Sorption of heavy metal ions from aqueous solution using acid-treated avocado kernel seeds and its FTIR spectroscopy characterization

This study reports the modification of surface chemistry of the avocado kernel seeds (i.e., Persea americana biomass) using both organic and mineral acids and their application in the heavy metal removal from aqueous solutions. The best conditions for the chemical treatment of this biomass using sulfuric, citric and tartaric acids have been identified using Taguchi experimental designs. The best acid-treated avocado seeds were used in the sorption of heavy metal ions: Cd2 +, Cu2 +, Ni2 +, Pb2 + and Zn2 + from aqueous solutions. Kinetic and equilibrium parameters of heavy metal sorption were determined. FTIR characterization of the modified avocado kernel seeds with tested acids was performed for determining the impact of chemical treatment on the surface modification and for identifying the functional groups involved in the metal uptake. Results showed that metal uptakes of acid-treated biomass can be increased up to 600%. In particular, citric and sulfuric acids are the most effective chemical agents for improving the metal sorption properties of avocado kernel seeds. Maximum sorption capacities of acid-treated avocado kernels ranged from 3.3 to 21.8 mg/g where the best removal performance was obtained for Pb2 + ions.