Phosphate Removal from Wastewater Using Calcium Silicate Hydrate Synthesized from Lake Sediment and Bivalve Shell

Excessive discharge of phosphorus (P) from wastewater into water bodies can lead to water eutrophication and deleteriously affects aquatic lives and the surrounding ecosystem. Hence, phosphorus removal from wastewater is necessary for the control of eutrophication of the receiving water bodies. This study investigated the removal of phosphate using calcium silicate hydrate (CSH) synthesized from Tonle Sap Lake sediment and bivalve shell, a kind of silica and calcium-rich abundant natural waste materials, respectively. The CSH was synthesized through a hydrothermal method at a temperature of 110 degrees C for 12 h with varying Ca/Si molar ratio from 0.83 to 1.5. The study on utilization of CSH for phosphate removal was done by batch experiments. The effect of Ca/Si molar ratio, contact time and initial pH on phosphate adsorption capacity was investigated. The result showed that the Ca/Si molar ratio of 1 is the optimum synthesis condition for phosphate removal. Based on Si released and FTIR results, the phosphate adsorption process occurred by ion exchange with silicate. The equilibrium data of phosphate adsorption fitted well with the Langmuir model and the maximum phosphate removal capacity onto CSH was 270.27 mg/g.