A study on treatment methods of spent pickling liquor generated by pickling process of steel

Metals to be coated require pre-treatment to remove rust or scale, impurities and inorganic contaminants. In steel industries, pickling process generates a considerable quantity of Spent Pickle Liquor (SPL) containing the dissolved metal salts of iron, chromium, copper, nickel and zinc as well as residual free acid. The waste generated by metal pickling and electroplating industries is identified as hazardous solid waste as per Indian Standards and United State Environmental Protection Agency (US EPA). This paper discusses the advantages and disadvantages of treatment methods of spent pickling liquor generated by pickling line of steel. The discussion shows that treatment method depends upon the quantity, quality and composition of SPL. Experimental modelling helps in better understanding of treatment process and also craft process more technically and economically feasible.