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. 2025 Mar 31;15(7):530.
doi: 10.3390/nano15070530.

Synthesis and Characterization of a Novel Sol-Gel-Derived Ni-Doped TiO2 Photocatalyst for Rapid Visible Light-Driven Mineralization of Paracetamol

Nicola Morante  1 , Katia Monzillo  1 , Vincenzo Vaiano  1 , Zukhra C Kadirova  2 , Diana Sannino  1
Affiliations

Synthesis and Characterization of a Novel Sol-Gel-Derived Ni-Doped TiO2 Photocatalyst for Rapid Visible Light-Driven Mineralization of Paracetamol

Nicola Morante et al. Nanomaterials (Basel). .

Abstract

The increasing presence of pharmaceutical contaminants, such as paracetamol, in water sources necessitates the development of efficient and sustainable treatment technologies. This study investigates the photocatalytic degradation and mineralization of paracetamol under visible light using nickel-doped titanium dioxide (Ni-TiO2) catalysts synthesized via the sol-gel method. The catalysts were characterized through Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and surface area measurements. Ni doping enhanced the visible light absorption of TiO2, reducing its band gap from 3.11 eV (undoped) to 2.49 eV at 0.20 wt.% Ni loading, while Raman analysis confirmed Ni incorporation with anatase as the predominant phase. The Ni(0.1%)-TiO2 catalyst exhibited the highest photocatalytic activity, achieving 88% total organic carbon (TOC) removal of paracetamol (5 ppm) after 180 min under optimal conditions (catalyst dosage, 3 g L-1). Stability tests demonstrated 84% retained efficiency over five cycles, with a kinetic rate constant of 0.010 min-1. Hydroxyl radicals were identified as the main reactive species. The catalyst maintained high performance in tap water, achieving 78.8% TOC removal. These findings highlight the potential of Ni(0.1%)-TiO2 as a cost-effective, visible light-active photocatalyst for the removal of pharmaceutical pollutants, with promising scalability for industrial water treatment applications.

Keywords: Ni-TiO2; catalyst stability; heterogeneous photocatalysis; paracetamol; pharmaceutical pollutants; slurry photoreactor; sol-gel synthesis; visible light driven.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Picture of the experimental apparatus scheme used for the paracetamol degradation tests.
Figure 2
Figure 2
Raman spectra of the undoped and Ni-doped TiO2 photocatalysts.
Figure 3
Figure 3
SEM and EDX of Ni(0.1%)-TiO2 photocatalyst: (a–c) three different magnifications of the aggregates, (d) spectrum sum, (e) titanium distribution, (f) oxygen distribution.
Figure 4
Figure 4
Kubelka–Munk spectra of TiO2 and Ni-doped TiO2 photocatalysts.
Figure 5
Figure 5
(a) Photocatalytic paracetamol degradation for direct photolysis and Ni-doped TiO2 photocatalysts; (b) TOC removal efficiency and apparent paracetamol discoloration kinetic constants for Ni-Doped TiO2 photocatalysts after 180 min of visible light irradiation.
Figure 6
Figure 6
Paracetamol TOC removal efficiency after 180 min under visible light, and apparent kinetic constant of degradation (k) values obtained by the stability tests.
Figure 7
Figure 7
(a) Paracetamol degradation registered for different photocatalyst dosages; (b) TOC removal efficiency after 180 min of irradiation and apparent kinetic degradation constant values obtained for different photocatalyst dosages.
Figure 8
Figure 8
(a) Paracetamol degradation for different initial pollutant concentrations; (b) TOC removal efficiency after 180 min of irradiation and apparent kinetic degradation constant values obtained for different initial paracetamol concentrations.
Figure 9
Figure 9
(a) Paracetamol degradation registered for the scavenger tests; (b) TOC removal efficiency after 180 min of irradiation and apparent kinetic degradation constant values obtained from the scavenger tests.
Figure 10
Figure 10
Proposed mechanism for charge carrier generation and reactive oxygen species (ROS) formation on the surface of Ni(0.1%)-TiO2 during the photocatalytic mineralization of paracetamol under visible light irradiation.
Figure 11
Figure 11
(a) Paracetamol degradation registered for the tests with different water matrix nature; (b) TOC removal efficiency after 180 min of irradiation and apparent kinetic degradation constant values obtained from tests with different water matrix nature.
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