Efficient Decolourisation of Astrazon Pink Dye Using Biocarbon Derived from Prosopis juliflora Shells: Kinetics, Isotherms, and RSM-Based Optimization for Sustainable Wastewater Treatment

This study investigates the efficiency of biocarbon derived from Prosopis juliflora shells in removing Astrazon pink dye from aqueous solutions. The biocarbon obtained from the thermochemical process was characterised using FTIR Spectroscopy, SEM microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), and XRD. Batch adsorption experiments were conducted to assess various factors, including the Potential of Hydrogen (pH), Dosage of biocarbon, Astrazon pink dye concentration, temperature, and Time of contact. Similarly, Adsorption isotherm models, including the Langmuir and the Freundlich isotherms, were used to evaluate the adsorption capacity. In contrast, pseudo-first-order and pseudo-second-order models were used to analyse the kinetics of dye adsorption. The interactive effects of selected variables on the removal of Astrazon Pink dye from synthetic water were determined using Response Surface Methodology (RSM). The maximum dye uptake, 98.54%, was achieved with a biochar dose of 8 g/L at 50 ppm dye concentration, pH 7.5, and 35 °C. The Freundlich adsorption isotherm model and the pseudo-second-order kinetic model are the better-fitting models for the dye adsorption process, with R2 values of 0.99. Consequently, the thermodynamic parameters indicate that the process is endothermic and spontaneous.