Flash Joule heating synthesis of cobalt/biochar composite for pollutant degradation: insights into reaction mechanism and process evaluation

초록

The rational design and controlled synthesis of high-efficiency catalysts are crucial for effectively removing refractory organic pollutants in sulfate radical-based advanced oxidation processes (SR-AOPs). Because of its short duration, high-temperature capability, high energy efficiency, and rapid heating and cooling rates, flash Joule heating (FJH) was employed to rapidly prepare a cobalt/biochar composite (CRSBC) using cobalt-rich slag (CRS) and spent coffee grounds (SCG) as raw materials. The FJH process instantly converted SCG into highly graphitized carbon while simultaneously reducing metal oxides in the CRS to low-valent and highly active forms, thus boosting catalytic performance. The synthesized catalyst, CRSBC-1, rapidly degraded Rhodamine B (20 mg L-1) with 100% efficiency in 15 min. The active metals in CRSBC-1 activated peroxymonosulfate (PMS) to generate radicals, while the conductive carbon matrix facilitated electron transfer and singlet oxygen formation. The PMS/CRSBC-1 system efficiently eliminated pollutants across a wide pH range (3.0-10.0) and in the presence of inorganic anions and dissolved organic matter. Continuous-flow experiments confirmed its strong potential in treating practical wastewater containing Rhodamine B. Additionally, life cycle assessment and cost analysis showed that the catalyst preparation had a minimal environmental impact (global warming potential (GWP) = 14.87 kg CO2 eq) and was cost-effective ($5.4873 kg(-1)). This study proposes an innovative approach for exploiting highly efficient SR-AOPs catalysts, paving the way for next-generation organic wastewater treatment.

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