Electrocatalytic Degradation Of Pesticide Wastewater By Rare Earth Elements Doped Dimensionally Stable Ti/PbO₂ Electrode

With the massive use of pesticides and the rapid development of pesticide production industry,pesticide wastewater from production process has caused serious detriment to aquatic ecosystem and human health.Electrochemical advanced oxidation process has unique advantages in pesticide wastewater treatment because of its wide application range,high efficiency,simple operation and environmental friendliness.The development of electrode material with high efficiency,low energy consumption,few cost and long service life is the core issue of electrocatalytic degradation of pesticide wastewater.In this thesis,several rare earth doped titanium-based lead dioxide electrodes have been prepared by one-step electrodeposition and used for the electrocatalytic degradation of wastewater containing pesticide?such as imidacloprid,atrazine and?-naphthoxyacetic acid?.The main contents are as follows:?1?A novel Ti/PbO₂-Tb electrode with high oxygen evolution potential,low charge transfer impedance,long service lifetime and wonderful electrocatalytic activity has been prepared by electrodeposition and further investigated for electrochemical degradation of imidacloprid wastewater.It turns out that 70.05%of COD and 76.07%of imidacloprid are removed at current density 8 mA cm^-2,pH 9,temperature 30°C,NaCl concentration 7.0 g L^-1 and electrolysis time 2.5 h.Furthermore,the kinetic behavior and the energy consumption in imidacloprid wastewater degradation process are studied.Under the optimum conditions,the recyclability of the electrode is tested,and the hydroxyl radical is determined as the main active substance in electrocatalytic degradation of imidacloprid pesticide wastewater by free radical trapping experiment.The degradation mechanism of imidacloprid is proposed by analyzing intermediates obtained by LC-MS.The present study provides a feasible strategy to degrade imidacloprid wastewater by Ti/PbO₂-Tb electrode.?2?A dimensionally stable Ti/PbO₂-Co-Sm electrode has been prepared by electrodeposition for efficiently electrocatalytic degradation of atrazine pesticide wastewater.Ti/PbO₂-Co-Sm electrode shows higher oxygen evolution potential,lower charge transfer resistance,longer service lifetime and outstanding electrocatalytic activity than Ti/PbO₂,Ti/PbO₂-Co and Ti/PbO₂-Sm electrodes.The degradation efficiency and COD removal efficiency of atrazine on Ti/PbO₂-Co-Sm electrode reach up to 92.55%and 84.47%under the optimal conditions(temperature 35°C,pH 5,current density 20 mA cm^-2,Na₂SO₄concentration 8.0 g L^-1 and electrolysis time 3 h),respectively.In addition,Ti/PbO₂-Co-Sm electrode exhibits wonderful recyclability under the optimal conditions.The hydroxyl radical is determined as the main active substance in the electrocatalytic degradation of atrazine pesticide wastewater by free radical trapping experiment.The degradation mechanism of atrazine pesticide wastewater is proposed by analyzing intermediates obtained by LC-MS.The results suggest that Ti/PbO₂-Co-Sm electrode is a promising candidate for electrocatalytic degradation of atrazine pesticide wastewater.?3?A dimensionally stable Ti/PbO₂-Co-Pr electrode has been prepared by electrodeposition for high-performance electrocatalytic degradation of?-naphthoxyacetic acid pesticide wastewater.Compared with Ti/PbO₂,Ti/PbO₂-Co and Ti/PbO₂-Pr electrodes,Ti/PbO₂-Co-Pr electrode shows higher oxygen evolution potential,lower charge transfer resistance,longer service lifetime and outstanding electrocatalytic activity.The degradation efficiency and COD removal efficiency of?-naphthoxyacetic acid on Ti/PbO₂-Co-Pr electrode reach up to 94.59%and 84.59%under the optimal conditions(temperature 35°C,pH 5,current density 12 mA cm^-2,Na₂SO₄ concentration 8.0 g L^-1 and electrolysis time 3 h),respectively.The degradation of?-naphthoxyacetic acid wastewater is in conformity with pseudo-first-order kinetics.Free radical trapping experiments reveal that hydroxyl radical is the main active substance in electrocatalytic degradation of?-naphthoxyacetic acid wastewater.The degradation mechanism of?-naphthoxyacetic acid wastewater is proposed by analyzing intermediates obtained by LC-MS.The results suggest that Ti/PbO₂-Co-Pr electrode is a promising candidate for electrocatalytic degradation of?-naphthoxyacetic acid pesticide wastewater.The results reveal that Ti/PbO₂-Tb,Ti/PbO₂-Co-Sm and Ti/PbO₂-Co-Pr electrodes are environmentally-friendly,efficient and cost-effective in the electrocatalytic treatment of pesticide wastewater.