Phosphate adsorption characteristics of alunite to be used as a cement additive

The adsorption of phosphate from aqueous solution by alunite has been investigated as a function of calcination temperature, particle size, pH, agitation time and initial phosphate concentration. Phosphate adsorption was seen to increase with increasing calcination temperature, decreasing adsorbent particle size and pH. The adsorption isotherm data were fitted to the Langmuir isotherm. The alunite exhibited the highest phosphate uptake capacity at 1073 K calcination temperature, at a particle size of 90-150 mum, at the initial pH of 5.0, at an equilibrium time of 60 min and at the initial phosphate concentration of 20 x 10(-4) mol/l. The adsorption capacity, Q, was 4.697 x 10(-3) mol/g at initial pH 5.0. (C) 2003 Elsevier Ltd. All rights reserved.