10.57647/ijc.2026.1601.05

Enhanced Photocatalytic Degradation of Turquoise Blue G (TBG) Dye Using Cu:ZnO/TiO2 Nanoheterojunction Photocatalyst

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  • Mangesh K. Lanjewar1,
  • Omprakash K. Mahadwad*2,
  • Pritam Patil3,
  1. Gujarat Technological University, Ahmedabad 382424, India
  2. Department of Chemical Technology, UPL University of Sustainable Technology, Ankleshwar 393135, India
  3. Department of Chemical Engineering, Shri S'ad Vidya Mandal Institute of Technology, Bharuch 392001, India

Received: 2025-07-07

Revised: 2025-10-31

Accepted: 2025-11-10

Published in Issue 2026-03-31

Published Online: 2025-11-25

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite

Lanjewar, M. K., Mahadwad, O. K., & Patil, P. (2026). Enhanced Photocatalytic Degradation of Turquoise Blue G (TBG) Dye Using Cu:ZnO/TiO2 Nanoheterojunction Photocatalyst. Iranian Journal of Catalysis, 16(1 (March 2026). https://doi.org/10.57647/ijc.2026.1601.05
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Abstract

Pure TiO2, ZnO, ZnO/TiO2, and Cu doped ZnO/TiO2 (Cu:ZnO/TiO2) heterojunctions (Type II) photocatalysts were successfully synthesized using a cost-effective room-temperature sol-gel (RTSG) method. Copper (Cu) doping levels ranged from 3 to 9 wt% relative to ZnO. The structural, morphological, optical, and surface chemical properties were characterized using XRD, FESEM, UV–Vis spectroscopy, XPS, and FTIR. Among all samples, 7 wt% Cu:ZnO/TiO2 exhibited a prominent red shift in the absorption edge (from 388.7 to 413.33 nm) and a narrowed band gap of 3.0 eV compared to 3.19 eV for pure TiO2, indicating enhanced visible-light absorption. This optimized photocatalyst demonstrated outstanding photocatalytic efficiency for the first-time degradation of Turquoise Blue G (TBG) dye, achieving 95% degradation within 2.5 h under UV irradiation-1.52 times higher than pure TiO2. The Chemical Oxygen Demand (COD) decreased by 77.78%, confirming effective mineralization. Kinetic analysis revealed that the degradation followed pseudo-first-order kinetics, validating the reaction’s rate dependence on dye concentration. The recycled photocatalyst retained 84.3% degradation efficiency and 60% COD reduction, indicating excellent reusability. Furthermore, the highest adsorption capacity was observed at lower pH (pH 4), favoring electrostatic attraction. These results establish 7% Cu:ZnO/TiO2 as a robust, reusable, and highly efficient photocatalyst for sustainable dye wastewater treatment.

Highlights

·        A novel 7% Cu:ZnO/TiO₂ (with copper doping concentrations varying from 3 wt% to 9 wt%) heterojunction (Type II) photocatalyst synthesized via a cost-effective room-temperature sol-gel method.

·        Enhanced visible-light absorption with band gap reduction from 3.19 eV to 3.0 eV.

·        This optimized photocatalyst demonstrated outstanding photocatalytic efficiency for the first-time degradation of Turquoise Blue G (TBG) dye, achieving 95% degradation within 2.5 h under UV irradiation-1.52 times higher than pure TiO2. The Chemical Oxygen Demand (COD) decreased by 77.78%, confirming effective mineralization.

·        Photocatalytic degradation followed pseudo-first-order kinetics with excellent reusability (84.3% after recycling).

·        Maximum adsorption capacity observed at lower pH (pH 4) with COD reduction up to 77.78%.

Keywords

  • Type II heterojunction photocatalyst; Sol-gel method; Turquoise blue G (TBG) dye; Photocatalytic degradation
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