Comparison as Effective Photocatalyst or Adsorbent of Carbon Materials of One, Two, and Three Dimensions for the Removal of Reactive Red 2 in Water

摘要

Photocatalytic degradation and removal by adsorption of the Reactive Red 2 (RR2) dye in the presence of different pristine and functionalized one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) carbon structures were investigated and compared, considering also the loading of catalyst/adsorbent. Previous to photocatalytic and adsorption evaluation, all carbon materials were characterized to verify functionalization, structural changes, and surface properties useful in the removal of this pollutant in water. Materials were analyzed by Raman and infrared spectroscopies, transmission electron microscopy, and besides, the pH of the point of zero charge (pH(pzc)) was determined by potentiometric titrations, and band gap by ultraviolet-visible spectroscopy through Tauc plot. Removal of RR2 increases with the load of carbon materials. One-dimensional materials showed better performance in the decolorization of RR2 dye, removing the whole color of the solution. RR2 removal values obtained by the photocatalytic and adsorption processes are very similar. Thus, the adsorption process predominates over the photocatalytic activity, only the samples of graphene and graphene oxide present slight photocatalytic activity. The adsorption process was strongly influenced by the carbon material dimension. However, other factors like surface oxygenated groups, surface area, and the shape of the carbon structures, as well as the structure and nature of the dye also play an important role in this process. Experimental adsorption data of all carbon materials were best fitted to pseudo second-order kinetic model, and, it is concluded that physisorption with strong interaction is the process by which carbon materials adsorb to the dye. Thus, the mechanism of RR2 adsorption on carbon materials is by the aromatic rings of the RR2 and delocalized electrons on carbon materials.