Dye adsorption of aluminium- and zirconium-based metal organic frameworks with azobenzene dicarboxylate linkers. (15th February 2022)

• Record Type: Journal Article
• Authors: Mogale, Refilwe; Akpomie, Kovo G.; Conradie, Jeanet; Langner, Ernst H.G.
• Is Part Of: Journal of environmental management. Volume 304(2022)
• Publication Date: 2022-02-15
• Subjects: azobenzene -- Metal-organic-frameworks -- Pore size distribution -- Dye -- Water stability; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.114166
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al 3+ (Al-AZB) and Zr 4+ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 ° C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m 2 /g) than the Zr-AZB (1098 m 2 /g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm 3 /g and 0.35 cm 3 /g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption. Graphical abstract: Image 1 Highlights: Syntheses of Zr- and Al-based MOFs with Azobenzene dicarboxylate linkers. Trans-cis photo-isomerization of the MOFs in suspension. Al-based MOF has higher dye adsorption capacity than the Zr-based MOF. Dye adsorption by the MOFs is a pseudo-second order kinetic process. Both MOFs were successfully regenerated and reused for dye adsorption.