Kambhu Ann, Gren Megan, Tang Wei, Comfort Steve, Harris Clifford E
Department of Civil Engineering, University of Nebraska, Lincoln, NE 68583-0531, USA.
Department of Biological Systems Engineering, University of Nebraska, Lincoln, NE 68583-0726, USA.
Chemosphere. 2017 May;175:170-177. doi: 10.1016/j.chemosphere.2017.02.044. Epub 2017 Feb 8.
1,4-dioxane is an emerging contaminant that was used as a corrosion inhibitor with chlorinated solvents. Metal-activated persulfate can degrade dioxane but reaction kinetics have typically been characterized by a rapid decrease during the first 30 min followed by either a slower decrease or no further change (i.e., plateau). Our objective was to identify the factors responsible for this plateau and then determine if slow-release formulations of sodium persulfate and Fe could provide a more sustainable degradation treatment. We accomplished this by conducting batch experiments where Fe-activated persulfate was used to treat dioxane. Treatment variables included the timing at which the dioxane was added to the Fe-persulfate reaction (T = 0 and 30 min) and including various products of the Fe-persulfate reaction at T = 0 min (Fe, Fe, and SO). Results showed that when dioxane was spiked into the reaction at 30 min, no degradation occurred; this is in stark contrast to the 60% decrease observed when added at T = 0 min. Adding Fe at the onset (T = 0 min) also severely halted the reaction and caused a plateau. This indicates that excess ferrous iron produced from the Fe-persulfate reaction scavenges sulfate radicals and prevents further dioxane degradation. By limiting the release of Fe in a slow-release wax formulation, degradation plateaus were avoided and 100% removal of dioxane observed. By using C-labeled dioxane, we show that ∼40% of the dioxane carbon is mineralized within 6 d. These data support the use of slow-release persulfate and zerovalent iron to treat dioxane-contaminated water.
1,4 - 二氧六环是一种新兴污染物，曾被用作氯化溶剂的腐蚀抑制剂。金属活化过硫酸盐可降解二氧六环，但反应动力学通常表现为在最初30分钟内迅速下降，随后下降速度减慢或不再变化（即达到平稳状态）。我们的目标是确定导致这种平稳状态的因素，然后确定过硫酸钠和铁的缓释配方是否能提供更可持续的降解处理方法。我们通过进行批量实验来实现这一目标，其中使用铁活化过硫酸盐处理二氧六环。处理变量包括将二氧六环添加到铁 - 过硫酸盐反应中的时间（T = 0和30分钟）以及在T = 0分钟时铁 - 过硫酸盐反应的各种产物（铁、亚铁和硫酸根）。结果表明，当在30分钟时将二氧六环加入反应中时，没有发生降解；这与在T = 0分钟时加入观察到的60%的降解率形成鲜明对比。在开始时（T = 0分钟）加入铁也严重阻碍了反应并导致平稳状态。这表明铁 - 过硫酸盐反应产生的过量亚铁离子会清除硫酸根自由基并阻止二氧六环的进一步降解。通过在缓释蜡配方中限制铁的释放，避免了降解平稳状态并观察到二氧六环100%的去除率。通过使用碳标记的二氧六环，我们表明约40%的二氧六环碳在6天内被矿化。这些数据支持使用缓释过硫酸盐和零价铁来处理受二氧六环污染的水。
