Khan Imran Ahmad, Khan Asad Ullah, Butt Muhammad Shoaib, Janjua Hussnain Ahmad, Uddin Emad, Deen Kashif Mairaj, Sadiq Rehan, Ahmad Nasir M
School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12 Sector, Islamabad 44000, Pakistan.
Atta Ur Rehman School of Applied Biosciences, National University of Science and Technology (NUST), Islamabad 44000, Pakistan.
ACS Omega. 2025 Jun 26;10(26):28178-28190. doi: 10.1021/acsomega.5c02815. eCollection 2025 Jul 8.
Membrane fouling remains a critical challenge in wastewater treatment that ultimately reduces flux, compromised water quality, and higher operational costs. This study addresses such fouling issues by grafting polyacrylic acid (PAA) polymer brushes onto graphene oxide (GO) via surface-initiated atom transfer radical polymerization (SI-ATRP) and incorporating the functionalized GO-PAA into polyether sulfone (PES) membranes. The functionalized graphene oxide with poly-(acrylic acid) (GO-PAA) was blended into a poly-(ether sulfone) (PES) membrane at different concentrations, and its effects on nanocomposite membrane performance were systematically analyzed. The nanocomposite membranes containing 0.5% GO-PAA demonstrated significant improvements in hydrophilicity and water flux, with a contact angle of 36° and a flux rate of 74 L/m·h at pH 7, compared to the pristine PES membrane with contact angle = 79° and flux rate of 30 L/m·h. Furthermore, the functionalized membranes have exhibited enhanced antifouling properties, with the flux recovery ratio improving from 38% (pristine PES) to 83%. The modified membranes also demonstrated superior dye removal efficiency at neutral pH, with rejection rates of 54% for methylene blue (MB) and 64% for methyl orange (MO) as compared to only 26% and 28% for the pristine membrane, respectively. The availability of hydrophilic groups in the GO and GO-PAA may explain the superiority of the nanocomposite membranes. As the pH shifted from 3 to 11, both water flux and dye rejection exhibited noticeable changes that resulted from the pH-driven structural transformations of the grafted PAA brushes. When the pH reaches 11, the carboxyl groups of PAA undergo deprotonation which induces chain elongation and partial pore blockage due to increase repulsive forces among the negatively charged carboxylate ions, resulting in enhanced dye rejection. Using response surface methodology (RSM), pH and transmembrane pressure were optimized to pH 11 and 6 bar to achieve dye removal efficiencies of 82.5% for MO and 91% for MB. These key experimental observations have provided valuable insights to design high-performance membranes for consideration in wastewater treatment systems.
膜污染仍然是废水处理中的一个关键挑战，它最终会降低通量、损害水质并增加运营成本。本研究通过表面引发的原子转移自由基聚合（SI-ATRP）将聚丙烯酸（PAA）聚合物刷接枝到氧化石墨烯（GO）上，并将功能化的GO-PAA掺入聚醚砜（PES）膜中来解决此类污染问题。将含有聚（丙烯酸）的功能化氧化石墨烯（GO-PAA）以不同浓度掺入聚（醚砜）（PES）膜中，并系统分析了其对纳米复合膜性能的影响。与接触角为79°、通量率为30 L/m·h的原始PES膜相比，含有0.5% GO-PAA的纳米复合膜在亲水性和水通量方面有显著改善，在pH值为7时接触角为36°，通量率为74 L/m·h。此外，功能化膜表现出增强的抗污染性能，通量恢复率从38%（原始PES）提高到83%。改性膜在中性pH值下还表现出优异的染料去除效率，亚甲基蓝（MB）的截留率为54%，甲基橙（MO）的截留率为64%，而原始膜的截留率分别仅为26%和28%。GO和GO-PAA中亲水性基团的存在可以解释纳米复合膜的优越性。随着pH值从3变为11，水通量和染料截留率都出现了明显变化，这是由接枝的PAA刷的pH驱动结构转变引起的。当pH值达到11时，PAA的羧基发生去质子化，由于带负电荷的羧酸根离子之间的排斥力增加，导致链伸长和部分孔堵塞，从而提高了染料截留率。使用响应面方法（RSM），将pH值和跨膜压力优化到pH 11和6 bar，以实现MO的染料去除效率为82.5%，MB的染料去除效率为91%。这些关键的实验观察结果为设计用于废水处理系统的高性能膜提供了有价值的见解。
