The synergistic effect of acid-etched g-C3N4 nanosheets and polyaniline nanofibers for the adsorption and photocatalytic degradation of textile dyes: a study of charge transfer mechanism and intermediate products

Abstract

In this paper, a novel optimized nanocomposite was synthesized using acid-etched g-C3N4 nanosheets (TGCN) and polyaniline (PANI) nanofibers via a facile in situ polymerization method. The physiochemical properties of the TGCN/PANI nanocomposites with the effect of TGCN amount were further investigated using various characterization techniques. The results obtained from the various techniques showed that the optical and chemical properties of the TGCN/PANI nanocomposites were closely dependent on the weight percent ratio of TGCN. The addition of PANI nanofibers in TGCN/PANI nanocomposites led to the increase in the surface area from TGCN to TGCN/PANI nanocomposites. The adsorption and photocatalytic degradation studies were performed for the toxic textiles dyes such as Methyl Orange (MO) and Congo Red (CR) using TGCN and optimized TGCN/PANI nanocomposites viz. TCP30, TCP50 and TCP80. The maximum degradation efficiency obtained by the TCP50 nanocomposites was up to 99.3% (MO) after 25 min and 96.3% (CR) after 150 min, higher than those of the TGCN, TCP30 and TCP80 nanocomposites. This enhanced degradation performance has been attributed to the lower recombination rate of the electron-hole pair, the positive surface charge, the superior absorption of visible light, and the large surface area. The degradation mechanism of CR revealed that the superoxide radicals and holes were the major active species. The degraded products of CR were further studied using LC-MS and the degradation pathway was proposed using an intermediate product study. The effect of pH and reusability of the TCP50 nanocomposite was also studied using the CR dye.