Electrochemical Vapor Generation Technology For Arsenic-containing Wastewater Treatment And Activated Carbon Regeneration

In recent years,China's heavy metal pollution emissions have been significantly reduced,but still at a higher level of emissions,and the total amount of low-concentration heavy metal wastewater is huge.The adsorption technology represented by carbonaceous materials is widely used in the treatment of arsenic-containing wastewater due to its simple operation and low cost.However,if the adsorbent after adsorption is not treated in time,it is easy to cause new pollution.In this paper,the hazards,sources and common arsenic removal technologies of arsenic-containing wastewater were systematically introduced,and the regeneration technology of carbonaceous materials was described.Then,electrochemical gas phase desorption of arsenic-containing wastewater,activated carbon and iron-modified activated carbon was performed.Working with regeneration,the details are as follows:Firstly,the arsenic-containing wastewater was treated by electrochemical vapor generation technology,and the influencing factors were systematically investigated.The data show that arsenic in the liquid phase can be electrochemically reduced to its gaseous hydride?AsH₃?,and the current density,electrode material,reduction time,pH of the waste liquid,flow rate,etc.have a significant effect on the gaseous transformation.When graphite is used as the working electrode,sulfuric acid-sodium sulfate?pH⁰.5?is used as the supporting dielectric,and the pump speed is 1.5 mL min-1 at a current density of 0.2 A cm^-2 for 120 min,the As?III?in the liquid phase The gaseous conversion rates were 85.91%(0.3 mg L^-1),75.53%(0.4 mg L^-1),65.87%(0.5mg L^-1),50.08%(0.6 mg L^-1),and 38.49%(0.7 mg L^-1),respectively;liquid and solid phase?electrode?residuals were 0²7.83%and 15.07³3.68%,respectively;indicating that electrochemical vapor generation technology can efficiently treat low-concentration arsenic wastewater to the gas phase.On this basis,the feasibility of electrochemical gas desorption regeneration after adsorption of arsenic-containing wastewater by commercial activated carbon was studied.The desorption rate and gaseous transformation of arsenic were tested systematically from the perspectives of electrolysis equipment,operating parameters and physicochemical properties of activated carbon,rate change in adsorption performance of activated carbon regeneration.It was found that for the activated carbon with a particle size of 10-20 A⁰,the desorption equilibrium can be achieved by reacting for 0.5 mol L^-1 H₂SO₄ medium,0.3 A cm^-2 current density,328 K temperature and 1.5ml min^-11 for 30 min.The two phases of dielectric and gas?AsH₃?are 7.27%and 88.71%,respectively.the specific surface area(S_BET)and pore size of the activated carbon after desorption are related to the desorption current,and the activated carbon after desorption at electrochemical heating,the increase of small pore structure on the surface leads to an increase in the adsorption capacity of secondary arsenic;while the pore structure decreases at chemical heating,the mesopores increase,and the regeneration performance deteriorates.In addition,the Bohem titration experiment confirms that the lactone group and phenolic hydroxyl group.Finally,FeSO₄ modified activated carbon was prepared by impregnation method and used for the adsorption and electrochemical desorption of As?III?.The results show that the desorption rate of 0.5 mol L^-1FeSO₄ modified activated carbon after As?III?adsorption in a 3 mol L^-1H₂SO₄ medium at a current density of 0.3 A cm^-2 for 120 min can reach 91.81%,solid-liquid gas three The phase contents were 14.83%,11.66%and72.15%,respectively.SEM,EDS and other characterizations showed that the iron particles deposited on the surface of activated carbon promoted the adsorption capacity of As?III?.Compared with chemical desorption,the surface pore structure remained better after electrochemical gas desorption,and the regeneration cycle was accomplished three times.The adsorption performance;the above experiments prove that the electrochemical vapor generation technology has application prospects in the field of arsenic resource recovery and carbon adsorbent.