Degradation of fomesafen in water by sodium persulfate activated with hydrochar optimized using deep eutectic solvent

The integration of hydrochar with advanced oxidation processes (AOPs) offers a green and efficient approach to water pollutant treatment. However, the real-world use of hydrochar is obstructed by the stringent preparation conditions typically required. This study introduces acidic deep eutectic solvents (DES) to replace water, enabling atmospheric-pressure hydrochar conversion at 150°C and overcoming the high temperature/pressure limitations of conventional hydrothermal carbonization (HTC), while also providing effective active sites for hydrochar-activated AOPs. Hydrochar was prepared from corn stover at atmospheric pressure and 150°C. For an aqueous fomesafen solution with a starting concentration of 40 mg/L, 0.3 g/L hydrochar catalyzed 5 mmol/L sodium persulfate, achieving a degradation and removal rate exceeding 80% in 100 min. The acidity of DES was found to positively correlate with the catalytic performance of the prepared hydrochar. In addition, key factors influencing the performance of hydrochar-based AOPs were investigated. Potential degradation mechanisms were also proposed.