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Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light.

Xu X, Ji F, Fan Z, He L - Int J Environ Res Public Health (2011)

Bottom Line: Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2).The thinner the soil is, the better the glyphosate degradation is.Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China. xuxuan@cqu.edu.cn

ABSTRACT
In this study, Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst was prepared via a sol-gel method, and Fe(3)O(4) particles were used as the core of the colloid. Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2). FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe(3)O(4) loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst, whereas photocatalysts modified by Fe(3)O(4)/SiO(2) present excellent visible light absorption performance and photocatalytic activity, especially when the Fe(3)O(4) loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe(3)O(4)/SiO(2)/TiO(2) has the best photocatalytic activity. The best moisture content of soil is 30%~50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

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Effact of soil thickness on glyphosate degradation: (a) Degradation curve; (b) Degradation mass curve.
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f8-ijerph-08-01258: Effact of soil thickness on glyphosate degradation: (a) Degradation curve; (b) Degradation mass curve.

Mentions: Soil samples (25 g, 50 g, 75 g, 100 g and 150 g) were placed separately in five glass dishes (120 mm diameter). Photocatalyst (0.5% Fe3O4/SiO2/TiO2) dosage and glyphosate standard stock solution amounts were 0.4 g/100 g (soil) and 4 mL/100 g (soil), respectively. Moisture content of soil was raised to 40%. The thicknesses of these samples were 2.2 mm, 4.1 mm, 6.2 mm, 8.4 mm and 10.5 mm after tiling. Degradation of glyphosate is shown in Figure 8(a) (sunlight intensity was 11.97 mW/cm2). In view of this figure, we can simply conclude that the thicker the sample was, the lower the degradation rate was, as 87.33% glyphosate was removed after 2 h irradiation when the soil thickness was 2.2 mm., whereas on the contrary, the removal rate was reduced to 38.21% when thickness was 10.5 mm. This is because the sunlight cannot reach deep inside the soil, so the necessary conditions for the photocatalytic degradation in this part of soil are absent and suggesting that the photocatalytic reaction only occurs in the surface part of soil and degradation decreases as the soil layer becomes thicker.


Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light.

Xu X, Ji F, Fan Z, He L - Int J Environ Res Public Health (2011)

Effact of soil thickness on glyphosate degradation: (a) Degradation curve; (b) Degradation mass curve.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3118888&req=5

f8-ijerph-08-01258: Effact of soil thickness on glyphosate degradation: (a) Degradation curve; (b) Degradation mass curve.
Mentions: Soil samples (25 g, 50 g, 75 g, 100 g and 150 g) were placed separately in five glass dishes (120 mm diameter). Photocatalyst (0.5% Fe3O4/SiO2/TiO2) dosage and glyphosate standard stock solution amounts were 0.4 g/100 g (soil) and 4 mL/100 g (soil), respectively. Moisture content of soil was raised to 40%. The thicknesses of these samples were 2.2 mm, 4.1 mm, 6.2 mm, 8.4 mm and 10.5 mm after tiling. Degradation of glyphosate is shown in Figure 8(a) (sunlight intensity was 11.97 mW/cm2). In view of this figure, we can simply conclude that the thicker the sample was, the lower the degradation rate was, as 87.33% glyphosate was removed after 2 h irradiation when the soil thickness was 2.2 mm., whereas on the contrary, the removal rate was reduced to 38.21% when thickness was 10.5 mm. This is because the sunlight cannot reach deep inside the soil, so the necessary conditions for the photocatalytic degradation in this part of soil are absent and suggesting that the photocatalytic reaction only occurs in the surface part of soil and degradation decreases as the soil layer becomes thicker.

Bottom Line: Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2).The thinner the soil is, the better the glyphosate degradation is.Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China. xuxuan@cqu.edu.cn

ABSTRACT
In this study, Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst was prepared via a sol-gel method, and Fe(3)O(4) particles were used as the core of the colloid. Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2). FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe(3)O(4) loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst, whereas photocatalysts modified by Fe(3)O(4)/SiO(2) present excellent visible light absorption performance and photocatalytic activity, especially when the Fe(3)O(4) loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe(3)O(4)/SiO(2)/TiO(2) has the best photocatalytic activity. The best moisture content of soil is 30%~50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

Show MeSH