Cypress fruit: A sustainable source of activated carbon for removal of Zn, Cu, and Ni.

In this study, Cypress fruit-based-activated carbon (ACCF) was employed to investigate the removal of Zn, Cu, and Ni from aqueous solutions. The efficacy of adsorbent removal was studied concerning adsorption characteristics such as pH, dose of adsorbent, temperature, initial ion concentration, and contact time. The adsorption of metal ions on the ACCF surface was verified through Fourier transform infrared, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Results revealed the best adsorption efficiencies for the investigated metal ions were attained in acidic to neutral medium for Zn and Ni, and neutral for Cu, with an adsorbent dose of 0.04 for Zn and Cu, and 0.08 for Ni. The most effective initial concentration for each of the three metal ions was 30 mg/L. Equilibrium was reached in 40 min for Zn and in 100 min for both Cu and Ni. When removing the ions simultaneously, equilibrium was achieved in 40 min. Kinetic studies revealed a pseudo-second-order adsorption mechanism for all investigated heavy metal ions. The equilibrium data were best described by the Freundlich isotherm model. The maximum adsorption capacities were: Zn (239.23 mg.g), Cu (134.95 mg.g), and Ni (45.93 mg.g). Thermodynamic analysis suggests these adsorption processes to be endothermic and spontaneous. Cypress fruit-based activated carbon demonstrated high efficiency in removing Zn, Cu, and Ni metal ions from aqueous solutions.