Sorption properties of regenerated keratin gels to size macromolecules in textile desizing wastewater
Objective The effective recycling of waste protein fiber resources is one of the important aspects to achieve green and sustainable development of textile industry.In this study,regenerated keratin gels were prepared from waste wool fibers and applied to the sorption treatment of textile desizing wastewater.By exploring the sorption performance and mechanism of keratin gels to two common types of sizes,the research foundation is provided for promoting the industrialized application of this method.Method On the basis of the preliminary study,the keratin polypeptides were extracted by "reducing agent-formic acid method",and then the polypeptides were modified by α-lipoic acid.These modified keratin polypeptides were prepared for creating regenerated gel materials by dialysis and freeze-drying.The sorption properties of the keratin gels to polyvinyl alcohol(PVA)size and starch size were studied,and the sorption mechanism was discussed by using the sorption kinetics and sorption isotherm model.Results The experiment was based on the"reduction pretreatment-formic acid dissolution method",by adding the modifier α-lipoic acid for grafting modification,and then by"dialysis-freezing"method to prepare the keratin gel material.The photograph of the gel structure illustrated that the keratin gel was relatively fluffy and dense,and the microscopic morphology presented the characteristics of uniform pores with the pore size of about 3-4 μm.In comparison with the chemical structures of wool,the keratin gel material retained the basic chemical structure of keratin molecule,in which the keratin amide Ⅱ band was blueshifted due to the transformation of the aggregation state of polypeptide molecules in the gel.Compared with the sulfur content on the surface of wool and keratin gel,the keratin gel was located at 169.58 eV and 170.68 eV.The results indicated that α-lipoic acid was effectively grafted to the sulfhydryl group on the keratin polypeptide macromolecular chain.In addition,the peak intensity of the gel at 21° increased significantly than those of the peak crystallinity of wool,and the test results exhibited that the molecular structure of the polypeptide modified by α-lipoic acid was optimized to a certain extent.The adsorption capacity and removal rate of keratin gel on PVA reached 16.278 mg/g and 30.013%,respectively,and the adsorption capacity and removal rate of starch slurry are 133.234 mg/g and 28.868%.Moreover,the kinetic model study showed that the adsorption of PVA and starch by keratin gel was in accordance with the quasi-secondary kinetic model,and the fit was close to 1.Thermodynamic model analysis presented that the adsorption of keratin for PVA was consistent with Langmuir model,and that starch was more suitable for the Freundlich model.Conclusion The keratin gel prepared in this study has uniform physical morphology and abundant pore structure,and its chemical properties are basically consistent with wool.The keratin gels have good sorption performance to PVA and starch size.Among them,the action mode of gels to PVA is mainly physical adsorption,while there may be chemical effects on starch.
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