Cyclic utilization of waste aluminum polishing solution by an efficient co-extraction system: Influence factors and extraction mechanism

Abstract

For the purpose of regenerating waste aluminum polishing solution and eliminating its potential threats to environmental safety, this work focuses on establishing a highly effective co-extraction system for the simultaneous recovery of H3PO4 and H2SO4 from this kind of hazardous wastes, and further reveals the main influence factors and extraction mechanisms. Through a series of screening experiments, a co-extraction system including tributyl phosphate and 1-butanol was successfully established, and the experimental results verified the suitability of this system for the regeneration of most H3PO4 and H2SO4 from waste aluminum polishing solution. The McCabe-Thiele diagram was used to determine that the whole extraction process was a counter-current process of 4-stage extraction and 2-stage stripping, which was capable of recovering most of H3PO4 and H2SO4. The main influence factors include phase ratio, temperature, and contact time, which have different degrees of influence on the recovery efficiency. The co-extraction mechanism of H3PO4 and H2SO4 has also been confirmed by the methods of FTIR, 1H NMR, 17O NMR and 31P NMR.