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Titanium(IV) Oxide Modified with Activated Carbon and Ultrasounds for Caffeine Photodegradation: Adsorption Isotherm and Kinetics Study

Zawadzki Piotr, Kudlek Edyta, Dudziak Mariusz

Journal of Ecological Engineering

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2020

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Vol. 21, nr 8

137--145

EN

In this paper the adsorption and photodegradation of caffeine (CAF) using modified photocatalysts were studied. The laboratory synthesis method of commercial titanium(IV) oxide, activated carbon and ultrasound was proposed. The adsorption effect of caffeine was described by the Langmuir and Freundlich isotherms. The effectiveness of CAF photocatalytic decomposition was evaluated as well as the parameters of the pseudo-first-order and pseudo-second-order reaction kinetics were estimated. It was determined that the caffeine adsorption fit both the Langmuir and Freundlich isotherms. The value of the experimental maximum adsorption capacity (qe) was the highest for TiO2 modified with activated carbon and ultrasounds (TiO2/AC/Us). The highest removal degree (over 99.0%) of CAF was observed for titanium(IV) oxide modified with activated carbon. Both photodegradation kinetics models show good or very good fit; however, the pseudo-first-order model shows better fit to the experimental data (R2 = 97–99%). After 20 minutes of the photodegradation process, the following efficiency order was determined: TiO2 < TiO2/AC < TiO2/AC/US. The results indicate that the combination of TiO2, activated carbon and ultrasound is an interesting alternative for the efficient degradation of caffeine, comparing to commercial TiO2.

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Kinetics of the Photocatalytic Decomposition of Bisphenol A on Modified Photocatalysts

Zawadzki P., Kudlek E., Dudziak M.

Journal of Ecological Engineering

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2018

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Vol. 19, nr 4

260--268

EN

This paper presents the evaluation of the photocatalytic kinetics of bisphenol A decomposition in the presence of commercial titanium(IV) oxide and modified photocatalysts (composites). The following modification methods were used: mechanical mixing, calcination and impregnation. The decomposition process was carried out with the addition of photocatalysts and activated carbon at doses of 100 mg/dm3 and 25 mg/dm3, respectively. The photocatalytic process was performed in a reactor from the Heraeus Company (Warsaw, Poland) with a volume of 0.7 dm3. The reactor was equipped with an immersed medium-pressure mercury lamp with a power of 150 W (λ = 200–580 nm). The degree of bisphenol A decomposition was determined by chromatographic analysis preceded by solid-phase extraction SPE. The qualitative-quantitative analysis was performed using a high-performance liquid chromatograph HPLC (UV detector, λ = 218 nm) from Varian (Warsaw, Poland). The dependence of the BPA decomposition on the duration of irradiation was found, wherein the modified photocatalysts were the most effective (from 75 to 90% after 15 minutes). The order of photocatalyst efficiency has been proposed as follows: TiO2<.sub> < TiO2/AC < Cdextran-TiO2/AC < Cmethanol-TiO2/AC< Cethanol-TiO2/AC < TiO2-AC. The highest degree of decomposition was observed in the presence of TiO2/AC (99%). Numerous studies suggest that the results of the TiO2 photocatalytic oxidation of organic substances fit well with the Langmuir–Hinshelwood (L–H) kinetic model. The kinetic parameters of the photocatalysis process were carried out according to the L-H model. According to the pseudo-first-order parameters, the results showed that the decomposition of bisphenol A was most intensive in the first 15 minutes of the process.

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Wpływ rodzaju fotokatalizatora i odczynu roztworu na efektywność fotokatalitycznego rozkładu bisfenolu A

Zawadzki P., Kudlek E., Dudziak M.

