Reclamation of Aluminum Finishing Sludges

摘要

The research study of the reclamation of aluminum-anodizing sludges was conducted in two sequential phases focused on enhanced dewatering of aluminum-anodizing sludges to produce commercial-strength solutions of aluminum sulfate, i.e., liquid alum. The use of high-pressure (14 to 15 bar) and a diaphragm filter press were shown to be effective in dewatering aluminum anodizing sludges to cake solids contents of 27% to 29% and 25% to 31%, respectively. These values were well above the 21% value required to justify pursuit of direct acidic extraction of aluminum. Commercial-strength solutions of aluminum sulfate with concentrations of 8% as A1203 were produced using conventional-neutralization, segregated-neutralization, and etch-recovery sludge cakes. The trace metal contents of the alum products were, in general, typical of commercial products.