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

Islam, Jahida Binte; Furukawa, Mai; Tateishi, Ikki; Katsumata, Hideyuki; Kaneco, Satoshi

doi:10.3390/chemengineering3020033

Cited by 39 publications

(18 citation statements)

References 26 publications

(29 reference statements)

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“…The photocatalytic reaction kinetics has been elucidated by Langmuir-Hinshewood (L-H) model explaining the relationship between initial concentration of Cr(VI) and reduction rate of Cr(VI). If the Cr(VI) concentration is very low, that is, 1 ≫ K[Cr(VI)], the reduction rate will aid to pseudo-first-order kinetic law [25,37].…”

Section: Influence Of Edta Additionmentioning

confidence: 99%

“…Normally, chromium (VI) species exist as chromate (CrO 4 2− ), dichromate (Cr 2 O 7 2− ), hydrogen chromate (HCrO 4 − ), ) have been observed only in solutions of pH < 0 or at a chromium (VI) concentration greater than 1 mol/L [41]. At low pH, Cr(VI) exists as HCrO 4 − mainly, while CrO 4 2− occures at pH > 6.5 [25]. The pH pzc of ZnO is 9 [42].…”

Section: Influence Of Phmentioning

confidence: 99%

“…Hence, it is essential to improve the photocatalytic activity of ZnO. The addition of sacrificial electron donors [25], composite formation such as ZnO/TiO 2 , ZnO/CuS and ZnO/ZnFe 2 O 4 [26,27] or/and metal doping can modify the photocatalytic properties of ZnO [28,29]. Recently, some common sacrificial electron donors, namely citric acid, EDTA, oxalic acid, formic acid and tartaric acid, have been tested on the reduction of Cr(VI) [3,30].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Influence Of Edta Additionmentioning

confidence: 99%

Section: Influence Of Phmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

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“…Complexes of hafnium have been predominantly used as Lewis acid catalysts in various organic transformations, such as the polymerization of cyclic esters, and as catalysts for the homo‐ and copolymerization of α‐olefins . Recently, Hf‐MOF compounds have been used as active catalysts for the activation of small molecules . Among the transition metals belonging to the electrophilic group 4, hafnium is the most oxophilic when compared to zirconium and titanium.…”

Section: Introductionmentioning

confidence: 99%

Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin‐2‐iminato) Hafnium Complexes

et al. 2020

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Imidazolin‐2‐iminato hafnium complexes of the type [(ImRN)Hf(CH2Ph)3] were synthesized (ImtBuN = 1,3‐di‐tert‐butylimidazolin‐2‐iminato); ImDippN = 1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐iminato. The complexes were crystallized and structurally characterized. Despite the oxophilicity of the hafnium center, both hafnium complexes were catalytically active in the hydroboration of aldehydes, ketones, and carbodiimides. Herein, we present the influence of different substrates bearing electron‐withdrawing or electron‐donating groups on the catalytic reactions. Based on stoichiometric reaction in each process, plausible mechanistic scenarios are presented.

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“…Conventionally, the photocatalytic method involves the migration of valence electrons to conduction band, when photocatalyst are irradiated under light having photons with more energy than bandgap of the photocatalyst [22]. So far, some significant photocatalysts, namely TiO 2 , ZnO, CuO, WO 3 , CdS, Fe 2 O 3 , ZnFe 2 O 4 , etc., were widely studied due to favorable band gap energy to be excited under UV irradiation, low cost and suitable chemical properties [23][24][25][26][27]. TiO 2 and ZnO photocatalysts are highly applicable owing to their nontoxicity, wide bandgap (E g = ~3.20 eV) and high photosensitivity [28].…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic degradation of a typical agricultural chemical: metalaxyl in water using TiO2 under solar irradiation

et al. 2020

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The photodegradation and mineralization of the metalaxyl [methyl N-(2,6-dimethyl-phenyl)-N-(methoxyacetyl)-alaninate], which is a popular benzenoid fungicide, was conducted in the presence of TiO 2 photocatalyst under solar irradiation. An initial metalaxyl concentration of 50 ppm was completely degraded in presence of TiO 2 after 30 min irradiation, while no degradation was observed in absence of TiO 2 under solar irradiation. The effect of different parameters, such as amount of TiO 2 , initial pH, light intensity, reaction temperature and irradiation time, on the photocatalytic degradation of metalaxyl was evaluated. The drop of total organic carbon as a consequence of mineralization of metalaxyl was detected during the photocatalytic process. The kinetics of photocatalytic degradation followed a pseudo-first order law according to Langmuir-Hinshelwood model, and the rate constant was 0.105 min −1. Ammonium ion and CO 2 were speculated as the end-products after completing degradation of metalaxyl. The five types of intermediate products were identified by GC-MS during the decomposition of metalaxyl. In order to investigate the degradation pathway of metalaxyl, the point charge and frontier electron density at each atom on the molecule were determined by using MOPAC stimulation. The degradation mechanism was proposed from the identified intermediates. The solar photocatalytic degradation method can become an effective technique for the treatment of metalaxyl-polluted water. Keywords Metalaxyl • Photodegradation • TiO 2 photocatalyst • Point charge • Frontier electron density • GC-MS All experiments were conducted at Mie University. Any opinions, findings, conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the view of the supporting organizations.

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

Cited by 39 publications

References 26 publications

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

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

Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin‐2‐iminato) Hafnium Complexes

Photocatalytic degradation of a typical agricultural chemical: metalaxyl in water using TiO2 under solar irradiation

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