Ultrasonic Spray Preparation Of Carbon Nanotubes And Research On Modified Chitosan Membrane

Membrane adsorption technology has the advantages of low cost,simplyoperator,selective enrichment of some compounds,and turns to be a valuablemethods.Also membrane separation technology has the advantages of low cost,highselectivity and able to treat low concentration wastewater in heavy metal ionwastewater treatment. Chitosan has good chelating absorption ability,but pure chitosanmembrane has the disadvantages of low mechanical strength and poorpermeability.The addition of polyethylene glycol can not make the water flux andrejection rate of the membrane achieve optimal results at the same time. The additionof acidulated carbon nanotubes can improve the mechanical strength and water flux ofthe membrane,and will not significantly lower rejection rate of the membrane.Thuschitosan,which has the advantages of good film-forming ability and good chelatingabsorption ability,was chosen to be a membrane forming material.PEG was chosen tobe a pore-forming agent.And CNTs,which has the advantages of good electric and heatconduction property,high mechanical strength and quasi-one-dimensionalnanostructure, also was added to the solution to preparing a membrane which has theadvantages of good water flux and good chelating absorption ability for dye andheavy metal ion. The research work is as follows.(1)Firstly the nonaligned and aligned carbon nanotubes was prepared by aultrasonic spray pyrolysis method,The influence of deposition position on themorphology of products was measured.It was found that the more Fe ratio on theposition,the position was easier to produce the nanotubes.Also the influence of volumeratio of cyclohexylamine to xylene on the morphology and tip situation of the CNTswas measured.It was found that when xylene was used solo as a carbon source,theproduced CNTs arranged disorderly.When the volume ratio of cyclohexylamine toxylene was used as35%,the produced CNTs had excellent directionality.And when thevolume ratio of cyclohexylamine was used as80%and90%,the produced CNTsarranged disorderly again.It also was found that when the volume ratio ofcyclohexylamine increased, the closed tips of CNTs was gradually opened at first,butwhen the volume ratio of cyclohexylamine reached80%, some open tips becameclosed again.(2)Secondly the chitosan,PEG and CNTs casting solution was prepared by the solution blending method.The viscosity and pH value of casting solution which hasdifferent reactants proportions was measured.Later these different membrane wasobserved under the SEM.The reactants proportion of0.022g/ml chitosan,0.022g/mlPEG1500and different content of CNTs was confirmed to be able to form porousstructure with high porosity and small pore size by a method of low temperatureheating with coagulating bath treatment after casting solution on a glass plate.(3)Thirdly the CNTs content of casting solution was changed,and the differentmembrane was observed under the SEM.It was found that30-50nm pores withhomogeneous distribution appeared on the membrane with the addition of CNTs, andthe porosity increased with the increase of CNT content.Then the Methyl orangeadsorption abilities of different membrane was studied. The adsorption experimentshowed that adsorption quantity of the membrane increased at first,then decreased withthe increase of CNTs content.Also the Copper sulfate solution filtration capacity wasstudied.The filtration experiment showed that water transport behaviour of membranewas improved with the addition of CNTs.At first the water flux of membraneincreased with the increase of CNTs content,but when CNTs content reached a certainvalue,the water flux decreased.The rejection rate of Cu2+increased with the increase ofCNTs content at first,and when CNTs content reached a certain value,the rejection alsodecreased.(4)Fourthly a revision experiments was conducted. It was to add polyvinylalcohol to the casting solution to change the compatibility of chitosan,CNTs and PEG,then to adjust the pore structure of the membrane.The SEM picture showed that thehigh porosity structure of the membrane was disappeared with the addition ofPVA.The addition of CNTs made the surface of membrane more smooth. With theincrease of CNT content,the membrane surface appeared the orderly and denselydistribution of CNTs. Also it was found that the tensile strength of the blendingmembrane was higher than the membrane without PVA.And the tensile strength of theblending membrane improved continually with the increase of CNTs content.