Performance Evaluation of a Co-Precipitated Magnetic Activated Carbon Column for Heavy Metal Removal from Synthetic and Spiked Municipal Wastewater

Abstract

Residual heavy metals in municipal wastewater effluents remain an environmental issue of concern to wastewater treatment plants. This is because it is difficult to achieve complete removal by conventional treatment processes. The performance of a co-precipitated magnetic activated carbon (CP-MAC) fixed-bed adsorption column was evaluated for chromium (Cr) and lead (Pb) removal in synthetic wastewater (SWW) and spiked municipal wastewater (SPWW) samples. Continuous flow experiments were conducted using a 8.50 g of CP-MAC bed at an optimized bed height of 18 cm. Also, the influent metal concentration used was 11 mg/L and flow rate of 6.30 mL/min. Performance was evaluated using breakthrough curve analysis, adsorption capacity, treated volume, removal efficiency, and bed utilization parameters. The results show that Pb consistently exhibited better adsorption behaviour than Cr under both wastewater conditions. Under SWW conditions, exhaustion adsorption capacities of 1.78 and 1.65 mg/g were obtained for Pb and Cr, respectively, while corresponding values under SPWW conditions decreased to 1.27 and 1.13 mg/g. In comparison to SWW, the more complex SPWW led to a decline in performance, with adsorption capacity reductions ranging from 28.65% to 31.51 %. Additionally, the breakthrough time decreased by 29.15% to 36.70%, and the total volume of wastewater treated before exhaustion dropped by 20.42% to 28.88%. These changes indicate a faster saturation of the adsorption bed and a shorter operational duration for the column. In addition, removal efficiencies of around 54.07% for Pb and 44.97% for Cr were maintained, demonstrating that the CP-MAC column retained its effectiveness even with the presence of competing ions and constituents in the wastewater. It becomes clear that wastewater matrix composition plays a significant role in fixed-bed adsorption performance and the results obtained using SWW alone are likely to overestimate treatment efficiency under practical operating conditions. Therefore, these results support the use of CP-MAC as a tertiary polishing adsorbent for the removal of residual heavy metals from municipal effluents.