Modification of sand with Fe-Zn oxides: an alternative strategy to improve adsorption of phosphate from artificial wastewater treatment

In this work, Fe-decorated quartz sand (FS), Fe-Mn bimetallic cation-decorated quartz sand (FMS) and Fe-Zn bimetallic cation-decorated quartz sand (FZS) were synthesised from ordinary quartz sand (QS). Iron, iron-manganese and iron-zinc oxides were stably formed on the surfaces of FS, FMS and FZS, respectively. The specific surface area of FZS (1.0497 m2/g) increased to more than 320% against that of QS (0.2482 m2/g). The obtained samples were evaluated for the removal of phosphate from artificial wastewater. Parameters that can affect adsorption process include solution phosphate concentration, pH and retention time, which were investigated by bath adsorption experiments. Under the optimal experimental conditions (pH value 4.0, initial concentration of phosphate 15 mg/l, temperature 25°C, retention time 150 min and adsorbent dose 5 g), the removal efficiency of phosphate by FS was higher than that of QS, FS and FMS and the maximum phosphate adsorption capacity (qmax) provided by FZS is 0.18 mg/g. Furthermore, the kinetics of phosphate adsorption fit well with the pseudo-second-order model, indicating that adsorption of phosphate on the Fe-Zn co-decorated quartz sand occurred through chemisorption, and the Langmuir adsorption isotherm model (R2 = 9944) is more suitable for adsorption capacity prediction than the Freundlich adsorption isotherm model (R2 = 0.9427). The results show that quartz sand can be modified effectively, which has great practical application potential in water treatment.