Immobilization of photocatalytically active TiO2 nanopowder by high shear granulation

Immobilization of photocatalytically active TiO2 nanopowder by high shear granulation

    Immobilization of photocatalytically active TiO 2 nanopowder by high shear granulation Caroline Goedecke, Regine Sojref, Thi Yen Nguy...

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    Immobilization of photocatalytically active TiO 2 nanopowder by high shear granulation Caroline Goedecke, Regine Sojref, Thi Yen Nguyen, Christian Piechotta PII: DOI: Reference:

S0032-5910(17)30484-9 doi:10.1016/j.powtec.2017.06.025 PTEC 12601

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Powder Technology

Received date: Revised date: Accepted date:

25 January 2017 15 May 2017 9 June 2017

Please cite this article as: Caroline Goedecke, Regine Sojref, Thi Yen Nguyen, Christian Piechotta, Immobilization of photocatalytically active TiO2 nanopowder by high shear granulation, Powder Technology (2017), doi:10.1016/j.powtec.2017.06.025

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ACCEPTED MANUSCRIPT Immobilization of photocatalytically active TiO2 nanopowder

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by high shear granulation

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Caroline Goedecke1, 2*, Regine Sojref1, Thi Yen Nguyen1, Christian Piechotta1 BAM Bundestanstalt für Materialforschung und -prüfung, Richard-Willstätter-Str. 11, 12489 Berlin, Germany

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Technical University Berlin, Fasanenstr. 1a, 10623 Berlin, Germany

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* Corresponding author: Caroline Goedecke, e-mail: [email protected]

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Abstract

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Nano-TiO2 powder is known to show high photocatalytic reactivity in the degradation of several organic pollutants. In this work, the powder was fixed on the surface of SiO2

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granules with the size of several micrometers using a high shear granulation process. Nanozirconia sol was applied as an inorganic binder. When the samples were

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tempered at 300 °C, they showed high stability in an aqueous solution for several hours. An energy dispersive x-ray spectroscopy (EDX) analysis confirmed that the cores and shells of the granules consisted solely of SiO2 and TiO2 respectively, and that ZrO2 was found throughout the whole granules. Methylene blue (MB) was employed as a model system to evaluate the photocatalytic activity of the TiO 2 nanopowder and coated granules. It was shown that the TiO2-coated granules lead to the degradation of MB under UV irradiation, whereas no effect was observed in the dark. After the degradation experiments the granules could be recovered and they remained active for further applications.

ACCEPTED MANUSCRIPT Keywords: heterogeneous photocatalysis, water treatment, advanced oxidation,

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nanozirconia, methylene blue

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1. Introduction

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In recent years scientific research in the field of environmental pollutants degradation

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has focused on advanced oxidation processes [1]. When hazardous organic compounds have to be removed from waste water, a semiconductor-based heterogeneous photocatalysis is a promising method because it often results in a

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complete mineralization of the pollutants.

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Among various semiconductors, titanium dioxide is the commonly used photocatalyst – a non-toxic, chemically inert substance with high photocatalytic activity. If titanium

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dioxide is illuminated with light of an energy higher than the band gap of the

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semiconductor, electron-hole pairs are generated on the surface of the TiO 2, which results in the formation of active oxidizing species such as OH radicals, which have

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the potential to remove toxic compounds. Dyes are frequently used in order to evaluate the capability of this technique. The efficiency of photocatalytic degradation of organic

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substances is known to depend on the choice of the TiO2 source as well as on the reaction conditions [2-4]. The composition of the powders, especially the anatase content, influences the activity of the TiO2 powder to a great extent [5, 6]. When TiO2 powder with a similar anatase content and different crystallite sizes are compared, the specific surface area is the key factor determining their photocatalytic activity [2]. Tempering processes, which are essential in powder immobilization for consolidation of coatings or compacts, are limited by possible loss of catalytic activity due to the decreasing anatase content and specific surface area. The critical temperature of the anatase-rutile phase transformation is influenced by the powder crystallite size. The

ACCEPTED MANUSCRIPT phase composition of the near-surface region of powder may differ from that inside the catalyst [5, 7].

