Effect of Metal Ion Concentration on the Biosorption of Al3+ and Cr6+ by Almond Tree (Terminalia catappa L.) Leaves

Abstract

The influence of initial metal ion concentration of the batch sorption of Al³⁺ and Cr⁶⁺ onto a low-cost biosorbent was investigated. The experimental results were analysed in terms of Langmuir and Freundlich isotherms. According to the evaluation using Langmuir equation, the monolayer sorption capacity obtained were 1.12mg/g and 2.67mg/g for Al³⁺ and Cr⁶⁺ respectively. The data further showed that sorption of the two metals onto the biomass increased with increase in initial metal ion concentration. The thermodynamic assessment of the metal ion – almond tree (Terminalia catappa L. biomass system indicates the feasibility and spontaneous nature of the process. ?G^o was evaluated as ranging from -4.56 to – 6.64 KJ mol^-1 and –4.03 to -6.10 KJ mol^-1 for Al³⁺ and Cr⁶⁺ sorption respectively. The order of magnitude of the ?G^o values indicates an ion exchange physiosorption process.

Keywords: Adsorption, Almond tree, Heavy metals removal, Phytoremediation, water treatment.