Method for recycling mixed-acid wastewater generated from metal pickling

Abstract

The invention discloses a method for recycling metal hydroxide sludge, generated after liquid alkali neutralization, and calcium fluoride sludge resources, generated after calcium chloride solution adding, from mixed-acid wastewater generated from steel industry pickling. The method mainly comprises the steps: subjecting the mixed-acid wastewater to reduction, then, adding liquid alkali, and carrying out concentrating by an ultramicro separator and press filtration by a press filter, so as to recycle metal hydroxide sludge (with the solid content of 50%); adding calcium chloride to produced water of the ultramicro separator, and then, carrying out precipitating, concentrating and pressure filtration, thereby recycling calcium fluoride sludge (with the solid content of 50%). According to the method, valuable metal ions and calcium fluoride sludge can be recycled from pickling mixed-acid wastewater, harmful dangerous solid wastes are not generated, the waste is changed into the valuable,the economic benefit of sewage treatment is improved, and the treatment cost is reduced.

Description

technical field [0001] The invention belongs to the field of disposal of sludge produced after the treatment of environmental protection wastewater, in particular to metal hydroxide sludge generated after neutralization with liquid caustic in the mixed acid wastewater produced by pickling in the iron and steel industry, and after adding calcium chloride solution The recycling method of calcium fluoride mud resource. Background technique [0002] With the rapid development of my country's technological economy, it has led to the rapid development of the steel industry. The original steel parts must be pickled before cold rolling, electroplating, and spraying to remove oxides on the surface and produce pickling wastewater. The main components of pickling wastewater are for SO 4 2- 、H + , Fe 2+ 、Na + 、Cr 6+ , F - 、Me n+ 、Ni 2+ etc. Pickling wastewater can generally be divided into neutral salt wastewater and mixed acid wastewater, and the main pollutants in mixed acid w...

AI Technical Summary

Problems solved by technology

[0005] (1) The amount of sludge is large, the sludge composition is complex, difficult to recycle, non-recyclable, and harmful. The sludge is mainly composed of hydroxide precipitation, excess lime, calcium fluoride, lime powder impurities, and PAC / PAM pharmaceutical water (accounting for about 50% to 65%) and other components; the content of valuable metal salts is very low, basically there is no re-smelting and recovery value, more impurities and water make the sludge a large amount, and due to the existence of heavy metals (such as Chromium compounds), this type of sludge has been included in the list of hazardous solid waste

Metal hydroxide sludge is mixed with calcium fluoride sludge, which is difficult to recycle

[0006] (2) The landfill disposal of sludge causes the waste of metal resources and the destruction of the environment. The sludge containing acid and chromium wastewater contains a large amount of valuable metal substances such as iron, chromium and nickel. Landfill disposal will not only It requires a high cost of hazardous solid waste disposal, and it also needs to occupy a large amount of land resources for landfill, which will affect the lives of surrounding residents and the quality of groundwater

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