Amari Samar, Darestani Mariam, Millar Graeme, Boshrouyeh Bob
School of Mechanical, Medical & Process Engineering, Faculty of Engineering, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia.
School of Mechanical Engineering, Western Sydney University (WSU), Sydney, NSW 2751, Australia.
Polymers (Basel). 2025 Apr 24;17(9):1155. doi: 10.3390/polym17091155.
This study explores the fabrication, structural characteristics, and performance of an innovative porous geopolymer membrane made from waste natural zeolite powder for Pb(II) removal, with potential applications in wastewater treatment. A hybrid geopolymer membrane incorporating polyvinyl acetate (PVAc) (10, 20, and 30 wt.%) was synthesized and thermally treated at 300 °C to achieve a controlled porous architecture. Characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), revealed the disappearance of characteristic C=O and C-H stretching bands (~1730 cm and ~2900 cm, respectively), confirming the full degradation of PVAc. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) indicated a total mass loss of approximately 14.5% for the sample with PVAc 20 wt.%, corresponding to PVAc decomposition and water loss. Energy-dispersive spectroscopy (EDS) elemental mapping showed the absence of carbon residues post-annealing, further validating complete PVAc removal. X-ray diffraction (XRD) provided insight into the crystalline phases of the raw zeolite and geopolymer structure. Once PVAc removal was confirmed, the second phase of characterization assessed the membrane's mechanical properties and filtration performance. The thermally treated membrane, with a thickness of 2.27 mm, exhibited enhanced mechanical properties, measured with a nano-indenter, showing a hardness of 1.8 GPa and an elastic modulus of 46.7 GPa, indicating improved structural integrity. Scanning electron microscopy (SEM) revealed a well-defined porous network. Filtration performance was evaluated using a laboratory-scale dead-end setup for Pb(II) removal. The optimal PVAc concentration was determined to be 20 wt.%, resulting in a permeation rate of 78.5 L/(m·h) and an 87% rejection rate at an initial Pb(II) concentration of 50 ppm. With increasing Pb(II) concentrations, the flux rates declined across all membranes, while maximum rejection was achieved at 200 ppm. FTIR and EDS analyses confirmed Pb(II) adsorption onto the zeolite-based geopolymer matrix, with elemental mapping showing a uniform Pb(II) distribution across the membrane surface. The next step is to evaluate the membrane's performance in a multi-cation water treatment environment, assessing the sorption kinetics and its selectivity and efficiency in removing various heavy metal contaminants from complex wastewater systems.
本研究探索了一种由废弃天然沸石粉制成的用于去除Pb(II)的创新型多孔地质聚合物膜的制备、结构特性及性能，其在废水处理方面具有潜在应用价值。合成了一种包含聚醋酸乙烯酯（PVAc）（10 wt.%、20 wt.%和30 wt.%）的复合地质聚合物膜，并在300℃下进行热处理以实现可控的多孔结构。包括傅里叶变换红外光谱（FTIR）在内的表征技术显示，特征性的C=O和C-H伸缩振动带（分别约为1730 cm和2900 cm）消失，证实了PVAc的完全降解。热重分析（TG）和差示扫描量热法（DSC）表明，含20 wt.% PVAc的样品总质量损失约为14.5%，这对应于PVAc的分解和水分损失。能量色散光谱（EDS）元素映射显示退火后无碳残留，进一步验证了PVAc的完全去除。X射线衍射（XRD）提供了对原始沸石和地质聚合物结构结晶相的洞察。确认PVAc去除后，表征的第二阶段评估了膜的机械性能和过滤性能。经热处理的膜厚度为2.27 mm，用纳米压痕仪测量显示其机械性能增强，硬度为1.8 GPa，弹性模量为46.7 GPa，表明结构完整性得到改善。扫描电子显微镜（SEM）揭示了一个轮廓清晰的多孔网络。使用实验室规模的死端装置评估了去除Pb(II)的过滤性能。确定最佳PVAc浓度为20 wt.%，在初始Pb(II)浓度为50 ppm时，渗透速率为78.5 L/(m²·h)，截留率为87%。随着Pb(II)浓度增加，所有膜的通量率均下降，而在200 ppm时达到最大截留率。FTIR和EDS分析证实了Pb(II)吸附在基于沸石的地质聚合物基质上，元素映射显示Pb(II)在膜表面分布均匀。下一步是评估该膜在多阳离子水处理环境中的性能，评估吸附动力学及其从复杂废水系统中去除各种重金属污染物的选择性和效率。
