Recovery of acid from pickling liquors

摘要

Steel rolling mills generate effluents, viz. acid rinse water and spent pickle liquor, laden with high concentrations of sulfuric or hydrochloric acid, and iron, during the pretreatment operations for removal of oxide scales from the surface of steel sheets. A conventional treatment process incorpo- rates neutralization, sludge separation, and further treatment of wastewater in solar evaporation ponds. Disposal of sludge creates environmental problems. An alternative resource recovery based process for treating hydrochloric acid-spent pickle liquors which envisages recovery of acid from the wastewater that may be recirculated to the pickling baths, has been developed on bench scale.