Synthesis Of Cellulose-based Hydrogels And Its Performance Testing

With increasingly concerned about exhausting of oil resources and environmentquestion, researchers have been focus on synthesis of polymer hydrogels using naturalor modification of natural polymers. Cellulose and its derivatives is an abundance ofgreen resource, with the advantages of water-solubility、renewable、biodegradable、biocompatibility、non-toxic. The salt tolerance is higher than starch and chitosan. Theabundant reactive groups (-OH) on the cellulose chains are convenient for graftpolymerization with hydrophilic vinyl monomers to derive novel material possessingnew properties. Various techniques have been proposed for initiated synthesis ofhydrogel, such as, chemical initiators, radiation, plasma induced and so on. A novelinitiation technique which is called as glow-discharge electrolysis plasma (GDEP) isemployed to prepare cellulosed hydrogels.Glow discharge electrolysis plasma (GDEP) is an unconventional electrolysis.In the glow-discharge area, there are some energetic species such as HO·, H·, HO2·,eaq–, H3O+gas, H2O2, etc, which could induce some unusual chemical reactions. Wesynthesis a series of cellulose based hydrogels by glow-discharge electrolysis plasmatechnique. Its swelling behaviors and adsorption properties were investigated in detail.This work can make the theoretical foundation for the hydrogel application inagriculture and horticulture, wastewater treatment and biomedical. The thesis isdivided into four chapters:Chapter1. The preparation methods, the progress of research and application ofcellulose-based hydrogels were made analysis and summary, and also proposed thequestions and trends in cellulosed hydrogels study.Chapter2. A novel composite carboxymethyl cellulose grafted poly (acrylic acid)is prepared in aqueous solution by glow-discharge electrolysis plasma technique.The influence factors on swelling capacity of AA/CMC hydrogel (i.e., dischargevoltage, discharge time, mass ratio of CMC to AA, degree of neutralization andcontent of cross-linking agent) was systematically investigated. The swellingbehavior of the synthetic hydrogels under different pH ranging from1to13and salt concentrations (NaCl, KCl, MgCl2, CaCl2and AlCl3) and their on-off switch wereinvestigated to evaluate their smart character. The absorbency of the hydrogel in thestudied salt solutions from highest to lowest is K+> Na+> Mg2+> Ca2+>Al3+>Fe3+.The adsorption of methylene blue (MB) and crystal violet (CV) on AA/CMChydrogel were preliminary studied. The results indicated that AA/CMC hydrogel haspH and salts sensitivity and exhibits reversible swelling-deswlling behavior. Thekinetics of the AA/CMC hydrogel for adsorption both cationic dyes follow thepseudo-second-order kinetic model.Chaper3. A carboxymethyl cellulose/poly(ethylene glycol)/acrylic acid(CMC/PEG/AA) superabsorbent hydrogel was prepared in aqueous solution by usingglow-discharge electrolysis plasma (GDEP) induced graft copolymerization ofcarboxymethyl cellulose (CMC), poly(ethylene glycol)(PEG) and acrylic acid (AA).The swelling kinetics in distilled water, rain water,0.9%NaCl solution, Yellow Riverwater and tap water were systematically investigated. The effects of temperature, pHand salts on equilibrium swelling capacities were evaluated. The adsorption behaviorof methylene blue on CMC/PEG/AA hydrogel was preliminary studied. The resultsshowed that the maximum equilibrium swelling capacities for distilled water, rainwater and0.9%NaCl solution were935,689and78g/g, respectively. The kineticcurves in Yellow River water and tap water exhibited a remarkable overshootingeffect, that is, the composite firstly swells to a maximum value, follows by a gradualdeswelling until the equilibrium. The maximum swelling capacity in distilled waterwas1115g/g at30℃. The hydrogel has pH and salts sensitivity and exhibitsreversible swelling-deswlling behavior. The MB equilibrium adsorption amount wasup to1878.8mg/g. The experimental data of dye was in a good agreement withLangmuir model and the pseudo-second-order kinetic model.Chapter4. AA/HEC superabsorbent hydrogels were synthesized by graftcopolymerization of acrylic acid onto hydroxypropyl cellulose (HEC) inhomogeneous aqueous using glow discharge electrolysis plasma technique. To obtainmaximization swelling capacity, the influence factors like discharge voltage,discharge time, mass of HEC and content of cross-linking agent were studied in detail.The sorption behavior of methylene blue on AA/HEC hydrogel was preliminary studied. The maximum swelling uptakes of the optimum hydrogel in distilled water,rain water were832.86,521.72g/g, respectively. What’s more, the hydrogel exhibitedpH-and salt-sensitivity and showed intelligent pH-and salt-reversibility. Theswelling kinetics follows the pseudo second order model. The adsorption process ofMB on AA/HEC hydrogel was in accordance with Langmuir model and thepseudo-second-order kinetic model.