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

Graphical abstract Highlights • A recrystallization-annealing strategy was developed to fabricate alkalinized g-C 3 N 4 and TiO 2 composite. • The C N bond was dissociated while C OH was formed. • Synergetic effect of adsorption and photocatalysis enhanced the degradation of methylene blue. Abstract This work reports the fabrication of alkalinized g-C 3 N 4 and its composite with TiO 2 via recrystallization-annealing strategy. The increased surface basicity boosted the fast adsorptive removal of methylene blue (MB) while the cooperated TiO 2 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. TiO 2 nanoparticles were uniformly distributed in the framework of alkalinized g-C 3 N 4 which increased the surface area of g-C 3 N 4. Na was incorporated into g-C 3 N 4 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-C 3 N 4 upon Na addition established a strong electrostatic interaction adsorption scenario with MB leading to higher adsorption efficiency of TiO 2 /Na-g-C 3 N 4 (90%) than pristine g-C 3 N 4 (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 TiO 2 /Na-g-C 3 N 4 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 TiO 2 /Na-g-C 3 N 4 and synergistic adsorption-photocatalytic oxidation approach. [ABSTRACT FROM AUTHOR]