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Different methods of immobilizing TiO2 powder for easy recovery of the photocatalysts

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after application have been proposed. TiO2-based pellets or granules have been used

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[8, 9] as well as coatings on various substrates including silicates or activated carbon [3, 10].

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For possible industrial application of TiO2-based photocatalysts to remove pollutants from the environment, cost-effective solutions with commercial materials are needed.

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TiO2-coating of porous ceramic tiles or concrete tubes and the incorporation of nanoTiO2 into self-cleaning photocatalytically active composite coatings were shown to be

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promising approaches to achieve these requirements [7, 11, 12]. Nevertheless, immobilization of nanometer and submicrometer sized catalyst powder,

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may offer an opportunity for the removal of pollutants from waste water in the future. High speed granulation is widely used in order to convert ultrafine powders into

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micrometer- or millimeter-sized granules. The complex interactions of parameters like the liquid to solid ratio, amount and properties of binder and wetting agents, granulation time and impeller speed influence the quality and the size distribution of the resulting granules [13]. After prolonged granulation time a “steady state” granulation is reached. At this point the comminution and the growth achieve equilibrium when the granule size distribution only depends on the liquid to solid ratio [14]. At the end of the granulation process a coating of "foreign particles" can be added to the surface of previously formed granules [15].

ACCEPTED MANUSCRIPT In this work, the properties and photocatalytic activity of TiO2 powder and granules have been investigated. The aim is to show a possible and commercially reasonable

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route to immobilize TiO2 powder in a way that keeps their photocatalytic activity.

2. Materials and methods 2.1.

Materials

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Two kinds of titanium dioxide (TiO2) powder with different particle sizes were used as

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photocatalytic active materials in this study - one submicrometer TiO2 (SB) (ReagentPlus®, Sigma Aldrich, Taufkirchen/Germany) and one nano TiO2 (N)

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(Aeroxide, P25, Evonik, Essen/Germany). Fused silica (Microsilica Grade 971, Elkem

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Refractories, Norway) was chosen as the inert host material for granule preparation. Methylene blue (MB) acquired from Riedel de Haën (Seelze, Hannover/Germany) was

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used in dye solution degradation experiments. Acetate-stabilized colloidal zirconium oxide sol (wt. %=20) purchased from Nyacol Nano Technologies (Ashland/USA) was

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selected as the granule binding agent. In order to ensure powder wetting Dispex Ultra FA 4480 surfactant (BASF) was added to the binder solution. 2.2.

Characterization of the powder and granules

The mean particle diameter (D50) of TiO2-SB and TiO2-N powder was determined with a DT1200 ultrasonic spectrometer. Low-temperature nitrogen adsorption was performed using a NOVA 2200 instrument in order to determine the specific surface area. Both instruments were supplied by Quantachrome Instruments, Odelzhausen/ Germany. For X-ray diffraction (XRD) measurements a Bruker D8 Discover X-Ray diffractometer equipped with a SoIX-detector (Bruker AXS GmbH, Karlsruhe/Germany) was used.

ACCEPTED MANUSCRIPT The samples were measured in transmission geometry in a range of 5-90 ° 2θ with Cu Kα1 radiation (λ=1.54056 Å) at 2 kW. The crystallite sizes were calculated with the

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Scherrer equation. The relative amount of anatase and rutile in the TiO 2 powder was

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determined using the Rietveld refinement method.

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SEM images of the original substances were obtained on a field emission scanning electron microscope (ZEISS Gemini Supra 40, Oberkochen, Germany) equipped with

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an energy dispersive X-ray spectrometer (Thermo NSS 3.1, Thermo Fisher Scientific, Waktham, USA / Bruker Quantax 400, Billerica, USA). Titania-coated and uncoated

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silica granules were embedded in paraffin and subsequently ground. The samples were characterized topographically with an environmental scanning electron

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microscope XL 30 (ESEM) (Fei, Hillsboro, USA) equipped with an energy dispersive

High-shear granulation

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X-ray spectrometer (EDAX, Mahwah, USA).

