Remediation of methylene blue dye from an aqueous solution using biomass-based nanocomposites

The discharge of residual dyes from manufacturing processes poses significant environmental risks. To address the need for efficient removal of the toxic dye methylene blue (MB) from water, a composite material was synthesized using biomass derived from banana peels and magnesium oxide (MgO) nanoparticles. Key operational parameters—including pH, contact time, composite dosage, and initial MB concentration—were systematically optimized to maximize MB adsorption. The composite was thoroughly characterized using advanced analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area analysis. The optimal conditions for MB adsorption were initially determined using the one-factor-at-a-time (OFAT) method and later confirmed through response surface methodology (RSM). The optimal parameters were found to be a pH of 7.6, a contact time of 30 min, an initial MB concentration of 80 mg/L, and a composite dosage of 20 mg. Under these conditions, the composite achieved an optimal MB removal efficiency of 96.45%. Kinetic analysis showed that the adsorption process followed a pseudo-second-order model, while equilibrium data aligned well with the Freundlich model. The composite exhibited a maximum adsorption capacity of MB was 76 mg/g of adsorbent. The adsorption mechanism involved chemisorption followed by physisorption, with electrostatic interactions playing a significant role. The collective findings underscore the efficacy of the agro-waste composite as a cost-effective adsorbent for removing MB from contaminated water. This study presents valuable insights into the potential application of such composites in environmental remediation efforts.