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Improving the carbon dioxide uptake efficiency of activated carbons using a secondary activation with potassium hydroxide

Zgrzebnicki M., Michalczyszyn E., Wrobel R. J.

Polish Journal of Chemical Technology

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2018

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Vol. 20, nr 3

87--94

EN

Secondary activation of commercial activated carbon (AC) ORGANOSORB 10-CO was carried out at 600, 700 and 800°C with mass ratios of potassium to AC (K/AC) in range 1–3. Crucial samples have shown following CO2 uptakes and SSA – 3.90 mmol/g and 1225 m2/g, 4.54 mmol/g and 1546 m2/g, 4.28 and 1717 m2/g for pristine material and samples obtained at 700°C with K/AC = 2 and at 800°C with K/AC = 3 respectively. Last sample also indicated significant mesopore volume increase in diameter range 2–5 nm, from 0.11 to 0.24 cm3/g. CO2 uptake increase was explained by formation of micropores up to diameter of 0.8 nm, which distribution was established from CO2 sorption using DFT. Surface chemistry of all samples has not changed during modification, what was proven by XPS. Moreover, deeper incorporation of potassium ions into graphite at higher temperatures was observed as confirmed with EDS, XPS and XRD.

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Preparation and characterization of titania powders obtained via hydrolysis of titanium tetraisopropoxide

Grzeskowiak M, Wrobel R. J., Grzechulska J., Przepiorski J

Materials Science Poland

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2014

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Vol. 32, No. 1

71--79

EN

TiO2 powders were prepared through the hydrolysis of titanium isopropoxide followed by calcination at temperatures of 200 °C to 600 °C. The obtained powders were characterized by N2 adsorption-desorption and X-ray powder diffraction. The results confirmed strong dependence between specific surface area of the TiO2 powders and both the conditions of the hydrolysis process and the calcination temperature. While calcination temperature strongly affected crystallinity of the product, no significant influence of the hydrolysis conditions on this parameter was observed. TiO2 powders prepared at various conditions were examined as catalysts for photodegradation of Acid Red 18 in water. Photoactivities of the prepared powders were influenced by both the amount of water used to hydrolyze the TiO2 precursor and the temperature of calcination process. TiO2 samples calcined at 500 °C appeared to be the most active and the photocatalytic activities of the prepared materials increased along with the amount of water used for the hydrolysis process.

3

Thermal stability of nanocrystalline iron

Wrobel R. J.

Materials Science Poland

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2012

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Vol. 30, No. 1

63-69

EN

Nanocrystalline iron was obtained by reduction of magnetite doped with structural promoters at 773 K and characterized by various methods i.e. thermal desorption of gases (BET), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Crystallite size distribution was determined using a novel method based on a phenomenon unique to nanomaterials, i.e. the dependence of the crystallite phase transition on the size of the crystallites. Thermal treatment of the nanocrystalline iron in a hydrogen atmosphere at 1073 K revealed that it is thermally unstable. The parameters of the log-normal crystallite size distribution were d0 = 15.3 nm, s = 0.35 and d0 = 23.5 nm, s = 0.17 for iron treated at 773 K and 1073 K, respectively. The corresponding average crystallite sizes determined from the Scherrer formula were 18 nm and 24 nm, respectively. The size distribution of the sintered materials clearly shows that the thermal stability is a function of the size of the crystallites, i.e. the smallest crystals are the least thermally stable. However, no increase in the contribution of crystallites above 35 nm has been observed. Application of this phenomenon combined with the determination of crystallite size distribution enables fine-tuning of the crystallite size distribution.