Fabrication of surface alkalinized g-C3N4 and TiO2 composite for the synergistic adsorption-photocatalytic degradation of methylene blue

This work reports the fabrication of alkalinized g-C3N4 and its composite with TiO2 via recrystallization-annealing strategy. The increased surface basicity boosted the fast adsorptive removal of methylene blue (MB) while the cooperated TiO2 enhanced the degradation of adsorbed MB via photocatalysis. The synthesized materials were characterized by XPS, SEM, TEM, PXRD, BET surface area, FT-IR, EDX and TG analyses. TiO2 nanoparticles were uniformly distributed in the framework of alkalinized g-C3N4 which increased the surface area of g-C3N4. Na was incorporated into g-C3N4 via thermal treatment, and the bond between C and N was dissociated while that between C OH was formed. The alkaline and negatively charged surface of g-C3N4 upon Na addition established a strong electrostatic interaction adsorption scenario with MB leading to higher adsorption efficiency of TiO2/Na-g-C3N4 (90%) than pristine g-C3N4 (80%). MB removal efficiency was further intensified (from 90% to 100% within 120 min) upon the sequential operation of adsorption followed by photocatalytic degradation over TiO2/Na-g-C3N4 under visible light irradiation. This study can be deemed of potential applications for the removal of MB and similar dyes on industrial level using the newly synthesized TiO2/Na-g-C3N4 and synergistic adsorption-photocatalytic oxidation approach.