Study of Equilibrium Adsorption of Orthophosphate on Alumina Adsorbents

This work is a part of a comprehensive study on economic re-utilization of a phosphate contaminated industrial water stream in a typical petrochemical plant in the Kingdom of Saudi Arabia. The experimental study is primarily the adsorption of orthophosphate at equilibrium conditions on 28x48 mesh Alcan Alumina AA 400G. A fixed amount of orthophosphate solution containing 10 mg/L of phosphorus is added to varying amounts of alumina adsorbent. The mixture is allowed to equilibrate over a period of time in excess of 24 hours. The phosphorous content is obtained by forming a molybdate complex and analyzed on the visible range of UV Spectrophotometer at 700 μm. The equilibrium isotherm data are obtained at pH of 4.5 and 6. A peak adsorption capacity of 12 -14 mg elemental phosphorus per gram adsorbent is observed. The data is fitted to both Freudlich and Sigmoidal Isotherm. Effect of activation and pH are presented.