| With the development of economyand people’s living standards improved, the safety of drinking water has attracted increasing attention. Taste and odor areperceived by the public as the primary indicators of the safety and acceptability of drinking water. In recent years,taste and odor events in drinking water treatment occur frequently around the world,leading to people’s life and production losses. Therefore, the study of drinking water treatment technology to remove taste and odor compounds foremergency of taste and odor events has important significance and value. 2,4,6-trichloroanisole (TCA), a typical earthy-musty odor compound frequently detected in drinking water treatmentwith a very lowthreshold odor number (<10ng/L), is difficult to be removed by the conventional water treatment process and Common oxidants. To explore the effective removal of TCA, persulfate(PS) activated by Fe2+to generate a strong oxidizing sulfate radical SO4-, was choosed to degrade TCA. Advanced oxidation processes(AOPs) with persulfate activated to form SO4·was originally applied to the soil and groundwater in-situ chemical remediation, and rare in application of the taste and odor compounds and other trace organic contaminants removing. Meanwhile, PS activated by Fe2+ is an environmentally friendly, mild way to generate SO4-·. Therefore, this study apply the strong oxidizingSO4-· generated from Fe2+ activating PS to removal of TCA which is resistant to oxidation.Degradation of TCA by PS activated with Fe2+ and the influencing factors were studied. The experimental results showed that:the optimal ratio of PS/Fe2+ is 1:1.5.TCA degradation fitted pseudo-first-order kinetics well during the first 10min, and the rate constants increased with increasing PS dosage and maximum TCA degradation occurred at pH7. Complexing agent citric acid and EDTA would make rapid reaction stage within 2min become apparent, but an excess of citric acid and EDTA will hinder the reaction slow stage. PS activated by Fe2+ with oxalate complexing appeared tobepoor in TCA removal, which may be due to competition forSO4-·in the reaction, thereby reducing the TCA removal;In addition, 1mg/L humic acid can promote the reaction and there was no more enhancement with increasing humic acid. Compared to only once dosing of Fe2+,stepwise dosing can promote TCA degradation, and the removal efficiency of TCA in 30min is comparable to that of 60min in only once dosing of Fe2+. PS activated by Fe2+ stemmed from Fe0 to degrade TCA was studied, and the acidic conditions were more conducive to corrosion of Fe0 to release more Fe2+, subsequently achieving better TCA removal. The Fe3+to Fe2+recycle is present in the reaction of TCA degradation, and Fe3+ can bereduced toFe2+by degradation intermediates of TCA, thereby generating a sustained activation of PS to degrade TCA in slow reaction stage. TCAdegradation intermediates by Fe2+/PS systemare mainly trichlorophenol (TCP).Analysis of the free radicals generated from Fe2+/PS system by electron paramagnetic resonance(EPR)showed that SO4-· is predominant in Fe2+/PS system at pH3; At pH7, both SO4-·and OH · are present in the system,playing an effective role at the same time; Otherwise, OH · is predominant in Fe2+/PS system at pH10,and little SO4-· is detected. Further, EPR absorption spectrum may have found a phosphate radical due tothe phosphate buffer to adjust pH.The degradation of GSM and 2-MIB by PS activated with Fe2+is not as effective as TCA, and 2-MIB is relativelyharder to be oxidized than GSM. The degree of difficulty of these three earthy-musty odor compounds from hard to easy was 2-MIB> GSM> TCA. |
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