Photocatalytic removal of Cr(VI) and Ni(II) by UV/TiO<sub>2</sub>: kinetic study

Siboni, M Shirzad; Samadi, M T; Yang, Jae‐Kyu; Lee, Seung‐Mok

doi:10.1080/19443994.2012.671144

Cited by 61 publications

(14 citation statements)

References 42 publications

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“…For UV irradiated TiO 2 , there are two kinds of Ti 3+ produced: inner Ti 3+ and surface Ti 3+ . The inner Ti 3+ usually acting as the recombination centre adversely affects photocatalytic activity; whereas the surface one is believed to be the reactive centre of the photocatalytic process [11].…”

Section: Resultsmentioning

confidence: 99%

“…Under acidic condition [5, 11]

\begin{matrix} right leftthickmathspace.5em \\ C {normalr}_{2} {normalO}_{7}^{- 2} + 14 {normalH}^{+} + 6 {normale}^{-} \to 2 C {normalr}^{+ 3} + 7 {normalH}_{2} O \\ E^{0} = 0.98 eV (SHE) \end{matrix}

Under neutral condition

\begin{matrix} right leftthickmathspace.5em \\ {normalCrO}_{4}^{- 2} + 8 {normalH}^{+} + 3 {normale}^{-} \to C {normalr}^{+ 3} + 4 {normalH}_{2} O \\ E^{0} = 0.56 eV (SHE) \end{matrix}

Under basic condition

\begin{matrix} right leftthickmathspace.5em \\ {normalCrO}_{4}^{- 2} + 4 {normalH}_{2} O + 3 {normale}^{-} \to Cr (OH)_{3} + 5 O {normalH}^{-} \\ E^{0} = 0.24 eV (SHE) \end{matrix}

Fig. 4 depicts how pH influences the rate at which CN reduces photocatalytically while Cr(VI) is also present in the range of 9.0–12.0.…”

Section: Resultsmentioning

confidence: 99%

“…However, there are normally more than one component in wastewaters by which treatment methods may be affected. Accordingly, this cost‐effective technique which can easily be installed may be regarded as a pre‐/post‐treatment method [4, 11]. Several works have been concerned with either pathogens or chemicals individually.…”

Section: Introductionmentioning

confidence: 99%

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Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV

Koohestani

2019

Micro & Nano Letters

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Cyanide (CN) and chromium (VI) are hazardous, toxic pollutants whose presence in water and wastewater can seriously affect human and its environment, hence the necessity of controlling these contaminants. In this work, by using TiO 2 /UV, the simultaneous photocatalytic reduction of Cr(VI) and oxidation of CN in aqueous suspensions were investigated. Variations of this study were pH, pollutant concentration, and reaction time. CN and total chromium were determined by Titrimetric method, and Colourimetric method, respectively. Maximum removal of chromium and CN occurs at pH 2.3 and 10, respectively. In the binary system, the electron-hole recombination is blocked and as a result, total efficiency increases. An increase in the initial concentrations of CN and Cr(VI) led to a rise in the reduction efficiency of Cr(VI) and CN up to an optimum amount, and then it went into decline as the concentration of the pollutants increased any further. The maximum quantum efficiency of Cr(VI) photoreduction with CN being present was calculated to be 23% at room temperature. Furthermore, the kinetic experimental was investigated and it became evident that the pseudo-first-order kinetic model is capable of defining Cr(VI) and CN both. Finally, based on the obtained results, a TiO 2 system is proposed to remove both pollutants.

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Section: Resultsmentioning

confidence: 99%

“…Under acidic condition [5, 11]

\begin{matrix} right leftthickmathspace.5em \\ C {normalr}_{2} {normalO}_{7}^{- 2} + 14 {normalH}^{+} + 6 {normale}^{-} \to 2 C {normalr}^{+ 3} + 7 {normalH}_{2} O \\ E^{0} = 0.98 eV (SHE) \end{matrix}

Under neutral condition

\begin{matrix} right leftthickmathspace.5em \\ {normalCrO}_{4}^{- 2} + 8 {normalH}^{+} + 3 {normale}^{-} \to C {normalr}^{+ 3} + 4 {normalH}_{2} O \\ E^{0} = 0.56 eV (SHE) \end{matrix}

Under basic condition

\begin{matrix} right leftthickmathspace.5em \\ {normalCrO}_{4}^{- 2} + 4 {normalH}_{2} O + 3 {normale}^{-} \to Cr (OH)_{3} + 5 O {normalH}^{-} \\ E^{0} = 0.24 eV (SHE) \end{matrix}

Fig. 4 depicts how pH influences the rate at which CN reduces photocatalytically while Cr(VI) is also present in the range of 9.0–12.0.…”

Section: Resultsmentioning

confidence: 99%

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Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV

Koohestani

2019

Micro & Nano Letters

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“…The photocatalytic reduction of Cr 6+ ions to Cr 3+ ions is presented depending on pH through Eqs. (2-4) [45].…”

