Alizarin Red S adsorption onto biomass-based activated carbon: optimization of adsorption process parameters using Taguchi experimental design

The paper describes the application of activated carbon prepared from biomass of Schima wallichii for adsorption of an anionic dye, Alizarin Red S. Characterization of the adsorbent was done using BET surface area analyzer, FT-IR, FESEM, etc. Batch mode experiments investigated removal studies and effects of process parameters—pH, adsorbent dose and dye concentration. Taguchi method along with ANOVA was carried out for experimental design for optimization of the process parameters, and the optimum condition was found to be at pH 3 at an adsorbent dose of 0.3 g for dye concentration of 200 mg L⁻¹. Adsorption isotherm and kinetics were fitted with the experimental data, and the validation of the models was assessed by applying reduced Chi-square test (χ²) and sum of the square of the errors. Adsorption isotherm was found to follow the Langmuir model with maximum adsorption capacity of 91.695 mg g⁻¹, while the rate of adsorption follows pseudo-second-order kinetics. Thermodynamic studies on the adsorption data showed that adsorption of Alizarin Red S onto Schima wallichii activated carbon was endothermic (positive Δ H°) and spontaneous (negative Δ G°). Regeneration studies showed adsorbent revealed efficiency of the regenerated adsorbent till the fourth regeneration cycle. This study anticipates that Schima wallichii biomass could be a potential precursor for the synthesis of activated carbon for removal Alizarin Red S dye from water. Its high surface area, total pore volume and higher carbon content along with its regeneration capacity make the prepared carbon a good adsorbent.