| With worldwide rapid development of industrialization process, the discharge of wastewater containing toxic pollutants becomes one of the major factors in water pollution and drinking water safety problems. Research shows that nano-materials has remarkable efficiency on the removal of toxic pollutants. However, for ordinary nano-materials, there exist problems such as difficult separation, easy pollution, high cost and so on, which seriously restrict the application in wastewater treatment field. As a new type of materials, nano-magnetic materials take on double characteristics of magnetic materials and nano-materials, which make it possible for nano-materials widely used in water treatment field.In this paper, nano-Fe3O4 particles have been prepared by chemical co-precipitation method, cheap iron salt and lye as the main raw materials, and have carried out the reaction controlled factors and the influences on the performances of the product. The experimental studies of nano-Fe3O4 removal of the humic acid, phosphorus, as well as PFOS are carried out. The factors affecting removal and the mechanisms are investigated. At the same time, the related flocculation experiments of Cetian Reservoir water are studied. The major findings are as follows:(1) The optimum preparation conditions of nano-Fe3O4 are that n (Fe2+)/n (Fe3+) is 1.4:2, temperature is 50℃, pH value is greater than 9.2, and use NH3·H2O as precipitant. It's obtained by characterization that nano-Fe3O4 has high degree of crystallinity, grain growth completely, belonging to an inverse spinel structure, the average particle size is about 11nm, surface area is 42.1994 m2/g, saturation magnetization is 73.10 emu·g-1, external magnetic field is helpful to sedimentation performance of nano-Fe3O4.(2) With the initial concentration, the removal of nano-Fe3O4 on the adsorption of humic acid increases first and then reduces. When the initial concentration is 15mg/L, the maximum removal rate reaches 30.56%. Langmuir and Freundlich isotherm equations can be good fit the curves of nano-Fe3O4 on the adsorption of humic acid, by the fitting get the adsorption equilibrium constant is 0.01, theoretical maximum adsorption capacity is 69.93mg/g.The flocculation removal rate of nano-Fe3O4 on the humic acid increases first and then decreases as the dosage increased. When the dosage is 1000mg/L and pH is 6, the removal rate is up to 21.86%.(3) The optimal conditions of phosphorus removal are as follows:the dosage is 0.25g/L, initial concentration of phosphorus is 0.4mg/L, pH is 3, temperature is about 25℃. The presence of interfering ions affects phosphorus removal by nano-Fe3O4, HCO3- is the most significant. The effect of phosphorus removal is related to the phosphatic morphology in water and the form of nano-Fe3O4. Nano-Fe3O4 on phosphorus removal rate is higher than nano-Fe3O4 composited SDBS. This is because some of adsorption points in the surface of nano-Fe3O4 are covered by SDBS, and the sulfonate produced by some of SDBS dissolved in water, has an electrostatic repulsion to the phosphatic. Langmuir and Freundlich isotherm equations can be good fit the curves of nano-Fe3O4 on phosphorus removal, by the fitting get the theoretical maximum adsorption capacity is 9.74mg/g. Nano-Fe3O4 on the adsorption of phosphorus is accord with quasi-second order kinetics equation, controlled by the Mechanism of chemical adsorption.(4) Nano-Fe3O4 on the adsorption of PFOS increases with dosage increased, when the dosage is 0.5g/L, the removal rate reaches 92.5%. Nano-Fe3O4 on PFOS removal is higher than nano-Fe3O4 composited SDBS, because of some of adsorption points in the surface of nano-Fe3O4 covered by SDBS. Magnetic and salinity will not affect nano-Fe3O4 on the adsorption of PFOS, and acidic environment is conducive to the removal of PFOS. Nano-Fe3O4 has nice removal rate on different initial concentrations of PFOS, the lowest removal rate is over 70%. Nano-Fe3O4 on the adsorption of PFOS is a fast process, showing adsorption irreversibility. Linear adsorption model can good fit the curve of nano-Fe3O4 adsorption of PFOS.(5) The experiment results of Cetian reservoir water are that when nano-Fe3O4 dosage is 400mg/L, TOC, turbidity and color reach the highest removal, and the removal rate is 49.1%, 80% and 88.4% respectively. CODMn, Mn2+, and Pb2+ also have good removal rate, the order is Pb2+ first, Mn2+ second and CODMn third. The effect of nano-Fe3O4 dosing is superior to PAC, as well as the other two composite nano-Fe3O4. Join quantitative cationic PAM can play a good role, while add PDADMAC is not obvious, and effects the removal of turbidity.In summary, nano-Fe3O4 has good removal rate on the phosphorus,PFOS and Pb2+, while ineffective to the removal of humic acid, which reflect the agency and high efficiency of nano-Fe3O4, and show that nano-Fe3O4 particle is a new water treatment materia as well as a good application prospect in water treatment.
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