Effluent treatment and by-product recovery from the sludge of an alumina plant

Abstract

During the recovery of vanadium pentoxide from vanadium containing sludge of alumina plants, huge amount of effluents containing NH3, P, V and NaCl, is generated. Due to its toxic nature, it can neither be discharged to land or water nor can be stored as such, hence a process has been developed to recover ammonia as salts and vanadium pentoxide to be recycled. Thus on using sulphuric acid, about 75% of ammonia was recovered as ammonium sulphate and while using HCl about 89% of ammonia was obtained as ammoniun chloride. On refluxing calcium vanadate with H2SO4 about 94% of V2O5 is obtained which may be recycled to the main stream of V2O5 plant.