scholarly journals Impacts of Mixing Mode on Photocatalytic Reduction of Hexavalent Chromium over Titanium Dioxide Nanomaterial under Various Environmental Conditions

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2291
Author(s):  
Chih-Chi Yang ◽  
Khanh-Chau Dao ◽  
Yo-Sheng Lin ◽  
Teng-Yun Cheng ◽  
Ku-Fan Chen ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Hexavalent Chromium ◽  
Species Distribution ◽  
Uv Light ◽  
Photocatalytic Reduction ◽  
Oxygen Effect ◽  
Strong Interactions ◽  
Nitrogen Gas ◽  
Key Factor ◽  
Hole Scavenger

This study explores the effects of initial Cr(VI) concentration, wavelength, hole-scavenger (absence and presence of salicylic acid), and oxygen conditions (aeration by air, nitrogen gas, and mechanical stir only) on photocatalytic reduction of hexavalent chromium over titanium dioxide photocatalyst and the chromic species distribution after photocatalysis. The experimental results show the existence of strong interactions between these factors. The factor of hole-scavenger was more important than the UV light wavelength condition for a reduction of 3 mg Cr(VI) L−1, whereas both factors became important when Cr(VI) concentration increased to 20 mgL−1. The higher the UV wavelength was, the less the amount of chromium retained on the TiO2 surface. The influence of oxygen-containing conditions in the solution on the reduction of 3 mgL−1 Cr(VI) was unobvious, whereas its influence became remarkable for the reduction of 20 mgL−1 Cr(VI) in the presence of SA. The interaction between oxygen-containing factor and other environmental factors, such as Cr(VI) concentration and scavenger presence (SA in this study), is a key factor about the degree of oxygen effect on Cr(VI) photo-reduction and the chromic species distribution. Simple stirring obtained better photocatalytic efficiency than aeration by air or nitrogen gas.

scholarly journals Photocatalytic Reduction of Hexavalent Chromium with Nanosized TiO2 in Presence of Formic Acid

2019 ◽  
Vol 3 (2) ◽  
pp. 33 ◽  
Author(s):  
Jahida Binte Islam ◽  
Mai Furukawa ◽  
Ikki Tateishi ◽  
Hideyuki Katsumata ◽  
Satoshi Kaneco
Keyword(s):  
Titanium Dioxide ◽  
Formic Acid ◽  
Tio2 Nanoparticles ◽  
Hexavalent Chromium ◽  
Oxidation Reaction ◽  
Photocatalytic Reduction ◽  
Nanosized Titanium Dioxide ◽  
Hole Scavenger ◽  
Nanosized Tio2 ◽  
Commercial Tio2

Nanosized titanium dioxide (TiO2) nanoparticles were used for the photocatalytic reduction of hexavalent chromium in the presence of formic acid. The photoreduction of Cr(VI) in the absence of formic acid was quite slow. When formic acid was added in the chromium solution as the hole scavenger, a rapid photocatalytic reduction of Cr(VI) was observed, owing to the consumption of hole and the acceleration of the oxidation reaction. Furthermore, three commercial TiO2 nanoparticles (AEROXIDE® P25; Ishihara Sangyo ST-01; FUJIFILM Wako Pure Chemical Corp.) were evaluated for the photoactivity of reduction of Cr(VI).

Photocatalytic reduction behavior of hexavalent chromium on hydroxyl modified titanium dioxide

2017 ◽  
Vol 206 ◽  
pp. 293-299 ◽  
Author(s):  
Yali Li ◽  
Yingying Bian ◽  
Hongxia Qin ◽  
Yaxi Zhang ◽  
Zhenfeng Bian
Keyword(s):  
Titanium Dioxide ◽  
Hexavalent Chromium ◽  
Photocatalytic Reduction ◽  
Reduction Behavior

scholarly journals A Study on the Photocatalytic Reduction of Some Metal Ions in Aqueous Solution Using UV- Titanium Dioxide System

