Enhancing the adsorption function of F- by iron and zirconium doped zeolite: Characterization and parameter optimization

This study presented an original study on the F- removal by Fe and Zr doped Gismondine-dominated Zeolite. Various modified zeolites are prepared by systematically adjusting the synthesis variables, namely pH, mass ratio of zeolite to modify agent (mZeolite:m( Fe+Zr)), mass ratio of Fe to Zr (Fe:Zr) to investigate their effects on the F- adsorption. The performance of prepared Fe-Zr-Zeolite on F- removal was examined through both statistic adsorption and dynamic adsorption. Results indicated that when the modified pH was 7, the Fe:Zr ratio was 1:1 and mZeolite:m( Fe+Zr) was 1:2, the modified natural zeolites which was named Fe-Zr-Zeolite showed the best removal efficiency on F-. Fe-Zr-Zeolite could remove over 80% when the initial concentration was less than 20 mg/L and F- adsorption followed pseudo-second-order adsorption kinetic and Langmuir adsorption isotherm, indicating that F- adsorption by Fe-Zr-Zeolite was chemically dominated. Besides, Fe-Zr-Zeolite had better removal efficiency of F- under acidic conditions than that under alkaline conditions, and the competing anions, typically, Cl-, NO3- and SO42- had negligible effect on F- removal by Fe-Zr-Zeolite. The dynamic adsorption test demonstrated that in order to maintain the high removal efficiency of F-, the filling thickness of Fe-Zr-Zeolite should be at least 30 cm and the small the flow rate is, the higher the F- removal efficiency will be.