Method for removing arsenic in surface water by activating pyrite with sulfite

Abstract

The invention provides a method for removing arsenic in surface water by activating pyrite with sulfite, and belongs to the technical field of advanced oxidation water treatment. The method for removing the arsenic in the surface water comprises the following steps that pyrite is added into the arsenic-containing surface water to obtain a mixed solution, the pH value of the mixed solution is adjusted to be nearly neutral or alkalescent, a sulfite solution is added, after mixing reaction, removal of the arsenic in the surface water is achieved, the arsenic concentration in the arsenic-containing surface water is 2-6 [mu] M, and the arsenic concentration in the surface water is 2-6 [mu] M. The temperature of the mixed reaction is 30-50 DEG C, and the reaction time is 60 minutes. The method disclosed by the invention can be used for treating arsenic-containing surface water, has wider applicability, and can be used for reducing the energy consumption and the equipment cost and ensuring the stability of reaction materials, so that the problems of high cost, low stability, low efficiency and the like when arsenic in the surface water is treated in the prior art are effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced oxidation water treatment, and particularly relates to a method for removing arsenic in surface water by activating pyrite with sulfite. Background Art

[0002] With the rapid development of industry, the discharge of arsenic-containing industrial waste water is increasing day by day, causing serious pollution to the water environment. In recent years, the problem of arsenic pollution has become increasingly prominent. Due to its characteristics such as "high toxicity", "difficult degradability" and "easy mobility", it greatly threatens the ecological balance and public health. Since As(V) has relatively low toxicity and is easy to adsorb and precipitate, etc., the arsenic pollution water treatment technologies mostly focus on the oxidation of As(III) and the adsorption of As(V). At present, there are many deficiencies in the traditional surface water arsenic removal methods: for example, in the precipitation method, the hydroxide precipitation method is greatly affected by the pH value, the precipitation effect is poor, and the added flocculant will introduce impurities; in the sulfide precipitation method, the sulfide is toxic, the precipitation is unstable, and the dosage is difficult to control, which is easy to cause secondary pollution; in the adsorption method, the adsorption capacity of activated carbon is limited, the regeneration is complex and it is easily interfered by impurity ions, and the mineral adsorption material has poor adsorption selectivity and slow kinetic process; in the ion exchange method, the resin cost is high, the regeneration is difficult and it is easily blocked by impurities in surface water.

[0003] It can be seen that the existing conventional treatment methods are difficult to achieve the deep removal of arsenic in surface water efficiently and economically. At the same time, the natural environment has limited ability to dilute and transform arsenic, resulting in the long-term residue of arsenic in water bodies, and then entering the human body through the food chain. Therefore, it is necessary to explore innovative surface water treatment technologies to provide new effective ways to solve the problem of arsenic pollution in surface water.

[0004] Advanced oxidation technologies can be used for the oxidation and removal of arsenic in surface water, and the degradation of arsenic pollutants can be achieved through various oxidation means. Taking the traditional advanced oxidation technology as an example, the cost of ozone oxidation method is high and the energy consumption is large, and the applicable pH range of Fenton oxidation method is narrow and H 2 O 2The utilization rate is relatively low. In addition, there are three common sulfur sources in advanced oxidation, namely S(Ⅳ) (sulfite), PMS (peroxymonosulfate), and PS (persulfate). Among them, PMS has poor stability and the aqueous solution has strong acidity after activation, and PS is expensive and has many reaction by-products. Sulfite has good stability, low price and no reaction by-products, and is an economical and potential oxidant. It shows certain advantages in the field of arsenic pollution treatment and can be activated by means such as UV irradiation, heating, electrolysis of transition metals and carbon materials. However, when using UV irradiation, heating or electrolysis to activate transition metals, there is a huge energy demand problem, which will lead to high energy consumption costs and maintenance costs, restricting the application of this technology in large-scale water treatment. In addition, carbon materials are difficult to maintain a stable reaction for a long time, unable to ensure the continuous and efficient removal of arsenic, and affecting the stability and persistence of the treatment effect. Therefore, there is an urgent need to develop a new type of green, environmentally friendly and highly efficient and persistent arsenic removal technology based on sulfite activation. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for removing arsenic in surface water by activating pyrite with sulfite, which can reduce energy consumption and equipment costs, ensure the stability of reaction materials, thereby effectively solving the problems of high cost, low stability and inefficiency in the current technology for treating arsenic in surface water, reducing the negative impact of arsenic pollution on the environment, providing reliable technical support for the purification and protection of water resources, and enabling the treated water quality to meet the standards by using this method.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A method for removing arsenic in surface water by activating pyrite with sulfite, comprising the following steps:

[0009] Adding pyrite to arsenic-containing (As(Ⅲ)) surface water to obtain a mixed solution, adjusting the pH value of the mixed solution to near neutral or weakly alkaline and adding a sulfite solution, and after mixing and reacting, the arsenic in the surface water is removed.

