Efficient adsorption of methyl orange and methylene blue dyes by a novel carbazole-based hyper-crosslinked porous polymer

Abstract In this paper, a new type of carbazole-based hyper-crosslinked porous polymer (HCP-CP) was prepared through a very simple “knitted” method. The carbazole and pyrrole as the aromatic building blocks was knitted by the methylene bond under the anhydrous FeCl3 as catalyst. The obtained novel polymer HCP-CP has a good adsorption properties of methyl orange (MO) and methylene blue (MB) organic dyes in aqueous solution due to its high surface area and rich nitrogen atoms. The effect of pH, adsorption time, different initial concentration of dyes and adsorption recycle performance were investigated in detailed. The optimum pH is 8 for the adsorption of MB and 6 for the adsorption of MO, respectively. Under the best condition, the Langmuir model fitted the adsorption isotherm well and the adsorption behavior follow pseudo-second-order kinetics. The maximum adsorption capacity of HCP-CP for cationic dye MB (qmax=751.88 mg/g) is more than twice higher than that of anionic dye MO (qmax=274.73 mg/g).These capacity differences may be owing to the stronger electrostatic interaction between the negatively charged nitrogen atoms of HCP-CP with the cationic dye MB than that of MO. Moreover, the used polymer HCP-CP still retain a removal percentage above 92% after 5 times adsorption-desorption recycle. Therefore, this work provided a convenient synthetic route to develop a novel hyper-crosslinked polymer with high capacity for the entrapment of dyes from aqueous solution.