(559d) Construction of a Stable ZIF-8 Layer on Ultrafiltration Membrane to Achieve Long-Term Fouling Resistance for Efficient Treatment of Produced Water

The produced water (PW) is being generated in an enormous amount as a byproduct during the extraction processes in the oil and gas industries. PW is devastating aquatic life and human life to a significant extent [Barron et al. Toxicol. Pathol. 40 (2012) 315–320]. The challenge is the adoption of an economically feasible technology for the treatment of PW. Among the various technologies available, membrane technology has proven to be one of the promising, emerging, and sustainable alternatives because it offers several advantages, i.e., compact module design, minimal chemical footprint, scalability, ease of operation, and significant energy efficiency [Jamaly et al. J. Environ. Sci. 37 (2015) 15– 30]. However, designing a high flux fouling-resistant membrane with long-term stable performance for the PW treatment is challenging. Surface modification, owing to facile processing and negligible environmental impact, is one of the preferred methods of membrane modification to improve the antifouling characteristics for the PW treatment applications [Alzahrani et al. J. Water Process Eng. 4 (2014) 107-133]. Several studies utilizing hydrophilic polydopamine as an antifouling coating and silane-based coupling agents have been reported in the literature. Further, polyvinylidene fluoride has been preferentially used as a base membrane for the membrane modification [Jiménez et al. Chemosphere 192 (2018) 186-208, Al-Ghouti et al. J. Water Process Eng. 28 (2019) 222-239, Ahmad et al. Desalination 493 (2020) 114643]. Recently, ZIF-8 nanoparticles have emerged as a promising nanomaterial for membrane modification for wastewater treatment applications due to their numerous advantages [Zhao et al. J. Membr. Sci. 625 (2021) 119158, Zhao et al. J. Membr. Sci. 625 (2021) 119154]. However, maintaining their stability in the long-term is a challenge. Therefore, in this study, a simple method was demonstrated to tailor the surface of a polyacrylonitrile (PAN) ultrafiltration membrane with a stable layer of ZIF-8 nanoparticles via redox-induced graft polymerization. The prepared membrane was referred to as the HyZifG membrane. Compared with the pristine PAN membrane, the HyZifG membrane showed higher hydrophilicity and lower surface roughness, and its pure water flux was also 30% higher. The membrane performance was tested with simulated feed, comprising an oil component, major ions, and a surfactant, at concentrations typical of oilfield PW [Fakhru’l-Razi et al. J. Haz. Mat. 170(2–3) (2009) 530-551]. The HyZifG membrane showed ~100% oil rejection efficiency and excellent antifouling property (>98% flux recovery). Interestingly, the modified membrane maintained its separation performance over a half-day-long filtration experiment, indicating its outstanding performance for oilfield produced water treatment. Such a performance was credited to the grafting layer-stabilized ZIF-8 layer, which resisted the attachment of foulants on the membrane surface, and selectivity allowed the water to pass through the membrane while rejecting the oil droplets. Upon comparison with the literature-reported membranes for the long-term oilfield produced water treatment, the HyZifG membrane showed excellent performance in terms of flux recovery ratio and oil rejection efficiency. Thus, the HyZifG membrane prepared via a simple method indicates its potential in treating produced water.