Fabrication of carbonized derivatives from a novel azo polymer as a precursor for the layered adsorption of iodine and bromine

Abstract

A nitrogen-rich polymer (AZO-TPA) was synthesized and employed as a precursor for calcined carbonized derivatives. After this polymer was activated with KOH, it was doped separately with melamine and urea, both of which are rich in carbon and nitrogen, and nine distinct carbonized derivatives were obtained through carbonization at various temperatures. Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) characterization revealed that the carbonized structures were rich in nitrogen functional groups, including pyridinic-N, pyrrolic-N, and N+–O- (nitrogen oxides), and possess additional active sites such as –OH and CO groups. The adsorption of bromine, iodine, and the fractional adsorption of bromine/iodine were investigated via the prepared carbonized derivatives. The results indicated that the polymer was successfully doped with urea and yielded carbonized derivatives at 600 °C (AZO-TPAU-600) which exhibited favorable adsorption capacity, particularly after KOH activation and urea doping (iodine vapor: 2782 mg g−1; bromine/iodine: 1854 and 867.55 mg g−1). In addition, the AZO-TPA-600 exhibited high selectivity for bromine adsorption in I2–Br2/cyclohexane solution, and the carbonized derivatives loaded with iodine/bromine could be efficiently desorbed via organic solvents, the adsorption capacity remains above 75 % even after 4 cycles. Finally, the adsorption mechanism was explained in detail.