Preparation Of Ag₂O-loaded And La,Ce-doped Zirconia And Its Performance On Arsenic Removal

In recent years,arsenic pollution occurs frequently,which is harmful to human health.The research of nano adsorption materials for arsenic removal is a hot spot.Zirconium based materials are nontoxic and stable,and suitable arsenic adsorption.Compared with As???,it's harder for As???removal,which usually need oxidation before adsorption.Therefore,the simultaneous oxidation adsorption technology are increasingly concerned.In this paper,a kind of composite material?Fe₃O₄@Re-ZrO₂@Ag₂O@ZrO₂?with core of Fe3O4 and shell of lanthanum and cerium doped zirconia and Ag₂O loaded was prepared.It can be recovered by magnetic separation and has good performance on arsenic removal.During the preparation,the hydrothermal temperature,reaction time,the amount of magnetic core,the doping ratio of lanthanum and cerium,the ratio of silver oxide loading and zirconium coating on the outer layer were optimized by characterization methods of TEM,SEM,VSM,BET,XRD,FT-IR,Zeta potential and XPS,to analyze the structure,morphology and chemical characteristics of the prepared materials.Combined with a series of arsenic containing water adsorption and catalytic oxidation experiments,the arsenic removal performance of the prepared materials was tested.On this basis,the arsenic removal mechanism of the prepared materials was explored.The conclusions are as follows:?1?The optimum preparation conditions were determined as follows:the ratio of magnetic core was 8%,the rdouble doping ratio of element was La:0.2%and Ce:0.7%,the amount of silver oxide loaded was 10%,the amount of outer layer zirconium coated was 10%?relative to the amount of inner layer zirconium coated?;the composite material was irregular particle with particle size of 100nm around,and the size of silver oxide was about 2nm,which is loaded on the surface of the material.In structure and performance characteristics,The material mainly exists in the form of amorphous zirconia with good magnetic separation ability,specific surface area and pore structure.The magnetic saturation strength is about 10emu/g,specific surface area is 263m2/g,porosity is 0.156cm3/g,and with rich hydroxyl groups on the surface.?2?Under the condition of no light,the performance and mechanism of arsenic removal were studied by a series of kinetic adsorption,isothermal adsorption and material characterization.The results show that the adsorption of the material is more in line with the quasi second-order kinetic model,which is mainly chemical adsorption.Particle internal diffusion,liquid membrane diffusion and adsorbent surface adsorption will affect the adsorption process.The isothermal adsorption process is more in line with the Langmuir model,which is a single molecular layer adsorption,the location of the active sites on the adsorbent surface is fixed,and there will be no adsorbate exchange.The As?III?and As?V?have best adsorption at pH 6 and pH 5,and the adsorption capacity can reach 48mg/g and 53mg/g respectively.In the adsorption process,the surface hydroxyl of the material is replaced by As.?3?Under the condition of light,the influence factors and mechanism of catalytic oxidation and adsorption were studied.The results showed that the material has a good catalytic oxidation performance with pH between 7 and 10,and it's better with pH increased.At the Initial As?III?concentration was 1 the amount of material was 300mg/L,the oxidation rate was 100%and the adsorption efficiency was 93%with saturated adsorption amount?total arsenic?of 43 mg/g.In coexisting ions,PO₄^3-and SO₄^2-have obvious impact on adsorption process while acid ions and Cl^-weaken the catalytic oxidation.In the process of catalytic oxidation,the form of Ag₂O is changed and finally exised as the stable form of Ag₂O-Ag,which make sure the Continuous progress of catalytic oxidation.The solution of NaOH+EDTA is selected to regenerate the material.5 hours regeneration at 30?,after 7 times of regeneration,the efficiency of catalytic oxidation and adsorption are 65%and 60%respectively.This paper has 44 pictures,7 tables,and 116 references.