Coprecipitates between iron oxides and biodegradable organic acids for boosting Fenton-like catalysis under neutral pH conditions.

While the role of dissociated and complexed forms of organic acids (OAs) on Fenton-like reactions has been widely investigated, the catalytic ability and detailed mechanisms of coprecipitates between iron oxides and OAs were still obscure. Herein, coprecipitates of iron oxides with eco-friendly organic acids including maleic acid (MAA), tetrasodium-N,N-bis(carboxymethyl)-L-glutamate (GLDA), and protocatechuic acid (PCA) possessing different C/Fe molar ratios (OA-FeOx, x: C/Fe molar ratios) were respectively prepared under ambient conditions. The coprecipitates exhibited eminent Fenton-like performance in removing various pollutants (e.g., rhodamine B, atrazine, sulfanilamide, bisphenol A, and phenol) under neutral pH conditions. Higher •OH accumulation, Fe(III)/Fe(II) cycling, and pollutant degradation rates were observed in the systems mediated by PCA-FeOx and GLDA-FeOx as compared with that by MAA-FeOx counterparts possessing the same C/Fe molar ratios. Higher level of dissolved and surface-bound Fe(III)/Fe(II) was identified as the main Fe species for improving the Fenton-like reactions in the PCA-FeOx and GLDA-FeOx mediated systems, respectively. Spectroscopic analysis demonstrated that OAs could promote the homolysis cleavage of Fe-OOH, thus contributing to improved Fe(III)/Fe(II) cycling and •OH production. This work provided a facile method for tailoring Fe-C catalyst in removing recalcitrant contaminants under neutral conditions, and provided insights into the underlying mechanisms of Fenton-like reactions catalyzed by Fe-C composites.