Preparation And Properties Of DMDAAC-modified Cellulose Filter Paper

Dyes are widely used in the process of dyeing the material.However,most organic dyes are toxic,non-biodegradable,teratogenic and mutagenic,posing a serious threat to human health and marine life,which affect the ecological balance greatly.About 10?15%of dyes are discharged to the nature due to incomplete washing and coloring.As the most abundant natural polymer compounds,cellulose is a biodegradable materials with high strength,high thermal stability and low-cost.It is of great scientific significance to develop a new cellulose-based material with high efficiency for adsorption of dyes.In this thesis,to prepare a cellulose-based material with the selective adsorption for anionic dyes,a cationic monomer diallyl dimethyl ammonium chloride(DMDAAC)was successfully grafted onto the surface of cellulose filter paper via atom transfer radical polymerization(ATRP).By controlling the molar ratio of monomer to initiator,the modified cellulose filter paper with different graft ratio(GR)was prepared.With the increase of monomer DMDAAC,the GR of Paper-PDMDAAC increased linearly.The surface composition and structure of the filter paper were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)and X-ray photoelectron spectroscopy(XPS).The results showed that DMDAAC was successfully grafted onto the surface of the cellulose filter paper.No obvious change in the morphology of the filter paper before and after modification can be observed by scanning electron microscopy(SEM),indicating the porous characteristics of the filter paper were maintained.The static water contact angle(CA)measurement showed that Paper-PDMDAAC had excellent hydrophilicity.The adsorption of anionic dye methyl orange by Paper-PDMDAAC was investigated.With the increase of graft ratio and decrease of pH value of methyl orange solution,the equilibrium adsorption capacity increased correspondingly.For the adsorption of different concentrations of methyl orange solution,Paper-PDMDAAC showed a quick adsorption equilibrium in low concentration with high decolorization ratio.With the increase of NaCl concentration in methyl orange solution,the adsorption capacity of methyl orange of Paper-PDMDAAC significantly decreased,and the adsorption equilibrium was very sensitive to the ionic strength in solution.When methyl orange is in solution of initial concentration of 100 mg/L with volume of 50 mL and pH of 4.6,more than 90%methyl orange was adsorbed by 75 mg of Paper-PDMDAAC with GR of 12.5%at 25 ?.The adsorption obeys the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model.The adsorption process was monolayer adsorption.By calculating with Langmuir formula,the theoretical maximum adsorption capacity of Paper-PDMDAAC with a GR of 12.5%for adsorption of methyl orange was 243.9 mg/g.And the Paper-PDMDAAC had a good adsorption effect on methyl orange after 6 cycles,indicating a good reusability and stability.The selective adsorption performance of Paper-PDMDAAC was studied using anionic dye methyl orange and cationic dye rhodamine B as an example.Paper-PDMDAAC with GR of 12.5%removed the methyl orange molecules quickly and efficiently,while for the rhodamine B solution,the decolorization ratio was extremely low.The separation effect of selective adsorption for methyl orange and rhodamine B mixture was more distinguished with the increase of graft ratio.When the GR reached 12.5%,the separation efficiency reached a stable state,and the highest decolorization ratio of methyl orange reached 99.1%,the lowest decolorization ratio of rhodamine B was 3.3%.The modified filter paper showed excellent selective adsorption for the mixed solution.The decolorization ratio of methyl orange was higher than 95%and rhodamine B was lower than 6%and the tensile strength was more than 28 kN/m2 after 6 cycles.Because the average pore size of filter paper is much larger than the size of dyes,the separation is not depend on physical interception.The selective adsorption of mixed dyes can be demonstrated by the electrostatic interaction between the Paper-PDMDAAC and the dye molecules,that is,the electrostatic attraction of Paper-PDMDAAC to the methyl orange molecules and the electrostatic repulsion to the rhodamine B.