Fabrication Of Ti/Sn-Ir-Ta Electrode And Its Degradation Of Benzene Organic Wastewater

Electrocatalytic oxidation is a green water treatment technology.The core is the anode with catalytic performance.The oxidation capacity,service life and degradation efficiency of the electrode are very important characteristics.Titanium coating electrode is dimensionally stable anode（DSA）,which has been widely concerned because of its long service life.In this experiment,Ti/Sn-Ir-Ta electrode was prepared by thermal decomposition using pretreated titanium plate as electrode substrate.Thermogravimetric differential scanning calorimetry was used to investigate the temperature of electrode preparation and determine the required temperature of calcined electrode.The accelerated life test of the modified electrode is over 17 hours,which proves that the electrode has a long service life.The electrode was characterized by SEM,EDS,XRD and XPS.SEM characterization results show that the electrode is slimy and accompanied by nanoparticles and crystal clusters.The EDS diagram based on the electrode surface coating shows that the precursor uniformly covers the electrode surface.By XRD analysis,it is found that titanium dioxide presents tetragonal rutile structure.Each element forms a solid solution by calcination at high temperature.The formation of solid solution makes the electrode more stable and increases the active site of the electrode.XPS shows that Sn exists in the form of Sn⁴⁺,Ir has three elemental valence states of Ir³⁺,Ir⁴⁺and Ir⁶⁺,and Ta exists in the form of Ta₂O₅.The electrochemical performance of the electrode was characterized by linear sweep voltammetry（LSV）,cyclic voltammetry（CV）and alternating current impedance（EIS）.The oxygen evolution potential of the electrode was 1.472 V and the chlorine evolution potential was 1.273 V.The electrode has higher voltammetry charge and lower charge transfer resistance.The contact angle test indicates that the electrode is a hydrophilic solid.Phenol and aniline solutions with different concentrations were prepared for degradation in order to further investigate the ability of the electrode to treat organic wastewater.Firstly,the influence of current density is investigated and the optimal current density is determined to save electric energy for subsequent experiments.The optimal current density of phenol and aniline degradation is 20 mA·cm^-2.Although the increase of current density promotes charge transfer and produces more hydroxyl radicals,the excessive current density will aggravate the side reaction,resulting in the decrease of current efficiency and the increase of energy consumption.Secondly,the effects of chloride ion concentration,initial concentration of organic matter and p H on Ti/Sn-Ir-Ta electrode electrocatalysis were investigated.The best chloride ion concentration of phenol and aniline degradation is 800 ppm and 600 ppm.Although high chloride ion concentration will increase the conductivity of the solution,it will also lead to intermediates generated by degradation and hinder the adsorption of phenol and aniline.Too low chloride concentration does not provide sufficient ion mobility and hypochlorite.Therefore,proper chlorine ion concentration should be selected to treat organic wastewater.The optimal initial organic concentration of phenol and aniline degradation is 250 ppm and 200 ppm,respectively.The effect of initial concentration on degradation is very obvious.Too high initial concentration of organic matter will not only compete for active sites,but also hinder diffusion.Too low initial concentration of organic matter can cause energy waste.When the actual wastewater is degraded,the organic matter content should be concentrated or diluted to a certain range.Under the experimental electrode system,phenol is suitable for the degradation in strong acid and aniline for the degradation in weak base.The ionization of phenol is inhibited under acidic conditions,and the reaction to form benzoquinone and catechol is hindered.Benzoquinone and catechol are difficult to degrade in electrocatalytic reaction.Aniline degrades more easily in alkaline condition because alkaline condition favors the formation of hydroxyl radical.