Tadashi Nishino

Musashi Institute of Technology, Laboratory of Inorganic Materials
(1-28 Tamazutsumi, Setagaya-ku, Tokyo 158 Japan)

Abstract

Surface phosphatizing treatment has usually been conducted for automobile bodies, hardware and other metals for the purpose of increasing corrosion resistance and paint adhesion. However, a large quantity of sludge containing iron phosphate (III) as the main ingredient is produced during the surface treatment. The sludge thus produced has been dumped and buried in specific areas. The present paper relates a fundamental study to dissolve the sludge with a simple operation and a proposal to reuse resouces to protect the global environment. The dissolution method comprised stirring the sludge in an aqueous suspension containing the hydrogen form of a strongly acidic ion exchange resin, abbr. as H-R. The initial ion exchange reaction between slightly dissociated metallic ion (s) in the sludge and H-R accelerates the following dissolution tendency, which results in the complete dissolution with liberation of phosphoric acid. The dissolution was conducted for synthetic hoepite, amain phosphatized crystal, iron phosphate (III) and a sludge accumulated in an automobile assembly plant.

Key words: ion exchange resin, sludge, dissolution, recycle