Granulation experiments were carried out with a high-shear batch type laboratory mixer (EL1 from Eirich, Hardheim/Germany). The mixer was equipped with a

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slow-rotating vessel (1 L), a fast-rotating mixing tool (pin agitator) and a wall scraper. An appropriate amount of fused silica host powder was chosen to fill about 30 % of the vessel volume with granules. Binder solutions were composed of zirconia sol, a wetting agent and ultrapure water. The zirconia solid matter concentration and Dispex Ultra FA 4480 content in the solution were adjusted to 12.5 and 3.3 wt. % respectively. The powder and binder solution were mixed to achieve granules with a moisture content within the range from 26 to 29 wt %. As a first step, SiO2 powder was de-agglomerated and wetted with the binder solution for 5 min with the vessel and mixing tool rotating in the same direction. Afterwards, the SiO2 granulation was performed with a counter-rotating vessel and mixing tool

ACCEPTED MANUSCRIPT (circumferential speed 20-30 ms-1). The granulation time was selected in the range of 2 to 20 min to ensure that no dry powder (<100µm) was left in the vessel. As a final

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step, 10 wt. % of TiO2 nanopowder was added to the silica granules and processed for

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30–60 s. The coated granules were dried at 85 °C overnight, then heated to 300 °C

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within 1 hour and annealed for 30 min under flowing air. Granules were fractionated by sieving. Small (<250 µm) and large (>1000 µm) granules were removed. The fractions between 250-500 µm and 500-1000 µm were used for photocatalytic degradation of

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MB in water. In order to evaluate the recovery of the titania coated granules, they were

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removed from the MB solution after the experiment with a folded filter. The residue was washed twice with 10 mL of ultra-pure water and dried at 110 °C overnight. Afterwards,

Photodegradation experiments

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further degradation experiments were performed with the recycled granules.

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The photocatalytic activity of TiO2 powder and the related granules was evaluated using methylene blue as a test substance. MB solutions were made by dissolving an appropriate amount of the dye in ultra-pure water to reach a final concentration of

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0.1 mmol L-1. The photocatalytic experiments were carried out in a double walled borosilicate reactor (100 mL volume, 8 cm in height and 4 cm in diameter). 80 mL of the MB solution were placed in the reactor. The solution was stirred with a magnetic stirrer and cooled to 8 °C during the reaction. 1.5 g of the granules were placed at the bottom of the reactor. Irradiation was carried out using a UV-radiation lamp (Pen-Ray, 111.3 mm, with λ=365 nm (UV-A) purchased from UVP, Upland/Canada). The experimental setup is shown in Figure 1. MB solution degradation experiments were performed for six hours. 1 mL samples were taken from the investigated solution every 30-60 min. The samples were diluted volumetrically in a ratio of 1:5 with ultra-pure water. The light absorbance of the diluted sample solutions was measured at 663 nm

ACCEPTED MANUSCRIPT with a UV-vis-spectrometer (5600 series, Unicam, Cambridge/UK) in order to

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determine the residual MB concentration.

Characterization of the TiO2 powder

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3.1.

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3. Results and Discussion

Two commercial kinds of TiO2 powder with high content of anatase crystalline phase

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were chosen to study the influence of different powder characteristics on their

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photocatalytic activity. The results of the characterization of the original substances with several analytical methods are shown in Table 1. From SEM images (see Figure 2) of TiO2-N it is evident that the size of

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non-agglomerated primary particles varies between 20 and 50 nm, which is consistent with the manufacturer's specifications. In contrast, the 100-200 nm primary particles of

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TiO2-SB form sintered clusters approximately 200-400 nm in size. By means of ultrasonic attenuation spectroscopy a D50 median particle diameter of 256 nm was

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determined for the submicrometer powder and a D50 of 43 nm for the nanopowder. These results confirm the particle dimensions of the SEM measurements. In agreement with the particle sizes, the specific surface area of the nanopowder was much higher than that of the submicrometer TiO2 (50 and 10 m2 g-1 respectively). Both the overall phase composition of the investigated powder and the corresponding crystallite sizes of the occurring phases were determined by means of XRD analysis (see Figure 3). The TiO2-SB powder fully consisted of anatase whereas the TiO2-N nanopowder was composed of approximately 20 % rutile and 80 % anatase. Different crystallite sizes were found for anatase (25 nm) and rutile (50 nm) in the nanopowder. The crystallite size of the pure anatase submicrometer powder was 75 nm.