Proceedings of ECOpole

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2017

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Vol. 11, No. 2

661--669

PL

Przedstawiono badania porównawcze efektywności rozkładu bisfenolu A (BPA) w procesie fotokatalizy, prowadzonym z udziałem komercyjnego ditlenku tytanu (TiO2) oraz własnych modyfikowanych fotokatalizatorów (kompozytów) otrzymanych na bazie komercyjnego TiO2, węgla aktywnego (AC) oraz alkoholu metylowego (C), tj. TiO2/AC i C-TiO2/AC. Określono wpływ początkowej wartości odczynu roztworu modelowego (w zakresie od 4 do 7) na skuteczność adsorpcji oraz rozkładu badanego mikrozanieczyszczenia za pomocą promieniowania ultrafioletowego (UV). Na podstawie przeprowadzonej analizy chromatograficznej HPLC stwierdzono, że stopień usunięcia bisfenolu A był wyższy w przypadku zastosowania modyfikowanych fotokatalizatorów niż dla komercyjnego TiO2. Prawdopodobnie było to związane z obecnością węgla aktywnego, który w układzie TiO2-AC czy też C-TiO2/AC pełni nie tylko funkcję nośnika fotokatalizatora, ale jest również czynnikiem zwiększającym potencjał adsorpcyjny kompozytu. W oparciu o kinetykę Langmuira-Hinshelwooda (L-H) wyznaczono również parametry kinetyczne przeprowadzonych procesów. Na podstawie obliczonych wartości pseudo-pierwszorzędowych stałych szybkości reakcji udokumentowano, że proces rozkładu bisfenolu A przebiega najintensywniej w pierwszych 15 minutach prowadzenia procesu. Z kolei wartość stałej szybkości reakcji k była wyższa dla modyfikowanych fotokatalizatorów niż dla komercyjnego TiO2. Nie zaobserwowano znaczącego wpływu pH roztworu na adsorpcję oraz rozkład BPA w obecności komercyjnego ditlenku tytanu. Natomiast zarówno sorpcja, jak i proces fotokatalizy realizowany przy udziale modyfikowanych fotokatalizatorów zależały od odczynu roztworu. Największy stopień rozkładu bisfenolu A zaobserwowano, naświetlając roztwór o pH 4.

EN

In this study the photocatalytic degradation of bisphenol A in the presence of titanium dioxide (TiO2) and own modified photocatalysts (composites) based on TiO2, activated carbon (AC) and methyl alcohol (C) i.e. TiO2/AC and C-TiO2/AC were investigated. The effect of initial pH (in the range from 4 to 7) of model solution were determined in order to adsorption effectiveness and decomposition of tested micropollutant under ultraviolet irradiation (UV). Based on chromatographic analysis (HPLC) results it was found that the decomposition of bisphenol A was higher for modified photocatalysts than for commercial TiO2. It was possibly associated with the presence of activated carbon, which in TiO2/AC and C-TiO2/AC system is not only a support for photocatalysts but also increases the adsorption capacity. Based on the Langmuir-Hinshelwood (L-H) model, the kinetic parameters of the photocatalysis process were carried out. According to the pseudo first-order parameters, the results showed that the decomposition of bisphenol A was most intensively in the first 15 minutes of the process. However the value of the k rate was higher for modified photocatalysts than for commercial TiO2. No significant effect of pH on adsorption and BPA decomposition in the presence of commercial titanium dioxide were observed. Whereas, both the sorption and photocatalysis carried out in the presence of modified photocatalysts depended on the pH of model solution. The highest degree of bisphenol A decomposition were observed by irradiating mixture at pH 4.

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Influence of titanium dioxide modification on the antibacterial properties

Rokicka P., Markowska-Szczupak A., Kowalczyk Ł., Kowalska E., Morawski A. W.

Polish Journal of Chemical Technology

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2016

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Vol. 18, nr 4

56--64

EN

Antibacterial properties of 15 titania photocatalysts, mono- and dual-modified with nitrogen and carbon were examined. Amorphous TiO2 , supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO2 , C-TiO2 , N-TiO2 ;2 and N,C-Ti2 2 calcined at 300°C, 400°C, 500°C, 600°C, 700°C). The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artificial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artificial sunlight irradiation. The efficiency of disinfection process conducted under artificial sunlight irradiation with carbon (C-TiO2 ) and carbon/nitrogen (N,C-TiO2 ) photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.