Hydrophobic Modification Of Cellulose And Preparation And Application Of Cellulose Hydrogel

It is well known that a series of unprecedented challenges from environment,energy and materials have been encountered with the rapid development of modern industry in 21 century.The plant fiber has the advantages of low cost,various application,easy degradation and good biocompatibility.However,the present of intramolecular and intermolecular hydrogen bonds and the absent of surface functional groups of cellulose limit the application of cellulose,especially in the field of composite materials and wastewater treatment.Nowadays,the regulations used to control the concentration of toxic metals in industrial effluents are becoming more and more stringent.Various strategies have been proposed for the removal of heavy metal ions from wastewater,including chemical precipitation,ion exchange,adsorption,ultra-and nanofilitration,reverse osmosis,electrochemical and electro dialysis techniques.Among these methods,adsorption has been recognized as effective and economic methods to treat wastewaters containing toxic metals due to its simplicity,effectiveness,ease of operation and reusability.In order to improving the adsorption capacity of heavy metal ions,epichlorohydrin,ethylene diamine and carbon disulfide were used for surface modification of cellulose.The modified cellulose derivative and sodium carboxymethyl cellulose(CMC-Na)were dissolved in sodium hydroxide/thiourea system and crosslinked with epichlorohydrin,from which the high efficiency and eco-friendly cellulose-based bioadsorbent was synthesized and employed to remove Pb2+,Cu2+ and Zn2+ from aqueous solutions.The effects of initial concentration of heavy metal ions,pH of solutions,temperature and ionic strength on the adsorption capacity of the bioadsorbent were investigated.The determination of adsorption isotherms showed that the adsorption of Pb2+,Cu2+ and Zn2+ followed the Langmuir model and the maximum adsorptions were as high as 558.9,446.2 and 363.3 mg·g-1,respectively,in single component system.The kinetic and thermodynamic studies indicated that the pseudo-second-order model was well fitted;and the adsorption was spontaneous and exothermic.The binary component system was better described with the competitive Langmuir isotherm model.The three dimensional sorption surface of binary component system demonstrated that the presence of Pb2+ decreased the sorption of Cu2+,but the adsorption amount of other metal ions was not affected.The results from FTIR and SEM-EDAX revealed that the adsorption of Pb2+,Cru2+ and Zn2+ on the bioadsorbent was mainly driven by coordination,ion exchange and electrostatic association.Cationic polymer latex,poly(St-co-AH/BA-co-DMAEMA-co-BMA),which having core-shell structure was synthesized by a two-step semi-batch emulsion polymerization technology with hexadecyl trimethyl ammonium chloride as surfactant,ethylene glycol dimethacrylate as crosslinker,2,2'-Azobis(2-methylpropionamidine)dihydrochloride as cationic initiator.The broad particle size distribution of latex leads to the adsorption of the latex onto fiber proceeding via two-stage equilibrium mainly due to the effect of latex particle size.The pseudo-first-order kinetic model was appropriate for the description of the kinetics of the first stage equilibrium at high latex concentration and the entire adsorption process at low concentration.In contrast,the pseudo-second-order kinetic model fitted the second equilibrium at high latex concentration well.The activation energy calculation suggested that the number of activated molecules was increased as the increase of adsorbent concentration,which might change the dominant adsorption mechanism.The activation energy at high concentration is higher than that at low concentration and the adsorption rate at high concentration is lower than that at low concentration.It can be concluded that the adsorption were control by activation control at high concentration and diffusion control at low concentration.The adsorption rate was less than 60%without additional emulsifier,and reached more than 90%when additional emulsifier was added,which accounted for the abnormal adsorption behavior with the extra-added emulsifier.In addition,the surface property of the modified cellulose fibers was also investigated via SEM,FTIR,BTE,TGA and contact angle measurements.The hydrophobicity of the modified cellulose fibers was enhanced significantly once the adsorption amount reached 196 mg ·g-1.The saturated adsorption capacity of cellulose fibers was as high as 520 mg · g-1 at 303 K due to the excellent combining effects of amphiphilic polymer with cellulose fiber.The results proved that the cellulose fiber modified with the latex became hydrophobic,allowing the as-modified cellulose to be potential reinforcements for biocomposite.Finally,the adsorption mechanism was proposed according to the adsorption process mainly governed by electrostatic interactions,hydrogen bond,?-? stack and chain entanglement.