Removal of methylparaben from aqueous effluents using biobased carbon material. Experimental and DFT calculations

The emerging contaminant methylparaben was successfully removed from aqueous effluents using three carbon-based materials (BoCM-1, BoCM-2, and BoCM-3). These materials were prepared from the agro-waste Butia odorata (Bo), using the proportion of Bo: ZnCl₂ of 1:1 (BoCM-1), 1:2 (BoCM-2), and 1:3 (BoCM-3). Surface area, pore size distribution, total pore volume, FTIR, Boehm titration, CHN elemental analysis, TGA, HI, and pH_pzc characterized these carbon-based materials. The kinetic data were best fitted using the fractal-like pseudo-first-order (FPFO) model to explore the adsorption of methylparaben on the three adsorbent materials. The kinetic studies also show that 95 % of the adsorbent saturation (t_0.95) adsorbent occurs < 8 min. The isotherm studies showed that the Liu isotherm model was the best to explore the adsorption results. The maximum values of Q_max at 45 °C (Liu) were 637.7 (BoCM-1), 869.9 (BoCM-2), and 398.7 mg g⁻¹ (BoCM-3). Using the nonlinear van't Hoff equation, the values of ΔH° values range from –22.82 to –33.27 kJ mol⁻¹, suggesting the adsorption process is physical. Simulated industrial wastewater was tested to check the performance of the carbon materials for potential use for actual wastewater treatment, attaining a maximum removal of 98.38 % using BoCM-2 material. DFT calculations provide a molecular picture of the physisorption of methylparaben on carbon-based materials.