Fabrication of Covalent Organic Framework-based Composite as Advanced Adsorbent for Removal of Cationic and Anionic Dyes from Water

Many industries give rise to dye-bearing effluents in their production processes. Textile industries, particularly, are major consumers of water and release a fair amount of color in their effluents. Adsorption techniques have been widely applied to the treatment of industrial wastewater [1]. In this work, the porous covalent organic framework-based (COF) composite which its structure was shown in Fig. 1 with superiorchemical stability and large surface area was synthesized. It was used as sorbents for simultaneous removal of harmful anionic and cationic dyes (tartrazine (Tart) and methylene blue (MB)) from aqueous solutions. The adsorption efficiency was followed by UV-Vis spectroscopy. Some methods such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, FT-IR, dynamic light scattering and zeta potential were used for characterization the adsorbent. The effects of pH and composition of composite on removal efficiency were examined. Higher removal efficiency was obtained at pH=10 for MB and pH=4 for Tart. Fifty percent of COF was selected as optimum composition of the composite. Adsorption kinetics and isotherm parameters were determined from the experimental data.Two models of first order, second order were used for kinetic and four model of Lungmuir, Freundlich, Temkin and D-R were fitted for isotherms. Based on experimental data removal of Tart was followed by second order and Freundlich model. Also, removal of MB was followed by second order and Lungmuir model. This advanced composite can remove both of cationic and anionic dyes at pH=7 with removal efficiency higher than 99.7% for MB with qm=151.5 mg/g and 80% for Tart with KF=24.7 ((mg/g)(L/mg)1/n).The results indicate that this composite adsorbs both MB and Tart efficiently and could be employed as effective adsorbent in wastewater treatment for the removal of cationic and anionic dyes.