Innovative low-cost engineered adsorbents based on waste eggshell for nickel removal from aqueous solutions

Abstract In contemporary sustainable economy, innovation is prerequisite to waste recycling into new efficient materials, designed to minimize pollution and conserve non-renewable natural resources. Water pollution is a global problem with health, quality of life, and food safety concerns. Thus, waste conversion into cheap, efficient adsorbent materials with high reusability is a challenge in wastewater recycling. In that context, starting from eggshell waste in this study, two new low-cost engineered adsorbents were prepared for the retrieval of nickel from aqueous solutions. Scanning electron microscopy (SEM) results show that, in the first eggshell-zeolite (EZ) adsorbent, the zeolite nanoparticles were loaded in the eggshell pores. The preparation for the second (iron(III) oxide-hydroxide)-eggshell-zeolite (FEZ) adsorbent led to double functionalization of the eggshell base with the zeolite nanoparticles, upon simultaneous loading of the pores of the eggshell and zeolite surface with FeOOH particles. Structural modification of the eggshell led to a significant increase of the specific surface, as confirmed by BET analysis. These features enabled the proposed adsorbents (EZ and FEZ) to remove nickel from aqueous solutions with high performance and adsorption capacities 321.1 mg/g and 287.9 mg/g, respectively. The results indicate that nickel adsorption on EZ and FEZ is a multi-molecular layer, spontaneous, and endothermic process. Concomitantly, desorption results reflect high reusability of these two adsorbents, collectively suggesting the use of waste in the design of new, low-cost, and highly efficient engineered adsorbents for environmental bioremediation