Abstract
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•Magnetic zirconium-iron oxide nanoparticle (MZION) was successfully synthesized.•The removal of phosphate could be effectively fulfilled using MZION.•MZION could be conveniently separated by magnet after adsorption.•The Fe/Zr molar ratios played a key role in adsorption capacity and magnetic separation.
In this study, magnetic zirconium-iron oxide nanoparticles (MZION) of different Fe/Zr molar ratios were successfully prepared using the co-precipitation method, and their performance for phosphate removal was systematically evaluated. The as-obtained adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Zeta potential analyzer, Fourier transform infrared spectroscopy (FT-IR) and Brunauer Emmett Teller (BET) specific surface area analysis. The effects of pH, ionic strength, and co-existing ions (including Cl−, SO42−, NO3− and HCO3−) were measured to evaluate the adsorption performance in batch experiments. The results showed that decreasing the Fe/Zr molar ratios increased the specific surface area that was propitious to adsorption process, but the adsorption capacity enhanced with the decrease of Fe/Zr molar ratios. Phosphate adsorption on MZION could be well described by the Freundlich equilibrium model and pseudo-second-order kinetics. The adsorption of phosphate was highly pH dependent and decreased with increasing pH from 1.5 to 10.0. The adsorption was slightly affected by ionic strength. With the exception of HCO3−, co-existing anions showed minimum or no effect on their adsorption performance. After adsorption, phosphate on these MZION could be easily desorbed by 0.1M NaOH solution. The phosphate adsorption mechanism of MZION followed the inner-sphere complexing mechanism, and the surface OH groups played a significant role in the phosphate adsorption. Additionally, the main advantages of MZION consisted in its separation convenience and highly adsorption capacity compared to other adsorbents.