Recycling processing method for stainless steel processing process wastewater grading precipitation

Abstract

The invention relates to a recycling processing method for a stainless steel processing process wastewater grading precipitation, which comprises the following steps: (1) deslagging and homogenizing acid-washing residual liquid and washing wastewater; (2) adjusting the pH to 4.0-5.5 by a CaCO3 filter bed to generate CaF2; (3) oxidizing Fe<2+> into Fe<3+> by an oxidizing agent to generate sedimentsof Fe(OH)2 and Fe(OH)3; after the Fe(OH)2 , the Fe(OH)3 and the CaF2 are deposited, recovering; (4) carrying out three-level alkali adding coagulation precipitation on the supernatant liquid of an oxidation precipitation pool; adjusting the pH to obtain a Cr sediment in the first-level alkali adding coagulation precipitation; acquiring a Ni sediment in the second-level alkali adding coagulation precipitation; carrying out the third-level alkali adding coagulation precipitation and adding a flocculating agent to remove residual heavy metal ions so that discharge water reaches the standard, wherein the alkali added into a grading reaction precipitation pool is NaOH, Ca(OH)2, CaO or Na2 CO3; (5) regulating the pH of the discharge water of the grading reaction precipitation pool to 6.0-8.0; discharging 0-20 percent of wastewater and filtering residual F<-> and suspended matters of 80-100 percent of wastewater to reach the standard and recycle; and (6) recycling the Cr-Ni metal or the compound thereof from the Cr sediment and the Ni sediment acquired by a third-level coagulation precipitation pool by a recycling device.

Description

technical field [0001] The invention belongs to the technical fields of environmental protection and chemical industry, and relates to a method for treating stainless steel processing process wastewater and resource recovery, in particular to a process for treating the stainless steel processing process wastewater up to the standard and recovering heavy metal ions such as nickel and chromium in the wastewater. Background technique [0002] Stainless steel is widely used because it is not easy to corrode, pit, rust or wear, and has high strength. Chromium-containing stainless steel also combines mechanical strength and high ductility, and occupies a large market share in industrial production, but its production and processing are seriously polluted. The mixed acid of nitric acid and hydrofluoric acid is used for pickling during processing, which will produce a large amount of high-acidity wastewater, which contains F - , Fe 2+ and heavy metal ions such as nickel and chromi...

AI Technical Summary

Problems solved by technology

[0010] The present invention aims at the characteristics of "three highs and one low" of current stainless steel processing wastewater (pickling residue discharged from pickling tanks and cleaning wastewater): high acidity (H + Concentration 1×10 -4 ~5mol / L), high fluorine content (≥50mg / L), high heavy metal concentration (≥200mg / L), COD Cr Low (≤300mg / L), a set of low-cost, easy-to-control, and efficient wastewater treatment process is proposed. Through graded precipitation, not only can the water meet the standard discharge and reuse, but also the nickel and chromium in the wastewater can be recovered

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