Dramatically enhanced degradation of recalcitrant organic contaminants in MgO_2/Fe(Ⅲ) Fenton-like system by organic chelating agents

摘要

Herein, the application of organic acids as chelating agent, including citric acid (CA), tartaric acid (TA), oxalic acid (OA) and ethylenediaminetetraacetic acid (EDTA), to enhance the degradation performance of MgO_2/Fe(HI) system was investigated in the terms of chelating agent dosage, Fe(Ⅲ) dosage, reaction temperature, initial solution pH and inorganic anion. When the molar ratio of MgO_2/Fe(Ⅲ)/chelating agent was 1 : 0.7 : 0.3, the degradation efficiencies of Rhodamine B (RhB) increased from 6.7% (without chelating agent) to 42.3%, 98.5%, 48.9% and 25.8% within 30 min for CA, TA, OA, and EDTA, respectively. The promotion effect was mainly attributed to the chelation between chelating agents and Fe(Ⅲ), rather than the acidification of chelating agents. The pseudo-first-order kinetic model well fitted RhB degradation in MgO_2/Fe(Ⅲ)/TA system, and the kinetic rate constant reached up to 0.295 min~(-1). Hydroxyl radical was confirmed to be the dominant active species to degrade organics in the MgO_2/Fe(Ⅲ)/TA system. Notably, the degradation system could work in a broad pH (3-11) and temperature (5-35 °C) range. Moreover, the MgO_2/Fe(Ⅲ)/TA system can also effectively degrade methylene blue, tetracycline and bisphenol A. This work provided a new, efficient and environmentally-friendly Fenton-like system for stubborn contaminant treatment.