Optimiazed Preparation Of The Keratin Sponge Film And Its Application

Feather is a kind of natural protein resources that can be recycled and reused by various processing. It is not only a waste of resources but also a cause of environmental pollution if feather is discarded as the waste. In recent years, the domestic and international research on the recycling of the feather keratin is a hotpot, and always concentrates on the soluble keratin, while investigations focused on the insoluble keratin residues are rarely reported. In this article, keratin sponge film was made of insoluble keratin residues extracted from the feather and had its structures characterized. Moreover, potential applications of the film in the environmental treatment of dye wastewater and heavy metal wastewater were studied to provide a new way for the regeneration of the waste protein resources.Firstly, the extracted methods of feather keratin as well as its applications in all aspects of life were reviewed, and its classification and composition were also introduced. The shortcomings existing in the process of keratin extraction were put forward and the progress made in the preparation of keratin film was especially reviewed.Secondly, insoluble keratin residues generated in the reduction reaction under the optimized condition of orthogonal experiments were made into keratin sponge films to avoid producing wastes again and improve the utilization rate of the keratin. With a smooth surface and bulk texture, the prepared sponge film had good flexibility and elasticity. Its fracture strength reached5.4MPa. The result of scanning electron microscope (SEM) showed that the film was stable and insoluble in the water, and had a rich pore structure which could be used as a potential adsorbent. The result of Fourier transform infrared spectroscopy (FT-IR) showed that more β-fold structure and random coil structure were contained in the secondary structure of the film. X-ray diffraction (XRD) showed that compared with raw feathers, a-helix structure in the film reduced significantly, while β-fold structure increased and crystallinity degree of the keratin became smaller. The thermogravimetric analysis (TGA) showed that the thermal stability of the film was slightly lower than that of the feathers. The film began to pyrolyze when the temperature was higher than200℃. The tests of SDS-Polyacrylamide gel electrophoresis (SDS-PAGE) showed that the molecular weight of the soluble keratin derived from the feathers generally distributed from10to50kDa, so the molecular weight of the film-standing above the range could be speculated approximately.Thirdly, adsorption of methylene blue (MB) on the film was studied to evaluate the film’s application in the treatment of dye wastewater. The results showed that the effect of temperature on the adsorption process was weak. The MB removal efficiency could reach its best to98.12%under the following conditions:temperature of25℃, pH of7.0, adsorbent dosage of0.06g, initial MB concentration of100mg/L and adsorption equilibrium period of24h. In the circumstances, the maximum absorption capacity was82.69mg/g with the maximum monolayer adsorption capacity151.5mg/g under the temperature of25℃. The adsorption process fitted both Langmuir model and Freundlich model, and it fitted Freundlich model better (R2=0.994). Kinetic studies showed that the adsorption process followed pseudo-second-order dynamic equation. Furthermore, both physical and chemical adsorption could be found in this process after the comparison of SEM and FT-IR characterization on the film before and after the adsorption.Finally, adsorption of Pb2+and Cd2+on the film was studied to evaluate the film’s application in the treatment of heavy metal wastewater. The results showed that under the temperature of25℃, Pb2+initial concentration40mg/L, adsorbent dosage of0.1g, pH of8.0and adsorption equilibrium period of4h, the maximum adsorption capacity of Pb2+was39.53mg/g. As for Cd2+, the maximum adsorption capacity was23.98mg/g under the temperature of25℃, Cd2+initial concentration20mg/L, adsorbent dosage of0.1g, pH of8.0and adsorption equilibrium period of2h. Based on the analyses of isotherm fitting, adsorption kinetics and thermodynamics, the results showed that the adsorption of Pb2+and Cd2+was an exothermic process and easy to carry. The adsorption of Pb2+fitted both Langmuir model and Freundlich model well and fitted Langmuir model better. The adsorption of Cd2+fitted these two models poorly but fitted more closely to Langmuir model. The adsorption process of Pb2+and Cd2+both followed pseudo-second-order dynamic equation, in which physical and chemical adsorption played an important role.In all, the outcome of this investigation will provide some theoretical support and practical reference for the reuse of renewable feather resources applied in the environmental field.