Removal of aluminum from aqueous solutions using sodium di-( n-octyl) phosphinate

Abstract

Sodium di-( n-octyl) phosphinate (NaL), was used as a ligand agent to remove aluminum from aqueous solutions. Aluminum was removed from the aqueous phase as an insoluble complex in the form AlL 3(S). The effects of the initial pH, between 1 and 7, and of the mole ratio of NaL to aluminum, between 0 and 6, were investigated. Adding acid to the initial solution decreases the removal of aluminum and precipitates phosphinate in the acid form as HL (S). Total removal of aluminum, as AlL 3(S), was obtained with an initial pH of 2.75 and a mole ratio between the ligand and aluminum of 3. The removal of aluminum was not affected by the presence of calcium or chloride in the range of concentrations and pH studied. Over 95% of the aluminum, free of precipitating agent, was recovered by addition of a 3 M NaOH aqueous solution to the precipitate, followed by extraction of the sodium phosphinate with diethyl ether. The aluminum was completely recovered from the precipitated AlL 3(S) in a solution at a concentration four times its concentration in the initial aqueous phase.