Activated carbon obtained from coffee husk waste activated by CaCl2 as support of TiO2 for the enhanced photocatalytic degradation of Victoria Blue B dye

Abstract

In this study, we demonstrated the viability of the production of activated carbon (AC) from coffee husk waste and their activation using CaCl2. In addition, the prepared AC was used as support for TiO2, and the TiO2/AC composite was employed as a photocatalyst in the Victoria Blue B (VBB) photodegradation. Specifically, the coffee husk was carbonized at 800 °C for 1 h and then activated with CaCl2 at 850 °C, varying the heating time by 0.5, 1, 2, and 4 h. The activated carbons (ACs) treated within 1 and 2 h presented the highest surface area and were used to support TiO2 prepared by the sol-gel method. The surface area did not decrease after dispersion, keeping about 700 m2.g−1, which suggested the uniform distribution of TiO2 onto the surface of the ACs, confirmed by SEM and TEM analysis. In addition, TEM analyses revealed a small particle size distribution of TiO2 nanoparticles (3.4 nm for TiO2/AC_1_350 and 4.8 nm for TiO2/AC_2_350), indicating that they do not have enough dimensions to block the AC pores structure. X-ray diffraction, TGA, and XPS analyses revealed the combination of TiO2 nanoparticles with AC, generating a hybrid material. The photocatalytic activity of the TiO2/AC composite is very fast, removing about 99 % of the VBB dye after 120 min of photocatalytic degradation. The recyclability of the TiO2/AC catalyst was also evaluated in three consecutive reactions, showing that the nanocomposite could be used for multiple degradations without a decrease in photocatalytic activity. Thus, this study proved the feasibility of using coffee husk wastes for AC preparation and its use as a photocatalyst in conjunction with TiO2.