Optimizing Biochar Preparation for Eco-friendly Adsorption of Polyphenols and Organic Compounds in Pilot-scale: an Application of Doehlert Designs

In Morocco, olive mill wastewater (OMWW) has become a serious environmental problem. This research pioneers the conversion of olive mill solid waste (OMSW) into high-quality biochar using Response Surface Methodology with three parameters, residence time, temperature, and heating rate. It combines multicriteria optimization with the desirability function and a Doehlert design to get the best results. Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurement, and ultimate and proximal studies were used to investigate the optimum. With a comparable BET surface area of 6.29 m²/g and methylene blue adsorption of 274 mg/g, the biochar yield was 27.7%. The resulting biochar is intended as an adsorbent, aimed at either recovering or uptaking polyphenols from OMWW. The nonlinear Freundlich isotherm model more accurately represented the experimental adsorption process, as evidenced by a high correlation coefficient (R² = 0.9909). The maximum polyphenol adsorption achieved was 23.23 mg/g, resulting in the elimination of 92.23% of polyphenols, along with 65.46% of total organic carbon (TOC) and 80.84% of chemical oxygen demand (COD). Hence, utilizing biochar for adsorption is an effective method for maximizing the recovery of polyphenols. Once detoxified, OMWW can be repurposed for various applications.