An eco-friendly removal of Cd(II) utilizing banana pseudo-fibre and Moringa bark as indigenous green adsorbent and modelling of adsorption by artificial neural network

Abstract

Heavy metal-contaminated water can be effectively treated using adsorbents made from abundantly available biomass. The present investigation was carried out to adsorb Cd(II) from synthetic solution by banana pseudo-stem (BP) and Moringa oleifera stem bark (MB). Adsorption efficiencies of both adsorbents were studied in the batch reactor by conducting experiments to determine the consequences of changes of pH, adsorbent dosages, initial Cd(II) concentrations, incubation time, and temperature. The process parameters were tuned to attain the highest possible removal percentage. The characterization of the adsorbents was performed by utilizing Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) for the fresh and metal-loaded adsorbents. Atomic absorption spectroscopy (AAS) was employed to calculate the amount of Cd(II) in an aqueous solution. The experimental data were entirely consistent with the pseudo-second-order model for BP and MB. The findings of the study illustrated the better adsorption efficiency of BP-derived adsorbent (≈ 99%) at optimum conditions over the MB (≈ 97%), and the corresponding adsorption capacities were 11.98 and 7.04 mg/g, respectively. The 4 (four) well-known isotherm models were attempted both in linear and non-linear forms. BP (R² =0.995) and MB (R² =0.994) were found to be best described by the Freundlich isotherm, which was selected based on the highest R² value. In thermodynamic studies, ΔH and ΔS were calculated for both the adsorbents. Cd(II) adsorption on BP and MB was endothermic, as evidenced by the positive ΔH. Finally, the prediction of the removal percentage was made by the artificial neural network (ANN) modelling. The present work developed regionally derived waste materials which are helpful for small-scale industrial units for their waste management in an economical and sustainable way.

Keywords: Adsorbent; Artificial neural network; Banana pseudo-stem; Isotherm; Kinetic model; Moringa oleifera stem bark.