Chemistry Department, University of the Free State, Bloemfontein, 9300, South Africa.
Chemistry Department, University of the Free State, Bloemfontein, 9300, South Africa; Department of Pure & Industrial Chemistry, University of Nigeria, Nsukka, Nigeria.
J Environ Manage. 2022 Feb 15;304:114166. doi: 10.1016/j.jenvman.2021.114166. Epub 2021 Dec 1.
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 (Al-AZB) and Zr (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/g) than the Zr-AZB (1098 m/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm/g and 0.35 cm/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.
金属有机骨架（MOFs）如 ZIF、MIL 和 UiO 型在染料吸附方面的高效性已经得到证实。最近，一类新兴的光响应型偶氮苯基 MOFs 在气体吸附方面找到了合适的应用。然而，关于它们在染料和其他水污染物吸附中的应用研究却很少。在这项研究中，合成了两种微孔光响应型偶氮苯二羧酸酯 MOFs，即 Al（Al-AZB）和 Zr（Zr-AZB），用于吸附刚果红（CR）染料。通过 FTIR、PXRD、SEM、TGA、BET 和孔径分析对合成的 MOFs 的表面和结构特性进行了表征。两种 MOFs 均为结晶态，在 300°C 以下热稳定，在室温下在水介质中稳定。Al-AZB 的比表面积（2718 m/g）高于 Zr-AZB（1098 m/g），这显著影响了 CR 的更高吸附。此外，Al-AZB 和 Zr-AZB 的孔体积分别为 0.86 cm/g 和 0.35 cm/g。Al-AZB 和 Zr-AZB 的最大吸附容量分别为 456.6 mg/g 和 128.9 mg/g，前者优于其他有潜力的吸附剂。准二级和 Langmuir 模型与 MOFs 上的染料吸附具有良好的相关性。热力学表明，CR 的吸附是随机的、吸热的，主要是化学吸附，而使用二甲基甲酰胺作为洗脱剂可以有效地再生和重复使用两种 MOFs。结果证明了合成的光响应 MOFs 作为高效、可重复使用的染料吸附材料的潜力。
