Activated carbons modified with sewage sludge derived phase and their application in the process of NO2 removal

Highly porous wood-based activated carbon was treated with species extracted from the surface of pyrolyzed sewage sludge. Their deposition on the external surface was visible by a change of the color of the carbon and on internal surfaces, by a decrease in porosity. The as-received carbon and its impregnated counterpart were heat treated at 950 °C at an inert atmosphere. Data for the adsorption on NO₂ was carried out from dry and moist (70% humidity) air. The results indicated that for all materials a significant amount of NO₂ was reduced to NO and released from the system. Heat treatment increases the capacity possibly as a result of an increase in basicity. The addition of the inorganic phase has a positive effect only when adsorption is run in moist conditions and inorganic nitrates and nitrites were formed. Otherwise, the NO₂ adsorbed and nitric and nitrous acids formed on the surface significantly increase the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates.     

Calcium Phosphate Materials Prepared from Precipitates with Various Calcium:Phosphorus Molar Ratios

Depending on the calcium:phosphorus molar ratio of the initial precipitates determined by precipitation conditions (calcium:phosphorus molar ratio of reactants and pH of reaction environment), after sintering at 1250°C, monophase, biphase, or triphase ceramics consisting of hydroxyapatite, β-tricalcium phosphate, α-tricalcium phosphate, and calcium oxide were obtained. The phase composition and properties—i.e., density, shrinkage, hardness, bending strength, and roughness—of the fractured surfaces of the isostatically re-pressed sinters were determined.     

High-pressure catalytic and thermal cracking of polyethylene

The thermal cracking and catalytic cracking processes of low-density polyethylene were studied in a closed autoclave. The compositions of gaseous and liquid products were analysed by means of GC/FID and GS/MS chromatographic methods. The fractional composition of liquid products was found by distillation. Increased temperature of PE depolymerisation process increases the production of gaseous products and low-boiling liquid compounds; more aromatic hydrocarbons are formed instead of alkenes. When a lower temperature and longer time are adopted for the process to reach the assumed conversion, more straight chained hydrocarbons are produced. The acidic aluminosilicate catalyst yields more low-boiling liquid fractions, more isoalkanes and more aromatics. The neutral alumina is favourable for the production of alkenes and vacuum gas oil fraction in comparison to a non-catalytic process. The Ni–Mo/Al₂O₃ catalyst is efficient in hydrogenation of depolymerisation products. The reaction products contain only saturated compounds then and no aromatics are formed.     

Formation and stability of barium aluminate and cerate in NOx storage-reduction catalysts

The formation and stability of BaAl₂O₄ and BaCeO₃ in Pt-Ba/Al₂O₃ and Pt-Ba/CeO₂ based NO_x storage-reduction (NSR) catalysts has been investigated using kinetic measurements, X-ray diffraction, thermal analysis and X-ray absorption spectroscopy. In as-prepared state, the Ba-component in the NSR catalysts was made up of amorphous BaO and BaCO₃. The formation of BaAl₂O₄ started above 850 °C, whereas the formation of BaCeO₃ was already observed at 800 °C and was faster than that of BaAl₂O₄. The stability of BaAl₂O₄ and BaCeO₃ in various liquid and gaseous atmospheres was different. BaAl₂O₄ was rapidly hydrated at room temperature in the presence of water and transformed to Ba(NO₃)₂ and γ-alumina in the presence of HNO₃, whereas BaCeO₃ was decomposed to much lower extent under these conditions. Interestingly, BaCeO₃ was transformed to Ba(NO₃)₂/CeO₂ in the presence of NO₂/H₂O at 300–500 °C. Also, the presence of CO₂ led to decomposition of barium cerate, which has important consequences for the catalyst ageing under NO_x-storage conditions and can be exploited for regeneration of thermally aged NSR-catalysts.     

Kinetic studies on copolycondensation processes. VI. Influence of copolycondensation temperature on tetrad distribution of the PDT/FT aromatic copolyterephthalate by 1H-NMR spectroscopy

¹H-NMR and Eu(fod)₃ lanthanide shift reagent were used to determine tetrad distribution of comonomer units of the PDT/FT copolyterephthalate obtained from terephthaloyl chloride (intermonomer) and 3,3′-dimethylbisphenol A and phenolphtalein (comonomers). Computer simulations of the terephthalic proton signal split into the lines of compositional tetrads were performed to obtain quantitative data. To characterize the microstructure of the copolymer samples synthesized at different temperatures, the degree of randomness and the degree of alternation were calculated. It was shown that the latter can differentiate the chains which seemed to be identical concerning the diad distribution only.     

Surface and interfacial FTIR spectroscopic studies of latexes. IX. The effect of homopolymer and copolymer structures on surfactant mobility in Sty/BA latices

The effects of homopolymer and copolymer compositions and structures in styrene/n-butyl acrylate (Sty/BA) latices on sodium dioctyl sulfosuccinate (SDOSS) surfactant mobility and its preferential concentration at the film–air (F–A) and film–substrate (F–S) interfaces were examined using attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy. It appears that the SDOSS concentration at the F–S interface is highest when the Sty/BA feed ratio is 50/50, and the excess of Sty results in migration of SDOSS surfactant to the F–A interface. This behavior is attributed to the increased glass transition temperature and diminished compatibility between surfactant molecules and copolymer latex. This study also shows that the primary factors that influence exudation to either F–A or F–S interfaces are surface tension of the substrate, glass transition temperature, water flux during coalescence, and compatibility between latex components. © 1995 John Wiley & Sons, Inc.     

The behaviour of high polar organic solvents at platinum electrode — II. Adsorption and electrode reactions of acetonitrile

The adsorption of acetonitrile and reduction of adsorbed molecules at platinized platinum electrode were studied by potentiodynamic and radiometric techniques. During acetonitrile adsorption the reversibly and irreversibly adsorbed species are formed. One electron reduction process occurs in the potential range 0.45-0.15 V. Below 0.15 V the deeper reduction of adsorbed acetonitrile takes place — the final products are ammonia and ethane. The differences of smooth and platinized platinum electrodes properties are briefly discussed.     

The assessment of microorganism growth in the membrane distillation system

Growth of microorganism in the membrane distillation (MD) system has been evaluated, and their presence on the membrane surface was studied using scanning electron microscopy (SEM) coupled with energy dispersion spectrometry (EDS). The membrane samples were collected from MD modules used for the following applications: concentration of salts and acids, production of demineralized water from tap water, separation of ethanol from fermentation broth in a membrane bioreactor and treatment of saline wastewater containing Pseudomonas and Streptococcus faecalis bacteria and Penicillium and Aspergillus fungi. The MD experiments were performed with polypropylene capillary membranes. SEM examinations of the membranes used for the treatment of saline wastewater indicated a significant amount of S. faecalis bacteria and Aspergillus fungi. The polypropylene membranes used did not reject S. faecalis bacteria, which were detected on the membrane surface on the distillate side. The presence of fungi in the membrane pores was observed only on the feed side. The contamination of the membrane surface by yeast cells was not observed in the case of the membrane bioreactor operated over one year. The running conditions of the MD process (such as elevated temperature, significant salt concentrations and low pH values) inhibited the growth of microorganism in the MD system.