电絮凝处理腐殖酸过程中阳极钝化影响因素分析

针对电絮凝(electrocoagulation，EC)处理腐殖酸(humic acid，HA)过程中电极易发生钝化，造成处理效能下降的问题，主要探究了阳极表面粗糙度、初始pH、初始HA浓度对于铝阳极钝化的影响，随后通过检测溶液中残留Al³⁺浓度和阳极板表面形貌，进一步分析了HA浓度对于铝阳极钝化发展的影响机制。结果表明：铝阳极钝化程度与阳极板表面算数平均粗糙度(arithmetic mean roughness，Ra)呈负相关，随着Ra从2 055 nm下降到270 nm，阳极板的电荷转移电阻(charge transfer resistor，Rct)从1 174.0 Ω·cm²增大到1 481.2 Ω·cm²；当溶液初始pH从3 提高到 7 时，极板的Rct从461.0 Ω·cm²增大到1 120.2 Ω·cm²，而当pH继续升高到 9 时，极板的Rct下降到169.5 Ω·cm²；铝阳极钝化程度随溶液初始HA浓度呈现先减小后增大的规律。HA的质量浓度从0 mg·L⁻¹ 提高到20 mg·L⁻¹ 时，对应极板的Rct从1 536.4 Ω·cm²减小到932.9 Ω·cm²，HA的质量浓度进一步上升至200 mg·L⁻¹时，对应极板的Rct又从932.9 Ω·cm²增大到1 403.2 Ω·cm²。本研究结果可为EC在实际应用中抑制阳极钝化提供参考。

Influence factors of anode passivation during humic acid electrocoagulation treatment

Aiming at the passivation problem of the anode during the electrocoagulation (EC) treatment of humic acid (HA) which can decrease the removal efficiency, the effects of surface roughness, initial pH, and initial HA concentration on the passivation degrees of aluminum anodes were investigated in this study. The passivation mechanism was further analyzed by detecting the concentration of residual Al3+ in the solution and the surface morphologies of the anodes. The results showed that the passivation degree of the aluminum anode was negatively correlated with the arithmetic mean roughness (Ra) of its surface. The charge transfer resistance (Rct) of the anode increased from 1 174.0 Ω·cm2 to 1 481.2 Ω·cm2 when Ra decreased from 2 055 nm to 270 nm. In addition, when the initial pH of the solution increased from 3 to 7, Rct of the anode increased from 461.0 Ω·cm2 to 1 120.2 Ω·cm2. And when the pH continued to rise to 9, Rct decreased to 169.5 Ω·cm2. The passivation degree of the anode first decreased and then increased with the increase of the initial HA concentration. When the HA concentration increased from 0 mg·L−1 to 20 mg·L−1, Rct of the corresponding anode decreased from 1 536.4 Ω·cm2 to 932.9 Ω·cm2. And when the HA concentration further increased to 200 mg·L−1, the corresponding Rct increased from 932.9 Ω·cm2 to 1 403.2 Ω·cm2. This study provides a theoretical and technical support for anode passivation mitigation in practical application of EC.