Synthesis of high quality boehmite and ?-alumina for phosphorus removal from water works sludge by extraction and hydrothermal treatment

Alum sludge from water treatment was calcined and extracted to synthesize high quality boehmite and gamma-alumina for phosphate removal. Synthesized boehmite and gamma-alumina were able to remove phosphate quickly and effectively. Boehmite (hydrothermal treatment at 60 degrees C) showed maximum phosphate removal (adsorption) of 61 mg P/g followed by gamma-alumina (50 mg P/g) and the boehmite hydrothermally treated at 120 degrees C (41 mg P/g). The degree of crystallinity gave more effect on phosphate adsorption of boehmite than that of gamma-alumina. The lower the pH, the more phosphate adsorbed on the boehmite and gamma-alumina (adsorb phosphate more than 4 times at pH 3 than at pH 11). Spectroscopic analysis (SEM-EDS and FTIR) indicates that phosphate are removed by ligand exchange, electrostatic attraction, and surface precipitation on the synthesized boehmite and gamma-alumina.