| As a carbon nanomaterial with a variety of oxygen-containing functional groups,GO has been widely used in the preparation of hydrogels.GA as a natural macromolecule,bears harmless,cheap and easy to obtain,has high biocompatibility and can be biodegradable.It contains hydroxyl(OH),carboxyl(COOH)and other groups.It has hydrophilic properties and is a good material for preparing biomass adsorbent.In this paper,GO was firstly prepared by the improved Hummers method,and then,with GA and GO as added components,2-acrylamide-2-methylpropylsulfonic acid(AMPS)and acrylamide(AM)as organic monomers,GO/GA-g-PAMPs and GO/GA-g-P(AMPS-co-AM)composite hydrogels were prepared by one-step hydrothermal method.The structure of the composite hydrogels was characterized by FTIR,XRD and SEM.The effects of GO content,GA content,salt solution concentration,solution p H,initial dye concentration,adsorption time and adsorption temperature on the adsorption properties of cationic dyes methylene blue(MB)and crystal violet(CV)were studied.The mechanism of adsorption was also discussed.The experimental results are as follows:(1)The GO/GA-g-PAMPs composite hydrogel was prepared by one-step hydrothermal method with GA as biomolecular additive,AMPS as organic monomer and GO as filler.The optimal preparation conditions of GO/GA-g-PAMPS hydrogel were determined with GO mass concentration of 0.3 g/L,GA of 0.3 g,AMPS of 2.0 g,and constant temperature reaction at 60℃.FTIR results showed that graft copolymerization of GO with polymer GA and organic monomer AMPS occurred.XRD results show that the composite hydrogel is amorphous,and GO reacts with other substances.The SEM showed that GO/ GA-G-PAMPS hydrogel had large pore diameter and obvious lamellar structure,indicating that GO and GA-G-PAMPS had good compatibility.the mechanical strength of GO/GA-g-PAMPS hydrogels was significantly enhanced.When GO mass concentration was 0.3 g/L,hydrogel dosage was 0.05 g,solution p H was 7,temperature was 50 ℃,and the initial mass concentration of dye was 200 mg/L,the adsorption capacity and adsorption rate of hydrogel to MB and CV were 395.68,381.70 mg/g,98.08 and 96.03 %,respectively.The results showed that the adsorption rate of MB and CV could reach 82.55 % and 81.23 % after 5 cycles.The adsorption isotherm and kinetics studies show that the adsorption of MB on the gel conforms to the Freundlich model,the adsorption of CV conforms to the Langmuir model,and the quasi-second-order kinetic model can better fit the adsorption process of MB and CV cationic dyes.The thermodynamic results show that the adsorption of MB and CV dye molecules by the hydrogel is a process of spontaneous,endothermic,and increased disorder.(2)The GO/GA-g-P(AMPS-co-AM)composite hydrogel was prepared under the optimal conditions of GO mass concentration of 0.3 g/L,GA of 0.3 g,AMPS of 2.0 g,PAM of 0.686 g,and constant temperature reaction at 60 ℃.The results of FTIR showed graft copolymerization of GO,GA,AMPS and AM.XRD results show that GO reacts with the polymer matrix.It can be seen from SEM that after the addition of GO,the gel surface is more rough and has a more definite porous surface,which reflects that GO has good compatibility in the polymer matrix and good distribution in the hydrogel.The mechanical properties of GO/GA-g-P(AMPS-co-AM)and GO/GA-g-PAMPS hydrogels have strong mechanical strength.Under the same experimental conditions as GO/ GA-g-PAMPS,the adsorption capacity and adsorption rate of hydrogels to MB and CV were 396.54,394.69 mg/g and 99.02,97.80 %,respectively,and the adsorption capacity was improved.The results of adsorption isotherm,kinetics and thermodynamics were the same as those of GO/GA-g-PAMPS.After 5 cycles of desorption,the adsorption rate of the gel to MB and CV could still reach 87.02 % and 84.76 %.Figure [35] table [10] references [87]... |
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