Effects of Heat and Chemical Pretreatments of Banana Peels for Metal Removal in Single and Multimetal Systems

Abstract

This study investigated and compared the influence of pretreatments (heat and chemical) on banana peels and their subsequent efficacy in removing toxic metals (Cu, Pb, Zn, Cd) from single and multimetal systems. Banana peels were pretreated using heat (autoclaving, microwaving, boiling) and chemical (acetic acid, nitric acid, NaOH, detergent, methanol, and DMSO) treatments, prior to biosorption tests. Results revealed that pretreatment using detergent enabled banana peels to biosorb metals at relatively higher amounts in both single (Cu-96.26%, Pb-96.72%, Zn-95.75%, Cd-96.92%) and multimetal (Cu-92.43%, Pb-95.91%, Zn-91.88%, Cd-94.42%) systems. Biosorption by detergent-treated peels were profoundly effective when 0.10 g was used, with initial metal concentration of 10 mg/l, agitation speed of 120 rpm and a solution with pH 5. Characterization of detergent pretreated banana peels via FTIR analysis showed that different pretreatments applied did not significantly modify the presence of functional groups. As such, the preexisting functional groups such as hydroxyl, amino, carboxyl, and carbonyl groups were deemed responsible for metal removal. SEM-EDX analysis on detergent pretreated peels suggested that improvement to metal removal may be attributed to enlarged pore size. This suggested that pretreatment with detergent, and as with most chemicals, presented a more feasible and economical approach than heat treatments to successfully enhance metal biosorption by banana peels for wastewater treatment.