| Heavy metals are generally difficult to degrade,toxic,and easy to accumulate,which seriously pollute the ecological environment and can be transferred to the human body through enrichment of the food chain,thus endangering human health.Therefore,it is urgent to control heavy metal pollution.Due to its small particle size,large specific surface area,high activity,and environmental friendliness,nano-zero-valent iron has became a research hotspot in past years to treat metal pollution in water,but it also has disadvantages of poor stability,easy agglomeration,and oxidation.Solid loading of nano-zero-valent iron is the main method to improve its activity and one of the important research directions to improve the disadvantages of nano-zero-valent iron.In this thesis,chitosan/vermiculite was selected as the carrier for loading nano-zero-valent iron(n ZⅥ),nano-zero-valent iron(n ZⅥ),chitosan / vermiculite(CTS/VMT),and chitosan / vermiculite-nano-zero-valent iron(CTS/VMT-n ZⅥ)were used as adsorbents for the removal of Cu(Ⅱ)and Cr(Ⅵ)from water bodies,respectively.The effects of different factors such as adsorbent dosing,initial concentrations of Cu(Ⅱ)and Cr(Ⅵ),and p H on the adsorption effect were investigated,and the reaction kinetics of Cu(Ⅱ)and Cr(Ⅵ)adsorption by different adsorbents were studied,and a preliminary analysis of the reaction mechanism was carried out.(1)nano zero-valent iron(nZVI)was prepared by liquid-p Hase reduction;chitosan/vermiculite(CTS/VMT)composites were prepared by using epichlorohydrin as a cross-linking agent;chitosan/vermiculite loaded nano zero-valent iron(CTS/VMT-n ZⅥ)was prepared by liquid-p Hase reduction with chitosan/vermiculite as a carrier.SEM,XRD,BET,FTIR,and other tests were used to characterize the structure and morp Hology of each material.SEM characterization showed that CTS was cross-linked on the vermiculite surface in the CTS/VMT composite without intercalation into the interlayer of vermiculite,FTIR showed that the prepared CTS/VMT-n ZⅥ,n ZⅥ was successfully loaded onto the CTS/VMT surface,thus effectively reducing the clustering of n ZⅥ.The n ZⅥ agglomeration was effectively reduced.(2)In the experiments of Cu(Ⅱ)removal from simulated wastewater,the effect of different materials of adsorbents on Cu(Ⅱ)removal was positively correlated with the adsorbent dosage,and the removal rate decreased with the increase of initial concentration,and the effect of p H on the removal effect was obvious,and the removal rate of Cu(Ⅱ)increased with the increase of p H at the experimental conditions of p H 2.0-6.0,and the effect of reaction temperature on the removal effect was not obvious.The effect of CTS/VMT-n ZⅥ on Cu(Ⅱ)removal was higher than that of n ZⅥ and CTS/VMT under the same conditions.The removal rate was 99.5%at the initial Cu(Ⅱ)concentration of 40 mg-L-1,the dosage of CTS/VMT-n ZⅥ of 0.3g-L-1,p H=6,and the reaction temperature of T=40°C,which was higher than that of n ZⅥ and CTS/VMT under the same adsorption conditions by 17.6% and 15.3%,respectively.(3))In the experiments on the removal of Cr(Ⅵ)from simulated wastewater,the effect of different materials of adsorbents on the removal of Cr(Ⅵ)was positively correlated with the adsorbent dosage,and the removal rate decreased with the increase of initial concentration,and the effect of p H on the removal effect was obvious,and the removal rate of Cr(Ⅵ)decreased with the increase of p H when the experimental condition of p H was between 3.0 and 11.0,and the effect of reaction temperature on the removal effect was not obvious.The removal rate of Cr(Ⅵ)by CTS/VMT-n ZⅥ was higher than the removal rate of Cu(Ⅱ)by n ZⅥ and CTS/VMT under the same conditions.The removal rate reached 100% at the initial Cu(Ⅱ)concentration of 20mg·L-1,CTS/VMT-n ZⅥ dosage of 0.5 g·L-1,p H=5,and reaction temperature T=40℃,which increased by 27.9% and 18.6% compared with n ZⅥ and CTS/VMT under the same adsorption conditions,respectively.and 18.6%,respectively.(4)In the adsorption kinetics study of CTS/VMT-nZVI for Cu(Ⅱ)and Cr(Ⅵ),both were more consistent with the quasi-secondary kinetic equations with maximum adsorption capacities of 47.55 mg·g-1(Cu(Ⅱ))and 24.15 mg·g-1(Cr(Ⅵ));n ZⅥ and The maximum adsorption capacities of CTS/VMT for Cr(Ⅵ)were smaller than those of CTS/VMT-n ZⅥ. |
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