Synergistic effect of rice husk-derived activated carbon modified by Ni/Al-layered double hydroxides for lead removal from industrial wastewater.

To enhance the adsorption efficiency of activated carbon for heavy metals, herein we synthesized a novel composite adsorbent by loading of nickel/aluminum layered double hydroxides (Ni/Al-LDH) onto a chemically modified Egyptian rice husk-derived activated carbon. The characterization techniques used for determining the chemical and surface structure of the prepared composite were including FTIR, XRD, SEM, and BET which confirmed the successful loading of LDH onto the prepared activated carbon surface. The modified activated carbon established significantly upgraded performance in eliminating lead ions from wastewater. Adsorption studies revealed that the process follows Freundlich isotherm and pseudo-second-order kinetics, indicating chemisorption as the rate-determining step. The maximum lead ions removal (using 50 ppm concentration solution) was 82% after 210 min at pH 7. The improved lead ions removal efficiency was attributed to the synergistic effect of the activated carbon's surface chemistry and the LDH's ion exchange properties. The presence of chelating groups like hydroxyl (-OH), amide (-CO-NH-), carboxylate (-COOH), and nitrogen-containing functional groups on the activated carbon surface, along with the hydroxide groups of the LDH, facilitates the complexation and adsorption of lead ions.