Facile preparation of coprecipitates between iron oxides and dissolved organic matter for efficient Fenton-like degradation of norfloxacin

As two important components of dissolved organic matter (DOM), dissolved black carbon (DBC) and humic acid (HA) possess different chemical and structural properties, which might influence their activities like metal complexation and mediating electron transfer. In this study, a series of coprecipitates of iron oxides (FeOx) and DOM (HA or DBC) having different C/Fe molar ratios (0.2–3.0) was prepared under ambient conditions, which exhibited excellent catalytic efficiencies upon Fenton-like degradation of norfloxacin (NOR). Pseudo-first-order rate constant of NOR oxidation catalyzed by DBC-FeOx (C/Fe=3.0, 1.13 h−1) was 30.5, 4.3–14.2, and 1.3–15.7 folds higher than those mediated by FeOx alone, HA-FeOx and DBC-FeOx coprecipitates having C/Fe molar ratios of 0.2 and 1.6, respectively. Due to the higher concentrations of surface-bound Fe(III)/Fe(II) in the DBC-FeOx mediated systems, improved Fe(III)/Fe(II) cycling rates, •OH accumulation and NOR degradation were observed as compared with those of counterpart systems mediated by HA-FeOx. Besides functioning in Fe-C complexation to accelerate FeOOH cleavage, carbonyl/carboxyl groups of the coprecipitates also serve as electron shuttles, both of which improved Fe(III)/Fe(II) cycling and •OH production. Our findings emphasized the influence of DOM source and compositions on Fe(III)/Fe(II) cycling and provided a facile approach of preparing Fe-C catalyst for contaminants elimination. [Display omitted] •Coprecipitates of FeOx and DOM (DBC or HA) were prepared under ambient conditions.•DBC-FeOx exhibited faster •OH production and NOR degradation than HA-FeOx.•NOR was degraded through defluorination, hydroxylation, and ring opening, etc.•DOM-FeOx accelerated Fe(III)/Fe(II) cycling in Fenton-like processes.•C=O/COOH enhanced Fe(III)/Fe(II) cycling via electron shuttling and complexation.