[0010] Further, the arsenic concentration in the arsenic-containing surface water is 2-6 μM, preferably 4 μM.

[0011] Further, the molar ratio of the arsenic-containing surface water to pyrite is 1:25.

[0012] Further, adjust the pH value of the mixed solution to 6-10, preferably pH = 8.

[0013] Furthermore, use 0.2 mol·L -1 of NaOH or 0.2 mol·L-1 of H 2 SO 4 Adjust the pH value.

[0014] Furthermore, the is 20 - 100 mM, preferably 50 mM; the sulfite solution is one of sodium sulfite solution, potassium sulfite solution, sodium bisulfite solution and potassium bisulfite solution, preferably sodium sulfite.

[0015] Furthermore, the molar ratio of the sulfite solution to pyrite is 1:1.

[0016] Furthermore, the temperature of the mixed reaction is 30 - 50 °C, preferably 40 °C, and the reaction time is 60 min.

[0017] Furthermore, the pyrite needs to be finely ground with an agate mortar before adding.

[0018] The second technical solution of the present invention:

[0019] A device for removing arsenic from surface water, used to implement the above method. The device for removing arsenic from surface water includes a water-jacketed reactor. The upper end of the water-jacketed reactor is provided with a water outlet, and the lower end is provided with a water inlet. The cooling circulation water device is connected to the water-jacketed reactor through the upper water outlet and the lower water inlet. A magnetic stirrer is arranged below the water-jacketed reactor, and the top of the water-jacketed reactor is sealed with a sealing plug.

[0020] Furthermore, the method for removing arsenic from surface water using the device includes the following steps:

[0021] Add arsenic-containing surface water with an arsenic concentration of 2 - 6 μM into the water-jacketed reactor, then add pyrite, turn on the magnetic stirrer to obtain a mixed solution, adjust the pH value of the mixed solution to 6 - 10, and control the temperature of the water-jacketed reactor at 30 - 50 °C through the cooling circulation water device. Then add a sulfite solution with a concentration of 20 - 100 mM into the water-jacketed reactor, seal and carry out the mixed reaction, and after the reaction ends, the arsenic in the surface water is removed.

[0022] Furthermore, the water-jacketed reactor is a cylindrical plexiglass reactor with a cooling circulation water jacket. The sealing plug is suspended with a pH electrode and provided with a sampling port, and an oxygen dissolved meter (DO meter) and an aeration port can also be set.

[0023] The principle of removing arsenic from surface water by the method of the present invention is as follows:

[0024] First, Fe(Ⅱ) rich in pyrite and S(Ⅳ) in sulfite are used to form Fe(Ⅱ)-S(Ⅳ) complex. Then, the complex is oxidized to Fe(Ⅲ)-S(Ⅳ), and electron transfer occurs between metal ion Fe(Ⅲ) and S(Ⅳ), generating Fe(Ⅱ) and SO 3 ·- , and this process completes the cycle of metal valence states and the generation of sulfur oxygen free radicals. SO 3 ·- will also be continuously oxidized to SO 4 ·- under sufficient oxygen conditions. SO 4 ·- will transform into HO· at high pH values. These ROS (reactive oxygen species) free radicals oxidize As(Ⅲ) to As(Ⅴ) which is easier to remove, solving the technical problem of low-cost and efficient treatment of arsenic in surface water.

[0025] Secondly, Fe-As co-oxidation also exists during the treatment process under near-neutral conditions, that is, Fe(Ⅱ) of pyrite hydrolyzes to form Fe(OH) 2 , and then Fe(OH) 2 and As(Ⅲ) in surface water form Fe(Ⅱ)-As(Ⅲ) complex. And oxygen is used to oxidize Fe(OH) 2 and Fe(Ⅱ)-As(Ⅲ) complex, generating Fe(Ⅲ) hydroxide colloid, Fe(Ⅲ)-As(Ⅲ) complex and H 2 O 2 . In this process, there are two ways for As(Ⅲ) to be oxidized to As(Ⅴ). One is that H 2 O 2 generated during the oxidation process oxidizes Fe(Ⅱ) in the Fe(Ⅱ)-As(Ⅲ) complex to the intermediate product Fe(IV), and the unstable Fe(IV) quickly oxidizes As(Ⅲ) to As(Ⅴ). The other is that H 2 O 2 directly oxidizes As(Ⅲ) to As(Ⅴ). The result is that Fe(Ⅱ) and As(Ⅲ) are co-oxidized to form insoluble Fe(OH) 3 and Fe(Ⅲ)-As(Ⅴ) complex, thus achieving the removal of As.

