Nitrate removal from aqueous solution: using zero-valent iron (Fe°) fixed on Ca-alginate bead

Drinking water pollution by nitrate in the world has a major environmental problem. The aim of this study was to investigate the synthesis and entrapment of nanoscale zero-valent iron (nZVI) in Ca-alginate beads for preventing the aggregation of Fe degrees particles in aqueous solution in order to remove nitrate efficiently. The nZVI with concentrations of 0.5 to 4 g Fe degrees was immobilized in the alginate bead by applying the barium and ferric ions to replacement of Fe degrees instead of the cations in the bead. The kinetics of the process was investigated by preparing the nitrate solution in concentrations of 20, 50, 100, 150, and 200 mg/L of NO3- at pH 2-10 and retention time 15-90 min. Nitrate removal efficiency by Fe degrees/Ca-alginate column was between 58% and 98% at retention time 90 min. Nitrate removal efficiency at pH 10 was 62% and also the removal efficiency at pH 4 was about 90%. The reduction capacity for nitrate has been increased with increasing time and nZVI dosage, while it decreased with increasing the nitrate concentrations and pH. This study results showed that the use of nZVI entrapped in Ca-alginate beads can be applied for in situ remediation of nitrate.