Recycling rice straw derived, activated carbon supported, nanoscaled Fe3O4 as a highly efficient catalyst for Fenton oxidation of real coal gasification wastewater

Abstract

Recycled rice straw was converted into an activated carbon support for nanoscaled Fe₃O₄. The resulting catalyst (Fe₃O₄MNPs/RSAC) was then evaluated for its effectiveness in the treatment of real coal gasification wastewater (CGW), which contained strong toxins and refractory pollutants that were poorly biodegradable. The results indicated that Fenton oxidation with the prepared catalyst was a highly efficient means of treatment for CGW over a wide pH range: the corresponding COD, cyanide and total phenols (TPh) removal efficiencies were 55.5, 46.5 and 85.5%, respectively. The treated wastewater was more biodegradable and less toxic, which aided in subsequent processing. The efficiency enhancement was attributed to the generation of more hydroxyl radicals and a possible reaction mechanism was proposed. Furthermore, Fe₃O₄MNPs/RSAC showed superior stability over ten successive runs. Moreover, heterogeneous Fenton oxidation by Fe₃O₄MNPs/RSAC also enhanced the aerobic biodegradation of CGW. Overall, 92.9% of COD and 98.5% of TPh were removed via the integration of Fenton oxidation and biological processing. Thus, the catalysis of Fenton oxidation by Fe₃O₄MNPs/RSAC was efficient, cost-effective and sustainable with a beneficial engineering application in the treatment of refractory wastewater, and a new and sustainable use for waste rice straw.