Arsenic And Fluoride Removal From Water By An Iron-Zirconium Oxide:Performance And Mechanism

Arsenic and fluoride contamination in ground water are occurring in many provinces of China and the frequent industrial activities also added excessive arsenic and fluoride into groundwater. Therefore, cost-effective technology for arsenic and fluoride removal received extensive attention. Iron-Zirconium oxide adsorbent was used for arsenic and fluoride removal in this study. The batch experiments (the adsorption effects were examined under varying conditions of adsorption time, pH, initial concentration, co-existing anions, et al.) and long-term dynamic effects were used to describe the performance of arsenic and fluoride on granular of iron-zirconium oxide. The EDX-Mapping, infrared (FTIR), X-ray photoelectron spectroscopy (XPS), release of sulfate, and other analytical techniques were explored to characterization the mechanism of arsenic and fluoride on iron-zirconium oxide.The powder of Iron-Zirconium oxide adsorbent had an amorphous strcture. The pore size distribution, surface area, crushing strength and mechanical strength of granular adsorbent were3.6-218μm,95.5m2·g-1,22.1±2.0N,9.1%±1.7%, respectively.The results of arsenic removal with Iron-Zirconium oxide adsorbent revealed that:the adsorption process was well fitted by pseudo-second-order kinetic model and was controlled by intrapartical diffusion; arsenic removal would not be effected by pH at a broad range (from3.0-9.0); the adsorption isotherms were well described by Langmuir isotherm equation; considering the normal concentration of co-existing anions and HA in natural groundwater, HCO3-and HA would take into account; the best desorption concentration of NaOH for granular adsorbent was3%; with an influent concentration of500μg·L-1and SV2h-1,2433bed volumes of water was obtained before effluent water of arsenic reaching10μg·L-1; the used granular adsorbent was inert and could be safely land filled:the adsorption sites on adsorbent for arsenic occurred at the particle surface; the mechnism of arsenic(V) removal was surface hydroxyl replacement during the adsorprion process and Fe-OH sites played key roles in arsenic removal.The results of fluoride removal with Iron-Zirconium oxide adsorbent revealed that:the adsorption process was well described by pseudo-second-order kinetic model; the adsorption process was mainly controlled by film diffusion in0.56h and then controlled by intrapatical diffusion; The adsorbent performed well over a wide pH range of3.5-9.0; the adsorption isotherms were fitted by Freundlich isotherm equation; considering the normal concentration of co-existing anions and HA in groundwater, HA and HCO3-would take into account; the best desorption concentration of NaOH for granular adsorbent was0.01mol·L-1; using actual groundwater as influent, about370,239and128BV of groundwater were treated before1.0mg·L-1was reached under SV of0.5,1and3h-1, respectively; the spent granular was inert and could be safely disposed of in landfill; fluoride could get into the whole granular adsorbent; the mechanism of fluoride removal was hydroxyl replacement and Zr-OH sites played key roles in F-adsorption.