| Arsenic pollution in water is a worldwide environmental problem,covering more than 70 countries and 230 regions.As an ecological sewage purification technology,constructed wetlands have great potential for arsenic removal,but the development of constructed wetlands is limited by the traditional fillers with low removal rate and low adsorption stability.In recent years,nanomaterials have shown excellent removal ability in water pollutant removal,which provides a new development direction for the removal of arsenic in constructed wetlands.In this study,microflower-like?-Bi2O3?MF-?-Bi2O3?was synthesized under hydrothermal conditions and loaded on porous zeolite spheres sintered at high temperature to prepare?-Bi2O3-loaded porous zeolite sphere fillers?Bi-PZSF?,their adsorption performances for As???/As???and the effects of interfering ions and pH on adsorption were studied respectively.Scanning electron microscopy-energy dispersive spectrometry?SEM-EDS?,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,Raman spectroscopy?Raman?and X-ray electron spectroscopy?XPS?were used to characterize MF-?-Bi2O3 before and after adsorbing As???/As???and analyse its adsorption mechanism.The main results were as follows:?1?MF-?-Bi2O3 synthesized under hydrothermal conditions showed a fluffy flower-like morphology and polycrystalline properties,consisted of a large number of nanosheets,had a specific surface area of 8.99 m2/g.After adsorption of As???and As???,MF-?-Bi2O3 maintained its micro-flower morphology,and EDS showed that the contents of As???and As???after adsorption were 5.58%and 2.06%,respectively.?2?The adsorption data of MF-?-Bi2O3 on As???/As???were well fitted by the pseudo-second-order model,indicating the process is a adsorption dominated by chemisorption.The maximum adsorption capacities of As???and As???were 115.05mg/g and 33.17 mg/g,respectively.MF-?-Bi2O3 also presented excellent sorption selectivity for As???/As???in the presence of competitive anions(NO3-and SO42-).MF-?-Bi2O3 could work well in a wide pH range of 4–11 and stability after adsorption.The adsorption mechanism indicated that the adsorption of As???/As???is mainly achieved by ion exchange with the surface hydroxyl groups occupying the MF-?-Bi2O3oxygen vacancies.?3?The porous zeolite spheres were extruded into balls with the raw material of a mixture of natural clinoptilolite powder?200 mesh?,sawdust?between 10-20 mesh?and soluble starch at a mass ratio of 10:1.5:1,and then sintered under high temperature.The production had good hardness with the maximum crushing force of 103.5 N and a specific surface area of 0.6784 m2/g.After loading?-Bi2O3,the specific surface area increased to1.7715 m2/g,and the content of Bi reached 17.07%.?4?The removal rate of arsenic by Bi-PZSF almost completely depended on the loading?-Bi2O3.Under the condition of pH range of 6–8,2 g of Bi-PZSF could completely remove arsenic?50 mL,5 mg/L?in arsenic solution.The arsenic removal rate of the natural zeolite and ceramsite at a same weight was between 4%and 13%.Bi-PZSF could maintain the arsenic removal rate of 100%when the concentration ratio of arsenic to interference ion was 1:10.The Bi-PZSF after adsorption of arsenic had strong stability at pH pH=6–8,which can effectively avoid secondary pollution. |
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