Sugar cane bagasse ash as low-cost adsorbent for the removal of methylene blue dye from aqueous solution

Cationic dyes such as methylene blue (MB) are widely used as coloring agents in various industries; however, they pose significant environmental concerns because of their toxicity and persistence in aquatic environments. Wastewater containing MB is commonly discharged from textiles, plastics, chemicals, and pharmaceuticals industries, where the dye is extensively applied during dying processes. Present study investigated the potential of sugarcane bagasse ash (SCBA) as a low-cost bioadsorbent for the removal of MB dye under synthetic wastewater conditions. SCBA was characterized using BET, XRD, FTIR, and SEM analytical techniques. The effects of solution pH, contact time, initial dye concentration, and adsorbent dosage were systematically evaluated as major adsorption parameters. The maximum MB removal efficiency (87.6%) was achieved at optimal conditions of pH 13, contact time of 120 min, initial dye concentration of 15 mg/L, and adsorbent dose of 3.5 g/L. In addition, the removal chemical oxygen demand (COD) from real textile effluent was investigated using SCBA, and the results demonstrated 74% COD removed efficiency. The regression coefficient (R2) values indicated that both the pseudo-second-order (PSO) and intraparticl diffusion (ID) kinetic models adequately described the adsorption process, suggesting that chemisorption and surface diffusion jointly controlled the adsorption mechanism. Furthermore, the equilibrium data were the best fitted by the Langmuir model, indicating a monolayer adsorption of dye molecules onto a homogeneous adsorbent surface without significant interactions. These findings demonstrate that SCBA is a promising and sustainable alternative adsorbent for removal of MB dye from wastewater.