State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Ultrason Sonochem. 2020 Dec;69:105248. doi: 10.1016/j.ultsonch.2020.105248. Epub 2020 Jul 4.
Reactive electrochemical membrane (REM) allows electrochemical oxidation (EO) water purification under flow-through operation, which improves mass transfer on the anode surface significantly. However, O evolution reaction (OER) may cause oxygen bubbles to be trapped in small-sized confined flow channels, and thus degrade long-term filterability and treatability of REM. In this study, ultrasound (ultrasonic vibrator, 28 kHz, 180 W) was applied to EO system (i. e. sonoelectrochemistry) containing titanium suboxide-REM (TiSO-REM) anode for enhanced oxidation of 4-chlorophenol (4-CP) target pollutant. Both experimental and modeling results demonstrated that ultrasound could mitigate the retention of O bubbles in the porous structures by destructing large-size bubbles, thus not only increasing permeate flux but also promoting local mass transfer. Meanwhile, oxidation rate of 4-CP for EO with ultrasound (EO-US, 0.0932 min) was 216% higher than that for EO without ultrasound (0.0258 min), due to enhanced mass transfer and OH production under the cavitation effect of ultrasound. Density functional theory (DFT) calculations confirmed the most efficient pathway of 4-CP removal to be direct electron transfer of 4-CP to form [4-CP], followed by subsequent oxidation mediated by OH produced from anodic water oxidation on TiSO-REM anode. Last, the stability of TiSO-REM could be improved considerably by application of ultrasound, due to alleviation of electrode deactivation and fouling, indicated by cyclic test, scan electron microscopy (SEM) observation and Fourier transform infrared spectroscopy (FT-IR) characterization. This study provides a proof-of-concept demonstration of ultrasound for enhanced EO of recalcitrant organic pollutants by REM anode, making decentralized wastewater treatment more efficient and more reliable.
反应电化学膜 (REM) 允许在流动操作下进行电化学氧化 (EO) 水净化，这显著提高了阳极表面的传质。然而，析氧反应 (OER) 可能导致氧气气泡被困在小尺寸的受限流动通道中，从而降低 REM 的长期过滤性和处理能力。在这项研究中，超声（超声振动器，28 kHz，180 W）被应用于包含氧化钛 REM（TiSO-REM）阳极的 EO 系统（即声电化学），以增强目标污染物 4-氯苯酚（4-CP）的氧化。实验和模拟结果都表明，超声可以通过破坏大尺寸气泡来减轻氧气气泡在多孔结构中的保留，从而不仅增加渗透通量，还促进局部传质。同时，由于超声空化效应增强了传质和 OH 的产生，超声增强的 EO（EO-US，0.0932 min）中 4-CP 的氧化速率（0.0258 min）比无超声的 EO 高 216%。密度泛函理论 (DFT) 计算证实，4-CP 去除的最有效途径是 4-CP 向[4-CP]的直接电子转移，随后由 TiSO-REM 阳极上水氧化产生的 OH 介导的后续氧化。最后，由于超声缓解了电极失活和结垢，TiSO-REM 的稳定性可以得到显著提高，这可以通过循环测试、扫描电子显微镜 (SEM) 观察和傅里叶变换红外光谱 (FT-IR) 表征来证明。这项研究为通过 REM 阳极增强超声强化 EO 难处理有机污染物提供了概念验证，使分散式废水处理更高效、更可靠。
