Thallium-containing wastewater treatment process

Abstract

The invention discloses a thallium-containing wastewater treatment process which comprises the following steps: (1) introducing thallium-containing wastewater into a Fenton oxidation pond, adding a Fenton reagent, adjusting the pH value by using lime milk, carrying out HDS process treatment, and filtering to obtain pretreated thallium-containing wastewater; (2) electrolyzing the pretreated thallium-containing wastewater by adopting a BDD electrolytic bath to obtain electrolyzed thallium-containing wastewater; and (3) mixing the electrolyzed thallium-containing wastewater with polymerization ferric chloride, and treating by adopting an ion exchange system. The treatment process provided by the invention ensures that the thallium concentration in the water body is continuously and stably reduced to an environmental limit value, and meets the emission standard of GB 3095-2012.

Description

Technical Field

[0001] This application belongs to the field of heavy metal wastewater treatment, and particularly relates to a process for treating thallium-containing wastewater. Background Art

[0002] Thallium is a rare and dispersed metal element widely distributed in the natural environment. Thallium is applied in the chemical, electronics, pharmaceutical, aerospace and optical industries, as well as superconducting materials and high-energy physics. Thallium has strong toxicity. Due to its highly toxic characteristics, during the mining and refining of minerals, if not properly treated and entering the environment, it will enter the human body along with the enrichment of the food chain, causing irreversible harm to human health.

[0003] Thallium mainly has two oxidation states, namely monovalent Tl + and trivalent Tl 3+ , and the former is more widely distributed in the natural environment and has stronger migration ability than the latter. Oxidation of Tl + is beneficial to removing thallium from wastewater. At present, the main processes for treating thallium-containing industrial wastewater in China are as follows: sodium sulfide precipitation method, oxidation adsorption method, electrochemical treatment method, and biological agent precipitation method. Among these numerous processes, the electrochemical treatment of thallium has the characteristics of fast response, high sensitivity and good accuracy, and has always been a research hotspot at home and abroad.

[0004] Electrochemical oxidation technology mainly removes pollutants in wastewater through an externally applied power source and electrode oxidation. Electrochemical oxidation technology has the advantages of small floor area, no addition of oxidants, and no secondary pollution, and is widely used in the treatment of heavy metal-polluted wastewater. The basic principle of electrochemical oxidation technology is: during the power-on process, oxidizing radicals generated on the electrode surface of the anode or under the action of the electric field oxidize and remove heavy metal ions in the wastewater. Summary of the Invention

[0005] This application provides a process for treating thallium-containing wastewater to solve the above problems.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A process for treating thallium-containing wastewater, comprising the following steps:

[0008] (1) Introduce thallium-containing wastewater into a Fenton oxidation tank, add Fenton reagents, then adjust the pH value with lime milk, perform HDS process treatment, and obtain pretreated thallium-containing wastewater after filtration;

[0009] (2) Electrolyze the pretreated thallium-containing wastewater using a BDD electrolytic cell to obtain electrolyzed thallium-containing wastewater;

[0010] (3) Mix the electrolyzed thallium-containing wastewater with polyferric chloride and then treat it using an ion exchange system.

[0011] Further, in step (1), the Fenton reagent includes a ferrous sulfate solution and a 30% hydrogen peroxide solution with a molar ratio of 1:9 - 11.

[0012] Further, based on the mass of the 30% hydrogen peroxide solution, the addition amount of the Fenton reagent is 0.8 - 1.5 mL / L.

[0013] Further, in step (1), the pH value is adjusted to 9.5 - 10.5 with lime milk, and the HDS process is carried out until the pH of the thallium-containing wastewater is 12 - 14.

[0014] Further, in step (2), the current density of the BDD electrolytic cell is 9 - 11 mA / cm 2 , and the electrolysis time is 10 - 15 min.

[0015] Further, the BDD electrolytic cell is composed of a BDD anode plate, a stainless steel cathode plate, a card slot, a T2 copper bar, a circulation pump, and a PVC water pipe.

[0016] Further, in step (3), the dosage of the polyferric chloride is 0.8 - 1.5 mg / L.

[0017] Further, in step (3), the ion exchange system is composed of an ion column, a PVC pipeline, a magnetic frequency modulation pump, and a PVC drainage and air intake valve. The ion column is filled with macroporous resin.

[0018] Further, the macroporous resin is CH-Tl7 type resin.

[0019] Further, the dosage of the macroporous resin is 1:5 - 20 of the volume of the thallium-containing wastewater.

[0020] Further, after the macroporous resin adsorbs the wastewater, sodium sulfite is used to reduce and desorb the thallium adsorbed in the macroporous resin to realize the recycling of the resin.

[0021] Further, the concentration of sodium sulfite is 100 g / L, the flow rate is 2 - 4 bv / h, and the desorption time is 4 - 6 h.

[0022] The beneficial effects of the embodiments of the present application compared with the prior art are as follows:

[0023] (1) When treating thallium-containing wastewater, the present application introduces the lime + HDS process on the basis of the Fenton oxidation process, which not only reduces the treatment reagent cost compared with the traditional liquid alkali treatment method, but also reduces the subsequent reagent cost.

