Enhanced removal of basic dye using carbon nitride/graphene oxide nanocomposites as adsorbents: high performance, recycling, and mechanism.

The presence of dyes in wastewater streams poses a great challenge for sustainability and brings the need to develop technologies to treat effluent streams. Here, we propose a mixture of high superficial area carbon-based nanomaterial strategy to improve the removal of basic blue 26 (BB26) by blending porous carbon nitride (CN) and graphene oxide (GO). We prepared CN and GO pristine materials, as well the nanocomposites with mass/ratio 30/70, 50/50, and 70/30, and applied them into BB26 uptake. Nanocomposite 50/50 CN/GO was found to be the better adsorbent, and the optimization of the adsorption revealed a fast equilibrium time of 30 min, after sonication for 2 min, nanocomposite 50/50, and BB26 dye loading of 0.1 g/L and 100 mg/L, respectively. The pH variation had great influence on BB26 uptake, and at ultrapure water pH, the dye removal capacity by the composite reached 917.78 mg/g. At pH 2, a remarkable removal efficiency of 3510.10 mg/g was obtained, probably due to electrostatic interactions among protonated amine groups of the dye and negatively charged CN/GO nanocomposite. The results obtained were best fitted to the pseudo-second-order kinetic model and the Dubinin-Radushkevich isotherm. The adsorption process was thermodynamically spontaneous, and physisorption was the main mechanism, which is based on weak electrostatic and π-π interactions. The dye attached to the CN/GO nanocomposite could be removed by washing with ethyl alcohol, and the adsorbent was reused for five consecutive cycles with high BB26 uptake efficiency. The CN/GO nanocomposite ability to remove the BB26 dye was 21 times higher than those reported in the literature, indicating CN/GO composites as potential filtering materials to basic dyes.