Phosphate removal from aqueous medium by kaolin-supported nano-scale zero-valent iron particles

In tis study, phosphate removal from aqueous medium by kaolin-supported nano scale zero-valent iron (K-nZVI) particles was investigated. Therefore, K-nZVI was prepared using the ferric iron chemical reduction method by borohydride in laboratory. Kaolin was used as a support material. In the study, nano scale zero-valent iron (nZVI) was also synthesized by using the same method without kaolin. When kaolin, nZVI and K-nZVI materials are used, the best removal efficiency was achieved using K-nZVI. To determine the most effective kaolin: nZVI mass ratio for phosphate removal, K-nZVI with different kaolin: nZVI mass ratios was prepared and the best phosphate removal efficiency was obtained with K-nZVI having a kaolin: nZVI mass ratio of 1:1. In the study, the effect of parameters such as initial solution pH, K-nZVI amount, initial phosphate concentration, temperature and chloride, sulfate and bicarbonate anions on phosphate removal efficiency were also examined. The removal efficiency was dependent on pH and the best removal efficiency was achieved at pH 3. For effective adsorption of phosphate, K-nZVI dosage of 0.5 g/L was sufficient. It was observed that phosphate removal efficiency decreased with increasing initial phosphate concentration and increased with raising temperature. Chloride and sulfate anions did not affect the removal efficiency, but the removal efficiency decreased in the presence of bicarcarbonate. Langmuir and Freundlich isotherm models were applied to equilibrium data and it was shown that Langmuir isotherm model achieved better fit than Freundlich isotherm model. It was also determined that the process of phosphate adsorption onto K-nZVI was well fitted the pseudo second order kinetic model. Phosphate from actual wastewater was effectively removed using K-nZVI. By considering the available data, it was understood that K-nZVI particles can be used successfully in the removal of phosphate from aqueous medium.