[0026] The prior art 1 with the publication number CN 115367859 A discloses a method for degrading organic arsenic by activating sodium sulfite with ferrous sulfide, mainly aiming at the problem that synchronous oxidation and in-situ adsorption removal of organic arsenic cannot be achieved. This method includes adding ferrous sulfide and sodium sulfite into water containing organic arsenic to achieve synchronous oxidation degradation and in-situ adsorption removal of arsenic in water. The prior art 2 with the publication number CN 119140588A discloses a method for passivating soil arsenic by using a ferrous sulfide and sulfite conjugate. In this heterogeneous system, the commonly existing sulfur transformation intermediate product sulfite (SO 3 2- ) is taken as the research object to study its passivation mechanism for trivalent arsenic (As(Ⅲ)) after coupling with ferrous sulfide. Compared with the prior art 1 and the prior art 2, the present invention is different in terms of treatment object, reaction principle, treatment effect and economic cost. Specifically:

[0027] (1) From the perspective of the treatment object, the prior art 1 mainly focuses on the treatment of wastewater containing organic arsenic, and the prior art 2 mainly focuses on the remediation of soil arsenic pollution. However, the present invention focuses on the treatment of arsenic pollution in surface water. The composition of surface water is complex, including various impurity ions and microorganisms, etc. The fact that the method of the present invention can treat surface water means that it has a wider applicability and can cope with more complex arsenic pollution situations.

[0028] (2) From the perspective of the reaction principle, the prior art 1 uses the structural iron on the surface of ferrous sulfide to activate sulfite radicals to produce active substances to oxidize organic arsenic and then adsorb inorganic arsenic. The prior art 2 is that ferric ions and sulfite ions couple to generate free radicals, which then oxidize trivalent arsenic and adsorb and passivate it. However, the present invention can generate a variety of ROS to participate in the arsenic removal process, and the reaction pathway is more diverse, which can more efficiently oxidize As(Ⅲ) into As(Ⅴ) that is easier to remove. It can be verified by experiments that the technology of the present invention has a high removal rate of As(Ⅲ), which can reach more than 80% at 60 minutes, and has good stability and is relatively less affected by external factors.

[0029] (3) From the perspective of the treatment effect, the prior art 1 mainly focuses on the degradation of organic arsenic and the adsorption of inorganic arsenic, and has certain requirements for the total arsenic removal rate. The prior art 2 focuses on the passivation transformation of trivalent arsenic in soil. However, the present invention not only has a good removal effect on As(Ⅲ), but also can maintain a high removal efficiency under different pH conditions. Experiments show that under weakly alkaline conditions, the oxidation efficiency of As(Ⅲ) is as high as 88.9%. At the same time, it is less affected by common anions.

[0030] (4) In terms of economic cost, although relatively inexpensive raw materials are also used in the prior art 1 and the prior art 2, pyrite in the present invention is widely sourced and low in price, and sulfite also has a relatively low cost. Moreover, the energy consumption during the reaction process is low, and no complex equipment or additional energy input is required, reducing the treatment cost. In terms of sustainability, the method of the present invention can efficiently remove arsenic under near-neutral conditions, reducing the use of acid-base adjustment reagents and the impact on the environment; the iron compound precipitates generated during the reaction process can settle naturally and will not introduce new pollutants, showing good environmental friendliness and sustainability.

[0031] In summary, compared with the prior art, the present invention has the following advantages and technical effects:

[0032] The method of the present invention can treat arsenic-containing surface water, has a wider applicability, and can also reduce energy consumption and equipment costs, ensuring the stability of reaction materials, thus effectively solving the problems of high cost, low stability, and low efficiency in the current technology for treating arsenic in surface water. Using this method, the treated surface water quality can meet the standards, and the method of the present invention will not introduce new pollutants, showing good environmental friendliness and sustainability, reducing the negative impact of arsenic pollution on the environment, and providing reliable technical support for the purification and protection of water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0034] Figure 1 is a schematic structural diagram of the device for removing arsenic from surface water in the present invention, where 1 is a water jacket reactor, 2 is an inlet, 3 is an outlet, and 4 is a magnetic stirrer;

[0035] Figure 2 is a schematic structural diagram of the top sealing plug of the device for removing arsenic from surface water in the present invention, where 5 is an aeration port, 6 is a sealing plug, 7 is a DO meter, 8 is a sampling port, and 9 is a pH electrode;

[0036] Figure 3 is the determination result of arsenic species at different sampling times in Example 1, Comparative Example 1, and Comparative Example 2, where Fe(II)+Na 2 SO 3 curve is for Example 1, Na 2 SO 3 curve is for Comparative Example 1, and the Fe(II) curve is for Comparative Example 2;

