Non-ferrous metal recycling in phosphating baths - comprises leaching the slurries with phosphoric acid and recycling the non-ferrous metal solns. obtd. in the phosphating bath for iron surface treatment

摘要

A process for non-ferrous (NF)-metal recycling in phosphate baths comprises leaching the NF-metal contg. slurries or suspensions with dil. phosphoric acid at pH 1.2-1.8 and 60-100 deg.C (or 30-120 mins., thus transforming esp. Zn, Ni and Mn completely into recyclable phosphoric acid solns., while NF-metal free iron phosphate remains as a useful residue. USE/ADVANTAGE - The process selectively separates NF metals (esp. Zn, Ni and Mn) which can be directly recycled to the phosphating bath used to treat surfaces of iron sheets to give them a protecting coating. Thus the losses of 50% Zn, 10% Ni and 10% Mn usually associated with the phosphating process are avoided. The iron phosphate residue is also useful. Simple leaching step is inserted between phosphating bath and solid/liquid sepn. The amt. of reagent used is low, no foreign reagents are used and there is thus no contamination of the bath. There is no waste water. The NF metal free iron phosphate residues are used as precursors for the prodn. of phosphorus fertilisers.