ACCEPTED MANUSCRIPT XRD analyses were also performed with powder annealed at 300 and 500 °C. No influence of the annealing procedure on the composition of both kinds of powder could

Photocatalytic degradation of methylene blue solutions with pure TiO 2

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3.2.

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be detected (Table 2).

powder

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During immobilization of photocatalytic active powder a certain decrease in activity is

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usually observed due to its partial incorporation in compact samples or by surface changes during the necessary tempering step. Therefore, the photocatalytic activity of the original TiO2 powder was investigated prior to the experiments with immobilized

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powder.

In Figure 4 the MB solution concentration (normalized to the initial concentration) is

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plotted against the reaction time. From Figure 4 (left) it is evident that the original TiO2-SB powder shows a certain photocatalytic activity which is slightly reduced due

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to the annealing of the powder at 500 °C. The MB degradation tests were carried out with the same mass of TiO2-N nanopowder (0.1 g), resulting in nearly complete removal of the test substance from the solution (Figure 4, right). No MB degradation was observed in the absence of UV radiation for both kinds of powder. Additional experiments were performed with 0.08 g of the TiO2 nanopowder in order to clarify the influence of the annealing temperature on its photocatalytic activity. As shown in Figure 5, the dye removal rate was found to depend on the chosen annealing temperature. It is obvious that the photocatalytic activity of the powder becomes lower as the annealing temperature increases. It can be assumed that the TiO2-N powder surface was altered during the annealing procedure, no changes in the overall composition

ACCEPTED MANUSCRIPT were detected after tempering (Table 2). Due to its noticeably higher activity only

Granule assembly and characterization

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TiO2-N was used for immobilization experiments.

Submicrometer-sized fused silica powder was agglomerated in a high-shear mixer with a binder solution in order to form granules with sizes in the range of several hundred

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micrometers. This technology is available on a laboratory as well as industrial scale.

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The economical use of TiO2 powder is possible when inert core granules are coated with a photocatalytic active substance. In preliminary experiments it was found that granulation of submicrometer fused silica (used as a host powder) was successful

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when the moisture content of the mixtures was approximately 26–29 wt. %. Mixtures containing less water were not fully agglomerated while a higher moisture content led

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to an excessive growth of irregularly shaped granules with sizes up to 10 mm. Besides moisture adjustment the addition of a wetting agent (Dispex Ultra FA 4480) was

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necessary in order to prevent the formation of large granules from non-uniform mixtures. When a nanozirconia sol-containing binder solution was used for granulation the overall moisture content of the mixture was adjusted to 26-29 wt.%. The SEM image shows that the non-fractioned silica granulate exhibits a broad particle size distribution with agglomerates assembled from smaller ones (Figure 6). These findings are in agreement with the work of Le et al. [16] explaining the variety in the shape and size of the granules caused by their formation mechanisms. Due to the technological process granules are continuously destroyed by the fast-rotating impeller while new ones are formed by agglomeration of the wet powder. After a certain time an equilibrium between granular comminution and powder agglomeration is achieved (steady state granulation [14]). In order to coat the silica granules with

ACCEPTED MANUSCRIPT photocatalytically active titania 10 wt. % TiO2-N was added after the silica granulation process was completed. The particle size distribution of titania-coated silica granules

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is shown in Figure 7. Different fractions of the granules were obtained for photocatalytic

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activity tests by sieving after tempering the granules at 300°C. The yield of the granule

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fractions chosen for photocatalytic activity tests (250–500 µm and 500-1000 µm) reached about 50 % and 25 % when granulation was performed with an impeller speed of 20 ms-1 within 5 min. At a higher impeller speed (30 ms-1) 45 % of the finer granule

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fraction and 35 % of the coarser one were generated despite the short granulation time

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(2 min). The granules remained stable in water while stirring them for several hours. Figure 8 shows the SEM image of the fine fraction (125-250 µm) of titania-coated silica

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granules. It is obvious that titania is located mainly on the surface of the irregularly

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shaped granules forming a layer with a thickness of approximately 5-10 µm.

