2.2. Metal finishing wastes
Three metal finishing wastes were obtained for this investigation.Metal finishing waste 1 (MW1) was a wastewater treatment filter cake from a mechanical surface treatment process used to produce a bright polished finish on copper fittings (supplied by Yorkshire Fittings Ltd). Metal finishing wastes 2 (MW2) and 3 (MW3) were the products of a tri-cationic phosphating operation involving zinc, nickel and manganese (supplied by Peugeot Citroën Automobiles, UK Ltd.). MW2 was the metal hydroxide filter cake produced at the effluent treatment plant. MW3 was the sludge removed directly from the phosphate bath by a plate and frame filter press.The metal finishing wastes were dried to constant weight and
ground to