A composite precipitant for removing phosphate or arsenate pollution from water, and its preparation method and use method

Abstract

The present invention relates to a composite precipitant for removing phosphate or arsenate pollution from water, and a preparation method and a use method thereof. The composite precipitant for removing phosphate or arsenate pollution from water comprises a precipitant A and a precipitant B, wherein the precipitant A comprises an ammonium salt solution and a strong acid solution; the ammonium salt is selected from at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium molybdate, and the strong acid is selected from at least one of nitric acid, sulfuric acid, and hydrochloric acid; the precipitant B comprises a solution prepared by a surfactant, and the surfactant is preferably at least one of a sulfonate, a quaternary ammonium salt, and a halogen salt. The composite precipitant of the present invention has excellent selectivity, anti-interference ability, and deep removal performance for phosphate or arsenate pollutants.

Description

Technical Field

[0001] The invention relates to water treatment technology, in particular to a composite precipitant for removing phosphate or arsenate pollution from water, and a preparation method and a use method thereof. Background Art

[0002] With the global population growth and the rapid development of agriculture and industry, eutrophication of water bodies has become an increasingly important problem that cannot be ignored. According to the 2020 "China Ecological Environment Bulletin" published by the Ministry of Environment, among the 110 important lakes (reservoirs) tested for nutrient status, 9.1% were oligotrophic lakes (reservoirs), 61.8% were mesotrophic, 23.6% were mildly eutrophic, 4.5% were moderately eutrophic, and 0.9% were severely eutrophic. It can be seen that the eutrophication of water bodies in my country is severe and the situation is not optimistic. People and nature are interdependent and influence each other. If the eutrophication of water bodies destroys the ecosystem as the initial result, then the final outcome must be a threat to human beings themselves. Therefore, under the current concept of sustainable development upheld by mankind, it is particularly important to seek prevention and control measures for eutrophic water bodies. Phosphorus is one of the main elements causing eutrophication of water bodies, but because the input pathways of phosphorus are diverse and complex, it is difficult to completely remove it. In addition, arsenic, which is in the same main group as phosphorus, has similar properties to phosphate in structure. It comes from natural volcanic eruptions or metal mineral mining and industrial wastewater, causing serious pollution to the natural environment. The inorganic form of arsenic is more toxic than the organic form. In order to protect human health, the World Health Organization (WHO) stipulates that the arsenic concentration in drinking water should not exceed 10μg / L. At present, various methods for removing phosphate or arsenate from water bodies are emerging in an endless stream, such as coagulation precipitation, ion exchange, adsorption, membrane separation, electrodialysis, etc. These methods have their own advantages and disadvantages and application environment limitations. Therefore, it is very worthwhile to explore a method for efficient, highly selective and deep removal of phosphate or arsenate from water bodies.

[0003] Currently, the main methods reported for removing phosphate or arsenate from water bodies are: ① biological method; ② chemical precipitation method; ③ adsorption method; ④ membrane filtration method; ⑤ electrochemical method. Among them, the biological method has a high removal rate, but the infrastructure it relies on is huge, costly, and complex to operate. Although the chemical precipitation method is low-cost, a large amount of chemical reagents need to be added during the process, which is easy to cause secondary pollution, and is greatly affected by the pH of the treated liquid. A large amount of sludge containing sediments needs further treatment. Although the electrochemical method is efficient, stable, and easy to control, it has high operating costs and consumes a large amount of electrode materials. Adsorption and membrane separation methods can recover the adsorbed or intercepted phosphate or arsenate, but the regeneration of the adsorbent will produce a large amount of concentrated brine containing arsenic and phosphorus, which requires secondary treatment. Summary of the invention

[0004] In view of the shortcomings of existing methods for removing phosphate or arsenate, the present invention proposes a composite precipitant for removing phosphate or arsenate pollution in water, and a preparation method and a use method thereof. The composite precipitant has excellent selectivity, anti-interference ability and deep removal performance for phosphate or arsenate pollutants.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A composite precipitant for removing phosphate or arsenate pollution from water, comprising precipitant A and precipitant B, wherein:

[0007] The precipitant A comprises an ammonium salt solution and a strong acid solution; the ammonium salt is selected from at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium molybdate, and the strong acid is selected from at least one of nitric acid, sulfuric acid, and hydrochloric acid;

[0008] The precipitant B comprises a solution prepared with a surfactant, and the surfactant is preferably at least one of a sulfonate, a quaternary ammonium salt, and a halogen salt.

[0009] Of course, the present invention can process phosphate and arsenate simultaneously, and it is only necessary to increase the dosage of precipitant A and precipitant B simultaneously.

