| Heavy metal is a kind of non degradable pollutants, it can persist in theenvironment and concentrate in biological and human body through biologicalamplification and food chain transmission. Heavy metal pollution is one of the mostimportant environmental issues. Therefore, it is necessary to develop the emergentwater treatment technology which can reduce hazards to human health and damage tothe ecological environment from heavy metal. Based on this situation anddevelopment requirements, three different organic-inorganic hybrid sorbents wereprepared and the adsorption properties of heavy metal ions were studied at the sametime, the results are as follows:1. PBMA/GMA-SiO2adsorbent was synthesized via reversible addition-fragmentationchain transfer(RAFT) polymerization by using butyl methacrylate(BMA) andGMA-functionalized silica particles as monomers. The structure and morphology ofPBMA/GMA-SiO2obtained were characterized by FT-IR, TGA, GPC, TEM andSEM. This new synthesized material was applied to remove heavy toxic metal Pb2+,Ni2+, Cd2+and Cu2+from water samples. The effects of contact time, temperature, pH,adsorbent dose and initial metal ions concentration on adsorption properties wereevaluated, as well as adsorption thermodynamics and kinetics were also examined.The results showed that the maximum adsorption capacity for Pb2+, Ni2+, Cd2+, Cu2+were found to be423.8,87.36,71.69,60.49mg/g as the pH was6.0, temperature was25, the initial concentration was600mg/L and absorption time was1h. Theadsorption kinetics could be best described by pseudo second-order kinetic model,compared with the Freundlich isotherm equation, the Langmuir isotherm equationwas more appropriate to describe the adsorption behavior. The adsorption rate was notonly controlled by intra-particle diffusion but also by extra-particle diffusion. Besides,the materials still show good adsorption capacity to metal ions after three times ofdesorption and adsorption.2. A hydrogel SiO2-g-GMA/β-CD-Ac was synthesized by the free-radicalcross-linking polymerization of SiO2-g-GMA and β-CD-Ac, and it was then used forthe adsorption of Cu2+, Pb2+, Cd2+and Ni2+metal ions from aqueous solutions. Thestructures and morphology of SiO2-g-GMA/β-CD-Ac were characterized by FT-IR, TGA, TEM and SEM, the adsorption behavior of Cu2+, Pb2+, Cd2+and Ni2+onSiO2-g-GMA/β-CD-Ac were studied. Results showed that the adsorption capacity,strongly depended on the pH of the solution, the maximum adsorption capacity forCu2+, Pb2+, Cd2+and Ni2+were found to be110.00,51.02,15.20,11.69mg/g as thepH was6, temperature was25, the initial concentration was400mg/L and absorptiontime was1h, respectively. The equilibrium data were fitted well by the Langmuirisotherm model (R2>0.99), where adsorption was an exothermic and spontaneousprocess. The results indicated that this adsorbent was better applicable for removingCu2+than Pb2+, Cd2+and Ni2+from waste waters.3. A novel Fe3O4@SiO2-MPS-CS magnetic hydrogel was synthesized by the sol-gelmethod. The structure properties of Fe3O4@SiO2-MPS-CS were characterized byFT-IR, XRD and VSM. The effects of chitosan content, contact time, temperature, pHand initial metal ions concentration on Pb2+, Ni2+, Cu2+, Co2+, Bi3+, Cd2+adsorptionproperties were evaluated, as well as recycling performance of Fe3O4@SiO2-MPS-CS,adsorption thermodynamics and kinetics were also examined. The results show thatthe adsorption quantity increases first and then decreases with the increase of chitosancontent, the maximum adsorption capacity for Pb2+, Ni2+, Cu2+, Co2+, Bi3+, Cd2+werefound to be62.23,32.01,30.37,25.95,15.71and14.51mg/g as the pH was6.0,temperature was25, the initial concentration was500mg/L, absorption time was2hand m(Fe3O4@SiO2-MPS): m(CS) was1:4, respectively. Kinetic studies showedthat the adsorption process obeys pseudo-second-order rate mechanism and theequilibrium data were fitted well by the Langmuir isotherm model. The adsorptionrate was not only controlled by intra-particle diffusion but also by extra-particlediffusion. |
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