Study On Degradation Of Organic Phosphine Scale And Corrosion Inhibitor By Electrochemical/Persulfate Coupling System

As typical organic phosphine scale and corrosion inhibitors,hydroxyethylidene diphosphonic acid（HEDP）and aminotrimethylene phosphonic acid（ATMP）widely exist in industrial water treatment systems.Due to the low conventional biodegradation rate of these scale inhibitors,the reuse and discharge of industrial wastewater treatment are limited.Advanced oxidation is an efficient method to degrade organic pollutants in water.In this paper,a separate plug flow reactor with boron doped diamond（BDD）as anode and iridium tantalum titanium as cathode was used to study the degradation efficiency of HEDP and ATMP by electrochemical/persulfate coupling system and electrochemical advanced oxidation（EAOP）system,and its degradation mechanism was discussed.The specific research contents and results are as follows:（1）The effects of current density,Na₂S₂O₈ concentration,temperature and p H value on the degradation of HEDP and ATMP were investigated in the electrochemical/persulfate coupling system.The experimental results showed that when the current density was 20 m A/cm²,the concentration of Na₂S₂O₈ was 5 mmol/L,p H=11 and the temperature was 60℃,the degradation rate of HEDP was the highest,which was 71.3%within 180 min;When the current density is 30 m A/cm²,the concentration of Na₂S₂O₈ is 5 mmol/L,p H=11 and the temperature is 60℃,the degradation rate of ATMP is the highest,which is 75.2%within 120 min.（2）The effects of solution flow rate,temperature,current density,p H value and electrolyte Na₂SO₄ concentration on the degradation of HEDP and ATMP were investigated in the electrochemical advanced oxidation system.The experimental results show that the degradation rate of HEDP is the highest when the current density is 30 m A/cm²,the concentration of electrolyte Na₂SO₄ is 0.1 mol/L,p H=11,the temperature is 30℃,the solution flow rate is 500 ml/min,and it can reach 99.7%in 90min;When the current density is 30 m A/cm²,the concentration of electrolyte Na₂SO₄is 0.05 mol/L,p H=9,the temperature is 50℃,the solution flow rate is 500 ml/min,the degradation rate of ATMP is the highest,and it can reach 99.7%in 80 minutes.（3）The degradation mechanism of pollutants in electrochemical advanced oxidation system was studied.The pseudo first order reaction rate constant of·OH and HEDP is（4.28±0.24）×10⁸ L/（mol·s）,the pseudo first order reaction rate constant of·OH with ATMP is（7.50±0.05）×10⁸ L/（mol·s）,the pseudo first-order reaction rate constant of SO₄^-·with HEDP is 0 and the pseudo first-order reaction rate constant of SO₄^-·with ATMP is（5.63±1.20）×10⁷ L/（mol·s）;The main active species produced in the system are·OH,SO₄^-·and persulfate,among which·OH plays a major role in the degradation of HEDP and ATMP;The steady-state concentration of·OH is 3.11×10^-6 mol/L.