Li Weijie,Zhang Fengying,Wang Weiku,Li Yinhui,Liu Yaodong,Lu Chunxiang,Zhang Zhengfang
Abstract
Cellulose was dissolved in LiCl/DMAc solvent system at various concentrations. Using rheological measurements, we observed that the cellulose solution becomes gelled upon heating and jelly-like during cooling. Interestingly, while phase separation occurs during heating (from room temperature to higher) along with a sol–gel transition, and this transition is irreversible, the cooling (from room temperature to lower) induced solution property transition from more viscous to more elastic is completely reversible. The structural changes of cellulose solution during heating and cooling cycles are in situ monitored by infrared spectroscopy, and we found that the temperature of the solution affects the interactions among DMAc, lithium cations, chloride anions, and the hydroxyl groups in cellulose chains. While heating induces phase separation and gelation of cellulose solutions, cooling simply turns the solution into a reversible jelly status. Also, when cellulose concentration increases, the gelation temperature caused by heating becomes significantly lower. Possible mechanisms of the rheological transitions of cellulose/LiCl·DMAc solutions during either heating or cooling are proposed in this study. Graphical abstract
The biodegradable biomass adsorbent (cellulose- g -PSS) was synthesized in LiCl/ N, N -dimethyl acetamide by the free-radical grafting polymerization reaction between sodium styrene sulfonate (SSS) and cellulose. Systematic optimization was conducted on many reaction parameters, including reaction time, monomer dosage, and reaction temperature. The grafting yield of cellulose- g -PSS was 50.16%. The chemical structures, physical, and chemical characteristics of cellulose- g -PSS were characterized by FTIR, SEM, PZC, 1 H NMR, XRD, TGA and XPS. An assessment was conducted to determine the sorption of Ce (III) on cellulose- g -PSS by changing the contact time, adsorbent dosage, pH, initial Ce (III) concentration, and NaCl concentration. The process of adsorption rapidly reached a state of equilibrium within a time frame of 25 min and was well explained using pseudo-second-order kinetic and Langmuir isotherm model. The maximum adsorption capacity for Ce (III) obtained from the Langmuir isotherm model was 84.80 mg·g −1 . The impact of NaCl concentration on the sorption of Ce (III) and XPS analysis showed that Ce (III) ions were adsorbed onto cellulose- g -PSS through ion-exchange mechanism. As a whole, cellulose- g -PSS exhibited great potential in rare earth wastewater treatment.
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