Improvement of the chemical synthesis efficiency of nano-scale zero-valent iron particles

This study investigates the synthesis conditions of nano-scale zero-valent iron (nZVI) formed by the chemical reduction method via an optimization process in order to enhance the nZVI's reactivity. The properties of nZVI particles were characterized by transmission electron microscopy, laser diffraction particle size analyzer and Xray diffraction. The performance of nZVI was evaluated using the nitrate and phosphorus solutions. The optimization results for the effective variables, namely concentration, delivery rate and liquid volume of sodium borohydride (NaBH4), precursor concentration (FeCl3), reaction temperature, mixing speed, pH and aging time were demonstrated the improvement in nZVI reactivity. The results confirm that nZVI proved high removal efficiency along with the lower particle size at NaBH4 concentration 16 g/L. The feeding rate of NaBH(4 )at 40 mL/ min can effectively reduce the particle size and increase the nZVI reactivity. Increasing the NaBH4 liquid volume greatly improved the reactivity. Reduction of reaction aging time to 5 min and employing the acidic reaction medium of 6 pH greatly improved the nZVI reactivity. The highest mixing speed of 1000 rpm enhanced the phosphorus adsorption efficiency. However, high nitrate reduction was observed at 500 rpm. Increasing the reaction temperature resulted in decreasing the average particle size and the highest reactivity was achieved at 90 degrees C. nZVI reactivity significantly was improved in the direction of low precursor concentration, and the highest efficiency was gained at 20 mg/L. In conclusion, the optimized parameters enhanced the overall efficiency of nZVI of nitrate reduction and phosphorus adsorption by 27% and 9.5% respectively.