Kang Wenda, Li Lujie, Yan Liming, Mao Wei, Wang Xueqing, Yu Hongtao, Ma Chuanjun
Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
National & Local Joint Engineering Research Center for Environmental Pollution Control of Petroleum and Petrochemicals, Dalian 116045, China.
Water Res. 2023 Apr 1;232:119694. doi: 10.1016/j.watres.2023.119694. Epub 2023 Feb 2.
Electrochemical softening is an effective technology for the treatment of circulating cooling water, but its hardness removal efficiency is limited because that nucleation and growth of scale crystals depended on cathode surface. In this study, a novel method was proposed to break through this limit via spatiotemporal management of nucleation and growth processes. A cube reactor was divided into cathodic chamber and anodic chamber via installing a sandwich structure module composed of mesh cathode, nylon nets, and mesh anode. Using this continuous-flowing electrochemical reactor, OH ̄ generated by water electrolysis was rapidly pushed away from cathode surface by water flow and hydrogen bubbles movement. As a result, a wide range of strongly alkaline regions was rapidly constructed in cathodic chamber to play a nucleation region, and homogeneous nucleation in liquid phase replaced heterogeneous nucleation on cathodic surface. Furthermore, the growth process of scale crystals in alkaline regions was monitored in situ. It took only 150 s of residence time to grow to 500 nm, which may be easily separated from water by a microfiltration membrane. With this new method, the precipitation rate was 290.8 g/(hˑm) and corresponding energy consumption was 2.1 kW·h/kg CaCO, both were superior to those reported values. Therefore, this study developed an efficient electrochemical softening method by spatial and temporal regulation of homogeneous nucleation and crystal growth processes.
电化学软化是一种处理循环冷却水的有效技术，但其除硬效率有限，因为水垢晶体的成核和生长依赖于阴极表面。在本研究中，提出了一种通过对成核和生长过程进行时空管理来突破这一限制的新方法。通过安装由网状阴极、尼龙网和网状阳极组成的夹层结构模块，将立方体反应器分为阴极室和阳极室。使用这种连续流动的电化学反应器，水电解产生的OH ̄被水流和氢气泡的运动迅速从阴极表面推开。结果，在阴极室中迅速构建了一个广泛的强碱性区域作为成核区域，液相中的均相成核取代了阴极表面的异相成核。此外，还对碱性区域内水垢晶体的生长过程进行了原位监测。仅需150秒的停留时间就可生长至500纳米，这可以很容易地通过微滤膜与水分离。采用这种新方法，沉淀速率为290.8克/(小时·米)，相应的能耗为2.1千瓦·时/千克碳酸钙，均优于报道值。因此，本研究通过对均相成核和晶体生长过程进行时空调控，开发了一种高效的电化学软化方法。
