Adsorption kinetics and isotherms of phosphate and its removal from wastewater using mesoporous titanium oxide

The adsorption of phosphate onto mesoporous TiO2 was investigated in order to reduce phosphorus concentrations in wastewater and provide a potential mode of phosphorus recovery. Three equilibrium isotherms were used to optimize and properly describe phosphate adsorption (R-2>0.95). The maximum capacity of phosphate on the adsorbent was found to be 50.4 mg/g, which indicated that mesoporous TiO2 could be an alternative to mesoporous ZrO2 as an adsorbent. A pseudo-second order model was appropriately fitted with experimental data (R-2>0.93). Furthermore, the suitable pH for phosphate removal by TiO2 was observed to be in the range of pH 3-7 in accordance with ion dissociation. In contrast, increasing the pH to produce more basic conditions noticeably disturbed the adsorption process. Moreover, the kinetics of the conducted temperature study revealed that phosphate adsorption onto the TiO2 adsorbent is an exothermic process that could have spontaneously occurred and resulted in a higher randomness of the system. In this study, the maximum adsorption using real wastewater was observed at 30 degrees C.