Abstract
ABSTRACT
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 incorporates 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. In this process 85% of the hydrochloric acid can be recovered from the pickling wastewater. At the same time 90% of the iron in the ferrous form could be recovered as ferrous sulfate. This recovered salt, which has commercial value, was found to be 86.5% pure. Studies regarding the development of the process are reported in this paper.
Key words:
Acid rinse; spent pickle liquor
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