Experimental Study On Removal Of Se(â…£) From Water By Nanometer Iron And Manganese Oxide

Compared with other fossil fuel energy,nuclear power,as a clean energy,has the advantages of less resource consumption,less impact on the environment and mitigation of climate warming.Among them,79Se（IV）is one of the products produced after nuclear fuel fission,with a half-life of 3.27×105years and a strong migration capacity.After ⁷⁹Se（IV）enters the environment,most selenium is dissolved in water in the form of soluble selenate(Se O₄^2-)and selenite(Se O₃^2-),posing a threat to the environment.The results show that Nano-Fe-Mn active materials have good adsorbability and reactivity.Therefore,this paper studies the adsorption of Se O₃^2-selenite with Nano-Fe-Mn oxide as adsorbent.The results show that the Nano-Fe and Mn active materials have good adsorption and reactivity.This study mainly carried out the following work:firstly,various influencing factors of Se（IV）in nano iron and manganese oxide adsorption fixed water were studied;The reaction products were characterized by X-ray electron spectroscopy（XPS）.Then,the reaction mechanism is preliminarily discussed by using chemical thermodynamics and kinetics theory and mathematical calculation method.The specific conclusions are as follows:（1）The dosage of Nano-iron and manganese oxide material was 0.1000g,and the adsorption rates were 99.6%,99.4%,99.1%,94.4%and 91.4%respectively after 5mg/L,10mg/L,20mg/L,30mg/L and 40mg/L in sodium selenite（Na Se O₃）solution.（2）The optimal reaction temperature for Se（IV）adsorption of nano-iron and manganese oxide material is about 35℃,and the equilibrium adsorption capacity is 84.3700mg/g.According to the Arrhenius formula,the reaction activation energy Ea=1.9239 k J/mol.（3）With the increase of p H,the ability of Se（IV）adsorption of Nano-iron and manganese oxides was gradually weakened.When p H=10.76,the adsorption rate was 8.32%.When p H=3.18,the maximum adsorption rate was 98.45%.The neutral and acidic environmental conditions are more conducive to the adsorption of Se（IV）.（4）Adding humic acid adsorption on nanometer iron manganese oxide material a little effects on the efficiency of the Se（IV）.When the concentration of humic acid was 2.5mg/L,the humic acid at this concentration would have a synergistic effect with the Nano-Fe and Mn oxide materials,thus increasing the removal rate of Se（IV）by the Nano-Fe and Mn oxide materials.At this time,the adsorption rate of the material was 97.98%.When the concentration of humic acid was 5mg/L and 50mg/L,the humic acid of these two concentrations would have antagonistic effect with the Nano-iron and manganese oxide materials,thus reducing the removal rate of Se（IV）of the Nano-iron and manganese oxide materials.At this time,the adsorption rate of the materials was 96.47%and95.84%.（5）among the influencing factors of Se（IV）in the adsorption and fixation water of nanometer iron and manganese oxide,the effect of p H on Se（IV）in the adsorption and fixation water of nanometer material is the largest,which is the main influencing factor.（6）Through the analysis of adsorption kinetic fitting results,it is concluded that the quasi-second-order kinetic equation is more suitable to describe the adsorption process of Se（IV）by Nano-iron and manganese oxides,and chemisorption plays a dominant role in the adsorption process.It can be seen that the lower the initial concentration,the faster the adsorption rate.The equilibrium adsorption capacities of the initial concentrations of Se（IV）solutions were 12.1359mg/g,23.5294mg/g,48.7805mg/g,70.4225mg/g and79.3651mg/g,respectively.（7）The adsorption process of Se（IV）by Nano-iron and manganese oxides is more in line with the Langmuir isotherm equation,which belongs to the single-molecule layer adsorption,and each adsorption site only contains one Se O₃^2-.The maximum saturated adsorption capacity at 35℃is 133.3333mg/g（8）XPS characterization results show that nanometer manganese iron oxide of iron Fe mainly exists in the form of Fe³⁺,Mn Mn mainly exists in the form of manganese Mn（IV）.The ratio of iron Fe to manganese Mn in nanometer iron and manganese oxide material is 1:2.5.The combined states of oxygen in nano-iron and manganese oxides are mainly M-O（O and metal）and M-OH（hydroxyl group and metal）.The removal process is due to the electrostatic and surface complexation of the hydroxyl on the surface of the nano-iron manganese oxide with Se（IV）.（9）In peristaltic pump flow rate of 0.1 m L/min and peristaltic pump velocity of certain situations,fill in Ghana m iron manganese oxide material thickness is 0.5 cm,1 cm,2 cm,its adsorption amount according to the thickness of the material is different from low to high respectively is 113.78mg/g,120.75 mg/g and 129.54 mg/g,shows that the thickness of the Nano iron manganese oxide material add the more thick,to reach adsorption equilibrium adsorption quantity before the more stable the smaller the curve slope and the trend of curve,the higher the adsorption efficiency.According to this study,the removal effect of Se（IV）in aqueous solution by nano-iron and manganese oxide is better,which provides a reliable theoretical and practical basis for further research on Se（IV）removal in aqueous solution by nano-iron and manganese oxide.