Microsphere pyridine-based covalent organic polymer for efficient methyl orange dye removal: Synthesis, characterization, and adsorption performance

Covalent organic polymers (COPs) are supposed to be propitious adsorbents for uptaking hydrosphere pollutants due to their unrivaled features including high stability, porous structure, and tunable surface functionality. Therefore, in this effort we aimed at forming a microsphere shaped pyridine-based COP through a new synthetic method. Many identification techniques including FT-IR, XRD, FE-SEM/EDS, zeta potential, BET, and TGA were employed to validate the successful construction of this nitrogen-rich polymer. Moreover, its capability for the uptake of methyl orange (MO) dye was evaluated. Based on the experimental results, the maximum adsorption capacity (q_max) of this prepared adsorbent under pH = 4, adsorbent amount = 6 mg, initial dye concentration = 200 mg/L, and time contact = 1.5 h conditions was obtained 113.8 mg/g. After determining the regression coefficient (R²) values, it was disclosed that the experimental data were matched well with the Langmuir model, representing the monolayer adsorption. Besides, no meaningful preference was observed toward PSO and PFO kinetic models, suggesting the adsorption proceeds through both physical and vigorous chemical interactions. Additionally, according to the thermodynamic investigations, the adsorption process is spontaneous and endothermic. These experimental findings and the various models examined, highlight the nitrogen-rich porous polymer as an effective candidate for the removal of methyl orange dye from effluent discharged into the aquatic environment by textile factories.