Semi-continuous recovery of chromium from waste water

The use of chromium(III) salts is under review by global industries. One of the options for better management of chromium is through recovery and reus e. Batch type processes for the recovery of chromium and subsequent use in tanning has already gained importance in the tanning industry. Here we desc ribe a novel semi-continuous method for the recovery of chromium(III) from tannery wastewaters containing the metal ion. In this system, sodium carbon ate is used as the alkali to precipitate chromium(III) as chromium(III) hyd roxide, instead of magnesium oxide, which is preferred for batch type syste ms. The hydrostatic pressure build-up and turbulence within the reactor is modulated to achieve online separation of chromium(III) hydroxide. Under st eady state conditions, the inflow into the reactor is matched by the outflo w. The outflow from the reactor can be discharged without causing ground-wa ter hardness.