Abstract
Abstract The increasing discharge of synthetic dyes into aquatic ecosystems, particularly from textile and allied industries, has intensified the search for sustainable and cost-effective wastewater treatment solutions. This study investigates the performance of biochar derived from coconut husk for the adsorption of Brilliant Green (BG) dye from aqueous solution. Coconut husks were subjected to pyrolysis at three different temperatures—600 °C, 700 °C, and 800 °C—to produce biochars, and chemically modified with KMnO₄. Preliminary screening identified the biochar pyrolyzed at 600 °C (B600) as the most efficient, and selected for further characterization and adsorption studies. B600 was characterized using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, and X-ray Diffraction revealed a porous surface morphology, the presence of oxygen-containing functional groups, and predominantly amorphous carbon structures. Influence of B600 dosage, initial BG concentration, contact time, and temperature were investigated via batch adsorption experiments. Optimal removal conditions were observed at 0.1 g dosage, 100 mg/L dye concentration, 60 min, and 60 °C. Isotherm modelling showed that the adsorption data best fit the Redlich-Peterson model, suggesting a heterogeneous multilayer adsorption process, while the Langmuir model yielded a maximum monolayer adsorption capacity of 154.01 mg/g. Kinetic analysis confirmed quasi-second-order behaviour, indicative of chemisorption, and intra-particle diffusion results suggested a two-stage mechanism involving both film and pore diffusion. Thermodynamic parameters revealed that the adsorption process was spontaneous, and endothermic. Overall, this study demonstrates that KMnO₄-modified coconut husk biochar is a promising, low-cost, and environmentally friendly adsorbent for dye-contaminated wastewater treatment.