Method for recycling and processing nickel in stainless steel pickling waste acid

Abstract

Disclosed is a method for recycling and processing nickel in a stainless steel pickling waste acid. The potential of hydrogen (pH) value of a mixed waste acid is adjusted to 3.5 to 4.5 by lime, hydrogen peroxide is added, a reaction is performed for 0.5 to 1 hour, then the pH value is adjusted again to 4.0 to 4.5 by the lime, then a flocculating agent is added to enter into a sedimentation tank to obtain a clear liquid and sludges, the clear liquid enters into a second reaction tank, the obtained sludges are subjected to a filter pressing to obtain a filter cake, the filter cake is subjected to a back washing by stainless steel factory workshop ground washing wastewater, and filter pressing water is transferred into the second reaction tank. The lime is added into the second reaction tank to adjust the pH value to 9.0 to 10.0, the flocculating agent is added, a formed solid-liquid mixture is transferred into a second sedimentation tank to be subjected to a solid-liquid separation, solids are subjected to the filter pressing to obtain a nickel mud, a sulfuric acid is added into a filter pressing liquor to adjust the pH of effluent to 7.0 to 8.0, and environmentally acceptable discharge can be achieved. By means of the method, the effective recycling of heavy metal nickel can be achieved, secondary pollutions are reduced, sludge qualities can be improved, and waste acid treatment emission requirements can be met.

Description

technical field [0001] The invention relates to a method for recovering heavy metals in waste acid treatment, in particular to a method for recovering nickel in stainless steel pickling waste acid. technical background [0002] The source of stainless steel pickling waste acid is mainly generated from the pickling of steel element blanks before electroplating and spraying on the surface. The liquid is mainly produced in the pre-pickling process. Pre-pickling is to remove the iron oxide scale on the surface of stainless steel pipe, using sulfuric acid pickling solution, the content of sulfuric acid should be 15%~20%, the content of ferrous sulfate should be less than 250g / L, the temperature of pre-pickling should be 50~72℃, after pre-pickling The surface of the stainless steel tube has a layer of black precipitates that cannot be removed in the sulfuric acid solution, that is, the oxides of chromium and nickel. Therefore, whitening pickling (final pickling) is required to r...

AI Technical Summary

Problems solved by technology

The advantage of electrodialysis is that the equipment is simple, the recovery efficiency is high, and the waste acid can be recovered and iron can be extracted. The disadvantage is that the power consumption is high

The roasting method and distillation method are operated at high temperature, and the service life of the equipment is short, and the acid gas, dust and air pollution caused by the high temperature make the environment difficult to maintain, and the furnace needs to be shut down every month to maintain the equipment, and the maintenance cost is high

The disadvantages of fluidized bed roasting and spray roasting are high equipment cost, limited scale, and air pollutant emissions

The chemical precipitation method has the advantages of good treatment effect, low investment, and easy operation, but the biggest disadvantage is that the amount of sludge is large, the sludge is difficult to dewater, and it is difficult to recycle, which affects its application and development.

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