Preparation of pyridine based porous organic polymers as new adsorbents to remove Congo red dye from aqueous media

Existence of pollutants in water sources is a global worry that needs the expansion of novel and efficient solutions. This study aimed to synthesize porous organic polymers (POPs) from triazine and di-aminopyridine to effectively eliminate the Congo red (CR) dye from water environments. Two porous organic polymers based on imine (POP-IB) and amine (POP-AB) groups were synthesized from the reaction of diamino-pyridine with trialdehyde for POP-IB and cyanuric chloride for POP-AB. The synthesized POPs were charactized by different techniques and exhibit good thermal and chemical stability, rendering them ideal for the removal of CR dye from aqueous solutions. Additionally, our study examined the optimization process, which involved adjusting various parameters such as pH, time duration, initial dye concentration, and the amount of adsorbent. The study showed that the maximum adsorption capacities for the CR dye were 104 mg g-1 with POP-IB at pH 6 over 240 min, and 63 mg g-1 with POP-AB at pH 5 over 180 min, respectively. Kinetic models suggest that the adsorption of CR dye onto these adsorbents is most accurately described by the pseudo-second-order. Moreover, the Langmuir isotherm provides the closest correlation with the adsorption isotherms for both POPs.