing the treatment cost of wastewater. In addition, each raw material component used in the composite thallium removal agent of the present invention has a wide source and low price, which is conducive to significantly reducing the processing cost. The composite thallium removal agent of the present invention has the advantages of low cost, good thallium removal effect, green environmental protection, etc. It is a new type of composite thallium removal agent that does not require oxidation conversion treatment and has a good thallium removal effect. It can be widely used to treat thallium-containing wastewater of various water qualities, and can achieve deep treatment of these thallium-containing wastewaters, with high use value and good application prospects.

[0028] (2) In view of the defects and shortcomings of existing thallium removal agents, such as poor thallium removal effect, low thallium removal efficiency, high thallium removal cost, secondary pollution, and step-by-step use, the present invention creatively provides a method for preparing a composite thallium removal agent for treating thallium-containing wastewater. Magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite, and water are used as raw material components, and they are mixed in a mass ratio of 10-14:5-8:4-7:2-4.5:0.5-3:1-3:100 to obtain a composite thallium removal agent with good flocculation effect and good precipitation effect. The composite thallium removal agent can be directly used to treat thallium-containing wastewater. It is not only simple to use and easy to store, but also can effectively remove thallium ions in wastewater, which is conducive to the large-scale treatment of thallium-containing wastewater.

[0029] (3) In view of the defects and shortcomings of the existing thallium-containing wastewater treatment process, such as poor thallium removal effect, complicated treatment process, low treatment efficiency, large amount of reagents, high treatment cost, difficulty in subsequent treatment and reuse, and risk of secondary pollution, the present invention creatively provides an application of a composite thallium removal agent in the treatment of thallium-containing wastewater, specifically: firstly, polyaluminum ferric sulfate and thallium-containing wastewater are mixed and stirred. In this process, polyaluminum ferric sulfate is used as a capture agent, which can serve as the nucleus of the precipitate to promote the subsequent precipitation reaction and strengthen the precipitation reaction. The method can achieve the desired effect. Further, the pH value of the mixed solution obtained after the polyaluminum ferric sulfate treatment is adjusted to 8-9, and a composite thallium removal agent is added. The effective components in the composite thallium removal agent react chemically with thallium ions and are quickly converted into large-particle thallium composite precipitates. Finally, a flocculant is added. The flocculation effect of the flocculant promotes the agglomeration of the thallium composite precipitates, improves the sedimentation effect, and effectively separates the wastewater from the thallium composite precipitates through filtration, thereby achieving deep purification and resource recovery of thallium-containing wastewater. In the present invention, by utilizing the combined effect of the processes such as "polyaluminium ferric sulfate+composite thallium removal agent+flocculating agent", thallium ions in wastewater can be quickly and deeply removed, not only can high-quality thallium-containing filter residue be obtained to realize the resource recovery and utilization of thallium, but also the water body can be effectively purified so that the thallium content in the filtrate is less than 5μg / L, meeting the thallium emission standard specified in the "Inorganic Chemical Industry Pollution Emission Standard" (GB31573-2015). The process has the advantages of simple process, convenient operation, low processing cost, high processing efficiency, good thallium removal effect, low secondary pollution risk, etc., and is of great significance for efficiently purifying thallium-containing wastewater and realizing the resource recovery and utilization of thallium. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the process of treating thallium-containing wastewater with the composite thallium removal agent in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0032] Embodiment 1:

[0033] The invention discloses a composite thallium removing agent for treating thallium-containing wastewater, which is composed of the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water; wherein the mass ratio of magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water is 12:6.5:5.5:3.1:1.9:1:100.

[0034] A preparation method of a composite thallium remover for treating thallium-containing wastewater of the present embodiment comprises the following steps: dissolving magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite pentahydrate in water according to the mass ratio of each raw material component in the composite thallium remover, and mixing them uniformly to obtain the composite thallium remover.

