Dynamics and characterization of an innovative Raschig rings–TiO2 composite photocatalyst

Raja, P.; Bensimon, M.; Kulik, A.; Foschia, Raphaël; Laub, D.; Albers, Peter; Renganathan, R.; Kiwi, J.

doi:10.1016/j.molcata.2005.04.060

Cited by 8 publications

(8 citation statements)

References 12 publications

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“…This support was selected since: (a) it resists the attack of the highly oxidative radicals generated by the oxone decomposition catalyzed by Mn 2+ or Cu 2+ [10,11], (b) it also resists he decomposition of oxone recently reported by Co 2+ -ions [12,13] and (c) provides a large surface area in the reactor to induce accelerated Orange II decomposition. The short photodiscoloration times attained in the minute range are impressive compared with times needed by the TiO 2 /RR photocatalyst to degrade organic compounds under similar experimental conditions irradiation [7][8][9]. The experimental evidence for the accelerated kinetic performance observed is provided by XPS spectroscopy by identifying unambiguously the strong oxidation properties of the Co 3 O 4 .…”

Section: Introductionmentioning

confidence: 85%

“…Thus, the catalyst immobilization is a necessary step to avoid the costly end-of-pipe separation step [6]. In our laboratory, the immobilization of TiO 2 on Raschig rings (RR) has been recently the subject of some recent studies concerning the degradation pollutants under light irradiation [7][8][9]. As a natural continuation of these studies, the present work addresses the fixation of Co 3 O 4 on Raschig rings to produce a catalyst that would accelerate oxone decomposition.…”

Section: Introductionmentioning

confidence: 98%

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Accelerated photodegradation (minute range) of the commercial azo-dye Orange II mediated by Co3O4/Raschig rings in the presence of oxone

Zhang

Bensimon²,

Laub³

et al. 2007

Journal of Molecular Catalysis A: Chemical

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The accelerated discoloration of Orange II by an innovative Co 3 O 4 /Raschig ring photocatalyst (from now on Co 3 O 4 /RR) is feasible and proceeds to completion using oxone as an oxidant within the surprisingly short time of ∼5 min. The preparation of Co 3 O 4 small clusters (2-10 nm in size) on RR is reported. The discoloration/mineralization of the azo-dye Orange II was carried out in a concentric coaxial photo-reactor and was a function of the Orange II and oxone concentrations, the solution pH and the recirculation rate. At bio-compatible pH-values, the concentration of Co-ions in solution after photocatalysis (15 min) was found to be between 0.5 and 2 ppm, within the limits allowed for treated waters. The generation of peroxide was observed as long as Orange II was still available in solution.By elemental analysis (EA), the amount of Co of the Raschig rings was determined to be ∼65% (w/w) before and after the photocatalysis. This confirms the stability observed during long-term operation of the Co 3 O 4 /RR catalyst. The sizes of the Co 3 O 4 clusters on the RR surface were determined by transmission electron spectroscopy (TEM). A non-uniform distribution of Co 3 O 4 particles on RR with sizes between 2 and 10 nm was found. The presence of Co-clusters on the RR-surface was confirmed by electron dispersive spectroscopy (EDS) showing 12.6% surface Co-enrichment before the photocatalysis and 18.8% surface enrichment after the photocatalysis. By confocal microscopy the irregularly thick shaped Co 3 O 4 on the Raschig rings was analyzed. The most striking observation is very large shift of Co2p3/2 line from 779.6 eV at time zero to 782.2 eV within 10 min after due to the photocatalysis taking place. This indicates a strong reduction of electron density on the cobalt atoms of Co 3 O 4 /RR and providing the evidence for the strong oxidation properties of this catalyst.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 98%

Accelerated photodegradation (minute range) of the commercial azo-dye Orange II mediated by Co3O4/Raschig rings in the presence of oxone

Zhang

Bensimon²,

Laub³

et al. 2007

Journal of Molecular Catalysis A: Chemical

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“…The present work will focus on the study of TiO 2 catalysts supported on borosilicate glass rings (raschig rings), which will allow the development and optimization of a photocatalytic degradation process based on the use of both UV and white light, taking advantage of the ability of the different crystal structures of TiO 2 , leading to a controllable photodegradation process of complex organic molecules by control of the free radical generation process on the supported TiO 2 catalysts, either by the energy of the incident light or the combination of different TiO 2 crystal structures, allocated on the vitreous support. The physically and chemically stable supported photocatalytic structures will yield reusable materials for the implementation of water decontamination strategies either for batch or continuous regime water treatment, providing stability to the TiO 2 particles, enhancement of the catalytic surface to the incident light as well as adsorption of the substrates for the degradation, combined with good mass transport through the material, by taking advantage of the intrinsic properties of the design of the raschig rings as packing material, for example, in engineering application of fractionation columns (Raja et al, 2005).…”

Section: Vbmentioning

confidence: 99%

“…The dried rings were added to an aqueous TiO 2 suspension (10 g/L for the synthesized TiO 2 catalysts or 1 g/L for the commercial TiO 2 samples) and left to rest for 30 min. Later, the solvent was evaporated by heating the suspension at 150 • C followed by elimination of residual organic matter by heating at 500 • C for 2 h in a muffle furnace (Raja et al, 2005). The TiO 2 support efficiency was calculated by determining the amount of TiO 2 supported on the rings (the total amount of rings used on the support step) by weight differences, and the resulting mass of TiO 2 supported was expressed as a percentage in relation to the total mass of TiO 2 used in the support step.…”

