Nitric acid aqueous solution recycling method, electrolytic processing method using it, nitric acid aqueous solution recycling liquid, and recycling system

摘要

PROBLEM TO BE SOLVED: To provide a method for recycling an aqueous nitric acid solution having excellent production stability. The recycling method of the present invention is a recycling method for reusing a waste liquid containing nitrate ions, water, and chromium ions so that the concentration of Cr6 + in the waste liquid is 5.0 ppm or less. It includes a reduction step of reducing Cr6 + contained in the waste liquid to Cr3 +, and a separation step of permeating the waste liquid containing Cr3 + through a reverse osmosis membrane to obtain a permeated liquid containing nitrate ions and water after the reduction step. .. [Selection diagram] Fig. 1