[0035] An application of the composite thallium removal agent prepared in the above embodiment in treating thallium-containing wastewater is to treat the thallium-containing wastewater by using a combined process of "polyaluminium ferric sulfate + composite thallium removal agent + flocculant". The treatment process flow chart is as follows: Figure 1 As shown, the following steps are included:

[0036] Take 100 mL of thallium-containing wastewater with a concentration of 3.41 mg / L, add 0.3 mL of polyaluminum ferric sulfate (PAFS) solution, the mass percentage concentration of which is 30%, and stir for 5 minutes. Use polyaluminum ferric sulfate as a capture agent and as the core of the precipitate to promote the subsequent precipitation reaction and enhance the effect of the precipitation reaction; add CaO emulsion to adjust the pH value to 8.5; add 1 mL of the composite thallium removal agent prepared in Example 1 for precipitation reaction, stir for 10 minutes, and use the composite thallium removal agent and The thallium ions in the wastewater undergo a precipitation reaction, so that the thallium ions in the wastewater can be quickly converted into thallium composite precipitates; finally, 0.3mL of polyacrylamide (PAM) solution (the mass percentage concentration of the solution is 0.1%) is added for flocculation treatment and stirred for 5 minutes. The flocculation effect of the flocculant is used to promote the agglomeration of the thallium composite precipitates in the wastewater and improve the sedimentation effect. The solution is allowed to stand for 30 minutes and filtered to obtain a filtrate and a filter residue. The filtrate is discharged after meeting the standards, and the filter residue is reused to recover heavy metals to complete the treatment of thallium-containing wastewater.

[0037] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of the composite thallium removal agent for thallium-containing wastewater was calculated. The results are shown in Table 1.

[0038] After sampling and analysis, the content of thallium (Tl) in the above filtrate was 1.7μg / L.

[0039] Embodiment 2:

[0040] The invention discloses a composite thallium removing agent for treating thallium-containing wastewater, which is composed of the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water; wherein the mass ratio of magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water is 12:6.5:5.5:3.1:1.9:2:100.

[0041] A preparation method of a composite thallium remover for treating thallium-containing wastewater of the present embodiment comprises the following steps: dissolving magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite pentahydrate in water according to the mass ratio of each raw material component in the composite thallium remover, and mixing them uniformly to obtain the composite thallium remover.

[0042] The application of the composite thallium removal agent prepared in the above-mentioned embodiment in treating thallium-containing wastewater is basically the same as the application method in embodiment 1, with the only difference being that the composite thallium removal agent prepared in embodiment 2 replaces the composite thallium removal agent prepared in embodiment 1.

[0043] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of the composite thallium removal agent for thallium-containing wastewater was calculated. The results are shown in Table 1.

[0044] Embodiment 3:

[0045] The invention discloses a composite thallium removing agent for treating thallium-containing wastewater, which is composed of the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water; wherein the mass ratio of magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite pentahydrate and water is 12:6.5:5.5:3.1:1.9:3:100.

[0046] A preparation method of a composite thallium remover for treating thallium-containing wastewater of the present embodiment comprises the following steps: dissolving magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite pentahydrate in water according to the mass ratio of each raw material component in the composite thallium remover, and mixing them uniformly to obtain the composite thallium remover.

[0047] The application of the composite thallium removal agent prepared in the above-mentioned embodiment in treating thallium-containing wastewater is basically the same as the application method in Example 1, with the only difference being that the composite thallium removal agent prepared in Example 3 replaces the composite thallium removal agent prepared in Example 1.

[0048] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of the composite thallium removal agent for thallium-containing wastewater was calculated. The results are shown in Table 1.

[0049] Comparative Example 1:

[0050] A composite thallium removal agent is composed of the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and water; wherein the mass ratio of magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and water is 12:6.5:5.5:3.1:1.9:100.

[0051] A preparation method of a composite thallium remover comprises the following steps: dissolving magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate and sodium citrate in water according to the mass ratio of each raw material component in the composite thallium remover, and mixing them evenly to obtain the composite thallium remover.

[0052] The application of the composite thallium removal agent prepared in the above comparative example in treating thallium-containing wastewater is basically the same as the application method in Example 1, with the only difference being that the composite thallium removal agent prepared in Comparative Example 1 replaces the composite thallium removal agent prepared in Example 1.

