Banana Peel Biochar as a Green Adsorbent for Sustainable Abatement of Methylene Blue, Methyl Orange and Heavy Metals As(V) and Ni(II).

Abstract

The contamination of water bodies by heavy metals and synthetic dyes presents a significant environmental challenge, necessitating the development of sustainable remediation strategies. Adsorption has emerged as a promising approach for wastewater treatment and biochar stands out as a low-cost, environment-friendly adsorbent. This study explores the potential of biochar made from banana peel (BPBC) for removing methylene blue (MB), methyl orange (MO), As(V), and Ni(II) from their aqueous solutions using spectrophotometry. The biochar was produced by pyrolyzing dry banana peels at 400°C in a Muffle Furnace and was characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. SEM images reveal surface roughness and pore development, indicating a heterogeneous and porous surface. BET analysis showed an increase in surface area and pore volume after pyrolysis, confirming mesoporosity. PZC for banana biochar surface was determined to be 5, which indicated that the biochar surface is positively charged at pH values below it. A maximum removal efficiency of 95.02% was observed for MB using 0.5 g of biochar in 30-min contact time with BPBC. Ni(II) and As(V) ions were removed with efficiencies of 81.86% and 54.80%, respectively, using 1 g of biochar. Adsorption kinetics data fit the pseudo-second order (PSO) model with R² values of 0.9958 and 0.9952 for 10 and 20 ppm MB solution, respectively. Adsorption data obeyed the Freundlich isotherm for MB, while As(V) adsorption on BPBC followed both the Freundlich and Langmuir isotherms. pH studies revealed enhanced adsorption of MO under acidic conditions (at pH 2.9), while MB showed best performance at neutral pH. Regeneration studies of BPBC for the removal of MO under acidic conditions showed a decrease in removal efficiency from 79.18% to 29.2% after the fourth cycle.