Abstract
This study demonstrates the sustainable valorization of anaerobic food waste digestate (FWD) into highly porous activated carbon (FWD-AC) and evaluates its efficacy in removing toxic hexavalent chromium [Cr(VI)] from industrial electroplating wastewater. FWD-AC was synthesized via chemical activation using phosphoric acid (H3PO4) followed by pyrolysis at 700°C. The resulting material exhibited a high specific surface area of 845.2 m²/g and a rich abundance of oxygen- and phosphorus-containing functional groups. Batch adsorption experiments revealed that the adsorption of Cr(VI) was highly pH-dependent, with maximum removal occurring at pH 2.0. The adsorption kinetics followed a pseudo-second-order model, and the equilibrium data were exceptionally well-described by the Langmuir isotherm model, yielding a maximum adsorption capacity of 142.8 mg/g at 298 K. X-ray photoelectron spectroscopy (XPS) analysis confirmed that the removal mechanism involved a combination of electrostatic attraction, surface reduction of Cr(VI) to Cr(III), and subsequent complexation of the reduced chromium species. Furthermore, FWD-AC successfully treated real industrial electroplating wastewater, reducing Cr(VI) concentrations to levels below regulatory discharge limits. These findings highlight the potential of utilizing food waste digestate as a low-cost precursor for producing high-value adsorbents, presenting a circular economy approach to waste management and industrial wastewater treatment.
