Recycling sulfuric acid solution containing metals, preferably test solutions from determination of chemical oxygen demand, involves redox-controlled separation of silver amalgam with iron and precipitation as hydroxide

摘要

In a process for recycling concentrated sulfuric acid solutions containing metals, (i) iron metal is used as precipitation reagent for redox-controlled removal of metals in the form of amalgam up to a potential of -450 to -550 mV versus a standard hydrogen electrode; (ii) the solution is treated with alkaline solution to a pH at which the metals are precipitated as hydroxides; and (iii) the precipitated metal hydroxides are separated.