[0010] The preparation process of the precipitant A is as follows:

[0011] 8.5-18.5g ammonium salt is dissolved in 100ml distilled water, and the mass percentage concentration (%) = (mass of solute / mass of solution) × 100%, and the mass percentage concentration of ammonium salt in the ammonium salt solution is 8.5% to 18.5%. Then add it to 300mL of 5.5-12.5mol / L strong acid to complete the preparation. It can be seen that the volume ratio of ammonium salt solution to strong acid solution is 1:4-1:2.

[0012] The preparation process of the precipitant B is as follows:

[0013] Take 0.01-1.0g of surfactant and dissolve it in 100mL of distilled water, and the mass percentage concentration (%) = (solute mass / solution mass) × 100%, and the mass percentage concentration of the surfactant in the surfactant solution is 0.01% to 1%.

[0014] The volume ratio of precipitant A to precipitant B is 1:100-1:20.

[0015] A method for removing phosphate or arsenate:

[0016] Measure or estimate the concentration of phosphate or arsenate (convenient and simple to measure);

[0017] Add precipitant B and precipitant A, and wait for the reaction to be completed;

[0018] Measure the residual concentration of phosphate or arsenate, and add a composite precipitant for secondary treatment as appropriate.

[0019] Or add too much at the beginning.

[0020] After the reaction is completed, the supernatant is filtered with a 0.45 μm filter membrane, and the phosphate in the filtrate is determined by a UV-visible spectrophotometer using the molybdenum blue method, or the arsenate in the filtrate is determined by an atomic absorption spectrophotometer, to prove that the phosphate or arsenate can be co-precipitated with the precipitant A or precipitant B, thereby achieving the removal of the phosphate or arsenate.

[0021] The principle of removing phosphate or arsenate in the present invention is:

[0022] The first step: arsenic / phosphate + molybdate = arsenic / phosphomolybdic acid;

[0023] Step 2: Arsenic / phosphomolybdic acid + quaternary ammonium salt of bromine == precipitation + ammonium bromide.

[0024] It can be seen from the above technical solutions that the present invention has the following advantages:

[0025] The present invention has the following advantages and effects:

[0026] (1) Precipitant A and precipitant B act as co-precipitants and react completely according to stoichiometry, and have a very excellent deep removal effect on extremely high or extremely low concentrations of phosphate or arsenate, and the precipitation process does not produce secondary pollution. The removal rate of phosphate and arsenate is 84-100% (1-40 mg / L), achieving efficient, highly selective, and deep coagulation and precipitation removal of phosphate or arsenate.

[0027] (2) The process is simple and easy to operate. The precipitation process does not consume too much energy and only requires simple oscillation.

[0028] (3) The raw materials of the precipitant are widely available and inexpensive, and have good application prospects in the treatment of a series of complex wastewaters containing phosphate or arsenate with high background values. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a bar graph of the removal efficiency of arsenate at different concentrations in the leachate of kitchen waste in Example 1;

[0030] Figure 2 It is a bar graph of phosphate removal efficiency at different concentrations in the leachate of kitchen waste in Example 1;

[0031] Figure 3 This is a flocculation diagram of arsenate or phosphate according to Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to allow those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below in conjunction with the accompanying drawings.

[0033] Example 1

[0034] In this embodiment, phosphate and arsenate were added to the leachate of kitchen waste for experiments. The difference between the two groups is that phosphate or arsenate is added, and other experimental conditions are the same.

[0035] Phosphate or arsenate is added to the leachate of food waste and mixed. The concentration of phosphate or arsenate is 10-50 mg / L. Precipitant A and precipitant B are added to the leachate of food waste as precipitants. The pure aqueous solution of phosphate or arsenate is used as a reference. Coagulation and precipitation are carried out for 10 minutes at room temperature. The results show that the removal rate of phosphate or arsenate is 100% at 10-40 mg / L, and the removal rate of pentavalent arsenic at 50 mg / L drops to 73%, while the removal rate of phosphate at 50 mg / L is still 100%. This shows that the precipitation is basically not affected by the high concentration of background organic matter or coexisting salt ions in the leachate.

[0036] (1) Operating conditions

[0037] Phosphate or arsenate mass concentration: 10-50 mg / L, addition amount: 0.1 mL; Preparation of precipitant A: 13.5 g ammonium molybdate dissolved in 100 mL distilled water, then added to 300 mL 9 mol / L sulfuric acid, precipitant A dosage: 0.3 mL; Preparation of precipitant B: 0.1 g hexadecyltrimethylammonium bromide surfactant dissolved in 100 mL distilled water, precipitant B dosage: 10 mL;

[0038] The leachate from food waste comes from Shanghai Wenxin Biotechnology Co., Ltd., and the dilution ratio of the leachate from food waste is 1:10 as an example for illustration.

