Highly efficient degradation of lactic acid by microwave-induced activated carbon catalytic oxidation process

High-concentration refractory coffee wastewater containing about 2000 mg/L of biotoxic lactic acid is treated by microwave technology. At a microwave power of 900 W, a large amount of activated carbon (AC) reduces the number of hot spots. After microwave radiation, the lactic acid concentration drops to 200 mg/L, with a removal rate of 90 %. CaO promotes the process. In the microwave-AC-CaO method, “hotspots” on AC generate free radicals. The effects of microwaves degrade lactic acid into CO 2 and H 2 O. The microwave-AC-CaO method can rapidly degrade lactic acid. And the degradation rate of lactic acid can be further improved by adding transition-metal oxides to modify AC.