Evaluation of Waste Eggshells for Adsorption of Copper from Synthetic and Swine Wastewater

Abstract

Abstract. Biomass-derived adsorbents are an attractive alternative to conventional water treatment methods. This study evaluated eggshells produced by the liquid egg and food processing industry for the adsorption of copper from aqueous systems. Research objectives were to (1) determine copper adsorption mechanisms and (2) evaluate copper adsorption by eggshells for the treatment of wastewater. Batch experiments were performed by contacting eggshells with copper solutions to obtain equilibrium, kinetic, and thermodynamic data to determine removal mechanisms and maximum adsorption capacity. Results suggested that the adsorption of copper followed a second-order kinetic model with a theoretical maximum adsorption capacity of 4.3 mg g-1 (20°C). In addition, eggshell adsorption was found to be a favorable process, with an activation energy of approximately 27 to 29 kJ mol-1, and followed similar mechanisms as its calcite analog. Data indicated that slightly acidic (pH = 6) to near-neutral pH conditions enhanced adsorption of copper. Additional experiments were performed using swine lagoon wastewater to evaluate the efficacy of eggshells to treat copper from lagoon wastewater. The data suggested that unmodified eggshells were effective for application in swine lagoon systems only under acidic conditions (pH = 4). Further research is needed to modify eggshells that can adsorb copper in lagoon wastewater at neutral and alkaline pH. Keywords: Adsorption, Copper, Eggshell, Swine lagoon, Water.