Step deep purification method for low-concentration arsenic-containing wastewater

Abstract

The present invention relates to a step-by-step deep purification method for low-concentration arsenic-containing wastewater. For low-concentration arsenic-containing wastewater, a step-by-step treatment method of primary arsenic removal and then deep arsenic removal is adopted, including the following process steps and conditions: primary arsenic removal, initially according to iron ( The mass ratio of aluminum) / arsenic is controlled at 4~10, and coagulant is added, and the pH value of the low-concentration arsenic-containing wastewater in the stirred reaction tank is adjusted to 7~9 with sulfuric acid or milk of lime, and the mass ratio of iron / arsenic is controlled at 4~9 in the follow-up. 10. The reaction time is 5~30min, the stirring line speed is 1.0~2.0m / s, after the coagulation and arsenic removal reaction, the solid-liquid separation is carried out to obtain the primary arsenic removal underflow and the primary arsenic removal overflow; for the deep arsenic removal, the primary arsenic removal The overflow is pumped to the reaction tank through the slurry, and the iron salt is added first, and the iron / arsenic mass ratio is controlled at 9~15, and the reaction is 5~20min, and then the polymer is added at a concentration of 0.1~0.3% and an amount of 3~10g / t The flocculant undergoes coagulation aeration and solid-liquid separation to obtain deep arsenic removal bottom flow and deep arsenic removal overflow, and the deep arsenic removal overflow reaches the standard and is discharged. After the method of the present invention, the concentration of arsenic in the aqueous solution is as low as 0.005 mg / L or less , has the advantages of less chemical consumption, less slag, and high efficiency.

Description

technical field [0001] The invention relates to a step deep purification method of low-concentration arsenic-containing wastewater, which is suitable for the application in the industries of environmental protection and comprehensive utilization of mine resources. Background technique [0002] Non-ferrous metals and rare and precious metals are national strategic resources and occupy an important position in the national economy. The extraction of non-ferrous metals and rare and precious metals still mainly comes from the development of corresponding mineral resources. According to incomplete statistics, the development of non-ferrous metal mineral resources is the main source of arsenic pollution. This is because arsenic is a sulfur-friendly element. There are as many as 300 kinds of arsenic-containing minerals, and most of them are mixed with gold, copper, and lead in the form of sulfides. , zinc, tin, nickel, and cobalt ores, with the development of mineral resources, mi...

AI Technical Summary

Problems solved by technology

At present, there are three main treatment methods for low-concentration arsenic-containing wastewater in various countries: iron salt method, adsorption method, and membrane separation. The iron salt method has the characteristics of simple treatment process and good treatment effect, but due to the low concentration of arsenic in water and few other impurities , so there are problems such as large consumption of chemicals, difficulty in solid-liquid separation, and poor stability of treatment indicators easily affected by the external environment; the adsorption method mainly uses resins, activated carbon, and biomass substrates loaded with iron salts (mainly iron hydroxide), etc. As an adsorbent, it removes arsenic from the aqueous solution through the chelation or adsorption of iron ions, and achieves the purpose of deep purification. The post-resin regeneration conditions are harsh, the regeneration efficiency is low, and the service life of the resin is far lower than expected. Membrane separation has the characteristics of good separation effect and simple operation, but there are also problems that need to be solved, such as long pretreatment process and easy loss of membrane components. question

[0004] In order to solve the above problems, Chinese patent CN 201210260206.9 discloses "a method for purifying wastewater containing heavy metals and arsenic", which treats wastewater containing heavy metals and arsenic by adding sulfuric acid or soluble sulfate to the wastewater to supplement sulfate Then add reducing agent to reduce high-priced manganese, chromium, vanadium, etc. in wastewater, then add calcium carbonate to pre-adjust the pH value of the solution, and finally add lime to neutralize, so that harmful elements such as heavy metals and arsenic in wastewater can be precipitated and wrapped in However, due to the poor stability of the calcium arsenate slag produced by it, it does not meet the national environmental protection standards; Chinese patent CN 207973618U discloses "a kind of dilute acid arsenic removal device for non-ferrous smelting flue gas purification", and its processing object is non-ferrous smelting Flue gas, the reaction mechanism is to use sodium sulfide or hydrogen sulfide to react with arsenic in dilute acid to produce arsenic filter cake, and this device is mainly used to improve the reaction efficiency and strictly control the arsenic content of the solution after the sulfidation reaction to 30mg / L Below, it is obvious that the discharge is seriously exceeding the standard; Chinese patent CN201810956090.X discloses "an arsenic removal membrane for treating arsenic-containing wastewater in mines", which is an arsenic removal membrane with multiple functions prepared by using bamboo pulp fiber, glass fiber and eggshell powder And use this membrane to filter arsenic slag, the concentration of arsenic in the solution after filtration can reach 0.01mg / L, the membrane works by physical barrier and physicochemical adsorption; And the method of recycling”, which is to filter the high-arsenic polluted acid, membrane distillation, acid concentration and recovery of condensed water, the concentrated acid is reduced, cooled and precipitated arsenic trioxide, and then vulcanized to remove arsenic and heavy metals, although it is adopted stepwise treatment method, but there are problems such as the need for further harmless treatment of hazardous waste generated by different principles; Chinese patent CN 201810008659 . "Application in "invented a method for treating wastewater containing trivalent arsenic, which is to feed trivalent arsenic wastewater and ferric iron solution at the same time, adjust the pH value of the mixed solution to 1.41-2.45, stir at room temperature, separate and precipitate Sulfur-free hydroxyarsenite, Fe 6 (AsO 3 ) 4 (HAsO 3 )(OH) 4 4H 2 O, there are relatively harsh requirements on the ratio and concentration of the reactants, and the stability of the product-free hydroxyarsenite is unknown; The harmless treatment method of arsenic-containing slag liquid in chemical gold extraction process" treats high-concentration arsenic-containing slag liquid produced by biological pre-oxidation of arsenic-containing gold concentrate-cyanide gold extraction process, respectively using the goethite method (50~ 90°C, 2~4h) and ferrous salt enhanced aeration (control) for harmless treatment, although the effect of iron ions is used, there are problems such as inapplicability of the method

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