A method for removing heavy metals in stainless steel pickling wastewater

Abstract

The invention relates to a method for removing heavy metals in stainless steel pickling wastewater. In this method, an anion exchange membrane and a cation exchange membrane are combined to form a double-membrane three-chamber electrodialysis cell, the middle chamber is between the anion and yang membranes, the anode chamber is on the one side of the anion membrane, and the cathode chamber is on the one side of the cation membrane. Add stainless steel pickling wastewater to the intermediate chamber, add dilute nitric acid to the anode chamber, and add complexing agent to the cathode chamber. With stainless steel as the cathode and graphite as the anode, direct current is applied. Under the action of an electric field, the selective permeability of the ion exchange membrane to anions and cations is used, so that the heavy metal ions in the wastewater are enriched in the cathode chamber in the form of metal complex anions, and the acid radical anions are enriched in the anode chamber. The method has the characteristics of simple operation and easy control of process parameters. It can not only remove heavy metal ions in stainless steel pickling wastewater, but also enrich and recover heavy metal ions.

Description

technical field [0001] The invention relates to a method for removing heavy metals in stainless steel pickling wastewater by electrodialysis. Background technique [0002] Stainless steel has excellent corrosion resistance, mechanical properties and beautiful surface, and is a widely used metal material. During the process of smelting, casting, rolling and heat treatment of stainless steel, a thin and dense oxide film will be formed on the surface, the main component of which is iron oxide (FeO, Fe 2 o 3 and Fe 3 o 4 ), chromium oxide (Cr 2 o 3 ), nickel oxide (NiO) and insoluble FeO Cr 2 o 3 、FeO·Cr 2 o 3 · Fe 2 o 3 , Ni·Fe 2 o 3 and other substances. In order to eliminate the adverse effect on the subsequent processing of stainless steel and maintain a good appearance, it is necessary to remove this layer of oxide film through surface treatment. The surface treatment process of stainless steel is mainly pickling, because Cr 2 o 3 、FeO·Cr 2 o 3 and FeO Cr...

AI Technical Summary

Problems solved by technology

[0005] Although the neutralization precipitation method can remove the heavy metal ions in the wastewater in the form of hydroxide precipitation, but because the precipitation (commonly known as stainless steel pickling sludge) contains heavy metal elements Cr and Ni, it is an industrial hazardous solid waste. If it is not treated Simple landfill will occupy a lot of land and easily cause secondary pollution

From the perspective of resource utilization of sludge, some researchers use it as an additive raw material to produce building materials. However, the resulting building material products have low market acceptance, especially the environmental safety under natural conditions still needs to be evaluated.

Images