Aqueous Phosphate Removal Using Bare and Ca-Alginate Entrapped Nanoscale Zero-Valent Iron

Abstract

Nanoscale zero-valent iron (NZVI) particles are used for the remediation of a wide variety of contaminants. They are inexpensive, non-toxic and environmentally compatible in-situ uses. NZVI particles have high reactive surface area and, hence, high reactivity. In this study, NZVI slurry was successfully synthesized in the laboratory and used for contaminant removal. Phosphate removal and recovery by NZVI from aqueous solutions was investigated in batch reactors. Batch studies conducted using different concentrations of phosphates (1, 5, and 10 mg PO43–/L with 0.4 g NZVI/100 mL) indicated ∼99% removal in 30 minutes and ∼80% recovery in 60 minutes. At high pH desorption is higher while at lower pH desorption is decreased. Efficacy of the slurry NZVI is compared with micro-ZVI particles. Bare NZVI was more effective than acid washed micro-ZVI particles for PO43– removal. Only 60% PO43– removal was observed with entrapped NZVI Recovery of phosphate from entrapped NZVI at pH 12 was only 30%.