[0053] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of the composite thallium removal agent for thallium-containing wastewater was calculated. The results are shown in Table 1.

[0054] Comparative Example 2:

[0055] A method for treating thallium-containing wastewater using a composite thallium removal agent is basically the same as the application method of Example 1, except that: in Comparative Example 2, no polyaluminium ferric sulfate (PAFS) solution is added.

[0056] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of thallium-containing wastewater by the treatment method was calculated. The results are shown in Table 1.

[0057] Comparative Example 3:

[0058] A method for treating thallium-containing wastewater using sulfide is basically the same as the application method of Example 1, with the only difference being that in Comparative Example 3, a ferrous sulfide solution is used instead of the composite thallium removal agent solution in Example 1, wherein the ferrous sulfide solution is prepared by mixing ferrous sulfide and water, and the mass ratio of ferrous sulfide to water is 3:100.

[0059] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of thallium-containing wastewater by the treatment method was calculated. The results are shown in Table 1.

[0060] Comparative Example 4:

[0061] A method for treating thallium-containing wastewater using sodium selenite is basically the same as the application method of Example 1, except that in Comparative Example 4, a sodium selenite solution is used instead of the composite thallium removal agent solution in Example 1, wherein the sodium selenite solution is prepared by mixing sodium selenite with water, and the mass ratio of sodium selenite to water is 3:100.

[0062] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of thallium-containing wastewater by the treatment method was calculated. The results are shown in Table 1.

[0063] Table 1 Comparison of the effects of different composite thallium removal agents on thallium-containing wastewater

[0064]

[0065] As can be seen from Table 1, the composite thallium removal agents prepared in Examples 1 to 3 have very good thallium removal effects, and can reduce thallium in wastewater to below 2 μg / L. The composite thallium removal agent prepared in Comparative Example 1 is not ideal for thallium removal because sodium selenite pentahydrate is not added, and cannot meet relevant emission standards. The method of Comparative Example 2 uses the process of "composite thallium removal agent + flocculant" to treat thallium-containing wastewater. Since polyaluminum ferric sulfate is not added as a capture agent, it is not conducive to the subsequent precipitation reaction, resulting in an unsatisfactory thallium removal effect, which cannot meet relevant emission standards. The method of Comparative Example 3 uses ferrous sulfide solution as a precipitant, and the thallium removal effect is not ideal, and cannot meet relevant emission standards. The method of Comparative Example 4, when sodium selenite solution is used alone as a precipitant, has a very poor thallium removal effect. It can be seen that in the present invention, by utilizing the combined action of the processes such as "polyaluminum ferric sulfate + composite thallium removal agent + flocculant", thallium ions in wastewater can be removed quickly and deeply.

[0066] Embodiment 4:

[0067] An application of the composite thallium removal agent of the present invention in treating thallium-containing wastewater is to treat the thallium-containing wastewater by using a combined process of "polyaluminium ferric sulfate + composite thallium removal agent + flocculant", comprising the following steps:

[0068] 100 mL of industrial wastewater from a nonferrous metal smelter was taken, the thallium content of the industrial wastewater was 5.673 mg / L, 0.3 mL of polyaluminum ferric sulfate (PAFS) solution was added, the mass percentage concentration of the polyaluminum ferric sulfate solution was 30%, and the mixture was stirred for 5 minutes. CaO was added to adjust the pH to 8.5, 1 mL of the composite thallium removal agent prepared in Example 1 was added for precipitation reaction, and the mixture was stirred for 10 minutes. The composite thallium removal agent was used to react with the thallium ions in the wastewater to react with the thallium ions in the wastewater so that the thallium ions in the wastewater could be quickly converted into thallium composite precipitates. Finally, 0.3 mL of polyacrylamide (PAM) solution (the mass percentage concentration of the solution was 0.1%) was added for flocculation treatment, and the mixture was stirred for 5 minutes. The flocculation effect of the flocculant was used to promote the agglomeration of the thallium composite precipitates in the wastewater and improve the sedimentation effect. The mixture was allowed to stand for 30 minutes, and filtered to obtain a filtrate and a filter residue. The filtrate was discharged after reaching the standard, and the filter residue was returned to recover the heavy metals, thereby completing the treatment of the thallium-containing wastewater.

