各向异性PVA木基水凝胶的制备及其铜离子吸附性能

Preparation and adsorption of copper ion properties of anisotropic PVA wood-based hydrogel

针对传统水凝胶生成的聚合物网络通常为各向同性,存在机械强度差、刚度低等问题。本研究以巴沙木为原料,通过冰模板法和淬火法,在定向排列的脱木素纤维素骨架中构筑具有纤维取向的聚乙烯醇(PVA)微纳网络,构建用于高效吸附水中铜离子的高强度各向异性PVA木基水凝胶(PWH),结合扫描电子显微镜、傅里叶红外光谱、X射线衍射、电子万能力学试验机表征复合水凝胶的形态结构和性能。实验结果表明:脱木质素工艺可以增加木质纤维的结晶度,PVA成功复合后保留了木材各向异性纤维骨架,脱木质素2 h的水凝胶(PWH-2)综合性能最优;PWH-2在5%应变下循环压缩80次后,样品能量损耗仅为0.022 8 MPa/mm,高度保持率高达97.37%,具有优异的抗压强度和弹性;PWH-2定向排列的多孔结构有助于铜离子在其内部迁移,提高吸附性能,在25℃、pH 5、铜离子质量浓度40 mg/L的模拟废液中,对铜离子的吸附率可达77.27%,经4次循环利用对铜离子的吸附率仍可达40.11%。动力学和等温线研究结果表明,PWH-2吸附铜离子过程满足拟一级动力学模型,遵循Langmuir等温线模型。该研究为构建高效可持续吸附重金属离子的高强度各向异性水凝胶提供理论参考,为生物质高值化利用提供新的方向。

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 direction 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 constructed 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 hydrogel 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 containing 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 0.0228 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 adsorption performance.In the simulated waste liquid,the adsorption rate of Cu 2+can reach 77.27%at 25℃,pH 5 and 40 mg/L Cu 2+mass concentration,and the adsorption rate of Cu 2+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.