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

Abstract In the current circular economy, innovation is requisite for waste reuse into new efficient materials designed to minimize pollution and conserve non-renewable natural reserves. Water pollution is a global problem with health, quality of life and food security reverberations . In this study were prepared two newly low-cost engineered adsorbents from eggshells for nickel retention from aqueous solutions. SEM results showed that, in the first adsorbent (EZ), the zeolite nanoparticles were loaded in the eggshell pores. The preparation route for the second adsorbent led to the double functionalization of the eggshell with the nano-sized particles of zeolite and simultaneously eggshell pores and zeolite surface loading with FeOOH particles. The eggshell structural modification was confirmed by the BET analysis. These features enabled the proposed adsorbents to remove nickel with high performance and adsorption capacities of 321.11 mg/g and 287.9 mg/g. The adsorption kinetics and isotherm data follow the Freundlich model (ΔG<0, ΔH<0; ΔS>0) and pseudo-second-order kinetics model. These results indicate that nickel adsorption on adsorbents is a multi-molecular layer, spontaneous and endothermic process. Subsequently, the desorption results exhibit the higher reusability of both adsorbents. This study's outcomes conclude the use of waste to design new, low-cost, and highly efficient engineered adsorbents.