Mechanisms and novel performance of ZrO2/Fe3O4 composite for phosphate recovery from wastewater

• We investigated phosphate adsorption, desorption & recovery using Fe 3 O 4 /ZrO 2 composite. • Adsorption properties of Fe 3 O 4 /ZrO 2 was investigated through kinetic, adsorption isotherm and thermodynamic analysis. • The physical adsorption mechanism of Fe 3 O 4 /ZrO 2 is occurred by electrostatic attraction. • Chemical adsorption is occurred on Fe3O4/ZrO2 surface by potential bidentate inter-complex and monodentate are formed. In this study, a composite material of Fe 3 O 4 with excellent physical adsorption and ZrO 2 with excellent chemical adsorption properties was synthesized to maximize the phosphate recovery efficiency in water. Fe 3 O 4 , ZrO 2 , and Fe 3 O 4 /ZrO 2 were prepared using co-precipitation and characterized using various surface and structural analysis techniques. Fe 3 O 4 exhibited both physical and chemical adsorption mechanisms, as evidenced by its pseudo-first- and pseudo-second-order kinetics during the adsorption/desorption process, while the dominant adsorption mechanism for ZrO 2 was chemical adsorption. The adsorption mechanism of Fe 3 O 4 /ZrO 2 shows physical adsorption by electrostatic attraction followed by chemical adsorption in which potential bidentate inter-complex and monodentate are formed. From the hydroxyl group analysis, it can be seen that the hydroxyl radicals increased by about 3.5 times or more due to the presence of Fe 3 O 4 on the surface of ZrO 2 . Overall, the synthesis of Fe 3 O 4 /ZrO 2 successfully improved the low adsorption performance of Fe 3 O 4 while ameliorating the disadvantages of ZrO 2 .