Abstract
Laboratory-scale fixed bed columns were designed and monitored to compare the mobility and removal of copper (Cu), manganese (Mn), and iron (Fe) from industrial wastewater using chemically modified rice husk (main filter medium). The first and third beds (A and C) were treated with sodium carbonates and phosphates, respectively, while the second bed (B) was rice husk ash. During the study, changes in the concentrations of these metals were monitored and measured for all treatments under an influent flow rate and hydraulic loading rate of 0.00288 m3/d and 0.508 m3/m2 d, respectively. Parameters that may influence the mobilization and removal rate of metals, including Redox and pH, were also monitored and measured. The experiment was conducted under ambient temperatures with redox potentials and pH ranging from −50 to 200 mV and 6.5 to 12, respectively. An accumulation in the Fe and Mn concentrations occurred during the first 6 weeks of system operation; a decline thereafter was noticed with Fe and Mn effluents of 28, 20, 15 mg/L and 29, 16, and 139 mg/L for treatments A, B, and C, respectively. There was however a stable decline in the Cu concentrations over time with a final effluent of 14 mg/L for all treatments. Under redox and pH ranging from slight reduction to oxidation and strong alkaline to acidic conditions, respectively, satisfactory Fe removal was accomplished through both A and C treatments, while a better Mn removal was achieved with A rather than C treatment. A greater removal of Cu was observed in A rather than B and C beds. It can be concluded that A was the best treatment among different modifications for Fe, Mn, and Cu removal from industrial wastewater. Furthermore, Redox potentials and pH were found to be imperative parameters controlling the mobilization and removal dynamics of Fe, Mn, and Cu.
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