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Preparation and Surface Wettability of Chitosan Membrane

Author: ZhouZuoZuo
Tutor: YuChunLing
School: Dalian University of Technology
Course: Environmental Engineering
Keywords: chitosan membrane surface struture wettability
CLC: O647
Type: Master's thesis
Year: 2011
Downloads: 49
Quote: 0
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Abstract


Wettability is an important feature of solid surface, usually is measured by contact angle(CA).It has been widely concerned that super-hydrophobic (contact angle above150°) andhydrophilic (contact angle less than10°) have the self-cleaning of the surface.Therefore,construction of super-hydrophobic (super-hydrophilic) interface of nano-materials has a greatsignificance both in basic and applied areas.This paper has successfully constructed thechitosan surface which is super-hydrophilic in air while super-oleophobic inwater.Furthermore,the thesis discusses how the surface structure and chemical compositionimpact on the wettability.The main contents include:The chitosan membrane with micro-nano-structures prepared by doctor-blade castingprocess with chitosan.The research showed that the concentration is in direct proportion tothe viscosity and the viscosity reduces as the time duration extends.When the concentration istoo low,the membranes prepared will be very brittle and difficult to be peeled off,when theconcentration is high,the membranes prepared can only form small hard lumps.Chitosanmembrane were made when concentration between2%and8%is suitable.The chitosanmembrane formed by2%acetic acid,moderate in thickness and easy to be release.Dry theprepared membranes respectively by means of oven drying,air drying and infrared drying. Itis discovered under the electron microscope that only oven drying can well protect thesurface structure of chitosan membranes.Use chitosan of different molecular weights to prepare chitosan solution for membranepreparation.It is observed under the scanning electron microscope that the surfacemorphologies of membranes greatly differ from each other.The surfaces oflow-molecular-weight membranes are overspread with small particles,while surfaces ofhigh-molecular-weight membranes are composed of smooth strips and scatteredaggregates.The pre-evaporation temperature has no remarkable influence on the surfacemorphologies of chitosan membranes.Chitosan membranes show hydrophilicity in air,contactangle range from0°to41.08°;showing the lipophilicity of membranes,with a contact anglerange from20.63°to48°;an oil droplet on chitosan membrane in water,showing oleophobic,with a contact angle range from134.18°to154.75°.After alkali solutiontreatment,contact angle of chitosan membrane changed. Increase the hydrophilic (oleophobic)substances can enhance the roughness of the hydrophilic (oleophobic) performance,tosuper-hydrophilicity (oleophobic) state of the membrane can achieve self-cleaning.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > The physical chemistry of surface phenomena
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