Preparation and adsorption of copper ion properties of anisotropic PVA wood-based hydrogel
As hydrophilic polymers with three-dimensional network structure,hydrogels are widely used in biomedicine,flexible electronic devices,wastewater treatment and other fields.However,the traditional hydrogels have problems of poor mechanical strength and low stiffness,which limit their large-scale practical applications.Wood is a kind of abundant renewable natural biomass resources,with cellulose fibers arranged neatly along the growth di-rection and multi-layer pore structure.The low toxicity,excellent mechanical properties,high water absorption and good biocompatibility of polyvinyl alcohol(PVA)can be combined with cellulose skeleton,making full use of the high tensile strength of natural wood and the flexibility and high water content of hydrogels to construct high strength anisotropic hydrogels.In this study,balsa wood was used to construct a PVA micro-nano network by ice template method and quench cooling method,and a high strength anisotropic PVA wood-based hydrogel(PWH)was construc-ted for efficient adsorption of copper ions in water,which solved the problems of isotropy,poor mechanical strength and low stiffness of traditional hydrogel polymers.The morphological structure and properties of the composite hydro-gel were characterized by the scanning electron microscope(SEM),Fourier infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and mechanical testing machine.By the previous-mentioned characterization,the technological conditions required for the optimum delignification time and the optimal adsorption effect of PWH in copper ions con-taining wastewater were studied.The results of the SEM,FT-IR and XRD showed that the crystallinity of the hydrogel(PWH-2)were improved after delignification for 2 h,and the anisotropic fiber skeleton of wood was retained after the PVA compositing,which showed the best comprehensive properties.The results of mechanical testing machine showed that the energy loss of PWH-2 was only 0.022 8 MPa/mm and the height retention rate was as high as 97.37%after 80 times of cyclic compression under 5%strain,and the sample had excellent compressive strength and elasticity.Orientated porous structure of the PWH-2 facilitated the migration of copper ions in its interior and improved the ad-sorption performance.In the simulated waste liquid,the adsorption rate of Cu2+can reach 77.27%at 25℃,pH 5 and 40 mg/L Cu2+mass concentration,and the adsorption rate of Cu2+can still reach 40.11%after four cycles of PWH-2.The results of kinetic and isotherm studies showed that the adsorption of copper ions by PWH-2 satisfied the pseudo-first-order kinetic model and followed the Langmuir isotherm model.This study provided theoretical reference for the construction of high strength anisotropic hydrogels with high efficiency and sustainable adsorption of heavy metal ions,presenting a new direction for high value utilization of biomass.
wood-based hydrogelpolyvinyl alcohol(PVA)anisotropiccopper ion adsorption
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