On the use of metal-organic framework-based adsorbent from recycled PET bottles for Eriochrome Black T removal

In this study, a metal–organic framework (MOF) adsorbent from recycled polyethylene terephthalate (PET) bottles was developed to effectively remove Eriochrome Black T (EBT) dye present in synthetic wastewater. A sustainable, “greener” route of MOF synthesis was adopted involving microwave-enabled depolymerization of PET to terephthalic acid (TPA) and conversion of the latter to its organic salt linker form. Results from differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) not only revealed the structure of the as-prepared MOF, but also proved the presence of EBT molecules on the adsorbent during the dye removal process. A ∼77% maximum removal was reached after 90 min and the adsorption was best explained by Langmuir model having 82.5 mg/g maximum monolayer capacity. Kinetic studies also showed the adsorption to be pseudo-second order with a two-stage intraparticle diffusion process. The effective performance of MOF on EBT removal was also verified by the presence of potential adsorbent-adsorbate interactions such as ionic, hydrogen bonding, and π–π stacking. Thus, the as-fabricated PET-derived MOF is considered a decent, value–added material acting as a sustainable adsorbent for organic dyes present in contaminated water.