{"title":"Photocatalytic degradation of methylene blue using TiO2 nanoparticles synthesized via the sol–gel method in acidic and neutral media","authors":"Souad Laghrib, Chems Eddine Gherdaoui, Ouafia Belgherbi, Naziha Benaskeur, Mokhtar Boudissa, Arjunan Kanagaraj, Noufel Aouffa","doi":"10.1007/s11144-025-02816-0","DOIUrl":null,"url":null,"abstract":"<div><p>Titanium oxide (TiO₂) is widely employed in medical and environmental applications, sensors, and photocatalysis due to its exceptional optical and chemical properties. However, the efficiency of current organic contaminant treatment technologies remains limited, particularly in achieving high photocatalytic activity under controlled conditions. This study addresses this gap by synthesizing TiO₂ powders using the sol–gel method in acidic and neutral media, investigating the effects of annealing temperature and solution nature on their structural, morphological, and optical properties, as well as their photocatalytic performance in methylene blue (MB) degradation. X-ray diffraction (XRD) analysis revealed that at annealing temperatures above 400 °C, only the anatase phase was observed, whereas increasing the temperature to 700 °C led to the predominant formation of the rutile phase in both media. Crystallite size increased with temperature, influencing the material’s photocatalytic efficiency. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of characteristic TiO₂ chemical bonds, some of which disappeared at elevated temperatures. Scanning electron microscopy (SEM) indicated the formation of spherical TiO₂ nanoparticles, while UV–Vis diffuse reflectance spectroscopy (DRS) demonstrated a bandgap energy reduction from 3.33 to 3.29 eV in acidic medium and from 3.17 to 3.13 eV in neutral medium with increasing temperature. Photocatalytic activity tests showed that TiO₂ powders synthesized in neutral medium exhibited superior degradation efficiency compared to those prepared in acidic medium, attributed to their smaller crystallite size. The catalysts prepared at 500 °C in acidic conditions and at 700 °C in neutral conditions demonstrated the highest MB degradation efficiency, with corresponding rate constants. Scavenger tests identified hydroxyl radicals (OH⋅) as the dominant reactive species responsible for MB degradation. These findings highlight the influence of synthesis conditions on TiO₂ properties and provide insights for optimizing photocatalysts for organic pollutant removal.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":750,"journal":{"name":"Reaction Kinetics, Mechanisms and Catalysis","volume":"138 3","pages":"1725 - 1745"},"PeriodicalIF":1.7000,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Reaction Kinetics, Mechanisms and Catalysis","FirstCategoryId":"92","ListUrlMain":"https://link.springer.com/article/10.1007/s11144-025-02816-0","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
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Abstract
Titanium oxide (TiO₂) is widely employed in medical and environmental applications, sensors, and photocatalysis due to its exceptional optical and chemical properties. However, the efficiency of current organic contaminant treatment technologies remains limited, particularly in achieving high photocatalytic activity under controlled conditions. This study addresses this gap by synthesizing TiO₂ powders using the sol–gel method in acidic and neutral media, investigating the effects of annealing temperature and solution nature on their structural, morphological, and optical properties, as well as their photocatalytic performance in methylene blue (MB) degradation. X-ray diffraction (XRD) analysis revealed that at annealing temperatures above 400 °C, only the anatase phase was observed, whereas increasing the temperature to 700 °C led to the predominant formation of the rutile phase in both media. Crystallite size increased with temperature, influencing the material’s photocatalytic efficiency. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of characteristic TiO₂ chemical bonds, some of which disappeared at elevated temperatures. Scanning electron microscopy (SEM) indicated the formation of spherical TiO₂ nanoparticles, while UV–Vis diffuse reflectance spectroscopy (DRS) demonstrated a bandgap energy reduction from 3.33 to 3.29 eV in acidic medium and from 3.17 to 3.13 eV in neutral medium with increasing temperature. Photocatalytic activity tests showed that TiO₂ powders synthesized in neutral medium exhibited superior degradation efficiency compared to those prepared in acidic medium, attributed to their smaller crystallite size. The catalysts prepared at 500 °C in acidic conditions and at 700 °C in neutral conditions demonstrated the highest MB degradation efficiency, with corresponding rate constants. Scavenger tests identified hydroxyl radicals (OH⋅) as the dominant reactive species responsible for MB degradation. These findings highlight the influence of synthesis conditions on TiO₂ properties and provide insights for optimizing photocatalysts for organic pollutant removal.
期刊介绍：
Reaction Kinetics, Mechanisms and Catalysis is a medium for original contributions in the following fields:
-kinetics of homogeneous reactions in gas, liquid and solid phase;
-Homogeneous catalysis;
-Heterogeneous catalysis;
-Adsorption in heterogeneous catalysis;
-Transport processes related to reaction kinetics and catalysis;
-Preparation and study of catalysts;
-Reactors and apparatus.
Reaction Kinetics, Mechanisms and Catalysis was formerly published under the title Reaction Kinetics and Catalysis Letters.
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