Removal of phosphate from aqueous solution by using thermally modified clamshell

The removal of phosphate (PO43-) from an aqueous solution by clamshell treated by heat process was investigated through batch experiments. The effects of initial phosphate concentrations, pH value, and contact time on the phosphate removal were carried out. The phosphate adsorption isotherm was described by the Langmuir and Freundlich models. As the result, the adsorption process correlated well to both models, and the theoretical maximum phosphate adsorption capacity was 319.0 mg/g by the Langmuir isotherm model. The influence of pH was investigated from 5 to 10, and the value of pH had no significant effect on phosphate adsorption capacity. This finding indicated the application of calcined clamshell in the large range of pH for phosphate removal. The phosphate adsorption capacity and phosphate removal efficiency were obtained at 209.0 mg/g and 38.7% at the initial phosphate concentration of 540 ppm at 25 degrees C for 24 h, respectively. The clamshell modified by heat treatment exhibited its substantial potential for fast and efficient phosphate removal in water and wastewater.