Mechanisms and adsorption capacities of ball milled biomass fly ash/biochar composites for the adsorption of methylene blue dye from aqueous solution

In this study, the biomass fly ash/biochar composite (BFA-Biochar) was effectively prepared using wheat straw and biomass fly ash by eco-friendly ball-milling method. The BFA-Biochar was characterized by scanning electron microscope (SEM-EDS), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared spectroscopy (FTIR) analysis, X-Ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). The methylene blue (MB) adsorption capacity of BFA-Biochar was considerably enhanced (Langmuir Qmax of 854.75 mg/g at 318 K), and showed high adsorption performance during wide pH value (pH 4–10). In addition, the MB adsorption capacity of BM-Biochar was two folds higher than raw biochar. It was found that the Pseudo-second-order adsorption kinetics and Freundlich isotherm model accurately described the adsorption process. Thermo-dynamical parameters (ΔGo, ΔHo and ΔSo) indicated the spontaneous and endothermic nature of the MB adsorption process. The increased electronic attraction and surface function were the main mechanisms of MB adsorption on BFA-Biochar. Therefore, BFA-Biochar can be used as environmentally friendly and effective adsorbents for MB dye removal from aqueous solutions.