| Fe3O4 nanoparticles (NPs) have been applied in lithium battery, catalyst, and adsorbent materials due to their superior performances such as special metal ferromagnetic properties, high surface activity and excellent biocompatibility. Carbon material as a kind of traditional adsorption materials, has advantages of large specific surface area and strong adsorption ability. Only considering volume, the smaller the particle size is, the bigger the specific surface area is and the better the adsorption performance presents. But the particles with small size are difficult to separate from water, leading to the cost increase and resource wastes. These problems can be solved by magnetic separation technology. Carbon materials with Fe3O4 core combine the advantages of the two parts of raw materials:strong adsorption ability and rapid separation from water. In this thesis, a series of Fe3O4/Carbon (Fe3O4/C) composites were synthesized and their adsorption performances were investigated. The specific research results are as follows:1. Preparation of Fe3O4 NPs by microfluid methodFe3O4 NPs with different morphology can be prepared by microfluid method at different conditions. Fe3O4 NPs are roundish with a average particle size of 8.3-9.7 nm at C(NaOH)=0.2-0.3 mol/L and v=20 mL/min. Fe3O4 NPs are uniform rod fibers with a average particle size of 8.4 nm at C(NaOH)=3.6 mol/L and v=20 mL/min. Fe3O4 NPs are neat hexagons with a average particle size of 100 nm at C(NaOH)=3.6 mol/L and v=5 mL/min.2. Preparation of Fe3O4/C composites by two-step process and their absorption abilityThree kinds of Fe3O4 NPs (commercial Fe3O4 (C-Fe3O4), Fe3O4 NPs obtained by co-precipitation (traditional adding method) (TA-Fe3O4) and Fe3O4 NPs obtained by microfluid (MF-Fe3O4)) were used as magnetic core for Fe3O4/C composites (C-Fe3O4/C, TA-Fe3O4/C and MF-Fe3O4/C). The composites were synthesized by hydrothermal process, and their adsorption performances were invesitigated. The effects of temperature, pH and cycle time on adsorption process were studied. Furthermore, the adsorption kinetics was also investigated. The adsorption capacity of C-Fe3O4/C, TA-Fe3O4/C and MF-Fe3O4/C were 76.4 mg/g,103.7 mg/g and 135 mg/g under the condition of C (RhB)=1 g/L, T=20℃ and pH=3, respectively. The absorption capacities of TA-Fe3O4/C and MF-Fe3O4/C still keep 88.1% and 88.7% of the first capacities after 5 times recycles, respectively. Under the conditions of different temperatures (20-70℃), the adsorption capacity offers upgrade firstly than descending latter tendency, and the maximum adsorbing capacity at T=60℃ were 141.2 mg/g and 170.1 mg/g, respectively. Under the conditions of different pH values (2-11), the adsorption capacity increases at first and then decreases, and the maximum adsorbing capacity at pH=9 were 122.6 mg/g and 154.5 mg/g, respectively. The both adsorption process were in accordance of the pseudo-second-order kinetic model, but due to the high concentration of RhB, they did not apply to the Freundlich equation.3. Preparation of Fe3O4/C composites by one-step process and their absorption abilityOne-step process synthesis of Fe3O4/C composites was achieved by coupling microfluid method with ultrasonic spray pyrolysis method. The structures and absorption abilities of those composites were investigated. The results suggest that the Fe3O4/C composites have good dispersion and uniform size, and the rough carbon layers were helpful to subsequent adsorption. The effects of RhB concentration, absorption temperature, pH and cycle time on adsorption process were studied. Furthermore, the adsorption kinetics were also investigated. The results show that the higher the RhB concentration is, the greater the adsorption quantity of Fe3O4/C presented. The adsorption capacity of Fe3O4/C was 154.6 mg/g under the condition of C (RhB)=1 g/L, T=20℃ and pH=3. They can be reused 5 times with an excellent adsorption rate of 80.1%. Under the conditions of different temperatures (20-70℃), the adsorption capacity offers upgrade firstly than descending latter tendency, and the maximum adsorbing capacity at T=60℃ was 183.6 mg/g. Under the conditions of different pH values (2-11), the adsorption capacity increases at first and then decreases, and the maximum adsorbing capacity at pH=9 was 169.4 mg/g. The adsorption process is in accordance of the pseudo-second-order kinetic model, and it did not apply to the Freundlich equation except the conditions of 100 and 250 mg/L... |
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