Thompson Jonathan R, Wilder Logan M, Crooks Richard M
Department of Chemistry, Texas Materials Institute, The University of Texas at Austin 105 E. 24th St., Stop A5300 Austin Texas 78712-1224 USA
Chem Sci. 2021 Sep 29;12(41):13744-13755. doi: 10.1039/d1sc03192a. eCollection 2021 Oct 27.
Here we use experiments and finite element simulations to investigate the electrokinetics within straight microchannels that contain a bipolar electrode and an unbuffered electrolyte solution. Our findings indicate that in the presence of a sufficiently high electric field, water electrolysis proceeds at the bipolar electrode and leads to variations in both solution conductivity and ionic current density along the length of the microchannel. The significance of this finding is twofold. First, the results indicate that both solution conductivity and ionic current density variations significantly contribute to yield sharp electric field gradients near the bipolar electrode poles. The key point is that ionic current density variations constitute a fundamentally new mechanism for forming electric field gradients in solution. Second, we show that the electric field gradients that form near the bipolar electrode poles in unbuffered solution are useful for continuously separating microplastics from water in a bifurcated microchannel. This result expands the potential scope of membrane-free separations using bipolar electrodes.
在此，我们利用实验和有限元模拟来研究包含双极电极和无缓冲电解质溶液的直微通道内的动电现象。我们的研究结果表明，在足够高的电场存在下，双极电极处会发生水电解，并导致沿微通道长度方向的溶液电导率和离子电流密度发生变化。这一发现的意义有两方面。首先，结果表明溶液电导率和离子电流密度的变化都显著有助于在双极电极极附近产生急剧的电场梯度。关键在于，离子电流密度的变化构成了溶液中形成电场梯度的一种全新机制。其次，我们表明在无缓冲溶液中双极电极极附近形成的电场梯度可用于在分叉微通道中连续地从水中分离微塑料。这一结果扩展了使用双极电极进行无膜分离的潜在范围。
