Cellulose Nanowhiskers’UV-Grafted With Poly (Acrylic Acid) And Its Adsorption Performance

Cellulose is one of the most abundant green natural polymer materials in nature, it can bereduced to nano size through sulfuric acid hydrolysis, and finally produced rod-like cellulosenanowhisker(CNW) with cholesteric phase liquid crystal property. We could observe texturesof cholesteric phase liquid crystal CNW with polarized optical microscopy. In this research,we investigated the impact of reaction raw materials, reaction time, pH values, thickness andcopper ion on the texture of CNW iridescent films. TEM images showed that average lengthof CNW is200nm and the average diameter is20nm. We could also found the pitch value ofCNW liquid crystal is500nm by SEM cross-sectional picture. The polarized opticalmicroscopy results showed that CNW iridescent films could generate a new dendritic textureafter adsorpting copper ions, this characteristic could be used for detecting and separatingcopper ions, even other heavy metal ions rapidly. In addition, CNW iridescent films wouldhave a board application prospect in the field of coatings as it could be formed on differentsubstrates such as glass, wood, plastic, etc..There are so many hydroxyl groups on CNW surface that we can modify CNW throughfunctional reaction of hydroxyl. New functional groups could be introduced to CNW surfaceto generate cellulosic materials with excellent performance via graft polymerization. In thisstudy, acrylic acid(AA) and low molecular weight poly(acrylic acid)(PAA) were fast graftedonto CNW surface by UV-initiation. And the two maximum grafting rate could reach to20.04%and35.62%respectively. The impacts of reaction conditions such as reactant ratio, reactiontime, initiator dosage and initiation time on the grafting experiment were investigated byorthogonal design. The characterization methods like Fourier Transform Infrared Spectrum(FTIR), X-Ray Diffraction(XRD) and13C-CP/MAS Nuclear Magnetic Resonance (NMR),proved the successful grafting experiments. TEM images showed after grafting, the size ofCNW-g-AA and CNW-g-PAA almost remained the same, but the dispersion improved.Meanwhile, according to zeta potentials tests, the stability of CNW suspension improved aftergraft copolymerization.Both CNW-g-AA and CNW-g-PAA had good adsorption properties for heavy metal ionsdue to the large amount of hydroxyl groups on their surfaces. We studied the static adsorptionexperiment for copper ion, and investigated many experiment influencing factors such asadsorption time, pH value, temperature and Cu2+initial concentration. The optimumconditions for Cu2+adsorption were obtained when the adsorption temperature was30℃, thepH value was4and the adsorption time were7h and5h respectively. The two maximum adsorption capacity were about66mg/g and124mg/g. The Langmuir equation and thepseudo-second order kinetic could be fitted for the Cu2+adsorption on CNW-g-AA andCNW-g-AA, and both of the adsorbents had good regeneration properties.