Abstract:

Electrochemical water softening represents an innovative and green approach for the descaling of industrial circulating cooling water system. However, in the undivided electrolytic cell, the generated H⁺ and OH^- at anode and cathode, respectively, cannot effectively separate, causing low water softening efficiency and high energy consumption. In this study, an asymmetric cathodic electrochemical water softening with zero electrode space was developed, which was consisting of a unilaterally insulated asymmetric cathode and particles packed anode. In this electrolytic reactor, the directional motion of H₂ bubbles from the asymmetric cathode could drive OH^- diffusion to the solution at the back of the cathode, while H⁺ could be carried away from the interface between anode and cathode by the gravitational seepage in the three-dimensional anode region. Theoretical calculations based on a mathematical model proved that transport rates of OH^- and H⁺ away from the electrodes induced by the H₂ bubble and gravitational seepage, respectively, were greater than their corresponding electro-migration rates. Thus, H⁺ and OH^- were effectively separated with high utilization of OH^- for hardness precipitation. The experimental results showed that the calcium hardness removal efficiency and removal rate were as high as 89.2% and 267.5g/(h·m²), respectively, at a current density of 15mA/cm² and a flow rate of 15mL/min, with an energy consumption of only 3.27kW·h/kg. An efficient electrochemical water softening reactor with using bubble motion and flow regulation strategies was developed, providing new idea for the design of electrochemical circulating cooling water descaling reactor.

Key words: electrochemical, water softening, asymmetric electrodes, diffusion, hydrodynamics

摘要：

电化学除硬是一种新型的绿色工业循环冷却水阻垢技术，但是传统单腔室电解过程产生的H⁺、OH^-无法高效分离，导致电化学除硬效率低、能耗高。对此，构建零极距、非对称式电解反应体系，单侧绝缘的非对称阴极调控H₂气泡的定向运动，驱动OH^-向一侧溶液扩散，而三维阳极区域内利用重力渗流作用将电解产生的H⁺带离反应区域，通过数学模型理论计算证明OH^-和H⁺分别在阴极氢气泡作用下的对流传质速率和在重力渗流作用下的迁移速率都高于其电迁移速率，从而实现H⁺、OH^-的高效分离，提升了OH^-的除硬利用率。实验结果表明，当电流密度为15mA/cm²、流速为15mL/min时，钙硬去除率和去除速率分别高达89.2%和267.5g/(h·m²)，而能耗仅为3.27kW·h/kg。本研究利用气泡运动和水流调控策略开发了一种高效的电化除硬装置，为电化学循环冷却水除垢反应器开发提供新思路。

关键词: 电化学, 水软化, 非对称电极, 扩散, 流体动力学