Synthesis Of (Cellulose/Chitosan)-Based Hydrogels And Its Adsorption Performance Of Methylene Blue Dye

With the rapid development of printing and dyeing industry in our country, more and more printing and dyeing wastewater is discharged into environmental water,which has seriously polluted ecological environment. Therefore the study on dye wastewater treatment method and technology has become the focus of attention. By virtue of its outstanding advantages, such as simpler operation, higher treatment efficiency and faster adsorption rate, adsorption method has been playing an important role in wastewater treatment. Hydrogel is widely used for adsorption and separation of the dyeamong many different adsorbents, as a high-performance,multi-functional and environmentally friendly sorbent. Using natural polymers, as raw materials, which are abundant in nature, renewable, inexpensive and readily biodegradable, prepared hydrogels have some significantadvantagessuch as low-cost,environment-friendlycharacter and improving resource utilization. In this thesis,chitosan and cellulose were selected as the basic raw materialsand a series of hydrogels were successfully synthesized througha graft-polymerization methodwith different functional monomers. The swelling behavior in different solution and adsorption properties for methylene blue dye were systemically studied. The thesis consists of six chapters as follows:Chapter 1.Concept, preparation methods, research progress and application of hydrogels were reviewed in detail andthe significance and content of this thesis were mainly introduced.Chapter 2. The reagents, instruments, preparation and characterization methods,as well asmain experiment contents were introduced.Chapter 3-6. Carboxymethylcellulose/chitosan/crylicacid?CMC/CTS/AA?,carboxymethylcellulose/chitosan/crylicacid/polyethyleneglycol?CMC/CTS/AA/PEG?,carboxymethylcellulose/chitosan/crylic acid/2-acrylamido-2-methylpropane sulfonic acid?CMC/CTS/AA/AMPS? and carboxymethylcellulose/chitosan/crylic acid/ b-cyclodextrin?CMC/CTS/AA/ b-CD? superabsorbent hydrogelswere synthesized in aqueoussolution, by employing N,N'–methylenebisacrylamide?MBA?as a crosslinker and ammonium persulfate?APS? as an initiator. The morphologies,structures and thermal stability ofthe prepared hydrogels were characterized by scanning electron microscopy?SEM?, Fourier transform infrared spectroscopy?FT-IR?and thermogravimetric analysis?TG?. Their swelling kinetics in distilled water and the influences of various pH values and salt solutions on the equilibrium swelling were discussed in detail. In addition, theadsorption behaviors of the superadsorbentshydrogels for methylene blue?MB? andthe effects of the experimental conditions including the dye initial concentration, pH value and adsorption time on the adsorption amounts were detailledly investigated. The resultsshowed that the hydrogels possessed excellentswellingperformances, pH-sensitivity and salt-sensitivity, andthe equilibrium swelling degrees of the hydrogels in salt solutions from highest to lowest were K⁺ > Na⁺ > Mg²⁺ > Ca⁺ > Al³⁺. At the same time, the hydrogels still showeda high adsorption amount capacity for MB. The adsorption isotherms and kinetics were in good agreementwith Langmuir equation and Pseudo-second-order equation respectively. The prepared hydrogels could not only absorb and hold water in complex environment, but also adsorb and remove dye,which promised wide applications in agriculture and wasterwater treatment.