Single and Dual Metal Impregnated Activated Carbons for the Removal of Lead and Chromium from Wastewater

Metal oxide impregnated activated carbon (IAC) has good affinity for heavy metals present in water. Zinc/copper impregnation by imbibing method was executed for the purpose of optimum tailoring of activated carbon (AC) for water purification purposes. Calcination of these samples was carried out to convert metals into their respective oxides in an inert atmosphere using a tube furnace. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The results helped to explore metal loading, metal dispersion and the final metal form onto AC. The surface area available for incoming metals was studied by Brunauer−Emmett−Teller (BET) theory. Heavy metal ions were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES) and studied by applying adsorption models, a variety of isotherms and altering various conditions. The system was feasible, spontaneous, had a major chemisorption mechanism and was overall endothermic. Adsorption studies make it clear that dual metals impregnation helped in maximizing active sites as compared to the same concentration of single metal. Weber and Morris model was used to find that intra particle diffusion and film diffusion, both processes occur during adsorption while Boyd model confirmed that film diffusion was rate determining phenomenon. 0.33 mmol/g of each zinc and copper IAC showed 96% removal efficiency of chromium(VI) and 98% for lead(II) at 30°C for 10 mg/L concentration, pH 3 and a dose of 4 g/L. Hence, imbibed AC is efficient, safe and economical adsorbent for water purification.