Synthesis and characterization of a novel fluorene-based covalent triazine framework as a chemical adsorbent for highly efficient dye removal

Covalent organic frameworks (COFs) are known as emerging candidates for textile wastewater treatment due to their high porosity and regular channel structure. In the current paper, a Fluorene-based COF (FLU-COF) was synthesized by a facile method directing a crystalline framework. After a full characterization of the FLU-COF with different methods, its ability in removing Sky Blue A, widely used color in the textile industry, was investigated. Optimizing the parameters effective on the adsorption process by using the Central Composition Design, led to finding the optimal dye removal condition to be as pH 5; temperature: 45 degrees C; absorbent dosage: 0.005 g; and contact time: 60 min. In this condition, the removal efficiency has reached over 99% with a maximum adsorption capacity of 299 mg. g(-1). The adsorption isotherm is consistent with the Langmuir model representing monolayer adsorption. Also, the kinetic investigations show the pseudo-second-order kinetics which means that the chemical interactions play an important role in dye removal. This is of important interest to make a laboratory method into an in-field method. Thus, a low-cost, simple, and portable method was introduced for investigation of the removal of Sky Blue A. In this regard, the ability of FLU-COF in removing dyes from aqueous solutions was examined by the mobile phone colorimetry as an alternative to the time-consuming laboratory methods. The comparison between the obtained results from mobile phone colorimetry and the traditional UV-Vis spectroscopy showed the accuracy of the method.