Jun Young Kim,Kang Hoon Lee,Jae Won Lee,Imtiaz Afzal Khan,Jong-Oh Kim
In this study, the removal efficiency of chemicals of emerging concerns (CECs) was evaluated under exposure to various doses of UV/H 2 O 2 -based oxidation processes in combination with membrane filtration for three cleaning cycles. Polyethersulphone (PES) and polyvinylidene fluoride (PVDF) materials based membranes were used for this study. The chemical cleaning of the membranes was performed by immersion of the membranes into 1 N HCl followed by adding 3000 mg.L −1 NaOCl for 1hr. Degradation and filtration performance was evaluated using Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) and total organic carbon (TOC) analysis. Membrane fouling analysis for assessing the comparative performance of PES and PVDF membranes was determined by specific fouling and fouling indices evaluation. Membrane characterization results show that the alkynes and carbonyl group formation are due to dehydrofluorination and oxidation of PVDF and PES membranes under the attack of foulants and cleaning chemicals, which resulted in a reduction of fluoride percentage and an increase in sulfur percentage in the PVDF and PES membranes. A decrease in the hydrophilicity of the membranes in underexposed conditions was observed and is consistent with an increase in dose. Degradation results of CECs follow with the highest removal efficiency of chlortetracycline (CTC) followed by atenolol (ATL), acetaminophen (ACT), and caffeine (CAF) degradation due to attack on the aromatic ring and the carbonyl group of CECs by OH exposure. Membrane exposed at 3 mg.L-1 dose of UV/H 2 O 2 -based CECs shows minimum alteration with higher filtration efficiency and lower fouling, particularly in PES membranes.
Degradation of capecitabine was conducted using electrochemical oxidation, UV/H 2 O 2 oxidation, and ozonation. Capecitabine was efficiently degraded by three advanced oxidation processes. The degradation rates of capecitabine achieved approximately 99.0% after 4 min of ozonation, 12 min of electrochemical oxidation, and 30 min of UV/H 2 O 2 oxidation. The mineralization rate obtained was merely 10.3% for ozonation at 60 min, compared to 91.7% for electrochemical oxidation and 55.3% for UV/H 2 O 2 oxidation. Capecitabine was degraded by oxidation, defluorination, hydrogenation, hydrolysis, ring and bond cleavage. Thus, multiple intermediates were generated during the degradation process, such as F - , formic acid, acetic acid, oxalic acid, and other intermediate metabolites with lager molecules. A total of eighteen metabolites, except for F - and carboxylic acids, were identified by QTOF-HRMS, where six of them could only be detected by the electrochemical oxidation process, two of them were by the UV/H 2 O 2 oxidation process, and one of them by the ozonation process. Electrochemical oxidation was the only process that could achieve over 90% removal of cytotoxicity and genotoxicity, and the metabolites were non-genotoxic after 60 min of reaction. The number of live cells decreased with the increasing reaction time in ozonation, demonstrating the higher toxicity of the intermediates in ozonation. Energy cost evaluation results suggested that the lowest energy consumption was achieved at 1.8 kWh/m 3 for 90% of capecitabine degradation with the O 3 dosage of 250 mg/h. Energy consumptions for 50% removal of cytotoxicity were 21.3 and 6.3 kWh/m 3 in electrochemical oxidation and UV/H 2 O 2 oxidation, respectively. The highest energy cost for 50% of genotoxicity removal was observed in electrochemical oxidation, while ozonation was identified as the most cost-effective process.
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