Potential of peanut shells as a biosorbent of Reactive Blue 203 dye in industrial effuentnt

Peanut shells (PS) were studied as a low-cost alternative biomaterial for removing Reactive Blue 203 dye from textile effluents. The crude biomass was characterized by chemical composition, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyses. The biomass's thermodynamic parameters and kinetic profile of the dye adsorption process were evaluated. The biomass presented a zero-charge point of 6.9, having a wide pH range favorable for the adsorption of the azo-anionic RB 203 dye. High crude fiber (69.25 g 100 g⁻¹), polysaccharides (glucan: 20.90 g 100 g⁻¹ and xylan: 8.90 g 100 g⁻¹), lignin (39.4 g 100 g⁻¹), mineral residue (6.2 g 100 g⁻¹) and mesoporous surface were observed, and the pH and temperature greatly influenced the adsorption behavior. The peanut shell particles were thermally stable up to close to 150 °C, with 4 mass-loss events observed throughout the thermogravimetric analysis. The adsorption rate was proportional to the square of the number of accessible adsorption sites, following a pseudo-second-order kinetic pattern, suggesting that surface reactions governed the adsorption process and that both surface homogeneity and interactions among the adsorbed dye were present. The biosorption isotherm followed Langmuir’s model [maximum adsorption capacity (q_max) of 49.30 mg g⁻¹], and the adsorption was exothermic and considered a physical mechanism. In tests with industrial dye effluent, the biomass showed a removal efficiency of 66.8% color, 65.3% BOD₅, and 74.1% COD. Peanut shells showed an excellent affinity for RB 203 dye adsorption, revealing its potential as a cheap biomaterial for treating effluents rich in color.