Section: Tio 2 Support On Raschig Ringsmentioning

confidence: 99%

Photocatalytic Degradation of Aqueous Rhodamine 6G Using Supported TiO2 Catalysts. A Model for the Removal of Organic Contaminants From Aqueous Samples

et al. 2020

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As a model for the removal of complex organic contaminants from industrial water effluents, the heterogeneous photocatalytic degradation of Rhodamin 6G was studied using TiO 2-derived catalysts, incorporated in water as suspension as well as supported in raschig rings. UV and Visible light were tested for the photo-degradation process. TiO 2 catalysts were synthesized following acid synthesis methodology and compared against commercial TiO 2 catalyst samples (Degussa P25 and Anatase). The bandgap (E g) of the TiO 2 catalysts was determined, were values of 2.97 and 2.98 eV were obtained for the material obtained using acid and basic conditions, respectively, and 3.02 eV for Degussa P25 and 3.18 eV for anatase commercial TiO 2 samples. Raschig ringssupported TiO 2 catalysts display a good photocatalytic performance when compared to equivalent amounts of TiO 2 in aqueous suspension, even though a large surface area of TiO 2 material is lost upon support. This is particularly evident by taking into account that the characteristics (XRD, RD, Eg) and observed photodegradative performance of the synthesized catalysts are in good agreement with the commercial TiO 2 samples, and that the RH6G photodegradation differences observed with the light sources considered are minimal in the presence of TiO 2 catalysts. The presence of additives induce changes in the kinetics and efficiency of the TiO 2-catalyzed photodegradation of Rh6G, particularly when white light is used in the process, pointing toward a complex phenomenon, however the stability of the supported photocatalytic systems is acceptable in the presence of the studied additives. In line with this, the magnitude of the chemical oxygen demand, indicates that, besides the different complex photophysical processes taking place, the endproducts of the considered photocatalytic systems appears to be similar.

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“…This approach has also been used to degrade several aromatic compounds in aqueous solution [8][9][10]. Our laboratory has reported Raschig rings coated by TiO 2 as a catalyst to degrade phenol-compounds [11], phenol [12] and chlorophenols [13]. This study addresses the preparation of Raschig rings coated with TiO 2 but adding small amounts of a 3d-transition element like Cu/Cu-ions to extend its absorption into the visible region with the objective of increasing the dye degradation kinetics under solar light.…”

Section: Introductionmentioning

confidence: 99%

Cu-decorated Raschig-TiO 2 rings inducing MB repetitive discoloration without release of Cu-ions under solar light

Suárez

Zhang

Teixidó

et al. 2017

Journal of Environmental Chemical Engineering

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A B S T R A C TThe methylene blue (MB) discoloration on innovative photocatalysts made up of Raschig-rings coated by pre-formed TiO 2 nanoparticles decorated with CuOx (RR@TiO 2 -Cu) is presented. The MB-discoloration was drastically accelerated by the subsequent addition of 0.004% Cu. This Cu-content being $3000 times below the TiO 2 present in the RR@TiO 2 samples led to MB-discoloration in shorter times. The Cu-ions released from the RR@TiO 2 -Cu 0.004% were determined 1ppb by inductively coupled plasma massspectrometry (ICP-MS). Cu-percentages >0.018% decreased the MB-discoloration kinetics due to the Cu acting as recombination sites for the photogenerated charges. The total organic carbon (TOC) reduction concomitant with the MB-discoloration is reported as well as the effect of the initial MB-concentration and pH on the discoloration kinetics. The Cu-addition shifted significantly the TiO 2 absorption into the visible region even when added in sub-microgram quantities (0.004%) to RR@TiO 2 as detected by diffuse reflectance spectroscopy (DRS). The Cu level added to RR@TiO 2 was too low to be detected by X-ray diffraction (XRD). The roughness of the RR@TiO 2 -Cu (0.018%-0.081% Cu) presented Rg-values between 11.8 nm and 23.9 nm. The RR@TiO 2 Cu presented agglomerate sizes of $200 nm for TiO 2 and for the Cu aggregates sizes of $20 nm. The MB discoloration kinetics and reuse of the RR@TiO 2 -Cu suggest the potential as a supported catalyst in environmental cleaning process. A reaction mechanism is suggested taking into consideration the role of the Cu 1+/2+ intra-gap states involving redox catalysis as detected by X-ray photoelectron-spectroscopy (XPS).

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Dynamics and characterization of an innovative Raschig rings–TiO2 composite photocatalyst

Cited by 8 publications

References 12 publications

Accelerated photodegradation (minute range) of the commercial azo-dye Orange II mediated by Co3O4/Raschig rings in the presence of oxone

Accelerated photodegradation (minute range) of the commercial azo-dye Orange II mediated by Co3O4/Raschig rings in the presence of oxone

Photocatalytic Degradation of Aqueous Rhodamine 6G Using Supported TiO2 Catalysts. A Model for the Removal of Organic Contaminants From Aqueous Samples

Cu-decorated Raschig-TiO 2 rings inducing MB repetitive discoloration without release of Cu-ions under solar light

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