[0037] Figure 4Determination results of arsenic species at different sampling times in Examples 1-3 and Comparative Example 3. Among them, the pH 8.0 curve is for Example 1, the pH 6.0 curve is for Example 2, the pH 10.0 curve is for Example 3, and the pH 4.0 curve is for Comparative Example 3;

[0038] Figure 5 Determination results of arsenic species at different times for each group in Example 1 and after adding anionic salts in Example 1. Among them, 0 mmol·L –1 The competitive anion curve is for Example 1, 1 mmol·L –1 NaCl is for the group with added NaCl, 1 mmol·L – 1 NaNO 3 is for the group with added NaNO 3 1 mmol·L –1 NaHCO 3 is for the group with added NaHCO 3 group;

[0039] Figure 6 Determination results of arsenic species at different times for each group in Example 1 and after adding PIPES buffer solution in Example 1. Among them, Fe(II)+Na 2 SO 3 The curve is for Example 1, Fe(II)+Na 2 SO 3 +PIPES curve is for Comparative Example 4;

[0040] Figure 7 Determination results of arsenic species at different sampling times in Example 1 and Comparative Example 5. Among them, the pyrite+Na 2 SO 3 curve is for Example 1, the vivianite+Na 2 SO 3 curve is for Comparative Example 5;

[0041] Figure 8 Determination results of arsenic species at different sampling times in Example 1 and Comparative Example 6. Among them, the pyrite+Na 2 SO 3 curve is for Example 1, the specularite+Na 2 SO 3 curve is for Comparative Example 6;

[0042] Figure 9 Determination results of arsenic species at different sampling times in Example 1 and Comparative Example 7. Among them, the pyrite+Na 2 SO 3 curve is for Example 1, the limonite+Na 2 SO 3The curve is Comparative Example 7. Detailed Description of the Invention

[0043] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0046] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0047] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0048] An embodiment of the present invention provides a method for removing arsenic from surface water by activating pyrite with sulfite, comprising the following steps:

[0049] Pyrite is added to arsenic-containing (As(III)) surface water to obtain a mixed solution, the pH value of the mixed solution is adjusted to near neutral or weakly alkaline, and a sulfite solution is added. After mixing and reacting, arsenic in the surface water is removed.

[0050] In some preferred embodiments of the present invention, the arsenic concentration in the arsenic-containing surface water is 2 - 6 μM, preferably 4 μM.

[0051] In some preferred embodiments of the present invention, the molar ratio of arsenic-containing surface water to pyrite is 1:25.

[0052] In some preferred embodiments of the present invention, the pH value of the mixed solution is adjusted to 6-10, preferably 8.

[0053] In some preferred embodiments of the present invention, 0.2 mol·L -1 of NaOH or 0.2 mol·L -1 of H 2 SO 4 is used to adjust the pH value.

[0054] In some preferred embodiments of the present invention, the concentration of the sulfite solution is 20-100 mM, preferably 50 mM; the sulfite solution is one of sodium sulfite solution, potassium sulfite solution, sodium bisulfite solution and potassium bisulfite solution, preferably sodium sulfite.

[0055] In some preferred embodiments of the present invention, the molar ratio of the sulfite solution to pyrite is 1:1.

[0056] In some preferred embodiments of the present invention, the temperature of the mixed reaction is 30-50 °C, preferably 40 °C, and the reaction time is 60 min.

[0057] In some preferred embodiments of the present invention, pyrite needs to be finely ground to about 200-400 mesh, i.e., the particle size is about 38 μm-76 μm, before being added.

[0058] The present invention also provides an apparatus for removing arsenic from surface water according to an embodiment, which is used to implement the above method. The structural schematic diagram of the apparatus for removing arsenic from surface water is shown in Figure 1 , and the structural schematic diagram of the top sealing plug is shown in Figure 2 , where 1 is a water jacket reactor, 2 is a water inlet, 3 is a water outlet, 4 is a magnetic stirrer, 5 is an aeration port, 6 is a sealing plug, 7 is a DO meter, 8 is a sampling port, and 9 is a pH electrode.

[0059] Specifically, the apparatus for removing arsenic from surface water used in the embodiments of the present invention includes a water jacket reactor 1. The upper end of the water jacket reactor 1 is provided with a water outlet 3, and the lower end is provided with a water inlet 2. The cooling circulating water device is connected to the water jacket reactor 1 through the upper water outlet 3 and the lower water inlet 2. A magnetic stirrer 4 is arranged below the water jacket reactor 1, and the top of the water jacket reactor 1 is sealed with a sealing plug 6.

