The Performance And Mechanism For The Removal Of As(Ⅲ)/As(Ⅴ) From Water By GO&FeCu

Arsenic（As）is classified as one of the most toxic heavy metal contaminant and its pollution has received global attention.Since its efficiency in operation and low cost,adsorption is considered to be one of the most promising technologies for arsenic removal when compared with other technologies.Therefore,it becomes a hotspot to develop high efficiency adsorbents for the removal of arsenic from contaminated water.It has been reported that metal oxide-based materials are very effective in the removal of arsenic.However,most of these adsorbents are apt to aggregation and difficult to be separated from aqueous solutions,which limit its application into practice.The presence of its high surface functional groups and large surface area provide the capability for graphene oxide（GO）to remove contaminants in water.In this study,we chosed graphene oxide sheet as a carrier and functionalized it with Fe₃O₄ and CuO via two steps.By optimizing the conditions,the composite adsorbent of9%GO2&Fe₃Cu₁ was synthesized,which can effectively solve the agglomeration problem of metal oxide nanoparticles.The adsorption experiments and various characterization methods were used to study the surface structure characteristics of the adsorbent,investigate the adsorption performance of arsenic and reveal the adsorption mechanism.The main research results are summarized as follows:（1）By optimizing the preparation conditions of the adsorbent,GO2 was selected（GO with three different oxidation degrees were prepared,namely GO1,GO2,and GO3）,the addition amount of GO2 was 9%and the iron-copper ratio was 3:1.The synthesised adsorbent was named 9%GO2&Fe₃Cu₁.The surface morphology and structural characteristics of this composite material were characterized by XRD,BET,VSM,TGA,FTIR,XPS,SEM and TEM.It was found that 9%GO2&Fe₃Cu₁ has a rich pore structure and a large specific surface area（159.60m²/g）.Also,it was confirmed that the adsorbent contains rich oxygen-containing functional groups on its surface and Fe₃O₄ and CuO are evenly distributed on the GO sheet.（2）The adsorption kinetic experimental results showed that the Elovich model provided the best correlation of the experimental data.The adsorption isotherm experimental results showed that the Sips model fitted As（Ⅲ）adsorption data much better and the Temkin model fitted As（Ⅴ）adsorption data much better.The maximum adsorption values of As（III）and As（V）were calculated to be 70.36mg/g and 62.58mg/g,respectively.As（V）adsorption was favored at acidic pH,whereas the adsorption of As（III）by 9%GO2&Fe₃Cu₁ was found to be effective over a wide pH range of 4-10.Competitive anions hindered the adsorption of As（III）and As（V）,especially the phosphate,while Ca²⁺and Mg²⁺increased the removal of As（III）and As（V）slightly.The XPS and FTIR analysis results of 9%GO2&Fe₃Cu₁ before and after adsorption with As（III）and As（V）confirmed that As（III）and As（V）adsorption was primarily through the complexation with the surface hydroxyl groups of the adsorbent.（3）The desorption results indicated that this adsorbent could be well regenerated using0.04mol/L NaOHsolutions.Afterfiveadsorption/desorptioncycles,9%GO2&Fe₃Cu₁ still maintained 66.3%and 79.3%of the initial adsorption capacity of As（Ⅴ）and As（Ⅲ）,respectively.When the adsorbent dosage was 120mg/L and the contact time was 3h,the arsenic concentration in the effluent of the dynamic experimental reactor can be lowered to the national drinking water standard.