Electrolysis of Gold from Filtration Waste by Means of Mechanical Activation
The intensification of the gold thiourea leaching from a filtration waste (Kosice, Slovakia) using mechanical activation as the pretreatment step has been studied. The leaching of “as-received“ sample in an acid thiourea solution resulted in 65 % Au dissolution. However, after mechanical activation in a planetary mill 99 % of the gold was leached. The optimum redox potential for electrolysis is in the range 500-523 mV for the gold extraction 99.79 % from the mechanically activated sample. The mechanical activation resulted in an increase of the specific surface area of the waste from 0.7 m 2 g -1 to a maximum value of 13.5 m 2 g -1 . The physicochemical changes in the filtration waste as a consequence of mechanical activation had a pronounced influence on the subsequent gold extraction.
A processing method of the goldsmith's and electronic Au-Ag-containing wastes
Sposob spracovania zlatnickych a elektronických Au-Ag odpadov Veľke množstva odpadov z elektrických a elektronických zariadeni sa hromadia v celej Europe. Každý spotrebiteľ vyprodukuje priemerne 16 kg tohto odpadu za rok, co v Europe predstavuje celkovo sesť milionov ton za rok. Ide o obrovske plytvanie zdrojmi. Znamena to taktiež veľke ekologicke nebezpecenstvo, keďže elektricke spotrebice a elektronicke zariadenia obsahuju vysoko toxicke ťažke kovy a organicke znecisťujuce latky. Podľa nových predpisov EU budu musieť výrobcovia odteraz platiť za zber a likvidaciu týchto výrobkov. Odpady usľachtilých kovov Au-Ag predstavuju siroku skalu typov a foriem odpadov s roznymi balastnými prvkami aj zložkami. Problematika spracovania odpadov s obsahom Au a Ag je vysoko aktualnou v celosvetovom meradle z hľadiska hodnoty a specifických vlastnosti týchto kovov ako aj ich nenahraditeľnosti v oblasti bankovnictva, zdravotnictva, priemyslu a v neposlednom rade aj v samotnej výrobe a predaji zlatnickych výrobkov. Predkladaný navrh možnosti spracovania Au-Ag zlatnickych a elektronických odpadov si kladie za cieľ ziskať zlato a striebro v kovovej forme. Aplikacia navrhovaneho procesu spracovania uvedených Au-Ag odpadov predstavuje pre spolocnosť praktický, ekonomický a zaroveň ekologický význam pri ich spracovavani. Ziskavanie zlata, resp. striebra z Au-Ag odpadov je mimoriadne doležite v podmienkach inflacneho vývoja, kedy tieto usľachtile kovy su stabilným zdrojom pokrývania potrieb spolocnosti.
Cross talk between redox signalling and metabolic activity of osteoblasts and fibroblasts in the presence of hydroxyapatite-based biomaterials influences bone regeneration
Regeneration of bone tissue defects that result from metabolic disorders, including periodontal diseases, can be supported by biomaterials based on hydroxyapatite. Despite of good biocompatibility of biomaterials they can cause oxidative stress and inflammatory processes as a result of mechanical interaction with surrounding tissues. Because osteoblasts are responsible for bone regeneration process in which gingival fibroblasts may also participate, the aim of the work was to investigate the influence of hydroxyapatite-based biomaterials (allogeneic and xenogeneic) and biomaterials combined with enamel matrix derivative (Emdogain) on osteoblast and fibroblast redox balance in the context of osteoblast proliferation and differentiation.
The results showed that examined substitutes were not cytotoxic in vitro, but affected redox balance of osteoblasts and fibroblasts (ROS level increase and GSH level decrease) which led to oxidative stress (MDA and protein carbonyl groups level increase) resulting in an increase of the Nrf2 and NFκB expression. The consequence of these changes was partial inhibition of proliferation and osteoblast differentiation. Emdogain alone and combined with biomaterials decreased ROS generation and increased GSH level in both osteoblasts and fibroblasts leading to reduction of transcription factors expression especially proinflammatory NFκB, which promoted osteoblast differentiation and mineralization process.