Simultaneous removal of organics and metals in fixed bed using gravel and iron oxide coated gravel

In this study the adsorption behaviors of uncoated and iron oxide coated gravel (IOCG) as low cost adsorbents towards the simultaneous removal of Fe, Ni, Zn, chemical oxygen demand (COD) and total organic carbon (TOC) from synthetic wastewater samples were analyzed in fixed bed columns. The effects of variable parameters such as column pack depth and influent concentration on the effluent concentrations via breakthrough curves were investigated. It was found that the removal efficiencies and adsorption capacities increased as the initial influent concentrations of metal ions and organic materials decreased and as the bed height increased for both adsorbents. The maximum adsorption capacities were observed for samples with 2-cm bed height and medium-strength wastewater concentration at 11 mL/min of flow rate. The maximum adsorption capacities were 1868 mg/L for COD, 27 mg/L for TOC, 0.43 mg/L for Ni, 1.15 mg/L for Zn and 1.13 mg/L for Fe for IOCG and 1854.6 mg/L for COD, 11.09 mg/L for TOC, 0.38 mg/L for Ni, 1.15 mg/L for Zn and 0.57 mg/L for Fe for gravel. IOCG resulted in slightly higher adsorption capacities than gravel for metal ions and organic materials. The use of IOCG and gravel as individual or mixed material in column studies will be a valuable strategy in the development of adsorption systems to remove mixed ions.