Reversible conversion superwetting coating with co/Zn bimetallic MOFs-based composites for efficient recovery and purification of oily wastewater

Carboxylated modified cotton fabrics via a diazotization reaction followed by in-situ growth of Co/Zn bimetallic MOFs. • The coating surface achieved a separation efficiency of over 99% for heavy-density oil/water mixtures and over 97% for light-density oil/water mixtures. • Degradation of most dyes and antibiotics by light and PMS activation synergistic catalysis. • Active sites of molecular structure and ecotoxicity of degradation products were investigated by DFT and T.E.S.T., respectively. In this paper, a diazotization reaction was first used to introduce carboxyl groups on the surface of cotton fabrics, and then Co/Zn bimetallic metal organic frameworks (MOFs)-based ZIF-67/8 were in-situ grown on the carboxylated cotton fabrics. Subsequently, 3-mercaptopropyltriethoxysilane (MPTES) formed a covalent bond with 10-undecenoic acid (UA) through a photo-initiated thiol-ene click reaction, and after the addition of polymethylhydrosiloxane (PMHS), it formed a strong covalent bond with the hydroxyl groups on cotton fibers through a hydrolysis condensation reaction. Hence, a polymer-functionalized Co/Zn bimetallic MOFs-based superwetting cotton fabric coating surface (PMHS/UA/ZIF-67/8-CF) was obtained. Polymer-functionalized MOFs coatings, exhibiting wettability reversible conversion capability, are favorable for the separation of different types of oil/water mixtures and maintaining excellent separation performance. Furthermore, the Co/Zn bimetallic MOFs exhibited efficient degradation by a dual-path mechanism through synergistic light-driven charge separation and PMS (peroxymonosulfate) activation. It exhibited excellent catalytic degradation properties for dyes such as phenothiazines, xanthenes, and azo compounds, as well as tetracene derivative antibiotics. In addition, the active sites of the molecular structure and the catalytic degradation pathways were investigated using density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) analysis, respectively. Ultimately, the toxicity of methylene blue (MB) and its degradation products was evaluated using the toxicity estimation software tool (T.E.S.T.). This work presents a promising research strategy for environmental wastewater treatment, demonstrating the potential of functional coatings with reversible conversion wettability and properties for degrading organic pollutants. Download: Download high-res image (416KB) Download: Download full-size image