Adsorption of heavy metals on litchi pericarp

Abstract

This project investigated litchi pericarp (LP) and modified litchi pericarp (MLP) as promising materials for removing toxic pollutants as Cd (II) and Ni (II) from aqueous solutions. Several batch assays were conducted to determine the adsorption capacity of LP and MLP as a function of pH, contact time, initial metal concentrations and adsorbent doses. The reusability of MLP after treating with five different HCl concentrations was also evaluated. LP showed to have good adsorption ability with the maximum metal removal yield of 78.8% for Ni (II) and 70.8% for Cd (II). MLP was proved to have a greater potential for metal removal with the highest yield of 99.52% for Ni (II) and 99.6% for Cd (II). At room temperature and an agitation speed of 220 rpm, the optimal conditions for Cd (II) removal by both LP and MLP were found at pH 4, 60 min contact time, 50 ppm initial metal concentration and 0.10 g adsorbent per 10 mL solution. The removal of Ni (II) reached the highest yield at the same conditions as Cd (II) except for contact time and the pH, which were 30 min and 6. The regeneration investigation result revealed that HCl was not an efficient reagent for regenerating MLP adsorbent.