[0039] Reaction vessel diameter: 2.5 cm, height: 15 cm;

[0040] Reaction temperature: room temperature.

[0041] (2) Experimental results

[0042] Phosphate or arsenate was added to the leachate of kitchen waste at a dilution ratio of 1:10, so that the concentration of phosphate or arsenate in the leachate was 10, 20, 30, 40, and 50 mg / L, respectively. 10 mL of precipitant B was added to each colorimetric tube containing leachate, and then 0.3 mL of precipitant A was added. The coagulation and precipitation were carried out at room temperature for 10 minutes. The removal results are shown in the table below. Figure 1 and Figure 2The colors of the coprecipitates formed by precipitants A and B with pure water without phosphate / arsenate, arsenate solution, and phosphate solution during the coagulation and precipitation process are shown in Table 2. Figure 3 .

[0043] Example 2

[0044] In this example, phosphate and arsenate were added to the water to conduct experiments. The difference between the two groups was that phosphate or arsenate was added, and other experimental conditions were the same.

[0045] Precipitant A and Precipitant B were used as precipitants to deeply remove trace phosphate or arsenate in water. The concentration of phosphate or arsenate in water was 1 mg / L. The pure aqueous solution of phosphate or arsenate was used as a reference, and coagulation and precipitation were performed for 10 minutes at room temperature. The removal rates of phosphate or arsenate at 1 mg / L were 94% and 100% respectively. This shows that this method can achieve the effect of deep removal of trace phosphate and arsenate in water.

[0046] (1) Operating conditions

[0047] Phosphate or arsenate mass concentration: 1 mg / L, added in an amount of 0.1 mL; Prepare precipitant A: 13.5 g ammonium molybdate is dissolved in 100 mL distilled water, then added to 300 mL 9 mol / L sulfuric acid, precipitant A dosage: 0.3 mL; Prepare precipitant B: 0.1 g hexadecyltrimethylammonium bromide surfactant or hexadecyltrimethylammonium chloride surfactant is dissolved in 100 mL distilled water, precipitant B dosage: 10 mL;

[0048] Reaction vessel diameter: 2.5 cm, height: 15 cm;

[0049] Reaction temperature: room temperature.

[0050] (2) Experimental results

[0051] When the precipitant A is the same, the removal results of 1 mg / L arsenate or phosphate by hexadecyltrimethylammonium bromide surfactant or hexadecyltrimethylammonium chloride surfactant are shown in Table 1.

[0052] Table 1 Removal efficiency of trace arsenate or phosphate

[0053]

[0054] Continue to add precipitant A and precipitant B to make the total amount of precipitant A reach 0.6 mL and the total amount of precipitant B reach 20 mL. The removal results of 1 mg / L arsenate or phosphate are shown in Table 2.

[0055] Table 2 Removal efficiency of trace arsenate or phosphate

[0056]

[0057] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. Application of a composite precipitant in removing phosphate and arsenate pollution from water, characterized in that: The composite precipitant comprises precipitant A and precipitant B, wherein the volume ratio of precipitant A to precipitant B is 1:100-1:20, wherein: The precipitant A comprises a mixed solution of an ammonium salt solution and a strong acid solution; the mass percentage concentration of the ammonium salt in the ammonium salt solution in the precipitant A is 8.5% to 18.5%, the concentration of the strong acid solution is 5.5-12.5 mol / L, and the volume ratio of the ammonium salt solution to the strong acid solution is 1:4-1:2, and the ammonium salt is ammonium molybdate; The precipitant B comprises a surfactant solution, wherein the surfactant is a hexadecyltrimethylammonium bromide surfactant or a hexadecyltrimethylammonium chloride surfactant; the mass percentage concentration of the surfactant in the surfactant solution is 0.01% to 1%.

2. The use according to claim 1, characterized in that The strong acid is selected from at least one of nitric acid, sulfuric acid and hydrochloric acid.

3. The use according to claim 1, characterized in that The water body is domestic water or leachate from kitchen waste or leachate from landfill.

4. The use according to claim 1, characterized in that The preparation method of the composite precipitant comprises the following steps: Preparation of precipitant A: Dissolve the ammonium salt in distilled water, the mass percentage concentration of the ammonium salt in the ammonium salt solution is 8.5%~18.5%; then add it to 9 mol / L strong acid to complete the preparation and set aside; Preparation of precipitant B: Dissolve the surfactant in distilled water and set aside for use; the mass percentage concentration of the surfactant in the surfactant solution is 0.01%~1%.

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