The Synthesis of NZVI and Its Application to the Removal of Phosphate from Aqueous Solutions

Abstract

Nanoscale zero valent iron (NZVI) was synthesized by the reduction of natural limonite under hydrogen conditions. The adsorption performance of the as-prepared NZVI on phosphate was evaluated through batch and column experiments. The removal of phosphate (PO₄³⁻) significantly decreased with an increase of pH from 2.0 to 11, whereas a remarkable increase of PO₄³⁻ removal was observed in the presence of SO₄²⁻ and S₂O₃²⁻. In addition, Cl⁻ and NO₃⁻ also improved phosphate removal at concentrations of more than 0.2 mmol/L. Kinetic studies indicated that the removal process of PO₄³⁻ on NZVI can be easily followed with the pseudo-second-order kinetic model. The removal of phosphate from the oxic system was significantly higher than that of the anoxic system, which was attributed to the formation of the secondary phase by the further oxidization of Fe²⁺. The adsorption capacity of the as-prepared NZVI of the oxic system was 16 mg/g, and the pH was 6.3. The column experiments further demonstrated that the as-prepared NZVI presented a high removal capacity for PO₄³⁻-P. These findings indicated that the as-prepared NZVI displayed an excellent ability to remove phosphate from aqueous solutions.

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