[0060] In some preferred embodiments of the present invention, the method for removing arsenic from surface water by a device comprises the following steps: adding surface water containing arsenic with an arsenic concentration of 2 - 6 μM into a water-jacketed reactor 1, then adding pyrite, starting a magnetic stirrer 4 to obtain a mixed solution, adjusting the pH value of the mixed solution to 6 - 10, and controlling the temperature of the water-jacketed reactor 1 at 30 - 50 °C through a cooling circulating water device. Then, adding a sulfite solution with a concentration of 20 - 100 mM into the water-jacketed reactor 1, sealing it with a sealing plug 6 for mixed reaction, and achieving the removal of arsenic in the surface water after the reaction ends.

[0061] In some preferred embodiments of the present invention, the water-jacketed reactor 1 is a cylindrical plexiglass reactor with a cooling circulating water jacket. The sealing plug 6 is suspended with a pH electrode 9, a dissolved oxygen meter (DO meter) 7, a sampling port 8, and an aeration port 5.

[0062] In the examples and comparative examples of the present invention, the arsenic species were determined by liquid phase - hydride generation - atomic fluorescence spectrometry (LC - HG - AFS).

[0063] The technical solution of the present invention is further described below through examples.

[0064] Example 1

[0065] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) (2 × 10 -6 mol) in a 500 mL volumetric flask, fully mix it, make up the volume, and transfer it to the water-jacketed reactor. Then, add 0.006 g (5 × 10 -5 mol) of pyrite finely ground with an agate mortar into the water-jacketed reactor. Control the temperature of the reaction solution in the water-jacketed reactor at 40 °C with a cooling circulating water device, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then, add 1 mL of a Na 2 SO 3 solution with a concentration of 50 mM (5 × 10 -5 mol). Start timing when the pH value accurately reaches the target value of 8.0. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add them to a 10 mL colorimetric tube containing 1 mL of HCl to make up the volume, and conduct the determination of arsenic species. The results are as Figure 3 shown (i.e., Figure 3 the Fe(II) + Na 2 SO 3 curve).

[0066] Comparative Example 1

[0067] Same as Example 1, except that only Na is added. 2 SO 3 solution, specifically:

[0068] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) (2×10 -6 mol) in a 500 mL volumetric flask. After mixing well, make up the volume and transfer it to a water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then add 1 mL of a Na 2 SO 3 solution with a concentration of 50 mM (5×10 -5 mol). Start timing when the pH value accurately reaches the target value of 8.0. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add it to a 10 mL colorimetric tube containing 1 mL of HCl to make up the volume, and conduct the determination of arsenic species. The results are as Figure 3 shown (i.e., the Na Figure 3 in 2 SO 3 curve).

[0069] Comparative Example 2

[0070] Same as Example 1, except that only pyrite is added, specifically:

[0071] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) (2×10 -6 mol) in a 500 mL volumetric flask. After mixing well, make up the volume and transfer it to a water-jacketed reactor. Then add 0.006 g (5×10 -5 mol) of pyrite finely ground with an agate mortar to the water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4Adjust the pH value to 8.0. Start timing when the pH value accurately reaches the target value of 8.0. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add them to a 10 mL colorimetric tube containing 1 mL of HCl for volume fixation, and conduct the determination of arsenic species. The results are as Figure 3 shown (i.e., Figure 3 the Fe(II) curve in

[0072] . It can be seen from Figure 3 that after the method of Example 1 is continuously implemented for 60 min, the content of As(III) in the wastewater solution is less than 20% of that at the time of no reaction (0 min), that is, the removal rate of As(III) can reach more than 80% at 60 min, and the removal rate gradually decreases as the reaction proceeds. After the continuous reaction of Comparative Example 1 and Comparative Example 2 for 60 min, the content of As(III) in the wastewater solution hardly changes much, and the removal rates are both lower than 10%. This shows that single pyrite or Na 2 SO 3 does not have the ability to oxidize and remove As(III), while the pyrite-Na 2 SO 3 system can act together to oxidize and remove As(III). The above results show that the method of the present invention can continuously, efficiently and economically remove the toxic non-metallic substance As(III) in surface water, while single pyrite or Na 2 SO 3 cannot achieve this.

