Synthesis of high quality boehmite and γ-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 γ-alumina for phosphate removal. Synthesized boehmite and γ-alumina were able to remove phosphate quickly and effectively. Boehmite (hydrothermal treatment at 60 °C) showed maximum phosphate removal (adsorption) of 61 mg P/g followed by γ-alumina (50 mg P/g) and the boehmite hydrothermally treated at 120 °C (41 mg P/g). The degree of crystallinity gave more effect on phosphate adsorption of boehmite than that of γ-alumina. The lower the pH, the more phosphate adsorbed on the boehmite and γ-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 γ-alumina.