Department of Environmental Technology, Wageningen University and Research, P.O. Box 17, 6700, AA Wageningen, the Netherlands; Department of Chemical Engineering and Polymer Science, Shahjalal University of Science and Technology, Sylhet, 3114, Bangladesh.
Department of Environmental Technology, Wageningen University and Research, P.O. Box 17, 6700, AA Wageningen, the Netherlands.
Environ Res. 2022 Aug;211:113057. doi: 10.1016/j.envres.2022.113057. Epub 2022 Mar 7.
Electrochemical oxidation is an effective technique for treating persistent organic pollutants, which are hardly removed in conventional wastewater treatment plants. Sulfate and chloride salts commonly used and present in natural wastewater influence the electrochemical degradation process. In this study, the effect of electrolyte composition on the active sulfate species (SO⁻ and SO⁻) formation, benzotriazole degradation-a model organic compound, and chlorinated by-products distribution have been investigated while using a boron-doped diamond (BDD) anode. Different NaSO:NaNO and NaSO:NaCl ratios with constant conductivity of 10 mS/cm were used in the experiments and applied anode potential was kept constant at 4.3 V vs. Ag/AgCl. The electrogenerated SO⁻ and SO⁻ formation were faster in 10:1 and 2:1 NaSO:NaNO ratios than in the 1:0 ratio. The OH-mediated SO⁻ production has prevailed in 10:1 and 2:1 ratios. However, OH-mediated SO⁻ production has hindered the 1:0 ratio due to excess chemisorption of SO⁻ on the BDD anode. Similarly, the faster benzotriazole degradation, mineralization, and lowest energy consumption were achieved in the 10:1 NaSO:NaNO and NaSO:NaCl ratio. Besides, chlorinated organic by-product concentration (AOX) was lower in the 10:1 NaSO:NaCl ratio but increased with the increasing chloride ratio in the electrolyte. LC-MS analysis shows that several chlorinated organic transformation products were produced in 0:1 to 2:1 ratio, which was not found in the 10:1 NaSO:NaCl ratio. A comparatively higher amount of ClO⁻ was formed in the 10:1 ratio than in 2:1 to 0:1 ratio. This ClO⁻ formation train evidence the effective OH generation in a sulfate-enriched condition because the ClO⁻ formation is positively correlated to OH concentration. Overall results show that sulfate-enriched electrolyte compositions are beneficial for electrochemical oxidation of biorecalcitrant organic pollutants.
电化学氧化是处理难生物降解有机污染物的有效技术，这些污染物在传统污水处理厂中很难去除。硫酸盐和氯化物盐通常在天然废水中使用并存在，会影响电化学降解过程。在这项研究中，使用掺硼金刚石（BDD）阳极研究了电解质组成对活性硫酸盐物种（SO₋和 SO₋）形成、苯并三唑降解（一种模型有机化合物）和氯化副产物分布的影响。实验中使用了不同的 Na₂SO₄:NaNO₃ 和 Na₂SO₄:NaCl 比值，电导率保持在 10 mS/cm 不变，施加的阳极电位保持在 4.3 V vs. Ag/AgCl。在 10:1 和 2:1 的 Na₂SO₄:NaNO₃ 比值中，电生成的 SO₋和 SO₋形成速度比 1:0 比值更快。OH 介导的 SO₋产生在 10:1 和 2:1 比值中占主导地位。然而，由于 SO₋在 BDD 阳极上的过度化学吸附，OH 介导的 SO₋产生阻碍了 1:0 比值。同样，在 10:1 的 Na₂SO₄:NaNO₃ 和 Na₂SO₄:NaCl 比值中，苯并三唑降解、矿化和最低能耗更快。此外，在 10:1 的 Na₂SO₄:NaCl 比值中，氯化有机副产物浓度（AOX）较低，但随着电解质中氯比例的增加而增加。LC-MS 分析表明，在 0:1 至 2:1 的比值中产生了几种氯化有机转化产物，而在 10:1 的 Na₂SO₄:NaCl 比值中没有发现这些产物。在 10:1 的比值中形成了较高量的 ClO₋，而在 2:1 至 0:1 的比值中则较少。ClO₋的形成表明在富硫酸盐条件下有效生成了 OH，因为 ClO₋的形成与 OH 浓度呈正相关。总体结果表明，富硫酸盐的电解质组成有利于电化学氧化生物难降解有机污染物。
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