Abstract
The effect of various factors on the photodecomposition of methylene blue (MB) by iron oxides calcined at various temperatures in various concentrations of oxalate solutions was investigated by illuminating with UV, visible and solar radiation. Iron oxides were prepared by a gel evaporation method and calcined at 200-700 °C. XRD showed that the as-synthesized iron oxides were amorphous, but formed maghemite (γ-Fe2O3) at 200-400 °C and hematite (α-Fe2O3) at ≥500 °C. The effect of the various iron oxides, their contents, the oxalate concentration and wavelength of the light source (UV, visible and solar) were all found to strongly influence MB photodecomposition. The optimal contents of the iron oxides increased greatly from 25 to 2000 mg/L at higher calcining temperatures. The MB photodecomposition rate at each optimal iron oxide content was related to the calcining temperature in the order 700 °C <uncalcined <500 °C <400 °C <300 °C. The MB degradation was confirmed to occur by visible light illumination. Excellent photodecomposition was found at pH 2-5, but the photodegradation decreased greatly at pH > 6, consistent with the presence of iron-oxalate complexes. A much higher concentration of hydroxyl radicals was generated in the present system compared with those from a commercial TiO2 (ST-01), as determined by the coumarin method. Since this process does not require the addition of hydrogen peroxide and shows good efficiency even under solar light, it is an economically viable method for pre-treating and/or decolorizing wastewaters containing dyes.
| Original language | English |
|---|---|
| Pages (from-to) | 2876-2884 |
| Number of pages | 9 |
| Journal | Water Research |
| Volume | 44 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - May 2010 |
| Externally published | Yes |
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Keywords
- Iron oxide
- Methylene blue
- Oxalic acid
- Photodecomposition
- Solar light
ASJC Scopus subject areas
- Water Science and Technology
- Waste Management and Disposal
- Pollution
- Ecological Modelling
Cite this
Various factors affecting photodecomposition of methylene blue by iron-oxides in an oxalate solution. / Gulshan, Fahmida; Yanagida, Sayaka; Kameshima, Yoshikazu; Isobe, Toshihiro; Nakajima, Akira; Okada, Kiyoshi.
In: Water Research, Vol. 44, No. 9, 05.2010, p. 2876-2884.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Various factors affecting photodecomposition of methylene blue by iron-oxides in an oxalate solution
AU - Gulshan, Fahmida
AU - Yanagida, Sayaka
AU - Kameshima, Yoshikazu
AU - Isobe, Toshihiro
AU - Nakajima, Akira
AU - Okada, Kiyoshi
PY - 2010/5
Y1 - 2010/5
N2 - The effect of various factors on the photodecomposition of methylene blue (MB) by iron oxides calcined at various temperatures in various concentrations of oxalate solutions was investigated by illuminating with UV, visible and solar radiation. Iron oxides were prepared by a gel evaporation method and calcined at 200-700 °C. XRD showed that the as-synthesized iron oxides were amorphous, but formed maghemite (γ-Fe2O3) at 200-400 °C and hematite (α-Fe2O3) at ≥500 °C. The effect of the various iron oxides, their contents, the oxalate concentration and wavelength of the light source (UV, visible and solar) were all found to strongly influence MB photodecomposition. The optimal contents of the iron oxides increased greatly from 25 to 2000 mg/L at higher calcining temperatures. The MB photodecomposition rate at each optimal iron oxide content was related to the calcining temperature in the order 700 °C 6, consistent with the presence of iron-oxalate complexes. A much higher concentration of hydroxyl radicals was generated in the present system compared with those from a commercial TiO2 (ST-01), as determined by the coumarin method. Since this process does not require the addition of hydrogen peroxide and shows good efficiency even under solar light, it is an economically viable method for pre-treating and/or decolorizing wastewaters containing dyes.
AB - The effect of various factors on the photodecomposition of methylene blue (MB) by iron oxides calcined at various temperatures in various concentrations of oxalate solutions was investigated by illuminating with UV, visible and solar radiation. Iron oxides were prepared by a gel evaporation method and calcined at 200-700 °C. XRD showed that the as-synthesized iron oxides were amorphous, but formed maghemite (γ-Fe2O3) at 200-400 °C and hematite (α-Fe2O3) at ≥500 °C. The effect of the various iron oxides, their contents, the oxalate concentration and wavelength of the light source (UV, visible and solar) were all found to strongly influence MB photodecomposition. The optimal contents of the iron oxides increased greatly from 25 to 2000 mg/L at higher calcining temperatures. The MB photodecomposition rate at each optimal iron oxide content was related to the calcining temperature in the order 700 °C 6, consistent with the presence of iron-oxalate complexes. A much higher concentration of hydroxyl radicals was generated in the present system compared with those from a commercial TiO2 (ST-01), as determined by the coumarin method. Since this process does not require the addition of hydrogen peroxide and shows good efficiency even under solar light, it is an economically viable method for pre-treating and/or decolorizing wastewaters containing dyes.
KW - Iron oxide
KW - Methylene blue
KW - Oxalic acid
KW - Photodecomposition
KW - Solar light
UR - http://www.scopus.com/inward/record.url?scp=77950954413&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77950954413&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2010.01.040
DO - 10.1016/j.watres.2010.01.040
M3 - Article
C2 - 20188391
AN - SCOPUS:77950954413
VL - 44
SP - 2876
EP - 2884
JO - Water Research
JF - Water Research
SN - 0043-1354
IS - 9
ER -