Enhanced Biosorption of Triarylmethane Dyes by Immobilized Trametes versicolor and Pleurotus ostreatus: Optimization, Kinetics, and Reusability

The discharge of synthetic dyes from industries poses severe environmental challenges, necessitating eco-friendly remediation strategies. This study investigated the biosorption of triarylmethane dyes Crystal Violet (CV), and Brilliant Green (BG) using self-immobilized and sponge-immobilized biosorbents of Trametes versicolor (strain CB8, CB8/S2) and Pleurotus ostreatus (strain BWPH, BWPH/S2). Tests were conducted with live and autoclaved biomass under varying conditions of dye concentration (100–400 mg/L), temperature (15–55 °C), and pH (2–10). Sponge-immobilized live biomass (CB8/S2 and BWPH/S2) showed superior performance, removing up to 90.3% and 81.7% of BG and 43.9% and 39.3% of CV, respectively, within 6 h, demonstrating 3–5 times higher efficiency than self-immobilized biomass for both dyes. Maximum sorption of 379.4 mg/g of BG and 48.9 mg/g of CV was achieved by CB8/S2 at 400 mg/L. Principal Component Analysis biplot confirmed immobilization efficacy, where Dim1 (85.9–91.8% variance) dominated dye concentration and contact time. The optimized conditions for BG removal by CB8/S2 was 20.85–32.17 °C and pH 3.4–6, and for CV, at pH 6.5–7.5 and 30 °C. The percentage of dye sorption data fitted well with the quadratic model (p < 0.05). Fourier transform infrared spectroscopy (FT-IR) analysis indicated that hydrogen bonding and electrostatic interactions facilitated dye binding onto fungal mycelium. Notably, sponge-immobilized biosorbents were reusable without additional treatment. The findings support fungal biomass immobilization as a viable strategy to augment the bioremediation potential in treating dye-laden wastewater.