Arsenic Removal By Calcined Layered Double Hydroxide Through Capacitive Deionization

In this paper,a variety of methods are used to prepare layered metal oxide materials used in capacitive deionization,and the "memory effect" of layered metal oxides is used to remove arsenic ions in water and to achieve the purpose of removing arsenic and purifying water.Compared with traditional arsenic removing technologies,capacitive deionization has the advantages of low energy consumption,high efficiency and environment friendly.It is a new desalination technology with great development prospect.In this study,we selected two kinds of layered metal oxide as the anode material.It was found that layered metal oxide has a good adsorption effect on heavy metal ions.The cathode material is activated carbon treated by nitric acid.This topic focused on the preparation of layered metal oxides and the application of capacitive deionization in the removal of arsenic ions in water.Besides,the effects on the adsorption of As(III)and As(V)in water of voltage,anode materials and initial concentration are investigated by single factor rotation method.(1)The Mg-Fe layered metal oxides were prepared by coprecipitation method.The corresponding oxides were obtained after high temperature calcination.The materials were used as anode material of CDI module.Activated carbon treated by nitric acid was used as cathode material.Afterwards,the modules were assembled and electrochemical arsenic removal tests were conducted.The test results showed that the prepared Mg-Fe layered metal oxide combined with CDI technology had good adsorption effects for arsenic in water.Under the same conditions,the adsorption capacity increased with the increase of voltage.When the voltage equals 1.2 V and the flow velocity of the peristaltic pump equals 3 mL/min,the adsorption efficiency of arsenic can reach more than 97%.When adsorbing As(III)and As(V),the maximum theoretical adsorption value of Langmuir reached 322 mg/g and 496 mg/g.In the adsorption process,arsenic ions can enter the intercalation layer of layered metal oxide,and there exists an obvious "memory effect".(2)Mg-Al layered metal oxide was prepared by one step hydrothermal method in alkaline condition.In order to increase its conductivity and charge transfer rate,the material was mixed with graphene.The Mg-Al metal oxide/graphene complex was obtained after high temperature calcination under nitrogen atmosphere.This material was used as the anode material of CDI module and activated carbon treated with nitric acid was used as cathode material.Afterwards,the modules were assembled and electrochemical arsenic removal tests were conducted.The test results showed that this method has good effects of arsenic removal.When the voltage equals 1.2 V and the flow velocity of the peristaltic pump equals 3 mL/min,the adsorption efficiency of arsenic can reach more than 99%.When adsorbing As(III)and As(V),the maximum theoretical adsorption value of Langmuir reached 849 mg/g and 81 mg/g.