2019 ◽  
pp. 1-7
Author(s):  
I. O. Ekwere ◽  
M. Horsfall ◽  
J. O. E. Otaigbe
Keyword(s):  
Aqueous Solution ◽  
Titanium Dioxide ◽  
Metal Ions ◽  
Metal Ion ◽  
Uv Light ◽  
Kinetic Studies ◽  
Photocatalytic Reduction ◽  
Alkaline Ph ◽  
Removal Of Metal ◽  
Removal Of Metal Ions

The photocatalytic reduction of Cu (II), Pb (II), Cd (II) and Cr (VI) ions in aqueous solution has been investigated. The photocatalyst utilized was nano titanium dioxide, composed of 80% anatase and 20% rutile; the UV light source was a 15 W UV bulb with a wavelength of 254 nm. The results obtained indicated a reduction efficiency order as follows; Cr6+ > Cu2+ > Pb2+ > Cd2+. It was observed that these results correlate with the respective reduction potentials of the metal ions. The effect of pH on the photocatalytic reduction of the metal ions was also carried out and results obtained indicated that with the exception of Cr (VI) ions, higher percentage removal of metal ions from their aqueous solution was recorded at alkaline pH than at acidic pH. This was attributed to an extensive formation of precipitate by the metal ions at alkaline pH. Kinetic studies revealed that the removal of metal ions from their solutions largely followed the pseudo- first-order kinetics. Therefore, the results of this study will be useful in metal ion removal from industrial waste water using photocatalytic process.

Simultaneous Cr(VI) Reduction and Naphthalene Oxidation in Aqueous Solutions by UV/TiO2

2007 ◽  
Vol 1045 ◽  
Author(s):  
Ricardo Guitierrez ◽  
Sergio o Flores ◽  
Omar Rios ◽  
Miguel Valenzuela
Keyword(s):  
Uv Light ◽  
Reaction Rates ◽  
Reduction Reaction ◽  
Photocatalytic Reduction ◽  
Photochemical Oxidation ◽  
Single System ◽  
Photochemical Reduction ◽  
Photogenerated Electrons ◽  
Hole Scavenger ◽  
Naphthalene Oxidation

AbstractThe photocatalytic reduction of Cr (VI) and oxidation of naphthalene using UV light and TiO2 were investigated with variations in the pH and Cr (VI)/naphthalene ratio. The photochemical reduction of Cr (VI) single system was not observed, whereas the photochemical oxidation of naphthalene was significantly high. However, the reduction reaction rates of Cr (VI) and oxidation of naphthalene were improved in the system UV/TiO2. The removal of Cr (VI) decreased dramatically with increasing pH, in contrast, the naphthalene removal was not influenced by the pH. The presence of naphthalene functioned as a hole scavenger enhancing the photocatalytic reduction of Cr (VI) by the photogenerated electrons, while the removal of naphthalene was decreasing at increasing Cr (VI) content.

scholarly journals Enhanced Solar Photocatalytic Reduction of Hexavalent Chromium in Seawater over Carbon Doped TiO2 Nanoparticles

2018 ◽  
Vol 28 (2) ◽  
pp. 17-26
Author(s):  
Yasser A. Shaban Yasser A. Shaban
Keyword(s):  
Hexavalent Chromium ◽  
Removal Rate ◽  
Reduction Rate ◽  
Pure Tio2 ◽  
Photocatalytic Reduction ◽  
Experimental Conditions ◽  
Carbon Doped ◽  
First Order Kinetics ◽  
Photocatalytic Removal ◽  
Hole Scavenger

The photocatalytic removal of hexavalent chromium Cr(VI) from polluted seawater has been successfully investigated by using carbon doped titanium oxide (CTiO2 ) nanoparticles under irradiation of natural sunlight. The photoactivity of CTiO2 was comparatively evaluated with pure TiO2 under the same experimental conditions. The effects of catalyst dose, initial Cr(VI) concentration and pH were studied and optimized. The highest removal rate was obtained at pH 3 and catalyst dose of 2.0 g L-1 . Furthermore, the existence of hole scavenger remarkably enhanced the reduction rate of Cr(VI). According to Langmuir–Hinshelwood model, the photocatalytic reduction of Cr(VI) using CTiO2 obeyed the pseudo-first-order kinetics

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