Barbituric acid derived covalent organic framework and its CNT composite as high-performance adsorbents for organic dye removal

Abstract

Herein, we report for the first time, the synthesis of Barbituric acid (BA) based Covalent Organic Framework (COF) and its composite with Carbon NanoTubes (CNT), for efficient and selective dye removal. The adsorbents were characterized using solid state 13C NMR, PXRD, FT-IR, BET, FEG-SEM and TGA. Higher porosity and surface area facilitates efficient adsorption process. Batch experiments for dye adsorption were performed for Malachite Green (MG) and Methyl Orange (MO) as well as mixed dye to determine the adsorption capacity, removal efficiency and adsorption mechanism. The experimental results best fits Langmuir isotherm model and follows Pseudo second order kinetics. The maximum adsorption capacity was as high as 553.55 mg/g and 226.12 mg/g for MG and MO respectively, using COF. The COF-CNT composite showed even higher values viz. 603.91 mg/g and 234.57 mg/g for MG and MO. Moreover, the adsorption performance of these adsorbents in binary dye mixture exhibited the potential of COF for dye separation and that of COF-CNT for simultaneous dye removal. Thermodynamic studies demonstrated endothermic and spontaneous adsorption process. The regeneration studies reveal the potential of these adsorbents to be reused for multiple cycles. These adsorbents with high adsorption efficiency can act as promising and recyclable materials for practical wastewater treatment.