High Uptake of the Carcinogenic Pararosaniline Hydrochloride Dye from Water Using Carbazole-Containing Conjugated Copolymers Synthesized from a One-Pot Cyclopentannulation Reaction

Three conjugated copolymers CAP1-3 were synthesized in one-step via a typical [3+2] cyclopentannulation reaction using a specially designed diethynyl carbazole synthon with various dibrominated polycondensed aromatic hydrocarbons (PAHs). The desired copolymers CAP1-3 were obtained in excellent yields, and their structures were confirmed by 1H- and 13C- nuclear magnetic spectroscopy (NMR), whereas gel permeation chromatography revealed weight-average molar masses (Mw) up to 19.9 kDa with a polydispersity index (PDI) in the range of 2.2-2.6. Interestingly, CAP1-3 exhibits an outstanding capacity to adsorb the carcinogenic pararosaniline hydrochloride dye (Basic Red 9, BR9) from aqueous solutions. Isothermal adsorption studies were carried out following the linear models of Langmuir and Freundlich, divulging an adsorption capacity maximum (qm) toward BR9 of 483.09 mg g-1. Investigation of the dye uptake mechanism on CAP1-3 revealed a pseudo-second-order kinetic model for the target copolymer that showed the highest uptake capacity. Recyclability tests disclosed an excellent adsorption efficiency of BR 9 reaching 93% after six cycles.