[0069] The filtrate was tested to obtain the concentration of residual thallium (Tl) in the filtrate, and the removal rate of thallium-containing wastewater by the treatment method was calculated. The results are shown in Table 2.

[0070] After sampling and analysis, the content of thallium (Tl) in the above filtrate was 2.1μg / L.

[0071] In this example, the effect of different pH values ​​on the thallium removal effect of thallium-containing wastewater was also investigated, as shown in Table 2. Except for the different pH values, other conditions were the same as those in Example 4.

[0072] Table 2 Comparison of Thallium Removal Effects of Thallium-Containing Wastewater under Different pH Conditions

[0073]

[0074] It can be seen from Table 2 that when the pH value of the thallium-containing wastewater / polyaluminium ferric sulfate system is 7 or 10, the thallium removal effect is not good and cannot meet the requirements; when the pH value of the thallium-containing wastewater / polyaluminium ferric sulfate system is between 8 and 9, the thallium removal effect is good, and the thallium content of the filtrate after treatment is <5μg / L, which can meet the thallium emission standards specified in the "Inorganic Chemical Industry Pollution Emission Standards" (GB31573-2015).

[0075] In this embodiment, the effects of different amounts of polyaluminium ferric sulfate solution on the removal of thallium from thallium-containing wastewater are also investigated, as shown in Table 3. Except for the different amounts of polyaluminium ferric sulfate solution, other conditions are the same as those in Example 4.

[0076] Table 3 Comparison of thallium removal effects of thallium-containing wastewater under different polyaluminium ferric sulfate solution dosage conditions

[0077]

[0078] It can be seen from Table 3 that when the dosage of the polyaluminum ferric sulfate solution is 0.1mL~0.4mL, the thallium removal effect is good, and the thallium content of the filtrate after treatment is <5μg / L, which meets the thallium emission standard specified in the "Inorganic Chemical Industry Pollution Emission Standard" (GB31573-2015); and increasing the dosage of the polyaluminum ferric sulfate solution has little effect on the thallium removal effect, so the dosage of the polyaluminum ferric sulfate solution is preferably 0.1mL~0.3mL, which is beneficial to reducing the cost of using the agent.

[0079] In this example, the effects of different amounts of composite thallium removal agents on the thallium removal effect of thallium-containing wastewater were also investigated, as shown in Table 4. Except for the different amounts of composite thallium removal agents, other conditions were the same as those in Example 4.

[0080] Table 4 Comparison of thallium removal effects of thallium-containing wastewater under different dosages of composite thallium removal agents

[0081]

[0082] It can be seen from Table 4 that when the dosage of the composite thallium removal agent is 0.3 mL, the thallium removal effect is not ideal, and the thallium in the filtrate is 5.7 μg / L, which does not meet the thallium emission standard specified in the "Inorganic Chemical Industry Pollution Emission Standard" (GB31573-2015); when the dosage of the composite thallium removal agent is between 0.5 mL and 2.0 mL, the thallium removal effect is good, and the thallium content of the filtrate after treatment is <5 μg / L, which can meet the thallium emission standard specified in the "Inorganic Chemical Industry Pollution Emission Standard" (GB31573-2015); because increasing the dosage of the composite thallium removal agent has little effect on the thallium removal effect, the dosage of the composite thallium removal agent is preferably 0.5 mL to 1.5 mL, which is beneficial to reducing the cost of the agent.

