Methylene blue and acid red adsorption on biochar made from modified sugarcane bagasse: A dynamic, equilibrium, and thermodynamic investigation

This study synthesized biochar adsorbents from chemically activated sugarcane bagasse using ZnCl2 at pyrolysis temperatures of 400, 500, and 600 degrees C. The modified bagasse biochar was used to remove methylene blue (MB) and acid red (AR) dyes. The surface characteristics of the modified bagasse biochars were analyzed using Scanning Electron Microscope (SEM), Fourier Transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. Batch adsorption experiments were conducted to assess the impact of various parameters on adsorption performance. Among the different bagasse biochar samples, Zn-BC-600 exhibited superior adsorption capacities for MB and AR with values of 182.225 and 43.324 mg/g, respectively. The adsorption efficiency was significantly influenced by pH, with optimal conditions at pH = 6.0 for MB and pH = 2.0 and 10.0 for AR. The adsorption process for MB and AR on Zn-BCs followed a pseudo-second-order kinetic model, indicating chemisorption as the primary mechanism. Adsorption isotherm studies revealed that Zn-BCs conform to the Freundlich model, proposing a multilayer adsorption due to the heterogeneity of the biochar surface. Regeneration experiments indicated that Zn-BCs could be reused for multiple adsorption cycles. In conclusion, the modified bagasse biochar showed strong adsorption affinity for both MB and AR, particularly for MB, making it a promising adsorbent for treating printing and dyeing wastewater.