[0073] Example 2

[0074] Same as Example 1, the difference is only that the pH value is adjusted to 6.0, specifically:

[0075] Prepare the wastewater to be treated containing 4 μmol·L –1 As(III) in a 500 mL volumetric flask, mix well and fix the volume, then transfer it to a water-jacketed reactor. Then add 0.006 g of pyrite finely ground with an agate mortar to the water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40°C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 6.0. Then add 1 mL of Na 2 SO 3The solution was timed when the pH value accurately reached the target value of 6.0. Samples (1 mL each time) were taken from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, they were quickly added to a 10-mL colorimetric tube containing 1 mL of HCl for volume fixation, and the determination of arsenic species was carried out. The results are as Figure 4 shown (i.e., Figure 4 the curve of pH 6.0 in

[0076] Example 3

[0077] Same as Example 1, the only difference is that the pH value was adjusted to 10.0. Specifically:

[0078] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) in a 500-mL volumetric flask. After fully mixing and homogenizing, it was fixed in volume and transferred to a water-jacketed reactor. Then, 0.006 g of pyrite finely ground with an agate mortar was added to the water-jacketed reactor. The temperature of the reaction solution in the water-jacketed reactor was controlled at 40 °C using a cooling circulating water device, and 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 were used to adjust the pH value to 10.0. Then, 1 mL of a 50-μM Na 2 SO 3 solution was added. The solution was timed when the pH value accurately reached the target value of 10.0. Samples (1 mL each time) were taken from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, they were quickly added to a 10-mL colorimetric tube containing 1 mL of HCl for volume fixation, and the determination of arsenic species was carried out. The results are as Figure 4 shown (i.e., Figure 4 the curve of pH 10.0 in

[0079] Comparative Example 3

[0080] Same as Example 1, the only difference is that the pH value was adjusted to 4.0. Specifically:

[0081] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) in a 500-mL volumetric flask. After fully mixing and homogenizing, it was fixed in volume and transferred to a water-jacketed reactor. Then, 0.006 g of pyrite finely ground with an agate mortar was added to the water-jacketed reactor. The temperature of the reaction solution in the water-jacketed reactor was controlled at 40 °C using a cooling circulating water device, and 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 were used to adjust the pH value to 4.0. Then, 1 mL of a 50-μM Na2 SO 3 Solution. When the pH value accurately reaches the target value of 4.0, start timing. Sampling is carried out from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively (1 mL is sampled each time). After sampling, it is quickly added to a 10 mL colorimetric tube containing 1 mL of HCl for volume fixation, and the determination of arsenic species is carried out. The results are as Figure 4 shown (i.e., Figure 4 the curve with pH 4.0 in

[0082] Figure 4 The curve with pH 8.0 in

[0083] represents Example 1. Figure 4 It can be seen that under the condition of pH = 4.0 (acidic, Comparative Example 3), after reacting for 60 min, the concentration of As(Ⅲ) did not change significantly (<1%). While under the near-neutral condition (pH = 6.0, Example 2), within the same reaction time, the oxidation efficiency of As(Ⅲ) increased to 24.0%. Under the weakly alkaline condition (pH = 8.0, Example 1), within the same reaction time, the oxidation efficiency of As(Ⅲ) increased to 88.9%. While under the condition of pH = 10.0 (alkaline, Example 3), within the same reaction time, the oxidation efficiency of As(Ⅲ) decreased to 84.2% instead. This result shows that appropriate alkaline conditions are beneficial to the activation of sulfite by Fe(Ⅱ), thereby leading to the oxidation of As(Ⅲ). In practical engineering applications, the pH can be controlled in an appropriate weakly alkaline environment to more quickly and low-cost remove As(Ⅲ) in surface water.

[0084] Investigate the influence of anions in arsenic-containing wastewater on its removal rate:

[0085] Based on Example 1, replace the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) prepared in Example 1 with wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) and 1 mmol·L –1 anion salt (NaCl, NaNO 3 or NaHCO 3 ). The remaining steps are the same as those in Example 1. The determination results of arsenic species at different times in each group after adding the anion salt are shown in Figure 5 ( Figure 5 the curve of 0 mmol·L –1 competitive anion represents Example 1, 1 mmol·L –1 NaCl represents the group with NaCl added, 1 mmol·L – 1 NaNO 3 represents the group with NaNO 3 added, 1 mmol·L–1 NaHCO 3 indicates the addition of NaHCO 3 group).

[0086] From Figure 5 it can be seen that in the Fe(II) sulfite system with 1 mmol·L –1 Cl - and NO 3 - After reacting for 60 min, the oxidation efficiency of As(III) decreased from 88.9% without adding anions to 82.7% and 83.6% respectively. Cl - 、NO 3 - The reaction rate constants with SO 4 · - are 2.6×10 8 and 5.0×10 4 L·mol -1 s -1 respectively, and their reaction products are Cl· and NO 3 ·. Cl - and NO 3 - compete with As(III) for SO4 ·- and Cl· and NO3· may cause the oxidation of As(III). Therefore, compared with sulfite, Cl - and NO 3 - weakly slows down the oxidation of As(III). Under the condition of adding HCO 3 - , after reacting for 60 min, the oxidation efficiency of As(III) rapidly decreased from 88.9% without adding anions to 42.9%. HCO 3 - can capture SO4 ·- and HO· generated in the solution, and their reaction rate constants are 2.8×10 6 and 8.5×10 6 L·mol -1 s -1 respectively. Due to the solubility product constant of Fe 2 (CO 3 ) 2 (pKsp = 10.5), so HCO 3 - can coordinate with Fe(III) and reduce the available Fe(III) of sulfite. Therefore, the inhibitory effect of HCO 3 - on As(III) may be due to its capture of free radicals in the solution or its competition with sulfite for Fe(III).

