Preparation And Methylene Blue Adsorption Of Yak Hair Keratin Based Composite Membrane

Keratin is a rich natural biodegradable polymer material that exists in animal hair,horn,and other tissues with a wide range of sources.Yak is a unique breed of cattle in China,with abundant wool production,but most of them cannot meet the standards of textile raw materials,and can only be treated as waste,wasting resources and polluting the environment.Therefore,research and utilization of yak hair can reduce the waste of yak hair resources.Melted urea was used to extract keratin from yak hair,the effects of temperature,dissolution time,and urea dosage on the extraction efficiency were investigated.The data show that the method has high dissolution and extraction rates for yak hair.When the dissolution temperature is 165℃,the contact time is 65 minutes,and the mass ratio of urea to yak hair is 11:1,the extraction rate reaches the highest,reaching 81.20%,at which time the dissolution rate is 94.25%.The extracted yak hair keratin and PVA were used to make composite films.The mechanical properties,thermal properties,and chemical structures of keratin films with different keratin contents were characterized.From the results it comes to that when the percentage by mass of keratin is 10%,the compound membrane reaches 44.563 MPa in term of tensile strength,and the breaking elongation is 138.892%.The breaking elongation of the compound membrane after adding keratin is somewhat lower than that of the pure PVA film.The prepared PVA/yak hair keratin composite membrane was imbedded into methylene blue dye solution,and the effect of percentage of keratin in the composite membrane on the purification outcome was brought into exploration;Control the adsorption capacity of the compound membrane at different time,temperature,and Cinit of methylene blue during the adsorption process,the thermodynamic parameters of the adsorption process were calculated,and the adsorption isotherm pattern and kinetic pattern was fitted.The results state clearly that the purification rate of methylene blue on the compound membrane follows an increasing trend of slowing down over time,and reaches adsorption equilibrium within 145 minutes,with an equilibrium adsorption rate of 74.0%.The adsorption data of different initial concentrations of methylene blue indicate that the composite membrane has a better adsorption effect on methylene blue solutions below 10 mg·L^-1 under the input amount of this experiment,reaching about 75%.In methylene blue solutions with higher initial concentrations,the adsorption rate of the composite membrane gradually decreases.The higher the keratin content in the composite membrane,the stronger the adsorption ability of the composite membrane to methylene blue.After the keratin content is increased from 0%to 5%,the adsorption rate for methylene blue is increased from 45.988%to 68.629%of the pure PVA membrane.In addition,the data found that high temperature has a negative effect on the adsorption capacity of the composite membrane,with the adsorption rate of 74.640%at a constant temperature of 10℃,and decreases to 53.518%when the temperature rises to 70℃.The parameters of thermodynamics for the adsorption process were calculated,it is extrapolated that the cleaning-up course of methylene blue on the composite membrane is a heat-releasing reduction process with a decrease of entropy,and the Gibbs free energy at various temperature conditions in the experimentΔG is less than 0.By adapting the isothermal adsorption model and kinetic equation for the purification course,it is found that the experimental data are more consistent with Langmuir model and the pseudo-second-order kinetic model.The PVA/keratin composite membrane was crosslinked with glutaraldehyde,and the mechanical properties,swelling rate,infrared spectroscopy,and methylene blue adsorption capacity of the crosslinked composite membrane were tested.The results show that glutaraldehyde can enhance the tensile strength of the compound membrane.When the glutaraldehyde ratio is 2.5%,the tensile strength of the compound membrane notches up54.108 MPa,and the breaking elongation of the membrane is 95.441%.After adding glutaraldehyde,the swelling rate of the composite membrane gradually decreases.The infrared spectrum shows that the crosslinked film has a C=N absorption peak and an enhanced ether bond absorption peak,which proves that glutaraldehyde diagonal protein and PVA were successfully crosslinked.However,glutaraldehyde has a certain negative effect on the adsorption capacity of the composite membrane.After adding a 2.5%mass fraction glutaraldehyde composite membrane,the equilibrium adsorption rate decreased from 72.156%to 61.795%.After adding 1%mass fraction glutaraldehyde,the adsorption rate of the composite membrane decreased,but the duration to culminate in the adsorption equilibrium was shortened from 145 min to 120 min.