Solution Absorption Enhanced By Electrochemical Oxidation For The Removal Of Styrene And Tetrahydrofuran From Waste Gases

The emission of volatile organic pollutants not only causes great waste of resources,but also causes serious pollutions to atmospheric environment and threats to human health.Styrene and tetrahydrofuran?THF?are two kinds of such volatile organic pollutants produced in chemical and pharmaceutical manufacturing processes,of which styrene is unsoluble and THF is soluble in water,respectively.In this study,electrochemical oxidation combined with solution absorption was used to remove and degrade styrene and tetrahydrofuran from exhaust gases.The effects of electrolyte type,sodium chloride concentration,current density,initial pH of the electrolytic solution and ultraviolet light irradiation on the removal of styrene and tetrahydrofuran were experementaly investigted.A cylindrical glass reactor was used in the experiment.The volume of the reactor is about 250 mL??30 mm×350 mm?,with a?10 mm×350 mm RuO₂/Ti electrode as the anode,and an inner wall lined with a stainless steel mesh as the cathode.The simulated exhaust gas is bubbled through the electrochemical oxidation zone then oxidatively degraded.Experimental results show that electrochemical oxidation combined with solution absorption can effectively remove styrene and tetrahydrofuran from gas stream.The removal of styrene and tetrahydrofuran in sodium chloride solution was significantly higher than in sodium sulfate solution.This is mainly due to the oxidative degradation of styrene and tetrahydrofuran by active chlorine?hypochlorous acid and hypochlorite?produced by electrochemical oxidation of chloride ions on the RuO₂/Ti electrode.It was found that the removals of styrene and tetrahydrofuran increased with the increase of sodium chloride solution concentration when the concentration of sodium chloride solution was in the range of 0⁰.55 mol/L.However,when the chloride ion concentration was further increased,the increae of the removals by electrochemical oxidation was not obvious weakened for both styrene and tetrahydrofuran.Increasing the current density can significantly resulted in the increase of the removals of styrene and tetrahydrofuran;when the current density increased to above53 mA/cm²,the electric energy consumption increased,but the increase of the removal of styrene and tetrahydrofuran was not obvious.It was also found that the removal rate of styrene and tetrahydrofuran decreased with the increase of the initial pH of the solution at the same current density.It was obviously the removal of styrene and tetrahydrofuran in acidic sodium chloride solution is significantly higher than that in alkaline solution.The optimal operation condition is that input current density is 53 mA/cm² in a0.55 mol/L NaCl solution and pH=1.When the inlet concentrations of styrene and tetrahydrofuran in waste gas are 900 mg/m³and 1000 mg/m³,respectively,the removal rates of above two compounds can reach 84%and 92%,respectively.It was also found when the electrochemical reaction reached a steady state and the ultraviolet lamp was irradiated,the removal rate of styrene and tetrahydrofuran can be increased.Analysis by gas chromatography-mass spectrometry revealed that?-butyrolactone was present in the solution after electrochemical oxidation of tetrahydrofuran.The presence of phenyl-1,2-ethanediol and benzaldehyde was detected in the solution after electrochemical oxidation of styrene.