Sono-assisted rapid dye removal by chromium-based metal organic frameworks derived from waste PET bottles: Characterization, kinetics and adsorption isotherms

Dye-contaminated wastewater causes serious environmental and human impacts, like dissolve oxygen deficit and cancer formation. Adsorption; especially sono-assisted adsorption is a cost-effective and clean treatment process for remediation of dye-contaminated wastewater. Metal organic framework (MOF) is an ideal adsorbent because of its extremely high surface area. However, the usage of organic solvent, like DMF would cause secondary pollution. Therefore, a green process for synthesizing of the metal organic framework (MOF): MIL-101(Cr) via waste PET bottle (called PET_MIL-101(Cr)) were developed and integrated sono-assisted adsorption for dye removal. The structure of PET_MIL-101(Cr) was characterized by FTIR, XPS, and XRD. These analytic results supported that MIL-101(Cr) can be successfully synthesized from waste PET bottles within 70.89% of conversion rate. Also, PET_MIL-101(Cr) exhibited microporous property containing 3055.5 m(2)/g of specific surface area. Functionalized PET_MIL-101(Cr), like nitrification (-NO2) and amination (-NH2), contributed additional electrostatic force and hydrogen bonding. According to the Langmuir isotherm model, the adsorption capacity of functionalized PET_MIL-101(Cr) was higher than the intrinsic one. The ligand (terephthalate acid) also generated 7C-7C stacking interaction which compensated the electro-repulsive force between adsorbents (PET_MIL-101(Cr) or functionalized PET_MIL-101(Cr)) and adsorbate (methylene blue, MB). The introduction of ultrasonication can be effectively shorten the saturation time of adsorption from 120 to 1 min. Based on the pseudo-second-order kinetics, sono-assisted adsorption performed 18 folds faster of adsorption rate than traditional adsorption. Moreover, sono-assisted adsorption capacity also can increase 88.7% of traditional adsorption capacity. This work provides an eco-friendly solution to address problematic aqueous contamination.