A treatment method for zinc smelting wastewater

Abstract

The invention discloses a treatment method for zinc smelting sewage, which specifically comprises the following steps: after neutralizing the zinc smelting sewage once with a neutralizer, slurrying and washing the filter residue, and performing secondary neutralization on the filtrate to obtain The filter residue is sent to the rotary kiln for volatilization, and the obtained filtrate is neutralized three times, and the filter residue obtained after three times of neutralization is returned for one neutralization as a neutralizing agent. The obtained filtrate is naturally purified and then subjected to deep membrane purification to finally obtain industrial boiler water and reused concentrated water . The method of the invention is simple, realizes zero discharge of zinc smelting sewage treatment and high-efficiency enrichment of heavy metals in zinc smelting sewage, achieves the purpose of resource utilization of valuable metals, and simultaneously produces high-quality gypsum slag as raw material for industrial gypsum production or cement The production raw materials are sold to achieve the purpose of turning waste into treasure; in the treatment method of zinc smelting sewage provided by the present invention, dangerous chemicals such as concentrated sulfuric acid or concentrated hydrochloric acid are no longer used, which reduces safety risks and production costs.

Description

technical field [0001] The invention relates to the technical field of sewage treatment, in particular to a treatment method for zinc smelting sewage. Background technique [0002] Zinc smelting sewage is acidic, generally acidic with pH=0.5~1.0, sometimes acidic with pH lower than 0.5, and contains a variety of heavy metals, mainly zinc, followed by lead, copper, cadmium and other metals, generally zinc content is 2.5~2.2g / L. Zinc smelting wastewater cannot be discharged directly and must be treated up to standard. At present, the traditional treatment process is mainly based on "lime neutralization method", which is to neutralize the sewage with lime, increase the pH value of the solution to hydrolyze and precipitate heavy metals, and achieve the purpose of purification. [0003] The specific treatment process is as follows: first neutralize once: use neutralizing agent lime milk or quicklime powder to neutralize the zinc smelting wastewater to a certain pH value, genera...

AI Technical Summary

Problems solved by technology

[0005] 1. Due to the high acid content of zinc smelting sewage, the acid content is generally at pH=0.5~1.0, and the pH value is lower than 0.5 when it is high. It is neutralized to pH=8~9 with a one-time neutralizer, although most of the heavy metals are hydrolyzed and precipitated In the slag, but the consumption of neutralizing agent is too large, a large amount of low-zinc gypsum slag is produced, that is, gypsum slag and heavy metal mixed slag hydrolyzed and precipitated, and further treatment is difficult

[0006] At present, there are mainly two ways to deal with this kind of slag. One is to sell it to cement factories as raw materials, but it contains a certain amount of zinc and other metals, which seriously affects the quality of its products and the safety of product use. restricted

The other is to use rotary kiln for comprehensive recovery, but the slag contains too low zinc and other metals and high gypsum content. A large amount of gypsum slag makes the operation of the rotary kiln very difficult and the production cost is high.

[0007] Many manufacturers only stockpile or carry out harmless landfill, resulting in a large backlog of funds and waste, and seriously increasing environmental risks

[0008] 2. In the deep hydrolysis purification from pH 8~9 neutralization to pH 10.5~11.5, the utilization rate of neutralizing agent lime milk or lime powder is too low, and 20%~30% are not used

This alkaline slag is hazardous waste, which contains lower zinc and other valuable metals. It is more harmful to the environment and cannot be stored. After burning, the water-quenched slag that has no impact on the environment is produced; some manufacturers return it to neutralization once and comprehensively utilize the alkali in it, but invisibly increase the amount of slag neutralized and deplete the metals in the slag

[0009] 3. For standard alkaline water with a pH value of 10.5-11.5 after treatment, concentrated sulfuric acid or concentrated hydrochloric acid needs to be added to adjust its pH value to between 6 and 9, and other new ions such as sulfate ions or chloride ions are introduced. It increases the environmental risk and also increases the production cost; if concentrated sulfuric acid is used to adjust the pH value, the newly introduced sulfate ion will seriously affect the subsequent deep membrane purification process

If the pH value is adjusted with concentrated hydrochloric acid, although the newly introduced chloride ions have little impact on the subsequent deep membrane purification process, the breadth of reuse is limited

[0010] 4. More importantly, both sulfuric acid and hydrochloric acid are dangerous chemicals, and they are precursors. The use of these drugs not only complicates the relevant procedures, but also increases the risk of personnel safety and environmental safety.

[0011] To sum up, how to solve the problems of large volume of hazardous waste, high processing cost, low safety factor and small reuse space is an urgent problem for current scientific research workers.

Images