Synthesis and Investigation of TiO2/g-C3N4 Performance for Photocatalytic Degradation of Bromophenol Blue and Eriochrome Black T: Experimental Design Optimization and Reactive Oxygen Species Contribution

Graphitic carbon nitride (g-C3N4) based photocatalyst was synthesized and the photocatalytic performance was investigated for the removal of Eriochrome Black T (EBT) and Bromophenol Blue (BPB) under UV irradiation. The prepared materials were characterized by SEM-EDX, XRD, Raman, FTIR and DRS. Higher degradation efficiency for the same initial concentrations of EBT and BPB in presence of TiO2/g-C3N4 have been achieved within 160 min of irradiation. The kinetic study showed that the photodegradation of BPB by TiO2/g-C3N4 follows pseudo-first-order kinetics with an R2 value of 0.98. The addition of persulfate (PS) in BPB solution improved the degradation yield from 8.81% to 80.14% within 20 min of UV light irradiation. A Box-Behnken model was developed from three factors and Response surface methodology (RSM) was employed to identify the optimum conditions for the treatment of BPB solution by TiO2/g-C3N4. The experimental values of degradation of BPB agreed with predicted values obtained from central composite design (CCD) analysis with an R2 value of 0.9999. The scavenger study revealed that superoxide radical anion (O2•−) plays a key role (68.89% of contribution) followed by OH• and h+ with 22.40% and 15.55% of contribution, respectively. This study has obviously exhibited the potential of TiO2/g-C3N4 composite as a promising catalyst for photocatalytic purposes.