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The SEM image of a cross section (see Figure 9) of a single granule coated with TiO2 was recorded and the corresponding element distribution was determined by an EDX linescan analysis. The analysis confirmed that the core of the granule was formed out

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of silica whereas the shell mainly consisted of titania with only a few small silica agglomerates incorporated into the shell. Zirconia was detected in both the silica host granule and the titania coating which indicates sufficient wetting of the powders by the binder solution during the granulation process. 3.4.

Photocatalytic activity of titania-coated silica granules

A photocatalytic evaluation was carried out with the methylene blue test system (see section 2.4.) [4]. Blank tests indicated that the degradation of MB can be attributed exclusively to the photocatalysis and no adsorption on the surface of the catalyst led to a reduction of the MB concentration (Figure 10). Experiments without the addition of

ACCEPTED MANUSCRIPT the catalyst showed that irradiation with the UV-lamp alone did not result in a degradation of MB. The experiments using 1.5 g of the titania coated silica granules

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led to a moderate degradation of MB (see Figure 10) while the addition of 2.5 g of the

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granules resulted in an almost complete removal of the dye under photocatalytic

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conditions (see Figure 11). Surprisingly, the smaller fraction (250-500 µm) showed lower photocatalytic activity despite the fact that a larger overall outer granule surface area could be assumed than for the coarse fraction (500-1000 µm). The reason for this

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may be the uneven structure of the titania layer as shown in Figure 9. Obviously, the

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layer originates from micrometer-sized titania agglomerates splashed on the surface of the silica granules. It can be imagined that the added amount of 10% titania covered coarser granules almost completely while it was not enough to cover the finer ones

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under these conditions. The titania content of different granule fractions was not investigated in this work. After the degradation experiments of MB, the granules were

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recovered and washed with ultra-pure water followed by a drying step. Figure 12 shows the results of the degradation of MB with regained TiO2 coated granules in comparison

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with the unused ones. It was shown that the catalysts completely retained their photocatalytic activity after the application. 4. Conclusion

The photocatalytic activity of two commercial kinds of TiO2 powder (nano- and submicrometer-sized respectively) was investigated by measuring their capability to degrade methylene blue. It was found that both kinds of powder could be materials for further photocatalytic applications. Under the defined experimental conditions an almost complete removal of methylene blue under UV-irradiation was achieved in the presence of small amounts of nanosized TiO2 powder. Titania-coated silica granules showing high photocatalytic activity were prepared in a high-shear mixer with the

ACCEPTED MANUSCRIPT addition of nanozirconia as an inorganic binder. Granules consolidated at 300 °C maintained their integrity in an aqueous solution for several hours. After degradation

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experiments the granules could be recovered for further applications.

Acknowledgement

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The authors thank S. Benemann and I. Feldmann for their SEM investigations and

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A. Marek for preparation of the SEM samples.

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Funding

This research did not receive any specific grant from funding agencies in the public,

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commercial, or not-for-profit sectors.

ACCEPTED MANUSCRIPT References [1] S.-Y. Lee, S.-J. Park, TiO2 photocatalyst for water treatment applications, Journal

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of Industrial and Engineering Chemistry, 19 (2013) 1761-1769.

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[2] Y. Xu, C.H. Langford, UV- or Visible-Light-Induced Degradation of X3B on TiO2 Nanoparticles: The Influence of Adsorption, Langmuir, 17 (2001) 897-902. [3] S.-M. Lam, J.-C. Sin, A.R. Mohamed, Parameter effect on photocatalytic

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degradation of phenol using TiO2-P25/activated carbon (AC), Korean Journal of

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Chemical Engineering, 27 (2010) 1109-1116.

