Removal of heavy metals from aqueous solutions using carbonised banana and orange peels

This research demonstrates the feasibility and efficacy of removing heavy metals from aqueous solutions using waste banana and orange peels. The fruit peels are carbonised, without the addition of chemical substances, to enhance their adsorption capacities. The adsorption capacities are studied in aquatic solutions containing individual and combined metal ions of hexavalent chromium (Cr⁶⁺), copper (Cu) and zinc (Zn). The selectivity of the adsorbents towards these metal ions is also exhibited. The results show that both fruit peels exhibit a better selectivity towards zinc ions, followed by copper and then hexavalent chromium. The effects of operational conditions, including pH, adsorbent dosage, contact time and concentration of metal ions, on the removal efficiency and uptake capacity of the carbonised fruit peels are investigated. The optimal adsorption for both adsorbents occurs within 30 min of exposure and at an adsorbent dose of 0.5 g. Additionally, the adsorption kinetics and isotherms, including pseudo-second-order, Langmuir and Freundlich, are modelled for the obtained data.