The suspended titanium dioxide nanoparticles (TiO₂NPs) become challenging in their large-scale wastewater treatment application due to the issue of separation and recovery after the treatment. Therefore, the designation of visible-light-driven-buoyant photocatalyst is proposed whereby the synthesized carbon (C), nitrogen (N) codoped TiO₂ NPs are immobilized onto the buoyant substrate to degrade diazinon in this work. The fabricated buoyant C,N-codoped TiO₂ NPs was characterized using X-ray diffraction, Fourier transform infrared, UV-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. This work aims to optimize and evaluate the ideal buoyant C,N-codoped TiO₂ NPs with high photocatalytic performance. The different ratios of C/N were performed for codoping of TiO₂ NPs. Preliminary results of the catalysts were obtained, including the bandgap energy of the synthesized catalysts with the ratio of 1%C/4%N, 2%C/3%N, 2.5%C/2.5%N, 3%C/2%N and 4%C/1%N was 2.81, 2.84, 2.89, 2.94 and 2.95 eV, respectively. The introduction of C and N into the photocatalyst contributes to wavelength absorption in the 400-460 nm range (visible light region). Photoluminescence (PL) analysis showed that all synthesized catalyst has a strong PL emission at 450 nm, consistent with their absorption wavelength. Among the synthesized catalysts, C,N-codoped TiO₂ NPs with the ratio of 2%C/3%N exhibited the lowest intensity, indicating the slowest recombination of electron-hole pairs. Consequently, it achieved the highest photocatalytic activity of diazinon under sunlight (89.18%%) within 4 hours. In this study, immobilization of the optimized C,N-codoped TiO₂ NPs onto the different substrates is discussed and their photocatalytic performance using diazinon as the model dye is also compared. Hence, we have offered an efficient fabrication method with optimized and high reusability buoyant photocatalyst. The optimized buoyant C,N-codoped TiO₂ NPs from a facile and cost-effective method that is expected to improve the photocatalytic treatment of wastewater.

Hooi Ling Lee

Universiti Sains Malaysia Pusat Pengajian Sains Kimia

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