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and Kinetics in Catalytic Removal of Methylene Blue with TiO2 Nanopowder, American

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Journal of Environmental Engineering, 2 (2012) 1-7.

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[5] F.-L. Toma, L.-M. Berger, I. Shakhverdova, B. Leupolt, A. Potthoff, K. Oelschlägel, T. Meissner, J.A.I. Gomez, Y. de Miguel, Parameters Influencing the Photocatalytic Activity of Suspension-Sprayed TiO2 Coatings, Journal of Thermal Spray Technology,

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23 (2014) 1037-1053.

[6] J. Zhang, Q. Xu, Z. Feng, M. Li, C. Li, Importance of the relationship between surface phases and photocatalytic activity of TiO2, Angewandte Chemie, 47 (2008) 1766-1769. [7] M. Hofer, D. Penner, Thermally stable and photocatalytically active titania for ceramic surfaces, Journal of the European Ceramic Society, 31 (2011) 2887-2896. [8]

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Matsunaga,

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Hori,

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Trichloroethylene in water using TiO2 Pellets, Water Research, 35 (2001) 1022-1028.

ACCEPTED MANUSCRIPT [9] E. Khaksar, M. Shafiee Afarani, A. Samimi, In Situ Solvothermal Crystallization of TiO2 Nanostructure on Alumina Granules for Photocatalytic Wastewater Treatment,

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Journal of Materials Engineering and Performance, 23 (2013) 92-100.

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[10] S.N. Hosseini, S.M. Borghei, M. Vossoughi, N. Taghavinia, Immobilization of TiO2

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on perlite granules for photocatalytic degradation of phenol, Applied Catalysis B: Environmental, 74 (2007) 53-62.

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[11] Y. Wang, Y. Li, W. Zhang, Q. Wang, D. Wang, Photocatalytic degradation and reactor modeling of 17alpha-ethynylestradiol employing titanium dioxide-incorporated

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foam concrete, Environmental science and pollution research international, 22 (2015)

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3508-3517.

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[12] Y. Zhou, M. Li, X. Zhong, Z. Zhu, P. Deng, H. Liu, Hydrophobic composite coatings with photocatalytic self-cleaning properties by micro/nanoparticles mixed with

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fluorocarbon resin, Ceramics International, 41 (2015) 5341-5347. [13] B. Daumann, X. Sun, H. Anlauf, S. Gerl, H. Nirschl, Mixing Agglomeration in a

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High-Shear Mixer with a Stirred Mixing Vessel, Chemical Engineering & Technology, 33 (2010) 321-326.

[14] R.F.T. Moo, Improved Control Of Granule Properties via "steady State" Granulation, Department of Chemical Engineering, Monash University, 2014. [15] A.S. Eric Serris, Alain Chamayou, Laurence Galet, Michel Baron, G.T. Philippe Grosseau, Dry coating in a high shear mixer: Comparison of experimental results with dem analysis of particle motions, Powders and Grains 2013, AIP Conference Proceedings, American Institut of Physics Publishing LLC, Sydney, Australia, 2013, pp. 779.

ACCEPTED MANUSCRIPT [16] P.K. Le, P. Avontuur, M.J. Hounslow, A.D. Salman, A microscopic study of granulation mechanisms and their effect on granule properties, Powder Technology,

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206 (2011) 18-24.

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Figure 1: Experimental setup for photocatalytic reaction.

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Figure 2: SEM images of TiO2-SB (left) and TiO2-N (right).

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Figure 3: XRD pattern of TiO2-N (top), TiO2-SB (middle) and reference spectra from

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PDF-2 2003 database of ICDD (International Centre for Diffraction Data) with

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anatase (purple) and rutile (orange) (bottom).

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Figure 4: Photocatalytic degradation of MB by TiO2-SB (left) and TiO2-N (right).

