| PFOS(Perfluorooctane Sulfonate, PFOS), which is a typical perfluorochemical, has good thermal stability and chemical stability. Since it is widely used in industrial and civil products due to its characteristics of hydrophobicity and oleophobicity, PFOS can be released into environmental media through various pathways and further bioaccumulated in food chain. Pervious studies show that industrial wastewater discharge is a major source of PFOS release. Currently, chemical degradation and absorption are the two main treatment methods for removing PFOS from wastewater. Because the concentrations of PFOS in wastewater are usually at low level, directly using chemical treatment is not effcient from the perspective of energy use. In addition, adsorption treatment only transfer PFOS from aqueous phase to solid phase rather than destruct it. Therefore, a suitable treatment for efficiently removing PFOS from wastewater is desired.A treatment process including adsorption of aqueous PFOS by efficient and reusable adsorption material, desorption, and chemical degradion of the concentrated PFOS in desorption solution is proposed in this study. Aminated magnetite nanoparticle was selected as the adsorption material. Its optimal synthesis method was studied. Its adsorption efficiency towards PFOS in synthetic wastewater and the influences of p H and co-present ions were examined, as well as, the responsible mechanism of adsorption removal was discussed. This study also investigates desorption of adsorbed PFOS from the synthesized aminated magnetite nanoparticle. Parameters examined includes desorption recovery rate and reuse of the magnetite nanoparticle. Finally, a screening of chemical degaration methods for aqueous PFOS was carried out.The optimal systhethic method of aminated magnetite nanoparticle was obtained. When use 100 mg magnetite nanoparticle as the raw material, using the mixture of 100 m L ethanol and 100 m L deionized water as the reaction medium and dosing 2 m L TEOS was recommended for the step of organic silane reaction. In the following synthetic step of amino modification, the preparation conditions of water/ethanol ratio of 5/100, 3-aminopropyl triethoxysilane dosage of 8 m L, and solution p H=5 are recommended for a reacting volume of 160 m L.The results of adsorption and desorption tests showed that aminated magnetite nanoparticle can efficiently remove PFOS from water. It showed higher efficiency in acidic condiotion. When solution p H was 4, a 95% removal efficiency was achieved. Co-present chloride, nitrate, and sulfate ions showed no influence to PFOS adsorption. In desortion test, aminated magnetite nanoparticle displayed high recovery rate for PFOS and reusability. Electrostatic adsorption was believed the predominant functioning mechanism for PFOS adsorption onto aminated magnetite nanoparticle. The semi-hydrophobic effect and micellar-half micelle interactions of PFOS molecules work in the adsorption process as well.The results of study of chemical degradation methods showed that sulfite/UV system can efficiently destruct PFOS in the desorption solution through reductive pathway with defluorization rate. Under the tested condition, the destruction rate of PFOS reached 95% and associated defluorization rate was 74%. |
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