35 research outputs found
Antioxidant Effect of Humic Substances from Hungarian Leonardite
Humic substances are natural substances that are continuously formed from the decay of plant residues. These materials have a very diverse range of properties, making them versatile. According to many new studies, these humic substances also exhibit antioxidant propensities. The aim of this paper was to shed light on whether humic substances really have antioxidant properties
Felületkémia és szelektivitás nagyfelületű szeneken = Chemical structure and performance of high surface area carbons
A hamumentes polimer alapĂş szeneken vizsgáltuk a felĂĽletkĂ©mia Ă©s a szorpciĂłs tulajdonságok közti kapcsolatot. MorfolĂłgiailag igen hasonlĂł, vĂzmentes Ă©s vizes közegben jellemzett oxigĂ©n, nitrogĂ©n Ă©s hidrogĂ©n heteroatomot tartalmazĂł szeneken mind gĹ‘z-, mind hĂgoldat adszorpciĂłs folyamatokban igazoltuk a felĂĽlet kĂ©miai tulajdonságainak meghatározĂł jellegĂ©t. A felĂĽleti tulajdonságok nem csak az egyensĂşlyt, de a folyamatok sebessĂ©gĂ©t is befolyásolják. Ăšj fĂĽggvĂ©nyt vezettĂĽnk be a pĂłruskitöltĹ‘dĂ©s nyomonkövetĂ©sĂ©re Ă©s ennek használhatĂłságát mind poláros, mind apoláros gĹ‘zök esetĂ©n bemutattuk. Vizsgáltuk további, elsĹ‘sorban fĂ©m heteroatomok beviteli lehetĹ‘sĂ©geit polimer alapĂş szĂ©nmátrix kialakĂtásának kĂĽlönbözĹ‘ stádiumaiban. MegállapĂtottuk, hogy lignocellulĂłz alapĂş szenek esetĂ©ben a Na Ă©s Si atomok bevitele (vĂzĂĽveges mĂłdosĂtás) gyakorlatilag nem befolyásolja a vizsgált szorpciĂłs tulajdonságokat, de kedvezĹ‘en hat a mechanikai tulajdonságokra. Amennyiben a fĂ©mionok hozzáadása a prekurzor polimer szintĂ©zise során ill. a pĂłrusos szerkezet rögzĂtĂ©se (szárĂtás) elĹ‘tt törtĂ©nik, a mátrix szerkezete, a fajlagos felĂĽlet Ă©s a pĂłrusszerkezet is jelentĹ‘sen mĂłdosul. UtĂłlagos kezelĂ©s esetĂ©n a porozitáshoz kapcsolhatĂł változásokat elsĹ‘sorban a pĂłrusok eltömĹ‘dĂ©se okozza. | The relationship between surface chemistry and sorption performance was studied on ash-free polymer-based carbons. In carbons that were morphologically similar and contained oxygen, nitrogen and hydrogen hetero atoms, the role of the surface chemistry was demonstrated in sorption processes from both the vapour and the liquid phase. The surface properties influence not only the adsorption equilibrium but play a role in the kinetics as well. A new function was introduced to follow the pore filling. Its applicability was shown for polar and nonpolar vapours. The possibility of introducing further, mainly metal, heteroatoms was studied at various stages of the carbon synthesis. In the case of lignocellulosic matrices we found that introducing Si and Na atoms (in the form of waterglass) results in improvement of mechanical strength rather than of the adsorption properties. When metal ions were added to the polymer precursor during the polymerization step or before the drying process, both the morphology and the porosity of the matrix can be severely influenced. Post-carbonization treatment, however, leads to obstruction of the pore entrance and thus a reduction of the accessible porosity