Degradation of synthetic organic compounds by sulfate- and hydroxyl radical-based advanced oxidation processes.

摘要

Currently, the contamination of water sources by synthetic organic compounds (SOCs) is one of the concerning environmental issues faced throughout the world. Among the existing SOCs, dyes and herbicides contribute to a large portion of the confirmed toxic organics and thus have to be removed prior to the discharge of the treated water. Against the background, the primary objective of this research work is to explore sulfate- and hydroxyl radical based advanced oxidation processes (AOPs) for the elimination of dyes and herbicides in water and wastewaters.;Firstly, an oxidation process using sulfate radical (SO4 ·-) activated by Fe(II)-mediated OxoneRTM process (FO) were evaluated by monitoring the degradation of Rhodamine B in aqueous solution. The effects of reactant dosing sequence, Fe(II)/Oxone RTM molar ratio and concentration, solution pH, and inorganic salts on the process performance were investigated.;To further improve the FO process, a novel electrochemically enhanced FO process (i.e. EFO) was proposed. In this process, once an electric current is applied between the anode (an iron sheet) and the cathode (a graphite bar), a predetermined amount of OxoneRTM is added to the reactor. Ferrous ions generated from the sacrificed Fe anode mediate the generation of SO4·- through the decomposition of Oxone RTM. The EFO process was evaluated in terms of a selected herbicide 2,4,5-Trichiorophenoxyacetic acid (2,4,5-T) degradation in aqueous solution.;Furthermore, the degradation of 2,4,5-T in aqueous solution by photo-assisted Fe(II)/OxoneRTM process (FOU) was explored and compared with the FO process. The effects of initial pH, [OxoneRTM], [2,4,5-T], and various anions on the decay of 2,4,5-T by the FOU process were examined in detail. The decay pathways of 2,4,5-T by UV alone, OxoneRTM/UV, and FOU processes were proposed. Additionally, the efficiencies of these processes were further examined in terms of mineralization and Cl- ion accumulation.;Finally, an improved process by incorporating the merits of EFO and FOU was developed, in which the solution treated under EFO system is simultaneously irradiated with UV light (i.e., EFOU). This EFOU process was examined through the degradation of 2,4,5-TCP under various operating conditions. Besides, a possible decay pathway of 2,4,5-TCP by EFOU process was also proposed.