[0024] (2) The Fenton-coupled BDD electro-oxidation process can efficiently oxidize Tl + to Tl 3+, which can not only improve the subsequent removal effect of thallium, but also enhance the enrichment effect of thallium by resin adsorption due to the higher chemical valence state of thallium.

[0025] (3) Use ferric chloride to form a strong complex ion group of tetrachlorothallium with thallium, strengthening the complexation with the resin in the ion exchange system.

[0026] (4) After the resin is saturated with adsorption, use sodium sulfite to reduce the adsorbed trivalent thallium to monovalent thallium, reduce the complexation of thallium on the resin, and achieve the enrichment of thallium and the regeneration of the resin. Description of the Drawings

[0027] Figure 1 Process flow chart of the thallium-containing wastewater treatment process of this application. Detailed Description of the Invention

[0028] It should be understood that the present invention is not limited to the specific compositions, methods or schemes described herein. In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present invention, which is only defined by the claims. The test methods used in the examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial sources.

[0029] Example 1

[0030] (1) The Fenton reagent is prepared by mixing a ferrous sulfate solution with a molar ratio of 1:9 - 11 and a 30% hydrogen peroxide solution. Based on the mass of the 30% hydrogen peroxide solution, the addition amount of the Fenton reagent in the Fenton oxidation tank is 0.8 - 1.5 mL / L. Adjust the pH to 10 with lime milk, and a plunger pump is installed at the bottom for sludge circulation to implement the HDS process. After circulating and reacting for 1 h, the pH rises above 12 and enters the BDD oxidation tank.

[0031] (2) Pass an electric current with a current density of 10 mA / cm 2 in the BDD electrolytic cell, and control the reaction time within 10 - 15 min. The electrolyzed liquid after the reaction enters the physicochemical reaction pool.

[0032] (3) Add 1 mg / L of ferric chloride in the physicochemical reaction pool, stir for more than 40 min and then enter the ion exchange system. The CH-Tl7 type resin is used in the ion exchange system, and the resin dosage is 1 / 10 of the volume of the thallium-containing wastewater to be treated, obtaining the treated wastewater.

[0033] Test Example 1

[0034] The wastewater with different concentrations was treated using the treatment process of Example 1, and the concentration of thallium in the treated water was detected using an inductively coupled plasma mass spectrometer.

[0035] Concentration of thallium-containing sewage to be treated (mg / L) 9.7 36.4 20.4 Concentration of thallium in water after treatment (μg / L) 0.046 0.083 0.063

[0036] Note: Samples of each concentration were determined in parallel three times.

[0037] The experimental results show that the concentration of thallium in the wastewater treated by the treatment process of this application is lower than 0.2 μg / L. The treatment process of this application ensures that the concentration of thallium in the water body remains continuously and stably low to the environmental limit, meeting the discharge standard of GB 3095-2012.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for treating thallium-containing wastewater, characterized in that: The following steps are involved: (1) introducing the thallium-containing wastewater into a Fenton oxidation tank, adding a Fenton agent, adjusting the pH value with lime milk, and performing HDS process treatment to obtain pretreated thallium-containing wastewater; (2) electrolyzing the pretreated thallium-containing wastewater using a BDD electrolytic cell to obtain electrolyzed thallium-containing wastewater; (3) The thallium-containing wastewater after electrolysis is mixed with polyferric chloride and then treated using an ion exchange system.

2. The thallium-containing wastewater treatment process according to claim 1, characterized in that: In step (1), the Fenton reagent comprises a ferrous sulfate solution and a 30% hydrogen peroxide solution in a molar ratio of 1:9-11. Based on the mass of the 30% hydrogen peroxide solution, the added amount of the Fenton reagent is 0.8-1.5 mL / L.

3. The thallium-containing wastewater treatment process according to claim 1, characterized in that: In step (1), the pH value of the lime milk is adjusted to 9.5-10.5, and the HDS process is performed until the pH of the thallium-containing wastewater is 12-14.

4. The thallium-containing wastewater treatment process according to claim 1, characterized in that: In step (2), the current density of the BDD electrolytic cell electrolysis is 9-11 mA / cm 2 , the electrolysis time is 10-15min.

5. The thallium-containing wastewater treatment process according to claim 1, characterized in that: In step (3), the amount of polyferric chloride used is 0.8-1.5 mg / L.

6. The thallium-containing wastewater treatment process according to claim 1, characterized in that: In step (3), the ion exchange system uses a macroporous CH-T17 type resin.

7. The thallium-containing wastewater treatment process according to claim 6, characterized in that: The dosage of the macroporous resin is 1:5-20 of the volume of the thallium-containing wastewater.

8. The thallium-containing wastewater treatment process according to claim 6, characterized in that: After the macroporous resin adsorbs thallium in the wastewater, sodium sulfite is used to reduce and desorb the adsorbed thallium.

9. Application of the thallium-containing wastewater treatment process as described in any one of claims 1 to 9 in treating thallium-containing wastewater.

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