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Figure 5: Influence of the annealing temperature on the photocatalytic degradation of

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an MB solution with 0.08 g of TiO2-N powder.

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Figure 6: SEM image of the non-fractionated SiO2 granules.

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Figure 7: Influence of the mixing tool circumferential speed and the granulation time

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on the granulate size distribution. Marked granule fractions (250–500 µm and

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500-1000 µm) were taken for MB solution degradation experiments.

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Figure 8: SEM image of titania coated silica granules (125-250 µm).

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Figure 9: SEM image of a cross section of a titania coated granule with the

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corresponding EDX linescan.

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Figure 10: Photocatalytic degradation curve of MB using 1.5 g of titania coated SiO2

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granules.

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granules (500 - 1000 µm).

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Figure 11: Photocatalytic removal of MB with different amounts of titania coated silica

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Figure 12: Comparison of the degradation of MB concentration under photocatalytic

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conditions using recovered and fresh granules.

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TiO2-SB

TiO2-N

particle size, D50/nm

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43

specific surface area/m2g-1

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crystal phase ratio, 100:0

89:11

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anatase: rutile/%

73-77 (anatase)

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crystallite size/nm

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properties

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Table 1: Results of analytical characterization of TiO2 powder.

24-25 (anatase) 46-47 (rutile)

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Table 2: Results of the structural analysis of TiO2-N, annealed at different

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temperatures, calculated from XRD data. 300 °C

TiO2-N

anatase 89 %

anatase 88 %

rutile 11 %

rutile 12 %

anatase 100 %

anatase 100 %

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TiO2-SB

500 °C

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TiO2-powder untreated

anatase 88 % rutile 12 % anatase 100 %

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Caroline Goedecke

PhD student, Bundesanstalt für Materialforschung und -prüfung, Germany, Division 1.8 – Environmental Analysis and Technische Universität Berlin, Department of Environmental Process Engineering

10/2007-10/2013

Diploma in Chemistry, Humboldt-Universität zu Berlin, Department of Chemistry

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01/2014-current

Dr. Regine Sojref

03/1992-current

Senior Scientist, Bundesanstalt für Materialforschung und -prüfung, Germany, Division 5.6 – Glass

ACCEPTED MANUSCRIPT Scientist, Akademie der Wissenschaften, German Democratic Republic, Central Institute for Inorganic Chemistry

10/1981 – 12/1985

PhD (Dr. rer. nat), D.I. Mendeleev University of Chemical Technology of Russia

09/1979 – 09/1981

Scientist, Kombinat Keramische Werke Hermsdorf, Germany

09/1974 – 08/1979

Diploma in Chemistry, D.I. Mendeleev University of Chemical Technology of Russia

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01/1985 – 02/1992

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Thi Yen Nguyen

Diploma in Chemistry, Humboldt-Universität zu Berlin, Department of Chemistry

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10/2007-04/2013

PhD student, Bundesanstalt für Materialforschung und -prüfung, Germany, Division 1.3 – Structure Analysis and Humboldt-Universität zu Berlin

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06/2013-current

Dr. Christian Piechotta

05/2005-current

Senior Scientist, Bundesanstalt für Materialforschung und -prüfung, Germany, Division 1.8 – Environmental Analysis

09/2003 – 04/2005

Postdoc, VLB-Berlin, Germany

ACCEPTED MANUSCRIPT PhD (Dr. rer. nat), Technische Universität Berlin, Department of Biotechnology

10/1994 – 04/1997

Diploma in Chemistry, Technische Universität Berlin, Department of Chemistry

04/1990 – 04/1994

Dipl. Ing (FH) in “Technical Chemistry”, Beuth University of Applied Science Berlin

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05/1997 – 09/2003

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Graphical abstract

ACCEPTED MANUSCRIPT Highlights SiO2 granules coated with TiO2 were generated using high shear granulation



the granules showed great photocatalytic activity



nanozirconia-bound granules retained their integrity in stirred aqueous

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multiple use of granules is possible

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solutions over several hours