[0087] Comparative Example 4

[0088] Explore the co-oxidation reaction of As(Ⅲ) and Fe(Ⅱ):

[0089] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ), 10 mmol·L –1 Na 2 SO 3 and 10 mmol·L –1 PIPES buffer solution (piperazine-1,4-diethanesulfonic acid buffer solution). After mixing well, make up the volume and transfer it to a water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then, continuously purge nitrogen into the reaction solution for 30 min. When the dissolved oxygen meter shows that the DO value is < 0.01 mg·L –1 , add pyrite treated by purging nitrogen, and introduce synthetic air (flow rate: 1 L·min -1 , 20.8% v / v O 2 , 79.2% v / v N 2 ) into the reaction solution to start timing the reaction. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add it to a 10 mL colorimetric tube containing 1 mL HCl to make up the volume, and conduct the determination of arsenic species. This example is repeated 3 times in a light-shielded environment, and each sample is continuously measured 2 times. The results are as Figure 6 shown (that is, Figure 6 the Fe(II)+Na 2 SO 3 curve represents Example 1, and the Fe(II)+Na 2 SO 3 +PIPES curve represents Comparative Example 4).

[0090] It can be seen from Figure 6 that under 10 mmol·L –1 PIPES solution, the As removal rate of the Fe(Ⅱ)-As(Ⅲ) co-oxidation system reaches about 50% at 60 min, and shows an obvious slowdown trend. Compared under the same conditions, Na 2 SO 3The removal rate of As(Ⅲ) by activated pyrite reached 87.5%. And there is data indicating that in the Fe(Ⅱ)-As(Ⅲ) co-oxidation system with the participation of sulfite, the oxidation of As(Ⅲ) mainly relies on the ROS generated by the Fe(Ⅱ)-S(Ⅳ) system. Among them, the PIPES buffer solution does not interfere with the oxidation of As(Ⅲ) and is only used as a buffer solution.

[0091] Comparative Examples 5-7 investigated the influence of different iron-containing ores on the removal of As

[0092] Comparative Example 5

[0093] Same as Example 1, the difference is only that the pyrite is replaced with an equal mass of vivianite (FePO 4 ), specifically:

[0094] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) in a 500 mL volumetric flask. After fully mixing and homogenizing, make up the volume and transfer it to a water-jacketed reactor. Then add 0.006 g of vivianite finely ground with an agate mortar to the water-jacketed reactor. Use the cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then add 1 mL of a solution with a concentration of 50 μM of Na 2 SO 3 When the pH value accurately reaches the target value of 8.0, start timing. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add it to a 10 mL colorimetric tube containing 1 mL of HCl to make up the volume, and conduct the determination of arsenic species. The results are as Figure 7 shown (that is, Figure 7 the pyrite + Na 2 SO 3 curve represents Example 1, and the vivianite + Na 2 SO 3 curve represents Comparative Example 5).

[0095] It can be Figure 7 seen that after continuously implementing for 60 min in Comparative Example 5, the content of As(Ⅲ) in the aqueous solution is less than 30% of that before the reaction, that is, the removal rate of As(Ⅲ) can reach 69.3% at 60 min, and the removal rate gradually decreases as the reaction proceeds. This shows that the vivianite + Na 2 SO 3 system can jointly act to oxidize and remove As(Ⅲ), but the overall effect is not as good as that of the pyrite-Na 2SO 3 system

[0096] Comparative Example 6

[0097] Same as Example 1, except that pyrite is replaced with an equal mass of siderite (FeCO 3 ), specifically:

[0098] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) in a 500 mL volumetric flask. After fully mixing and homogenizing, make up the volume and transfer it to a water-jacketed reactor. Then add 0.006 g of siderite finely ground with an agate mortar to the water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then add 1 mL of a solution with a concentration of 50 μM of Na 2 SO 3 solution. Start timing when the pH value accurately reaches the target value of 8.0. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add it to a 10 mL colorimetric tube containing 1 mL of HCl to make up the volume, and conduct the determination of arsenic species. The results are as Figure 8 shown (that is, Figure 8 the pyrite + Na 2 SO 3 curve represents Example 1, and the siderite + Na 2 SO 3 curve represents Comparative Example 6).

