Degradation of 1,4-dioxane in water with heat- and Fe2+-activated persulfate oxidation

This research investigated the 1,4-dioxane (1,4-D) degradation efficiency and rate during persulfate oxidation at different temperatures, with and without Fe2+ addition, also considering the effect of pH and persulfate concentration on the oxidation of 1,4-D. Degradation pathways for 1,4-D have also been proposed based on the decomposition intermediates and by-products. The results indicate that 1,4-D was completely degraded with heat-activated persulfate oxidation within 3-80 h. The kinetics of the 1,4-D degradation process fitted well to a pseudo-first-order reaction model. Temperature was identified as the most important factor influencing the 1,4-D degradation rate during the oxidation process. As the temperature increased from 40 to 60 degrees C, the degradation rate improved significantly. At 40 degrees C, the addition of Fe2+ also increased the 1,4-D degradation rate. Interestingly, at 50 and 60 degrees C, the 1,4-D degradation rate decreased slightly with the addition of Fe2+. This reduced degradation rate may be attributed to the rapid conversion of Fe2+ to Fe3+ and the production of an Fe(OH)(3) precipitate which limited the ultimate oxidizing capability of persulfate with Fe2+ under higher temperatures. Higher persulfate concentrations led to higher 1,4-D degradation rates, but pH adjustment had no significant effect on the 1,4-D degradation rate. The identification of intermediates and by-products in the aqueous and gas phases showed that acetaldehyde, acetic acid, glycolaldehyde, glycolic acid, carbon dioxide, and hydrogen ion were generated during the persulfate oxidation process. A carbon balance analysis showed that 96 and 93 % of the carbon from the 1,4-D degradation were recovered as by-products with and without Fe2+ addition, respectively. Overall, persulfate oxidation of 1,4-D is promising as an economical and highly efficient technology for treatment of 1,4-D-contaminated water.