Synthesis Of Nanoscale Zero-valet Iron/Mesoporous Carbon For Cadmium And Vanadium Removal From Aqueous Solution

As the modern economy developed rapidly,water pollution incidents occurred frequently around the world.The current situation of water pollution in China should not ignore the issue and need more further attention on it.In China,the metal pollutants are a kind of common water pollutants.Some of them are not easily eliminated or biodegradable and they would accumulate constantly in the whole food chain.This paper selected two kinds of metal pollutants as examples:the first one is Cadmium which was listed as one of five emphasized metal pollutants in China;the second one is Vanadium which was less researched currently and can lead to a certain harm to humanities with excessive quantity.At the present stage,the main eliminate methods of Cadmium and Vanadium in water are absorption,membrane separation,chemical precipitation,electrolysis,biological methods,etc.But there are some deficiencies among these methods such as high cost,easy to produce secondary pollution and long repair circle.The nanoscale zero-valent iron(hereinafter referred to as nZVI),as a highly efficient reducing materials,was applied in the elimination of heavy metal wastewater.It is also a kind of environment remediation materials with good application prospects.But due to the drawbacks of easy to reunite,easy oxidation and poor mobility,the nZVI was restricted to be used widely.To solve the drawbacks of the nZVI,this research took mesoporous carbon as matrix and used liquid phase reduction method prepared nanoscale zero-valent iron/mesoporous carbon(hereinafter referred to as nZVI/DMC).Then eliminated the Cd(II)and V(V)which used in aqueous solution.By the single-factor experiment and different factors of representation analysis explores with the impact of eliminating effects and mechanisms,the research got the main conclusions are as follows:1.The research loaded the nZVI successfully onto the surface of mesoporous carbon.As the polyethylene glycol 4000 of dispersant and as the mesoporous carbon of support materials can prevent nZVI from reuniting to a certain extend.But because of the impact of the air,there was still a small number of Fe0 which was oxidized to Fe2O3 and attached to the surface of the nZVI/DMC.2.The result of eliminating Cd(Ⅱ)from aqueous solution by nZVI/DMC showed:The eliminated effect of nZVI/DMC to Cd(Ⅱ)was effective.Compared with commercial nanometer iron powder,the eliminating effect was promoted greatly;When the pH of the solution is in the range of 4-9,the eliminating rate of Cd(Ⅱ)can reach more than 98%;The eliminated process of Cd(Ⅱ)on NZVI/DMC is more in accordance with the quasi-second-order dynamics.The adsorption material of Cd(Ⅱ)is mainly chemical adsorption;The eliminating process of Cd(Ⅱ)on nZVI/DMC is more consistent with Langmuir model and the reaction is an endothermic and spontaneous process with increasing freedom.The maximum adsorption capacity of material was 134.41 mg/L under 25℃;The NZVI on the surface of the material was involved in the process of eliminating Cd(Ⅱ)and reacted to form FeO,Fe(OH)x,FeOOH or FexOy.The iron hydroxide is the main iron species on the surface of the material which haven’t occurred the reduction of Cd2+during the reaction processes.3.The result of eliminating V(Ⅴ)from aqueous solution by nZVI/DMC showed:Under the premise of the same dosage and initial concentration of pollutants,the adsorption capacity of nZVI/DMC is 6.04 times than commercial nZVI;The average eliminating rate of V(Ⅴ)was more than 90%when the pH of the solution was in the range of 4-10,and the maximum rate was 94.86%;The eliminated process of V(Ⅴ)by nZVI/DMC is more in accordance with the quasi-second-order dynamics.The adsorption of V(Ⅴ)is mainly chemical adsorption;The eliminating process of V(Ⅴ)by nZVI/DMC is more consistent with Langmuir model.The adsorption of monolayer was dominant,and it was a spontaneous process with exothermic and reduced degree of freedom.The maximum adsorption capacity of nZVI/DMC was 176.68 mg/L under 25℃.The nZVI was involved in the process of eliminated Cd(Ⅱ)and transformed into Fe(Ⅱ)and Fe(Ⅲ)compounds such as Fe2O3,FeO,FeOOH,FeO(OH),etc.The V(Ⅴ)in solution is reduced to V(Ⅳ)which is deposited on the surface of the materials mainly in the form of VO2.