Removal Of Nitrates And Nitrites In Water By Modified Capacitive Deionization Activated Carbon Electrode

In recent years,water pollution caused by nitrate and nitrite have become increasingly serious due to the discharge of industrial nitrogenous wastes and the extensive use of agricultural nitrogen fertilizers.A large amount of nitrate into the water will cause the eutrophication of the body,the intake of nitrates in the human body after the reduction of carcinogenic nitrite,and cause poisoning symptoms.Removal of nitrate and nitrite in water are commonly used in the physical and chemical treatment of ion exchange,electrodialysis,distillation and reverse osmosis,these methods have disadvantages of high energy consumption,low efficiency and easy to cause secondary pollution.Capacitive deionization technology?CDI?is a kind of electrostatic desalination technology which is easy to use,has low operation and maintenance cost,and has the advantages of clean energy saving and environmental protection,and has wide application prospect in desalination and industrial wastewater treatment.It has great theoretical and practical significance to study the modification of CDI activated carbon electrode materials and try to use CDI technology for the treatment of nitrate and nitrite wastewater.In this paper,activated carbon was used as the electrode material and foamed nickel as the substrate to prepare the activated carbon electrode.The effect of the device structure,the number of electrodes and the spacing between the electrodes on adsorption effect were studied.Explore the adsorption potential and energy consumption of the device under different working voltage and influent flow to remove nitrate and nitrite,and the adsorption characteristics of mixed ions were also studied under the background ion conditions.At the same time,using phosphoric acid to oxidate activated carbon under certain experimental conditions to change it's surface chemical properties and pore size,and then study the adsorption effect of the electrode on the nitrate and nitrite before and after the modification.The cycling performance and current efficiency of the electrode before and after modification were also studied.The capacitance deionization of the electroabsorption device is determined by the electrode material properties?specific surface area,pore size structure,surface chemical properties?,device configuration?electrode logarithm,electrode spacing,assembly method?and operating conditions?operating voltage,inlet flow rate,solution concentration?.The electric adsorption capacity per unit mass of the activated carbon electrode is 11.47 times of that of the graphite electrode.When the electrode spacing is 1.0 mm and the number of the electrodes is 9 pairs,the electro-adsorption performance of the device can be improved by the use of fold line flow mode,The voltage and influent concentration affect the thickness of the electrode layer and the flow rate has an effect on the stability of the electric double layerAfter the modification of phosphoric acid,the specific surface area of activated carbon increased by 10.71%,the mesopore ratio increased,and the total pore volume increased from 0.900 cm3/g to 1.038 cm3/g.The surface hydrophilicity and wettability of activated carbon increased due to the number of oxygen functional group improved.The specific capacity increased by 11.70%.After the electrode was modified,the specific adsorption capacity of NO₃^-was increased by 22.26%.When the nitrate and nitrite are removed,the current efficiency was improved and the energy consumption per unit was reduced.The presence of chloride ions in the background would compete for the adsorption sites on the electrode surface,reducing the adsorption effect on nitrate and nitrite.The adsorption capacity of the activated carbon was improved after the phosphoric acid oxidation,and the mesopores reduced the migration resistance of the charged ions to the electrode surface.After the modification,the electrode adsorption/desorption cycle was shortened and the electrode recycling performance was improved.