Enhanced photocatalytic degradation of direct blue 71 dye using TiO₂-PAA-GO composite in aqueous solution

Abstract

In this work, we successfully synthesized a TiO2-PAA-GO hydrogel photocatalyst (GO: graphene oxide; PAA: poly acrylic acid) using a hydrothermal method. The XRD, FTIR, SEM, and XPS results demonstrated the formation of cross-link bond within the TiO2, GO, and PAA nanocomposite. TiO2 nanomaterials, with a particle size of approximately 5 nm, were uniformly distributed on GO layer, and have a high surface area (156 m2/g). We then applied the TiO2-PAA-GO composite to remove direct blue 71 (DB-71) from water, achieving up to 98.16% removal. This success was due to (i) the reduction in bandgap energy, (ii) reduced electron and hole recombination, (iii) increased output of generated electrons, and (iv) high specific surface area. We also investigated the efficiency of DB-71 degradation, considering the initial concentration of DB-71, pH, contact time, catalyst mass, and the role of reactive radicals. After six reaction cycles, over 95% of the DB-71 was removed from the aqueous medium using the TiO2-GO-PAA photocatalyst.