Section: Influence Of Phmentioning

confidence: 99%

Enhanced photocatalytic reduction of toxic Cr(VI) with Cu modified ZnO nanoparticles in presence of EDTA under UV illumination

et al. 2019

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In this study, the photocatalytic reduction of Cr(VI) to Cr(III) in aqueous solution using 1 wt% Cu/ZnO photocatalyst in presence of ethylenediaminetetraacetic acid (EDTA) under UV irradiation was investigated. The photocatalytic Cr(VI) reduction with ZnO under UV irradiation was significantly low. A fast Cr(VI) reduction with ZnO was recorded in presence of EDTA. Results demonstrated that the rate constant raised from 1.6 × 10 −2 to 7.5 × 10 −2 min −1 with 20 ppm EDTA addition. The optimum reduction (90%) was observed within 30 min at pH 3. The reduction efficiency of Cr(VI) was evidently increased from 6% to 99%, with increasing ZnO dosages up to 40 mg. The role of co-catalysts such as Au, Ag, Cu and NiO was also studied. The addition of Cu ion remarkably accelerated the reduction of Cr(VI), compared with ZnO/ EDTA system alone. The Cu motivated ZnO/EDTA system completed the 99% reduction within only 30 min. The Cu ions were reduced to metallic copper and Cu 2 O by conduction band electrons of ZnO. The electron-hole recombination was gently declined by the shallow electron trapping of Cu. On the other hand, EDTA could be performed in two ways by forming Cr(III)-complex and separating Cr(III) from ZnO surface and by consuming valence band holes. The Cu modified ZnO photocatalyst was characterized by N 2 adsorption-desorption isotherm, TEM, EDX, XPS, DRS and PL spectra. We evaluated the influence of pH, photocatalyst dosage, initial concentration of EDTA and initial concentration of Cu 2+ ion (Cu doping amount) on photocatalytic reduction of Cr(VI). The pseudo first order kinetic reaction was confirmed for this reduction process. Herein, a probable mechanism of this photocatalytic reduction process was also presented.

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“…After the hole-electron pairs are separated, the electrons can reduce Cr(VI) to Cr(III), and the holes may lead to generation of O 2 in the absence of organics (Shirzad Siboni et al 2012). Therefore, in a complete inorganic aqueous solution, the net photocatalytic reaction is the threeelectron reduction of Cr(VI) to Cr(III) with oxidation of water to oxygen, which is a kinetically slow fourelectron process.…”

Section: Introductionmentioning

confidence: 99%

Preparation of TiO2/Silicalite-2@CoFe2O4 Magnetic Composites and Evaluation of their Photocatalytic Activity in Cr(VI) Removal

Cheng

Pan

et al. 2015

Water Air Soil Pollut

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Magnetic nanoparticles of CoFe 2 O 4 were synthesized by co-precipitation method. The magnetic material silicalite-2@CoFe 2 O 4 (SC) was prepared by using tetrabutylammonium hydroxide as the template, tetraethoxysilane as the silica source and CoFe 2 O 4 as the magnetic core. TiO 2 /silicalite-2@CoFe 2 O 4 (TSC) magnetic photocatalyst was prepared by sol-gel technique using SC particles as the supporter and tetrabutyltitanate as the titanium source. The samples were characterized by X-ray diffraction, scanning electron microscopy, N 2 adsorption-desorption, Fourier transform infrared spectroscopy, and ultraviolet (UV)-visible diffuse reflectance spectra. The reduction of Cr(VI) in aqueous solution by UV/TSC process was studied under various operating conditions. The results demonstrate that the as-synthesized TSC has high photocatalytic activity due to the high dispensability of TiO 2 provided by silicalite2@CoFe 2 O 4 . The removal of Cr(VI) reached 72.9 % by using 0.6 g/L of TSC under the optimum conditions within 180 min. The photocatalytic reduction of Cr(VI) by TSC followed the Langmuir-Hinshelwood kinetic model. At the end of the reaction, TSC could easily be recovered and could be reused without the significant loss of the catalytic activity.

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Photocatalytic removal of Cr(VI) and Ni(II) by UV/TiO₂: kinetic study

Cited by 61 publications

References 42 publications

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV

Enhanced photocatalytic reduction of toxic Cr(VI) with Cu modified ZnO nanoparticles in presence of EDTA under UV illumination

Preparation of TiO2/Silicalite-2@CoFe2O4 Magnetic Composites and Evaluation of their Photocatalytic Activity in Cr(VI) Removal

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Photocatalytic removal of Cr(VI) and Ni(II) by UV/TiO2: kinetic study

Cited by 61 publications

References 42 publications

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO 2 /UV

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO 2 /UV

Enhanced photocatalytic reduction of toxic Cr(VI) with Cu modified ZnO nanoparticles in presence of EDTA under UV illumination

Preparation of TiO2/Silicalite-2@CoFe2O4 Magnetic Composites and Evaluation of their Photocatalytic Activity in Cr(VI) Removal

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Photocatalytic removal of Cr(VI) and Ni(II) by UV/TiO₂: kinetic study

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV

Photocatalytic removal of cyanide and Cr(IV) from wastewater in the presence of each other by using TiO ₂ /UV