Development of Zeolite Loaded Mg-La-Fe Ternary (hydr) oxides for Treatment of Low Concentration Phosphate Wastewater

Abstract

A novel Mg-La-Fe ternary (hydr)oxide magnetic zeolite adsorbent (MLFZ) was prepared using the hydrothermal method and employed for effective phosphate removal in this study. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the MLFZ presented an amorphous surface with Mg, Fe, and La dispersed on the surface of the zeolite. The isothermal adsorption and kinetics results showed that the adsorption behavior of the MLFZ was consistent with that of the Langmuir isothermal model and quasi-second-order kinetics model. A relatively fast adsorption of phosphate with a short equilibrium time of 30 min was observed in the kinetics experiment, and the maximum adsorption capacity of the MLFZ was 13.46 mg·g-1 in the equilibrium adsorption isotherm study. The MLFZ showed effective adsorption performance over a wide pH range from 3.0 to 9.0. Moreover, the coexisting ions had an insignificant effect on phosphate adsorption. The MLFZ could easily be recovered using a magnet. After five adsorption-desorption cycles, the phosphate removal efficiency was maintained at approximately 90%. The FTIR, XPS, and Zeta potential analysis confirmed that the adsorption mechanisms were attributed to the surface deposition, electrostatic adsorption, and the inner complex formation by ligand exchange between lanthanum and phosphate. Furthermore, the MLFZ demonstrated high efficiency in scavenging phosphate from a natural pond (phosphate concentration decreased from 0.86 mg·L-1 to 0.013 mg·L-1), indicating that the MLFZ was an ideal material for phosphate management and treatment.