Abstract:

Hydroxyethylidene diphosphonic acid (HEDP) is a typical organic phosphine corrosion and scale inhibitor. It widely exists in industrial water treatment system. Its conventional biodegradation rate is less than 5%. It has become a restrictive factor for industrial wastewater treatment, reuse and efflux. The degradation efficiency of HEDP by electrochemical advanced oxidation method was explored, and the effects of key parameters such as current density, Na₂SO₄ concentration, pH, temperature and solution flow rate on the degradation rate of HEDP were investigated. The degradation mechanism of HEDP was explored by electron spin resonance test, radical quenching method and kinetic experiment. The results showed that the degradation rate of HEDP was the highest when the current density was 30 mA/cm², the concentration of electrolyte Na₂SO₄ was 0.1 mol/L, pH=11, the temperature was 30℃, the solution flow rate was 500 ml/min, and it could reach 99.7% in 90 min. The electrochemical advanced oxidation system used in the study mainly produces hydroxyl radical (·OH) and sulfate radical (SO{}_{\mathrm{4}}^{-}·). Only ·OH can degrade HEDP. The reaction rate constant of ·OH and HEDP is (4.28±0.24)×10⁸ L/(mol·s)。

Key words: electrochemical advanced oxidation, radical, HEDP, degradation, kinetics

摘要：

羟基亚乙基二膦酸（HEDP）是典型的有机膦缓蚀阻垢剂，广泛存在于工业水处理系统中，其常规生物降解率低于5%，已成为工业废水处理回用和外排的制约因素。为此，探索了电化学高级氧化法对HEDP的降解效能，考察了电流密度、Na₂SO₄浓度、pH、温度及溶液流速等关键参数对HEDP降解率的影响；利用电子自旋共振测试，自由基猝灭方法和HEDP降解动力学探讨了HEDP的降解机制。结果表明，电流密度为30 mA/cm²，电解质Na₂SO₄浓度为0.1 mol/L，pH=11，温度为30℃，溶液流速为500 ml/min时HEDP降解率最高，90 min内可达99.7%；研究采用的电化学高级氧化体系产生羟基自由基（·OH）和硫酸根自由基（SO{}_{\mathrm{4}}^{-}·），仅·OH可以降解HEDP，·OH与HEDP的反应速率常数k_•OH，HEDP=（4.28±0.24）×10⁸ L/（mol·s）。

关键词: 电化学高级氧化, 自由基, HEDP, 降解, 动力学