[0083] It can be seen from the above results that compared with conventional thallium removal agents, the composite thallium removal agent of the present invention has the advantages of low cost, good thallium removal effect, and green environmental protection. It is a new type of composite thallium removal agent that does not require oxidation conversion treatment and has a good thallium removal effect. It can be widely used to treat thallium-containing wastewater of various water qualities, and can achieve deep treatment of these thallium-containing wastewaters. It has high use value and good application prospects. In addition, in the present invention, by utilizing the combined effect of the processes such as "polyaluminum sulfate iron+composite thallium removal agent+flocculating agent", thallium ions in wastewater can be quickly and deeply removed, not only can high-quality thallium-containing filter residues be obtained to realize the resource recovery and utilization of thallium, but also the water body can be effectively purified, so that the thallium content in the filtrate is <5μg / L, meeting the thallium emission standard specified in the "Inorganic Chemical Industry Pollution Emission Standard" (GB31573-2015). It has the advantages of simple process, convenient operation, low processing cost, high processing efficiency, good thallium removal effect, and low secondary pollution risk, which is of great significance for efficiently purifying thallium-containing wastewater and realizing the resource recovery and utilization of thallium.

[0084] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A composite thallium removal agent for treating thallium-containing wastewater, characterized in that: The composite thallium removal agent comprises the following raw material components: magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite; the mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate and sodium selenite is 10-14:5-8:4-7:2-4.5:0.5-3:1-3.

2. The composite thallium removal agent for treating thallium-containing wastewater according to claim 1, characterized in that: The composite thallium removal agent also includes water. The mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water is 12:6.5:5.5:3.1:1.9:1:100, and the sodium selenite is sodium selenite pentahydrate.

3. A method for preparing a composite thallium removal agent for treating thallium-containing wastewater, characterized in that: The following steps are involved: Magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water are mixed to obtain a composite thallium removal agent; the mass ratio of the magnesium sulfate, potassium phosphate, ferrous sulfide, sodium alginate, sodium citrate, sodium selenite and water is 10-14:5-8:4-7:2-4.5:0.5-3:1-3:

100.

4. Use of the composite thallium-removing agent as claimed in claim 1 or 2 or the composite thallium-removing agent prepared by the preparation method as claimed in claim 3 in treating thallium-containing wastewater.

5. The use according to claim 4, characterized in that: The following steps are involved: S1, mixing polyaluminium ferric sulfate and thallium-containing wastewater, stirring to obtain a mixed solution A; S2, adjusting the pH value of the mixed solution A obtained in step S1 to 8-9 to obtain a mixed solution B; S3, adding a composite thallium removal agent to the mixed solution B obtained in step S2 to carry out a precipitation reaction to obtain a mixed solution C; S4. Add a flocculant to the mixed solution C obtained in step S3 for flocculation treatment, let it stand, and filter to complete the treatment of the thallium-containing wastewater.

6. The use according to claim 5, characterized in that: In step S1, the polyaluminum ferric sulfate is added to the thallium-containing wastewater in the form of a polyaluminum ferric sulfate solution, the volume ratio of the polyaluminum ferric sulfate solution to the thallium-containing wastewater is 0.1-0.3:100, and the mass percentage concentration of the polyaluminum ferric sulfate solution is 25%-35%; In step S3, the volume ratio of the composite thallium removal agent to the thallium-containing wastewater is 0.5-1.5:100; In step S4, the volume ratio of the flocculant to the thallium-containing wastewater is 0.1-0.3:100, the flocculant is a polyacrylamide solution, and the mass percentage concentration of the polyacrylamide solution is 0.1%.

7. The use according to claim 6, characterized in that: The volume ratio of the polyaluminium ferric sulfate solution to the thallium-containing wastewater is 0.3:100; the volume ratio of the composite thallium removal agent to the thallium-containing wastewater is 1-1.5:

100.

8. The use according to claim 7, characterized in that: The concentration of thallium in the thallium-containing wastewater is ≤100 mg / L.

9. The use according to any one of claims 5 to 8, characterized in that: In step S1, the stirring time is 3 min to 10 min; In step S2, calcium oxide is used to adjust the pH value of the mixed solution A obtained in step S1; In step S3, the precipitation reaction time is 8 min to 15 min; In step S4, the flocculation treatment time is 5 min to 10 min, and the standing time is 30 min to 60 min.

10. The use according to any one of claims 5 to 8, characterized in that: Step S4 also includes the following processing: collecting filter residues produced during the filtering process, and recovering thallium from the filter residues.

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