Kinetic studies of Cd (II) and Pb (II) ions biosorption from aqueous media using untreated and chemically treated biosorbents

Untreated and chemically treated Albizia coriaria, Erythrina abyssinica and Musa spp. were studied in batch for uptake of Cd²⁺ and Pb²⁺ ions at pH 2.0–9.0 and agitation time of 30–390 min. Optimum biosorption conditions were pH 4 for Pb²⁺ ions and pH 5 for Cd²⁺ ions, contact time was 3.5 hours at 24 ± 1 °C for 10 mg/L biosorbent dosage and initial metal ions concentration of 20 mg/L. Chemical treatment had a 10–17% biosorption efficiency enhancement for Cd²⁺ ions and a 1.6–2.3% reduction effect for Pb²⁺ ions. The sorption capacities for Cd²⁺ and Pb²⁺ ions for treated biosorbents were 1.760–1.738 mg g⁻¹ compared to 1.415–1.539 mg g⁻¹ for untreated materials. The pseudo second-order model suitably fitted the Cd²⁺ and Pb²⁺ ions biosorption data with regression coefficients (R²) of 0.9784–0.9999. Fitting of the Ho model to the experimental data showed that the biosorption mechanism for both metal ions studied was mainly a chemisorption process. Therefore, treated A. coriaria, E. abyssinica and Musa spp. were potential biosorbents for remediation of Cd²⁺ ions and the untreated materials suitable for removing Pb²⁺ ions from contaminated aqueous media.