Modified coal tar pitch was prepared by Friedel-Crafts reaction with 9,10-bis(chloromethyl)anthracene (BCMA). With the aid of IR and Raman’s spectroscopy it was found that BCMA reacted completely with aromatic components of pitch. This modification leads to a significant increase of the carbonisation residue of coal tar pitch without the structure of carbonisate being greatly affected., Jaroslava Svítilová, Vladimír Machovič and František Kolář., and Obsahuje bibliografii
Considerable amount of waste in the form of polyethylene terephthalate (PET) bottles could be utilized in the form of dispersed microreinforcement in concrete. PET fibres, however, have poor wettability and adhesion to cement paste, which can be modified by alkaline hydrolysis with sodium hydroxide at elevated temperature. The alkaline treatment was used to increase fibre surface, which was followed by changes in the structure of the interfacial transition zone (ITZ) and interfacial bond between fibre and cementitious matrix. Raman microspectroscopy mapping was employed to study microstructural changes of ITZ within the distance 0 - 250 μm from a PET fibre. The band at 357 cm-1 corresponding to the Ca-O bond vibration in portlandite was used to determine its distribution. For determination of the relative abundance of ettringite, the SO42- stretching vibration at 987 cm-1 was used. The most intensive bands of portlandite and ettringite were found within the distance 0 - 50 μm from an unmodified PET fibre. Besides the elevated concentration of these minerals, abundant pores occur in this region. In the case of alkaline modified PET fibres the ITZ zone was not found., Vladimír Machovič, Ladislav Lapčák, Lenka Borecká, Miloslav Lhotka, Jana Andertová, Lubomír Kopecký and Linda Mišková., and Obsahuje bibliografii
Arsenic, antimony and selenium belong to toxic contaminants with high environmental risk. In contrast to metal cationic contaminants (Be, Zn, Cd, Hg Pb, etc.) the metalloids and nonmetals of groups 5 and 6 of periodic system generally form the oxyanions in two oxidizing states (i.e. arsenates and arsenites, antimonates and antimonites, as well as selenates and selenites) in dependence on redox potential and pH value. It is well known that above mentioned oxyanions have a strong adsorption affinity to hydrated oxides and/or oxides hydroxides of Fe, Al and Mn, preferably Fe forming stable surface complexes. In fact, commercially produced Fe oxides-based sorbents are too expensive for strongly contaminated aqueous systems. Aluminosilicates have opened new possibilities in sorption technology due to favourable surface properties, availability, environmental and economical reasons, but they are not selective sorbents of anionic contaminants thanks to a low pHZPC. A simple Fe/Al/Mn pre-treatment of raw aluminosilicates can significantly improve their sorption affinity to oxyanionic contaminants, including arsenites and arsenates, selenites and selenates and antimonites and antimonates, respectively. Different types of natural and/or second-rate clays (metakaolines with the large content of Fe, raw bentonites and natural clinoptilolite-rich tuff, ) from Central European localities were used for FeII, FeIII, AlIII and MnII pre-treatment., Barbora Doušová, Lucie Fuitová, Lenka Herzogová, Tomáš Grygar, David Koloušek and Vladimír Machovič., and Obsahuje bibliografii
The structural changes of interfacial transition zone of two concrete systems reinforced by polypropylene/polyethylene and basalt fibers were studied by Raman microspectroscopy. The interfacial transition zone was found in the 0-20 μm in vicinity of quartz/feldspar aggregate surface. The calcium carbonate, ettringite and alite and belite bands were used for determination of interfacional transition zone size by Raman spectroscopy. Similar behaviour has been shown the cement matrix in neighbourhood of PP/PE fibers. There is not observed any concentration gradient of cement hydration product in the vicinity of 1 μm diameter basalt fiber., Vladimír Machovič, František Kolář, Petr P. Procházka, Šárka Pešková and Pavel Kuklík., and Obsahuje bibliografii
A combined sorbent was prepared by impregnation of lignite mined in the South Moravian Coalfield, Czech Republic, with chitosan. Sorption performance of the combined sorbent and the untreated lignite was tested for Co(II), Cu(II), and Cd(II) in equilibrium sorption experiments with respect to pH and metal concentration. The amount of metal retained by the sorbent was determined by instrumental neutron activation analysis in the short time irradiation mode with epithermal neutrons. For pH~5, sorption isotherms were determined and fitted using the Langmuir and Freundlich models. The results have been compared with those obtained previously for similar combined sorbent based on naturally oxidized coal mined in the Sokolov Basin, Czech Republic. It has been shown that the effect of chitosan on sorption efficiency of the chitosan-doped coal sorbents strongly depends on solution pH, and type of coal and metal., Martina Havelcová, Jiří Mizera, Vladimír Machovič, Lenka Borecká, Oldřich Přibyl and Ivana Krausová., and Obsahuje bibliografii