Constructing discontinuous silicon-island structure with low surface energy based on the responsiveness of hydrophilic layers to improve the anti-fouling property of membranes

• Published in: Journal of membrane science 2022-10, Vol.659, p.120770, Article 120770
• Main Authors: Ma, Ronghua, Lu, Xiaolong, Zhang, Shaozhe, Ren, Kai, Gu, Jie, Liu, Chao, Liu, Ziqiang, Wang, Hanli
• Format: Article
• Language: English
• Subjects: Anti-oil-fouling; Cleaning pH-responsiveness; Hydrophobic/underwater super-oleophobic; Oil-water separation; Silicon-island structure
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2022.120770

In recent years, membrane separation technology has been widely used in various fields. And for the increasingly severe oily wastewater system, there is an increasing demand for the anti-fouling properties of the membranes. Based on the concept of fluorine-free, non-toxic, environmental-friendly and low-cost, this study constructed a discontinuous silicon-island structure with low surface energy on the surface of the hydrophilic membrane, which endows the PVDF-CTFE membrane with fouling resistance and cleaning pH-responsiveness. The discontinuous silicon-island structures were constructed by introducing SiO2 nanoparticles on the super-hydrophilic layer of the PVDF-CTFE membrane modified by itaconic acid, and then hydrophobically treated with polydimethylsiloxane (PDMS). The experimental results exhibited that the modified membrane reached the hydrophobic and underwater super-oleophobic state when treated by PDMS for 1.0 h. The water contact angle (WCA) and the underwater oil contact angle (OCA) were 124° and 151°, respectively. Furthermore, the water flux remained at 186 L m−2 h−1 with no serious pore-plugging. Moreover, the water flux decay rate (FDR) remained below 19.6%, when modified membrane treating soybean oil/water emulsion for 6 cycles, presenting an excellent anti-fouling performance. Additionally, the water flux recovery rate (FRR) was over 99.3% after alkali cleaning, indicating the modified membrane possessed excellent cleaning pH-responsiveness. The above analysis exhibited that the synergistic effect of hydrophilic micro-domains and oleophobic micro-domains not only slows down the attachment of hydrophobic pollutants but also promotes the separation of hydrophobic pollutants during chemical cleaning, which greatly improves its anti-fouling performance and expands its application prospect. [Display omitted] •The discontinuous silicon-island structure with low surface energy was constructed based on the super-hydrophilic layer.•The anti-oil-fouling performance of the modified membrane was significantly improved.•Hydrophilic base membrane retained pH-responsiveness for cleaning.•Silicon-island structure was constructed with SiO2-PDMS to avoid the use of toxic compounds containing “fluorine".