Equilibrium and Kinetics Studies of Phosphate Removal from Solution onto a Hydrothermally Modified Al-Si-Fe-Ca Composite Adsorbent

Abstract

A novel Al–Si–Fe–Ca composite material for phosphate removal in wastewater treatment was made by using Al (OH)3,Fe2O3,CaO and silica powder as raw materials. Sorption data modelling with a pH range of 3–12, P concentrations of 3,5,7,9, 11,13, 15mg L−1, and an ambient temperature of 23°C indicated that an optimal removal of P occurred at pH 6.0. A maximum removal of 99.68% was found for 11mg L−1(pH of 6). Langmuir isotherm best described theadsorption processwith a maximumadsorption capacity of 8.60mg g−1. Three kinetic models (apseudo-first-order, a pseudo-second-order (PSO) and Elovich) were also applied,and the results showed that the PSOmodel best described the data. SEM and EDAX analysis confirmed that P was adsorbed to the surface of the composite material. This study demonstrates that the composite adsorbent is suitable for use in wastewater treatment, with P removal of the solids being preferential and spontaneous.