Nenad Radić

Nanocrystalline CeO2-δ as effective adsorbent of azo dyes.

Ultrafine CeO2-δ nanopowder, prepared by a simple and cost-effective self-propagating room temperature synthesis method (SPRT), showed high adsorption capability for removal of different azo dyes. Batch type of adsorption experiments with fixed initial pH value were conducted for the removal of Reactive Orange 16 (RO16), Methyl Orange (MO), and Mordant Blue 9 (MB9). The equilibrium adsorption data were evaluated using Freundlich and Langmuir isotherm models. The Langmuir model slightly better describes isotherm data for RO16 and MO, whereas the Freundlich model was found to best fit the isotherm data for MB9 over the whole concentration range. The maximum adsorption capacities, determined from isotherm data for MO, MB9, and RO16 were 113, 101, and 91 mg g(-1) respectively. The adsorption process follows the pseudo-second-order kinetic model indicating the coexistence of chemisorption and physisorption. The mechanism of azo dye adsorption is also discussed.

Ethylene oxide removal in combined sorbent/catalyst system

The investigation of ethylene oxide (EtO) catalytic incineration over Pt/Al 2 O 3 catalyst conducted in fixed bed reactor (diameter of 315 mm) showed that significant degree of EtO adsorption occurred when the inlet gas temperature was lower than ignition temperature (180°C). This observation was a basis for the development of a hybrid reactor for EtO removal using modified spouted bed with draft tube loaded with Pt/Al 2 O 3 catalyst. The annular region of the bed was divided in two sections, the hot (reaction) section contained about 7% of catalyst and it behaved as a catalytic incinerator, while the cold (sorption) section, with the rest of the catalyst, behaved as an sorber. The catalyst particles recirculated between two sections by using a draft tube riser. To formulate the process parameters dynamics of EtO sorption on Pt/Al 2 O 3 catalyst and Al 2 O 3 support were studied. The proposed system for EtO removal gives the same efficiency as the fixed bed catalytic converter. The experimental data show that process is attractive for low EtO concentrations, because it enables significant energy savings. At steady state conditions temperature in the sorption section of 80-100°C was maintained. In the reaction section initial heating to the temperature of 200°C is sufficient to start up selfsustained deep EtO oxidation.

A Study of Water Influence on Carbon Monoxide Adsorption and Oxidation on Nanocrystals of: γ-Fe2O3, Au/Fe2O3 and MnxZn1-xFe2O4

In this paper the adsorption and oxidation of CO on nanocrystalline Au/γ-Fe2O3, Au/α- Fe2O3, γ-Fe2O3 and a series of mixed ferrite with MnxZn1-xFe2O4 composition are investigated. The catalysts were prepared by co-precipitation method and characterized using X-ray diffraction (XRPD), specific surface (BET), transition electron spectroscopy (TEM) and magnetization measurements. A temperature programmed desorption (TPD) study of the water and CO interaction with nanocrystalline adsorbents is presented. The catalytic activities towards CO oxidation increased in the following order: γ-Fe2O3 < MnxZn1-xFe2O4 < Au/γ-Fe2O3 .

Removal of volatile organic compounds from activated carbon by thermal desorption and catalytic combustion

The thermal desorption of saturated activated carbon discharged from an industrial adsorber and catalytic oxidation of desorbed products over a Pt/Al2O3 catalyst were investigated. The activated carbon is almost completely regenerated by flushing with air at 200°C for 30 min. Desorbed products are fully oxidized over the Pt/Al2O3 catalyst above 275°C.

Preparation of ZrO2 and Al2O3 Thin-Films on Stainless Steel by Spray Pyrolysis

We have investigated the deposition of ZrO2 and Al2O3 films on a stainless steel (SS) substrate by spray pyrolysis method. The ZrO2 films were deposited from aqueous solution of zirconium dinitrate oxide. For Al2O3 films, a boehmite sol was used. The specific surface areas of samples were determined by the BET-method and sample surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The spray pyrolysis method permits the preparation of ZrO2 and Al2O3 thin films on SS with good adhesion. This method enables preparation of oxide layers with relatively high specific surface area, suitable for applications as catalysts supports.

Preparation and Characterization of Al2O3 Thin Films for Catalytic Activity Studies

In the present work, the surface properties of various Al oxide films were investigated. The oxide films were produced on a stainless steel by spray pyrolysis and cathodic deposition methods. The films obtained represent typical layers that can be used as a support in model systems to investigate alumina-based catalysts. Information about the chemical environment of the Al and O ions in the oxide films depending on the preparation conditions has been deduced from the binding energies of the Al 2p and O 1s electron core levels and corresponding Auger parameters.

Prevention and control of dimethylamine vapors emission: Herbicide production plant

The widely used herbicide, dimethylamine salt of 2,4-dichlorophenoxy acetic acid (2,4-D-DMA), is usually prepared by mixing a dimethylamine (DMA) aqueous solution with a solid 2,4-dichlorophenoxy acetic acid (2,4-D). The vapors of the both, reactants and products, are potentially hazardous for the environment. The contribution of DMA vapors in overall pollution from this process is most significant, concerning vapor pressures data of these pollutants. Therefore, the control of the air pollution in the manufacture and handling of methylamines is very important. Within this paper, the optimal air pollution control system in preparation of 2,4-D-DMA was developed for the pesticides manufacturing industry. This study employed the simple pollution prevention concept to reduce the emission of DMA vapors at the source. The investigations were performed on the pilot plant scale. To reduce the emission of DMA vapors, the effluent gases from the herbicide preparation zone were passed through the packed bed scrubber (water scrubbing medium), and the catalytic reactor in sequence. The end result is a substantially improved air quality in the working area, as well as in the urbanized areas located near the chemical plant.