[0099] It can be seen from Figure 8 that after 60 min of continuous implementation in Comparative Example 6, the content of As(Ⅲ) in the aqueous solution is less than 40% of that before the reaction, that is, the removal rate of As(Ⅲ) can reach 60.9% at 60 min, and the removal rate gradually decreases as the reaction proceeds. This shows that the siderite-Na 2 SO 3 system can jointly act to oxidize and remove As(Ⅲ), but the overall effect is not as good as the pyrite-Na 2 SO 3 system with a removal rate of 87.5%.

[0100] Comparative Example 7

[0101] Same as Example 1, except that pyrite is replaced with an equal mass of limonite (Fe 2 O 3 ·nH 2(0), specifically:

[0102] Prepare the wastewater to be treated containing 4 μmol·L –1 As(Ⅲ) in a 500 mL volumetric flask. After fully mixing and homogenizing, make up the volume and transfer it to a water-jacketed reactor. Then add 0.006 g of limonite finely ground in an agate mortar to the water-jacketed reactor. Use a cooling circulating water device to control the temperature of the reaction solution in the water-jacketed reactor at 40 °C, and use 0.2 mol·L –1 NaOH and 0.2 mol·L –1 H 2 SO 4 to adjust the pH value to 8.0. Then add 1 mL of a solution with a concentration of 50 μM of Na 2 SO 3 solution. Start timing when the pH value accurately reaches the target value of 8.0. Take samples (1 mL each time) from the sampling port at 0, 2, 5, 10, 20, 30, 40, and 60 min respectively. After sampling, quickly add it to a 10 mL colorimetric tube containing 1 mL of HCl to make up the volume, and conduct the determination of arsenic species. The results are as Figure 9 shown (that is, Figure 9 the pyrite + Na 2 SO 3 curve represents Example 1, and the limonite + Na 2 SO 3 curve represents Comparative Example 7).

[0103] It can be seen from Figure 9 that after continuously implementing Comparative Example 7 for 60 min, the content of As(Ⅲ) in the aqueous solution is less than 30% of that before the reaction, that is, the removal rate of As(Ⅲ) can reach 75.2% at 60 min, and the removal rate gradually decreases as the reaction proceeds. This shows that the hematite-Na 2 SO 3 system can act together to oxidize and remove As(Ⅲ), but the overall effect is not as good as the pyrite-Na 2 SO 3 system with a removal rate of 87.5%.

[0104] Combining Figure 7 , Figure 8 and Figure 9 the experimental results of Example 1 and Comparative Examples 5-7 in

[0105] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for removing arsenic from surface water by activating pyrite with sulfite, characterized in that: The following steps are involved: Pyrite is added to arsenic-containing surface water to obtain a mixed solution, the pH value of the mixed solution is adjusted to near neutral or weak alkaline, and a sulfite solution is added. After mixed reaction, arsenic in the surface water is removed.

2. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The arsenic concentration in the arsenic-containing surface water is 2-6 μM.

3. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The molar ratio of the arsenic-containing surface water to pyrite is 1:

25.

4. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The pH value of the mixed solution was adjusted to 6-10.

5. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The concentration of the sulfite solution is 20-100 mM.

6. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The molar ratio of the sulfite solution to pyrite is 1:

1.

7. The method for removing arsenic from surface water by sulfite-activated pyrite according to claim 1, characterized in that: The temperature of the mixed reaction is 30-50° C., and the reaction time is 60 minutes.

8. A device for removing arsenic from surface water, characterized in that: The device for removing arsenic from surface water for implementing the method described in any one of claims 1 to 7 comprises a water-jacketed reactor, wherein a water outlet is arranged at the upper end of the water-jacketed reactor, and a water inlet is arranged at the lower end, a cooling circulating water device is connected to the water-jacketed reactor via the upper water outlet and the lower water inlet, a magnetic stirrer is arranged below the water-jacketed reactor, and the top of the water-jacketed reactor is sealed with a sealing plug.

9. The device for removing arsenic from surface water according to claim 8, characterized in that: The method for removing arsenic from surface water using the device comprises the following steps: Arsenic-containing surface water is added to the water-jacketed reactor, and then pyrite is added. The magnetic stirrer is turned on to obtain a mixed solution, the pH value of the mixed solution is adjusted, and the temperature of the water-jacketed reactor is controlled by the cooling circulating water device. Then, a sulfite solution is added to the water-jacketed reactor, which is sealed with a sealing plug, and the mixed reaction realizes the removal of arsenic in the surface water.

10. The device for removing arsenic from surface water according to claim 8, characterized in that: The water-jacketed reactor is a cylindrical organic glass reactor with a cooling circulating water jacket, and the sealing plug is hung with a pH electrode and is provided with a sampling port.

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