Mineralna vlakna, fibroza i azbestna tjelešca u plućnom tkivu radnika koji su bili izloženi azbestnom cementu

Samples of lung tissue taken from deceased asbestos-cement workers, with (N = 7) and without (N = 69) mesothelioma, and from individually matched controls (N = 96) were examined. The number of asbestos bodies and the grade of fibrosis were determined with light microscopy, and the type, size, and number of fibres with transmission electron microscopy and energy dispersive X-ray spectrometry. The asbestos content was, as expected, higher among the exposed workers than among the controls. Chrysotile was the major fibre type in terms of fibre count. Conversion to fibre mass reversed the pattern to a predominance of amphibole fibres, and accentuated the differences between exposed workers and controls. Duration of exposure and the number of asbestos bodies displayed significant associations with all the singular amphiboles (amosite, crocidolite, tremolite, and anthophyllite), but not with chrysotile. Fibrosis was related to the tremolite content, but not to chrysotile, both among exposed workers and controls. The workers with mesothelioma had higher levels of crocidolite and tremolite than the other asbestos-cement workers.Ispitivani su uzorci plućnog tkiva umrlih radnika koji su bili izloženi azbestnom cementu, s mezoteliomom, i bez njega, i njihovim odgovarajućim kontrolama. Broj azbestnih tjelešaca i stupanj fibroze određeni su svjetlosnim mikroskopom, a tip, veličina i broj vlakana elektronskom mikroskopijom i rendgenskom spektrometrijom. Sadržaj azbesta bio je veći kod izloženih radnika negoli u kontrola. Krizotilna vlakna bila su najbrojnija među formiranim vlaknima. Nađena je da je duljina izloženosti i broj azbestnih tjelešaca u korelaciji sa svim pojedinačnim amfolitima (amozit, krocidolit, tremolit i antofilit), ali ne i s krizotilom. Nalaz fibroze bio je u korelaciji s tremolitom, za razliku od krizolita, i to u eksponiranih i kontrolnih radnika. Uzorci plućnog tkiva radnika s mezoteliomom sadržavali su više krocidolita i tremolita od drugih radnika koji su bili izloženi azbestnom cementu

Bacterial oxidation of an arsenical gold sulphide concentrate from Olympias, Greece

Δημοσίευση σε επιστημονικό περιοδικόSummarization: The application of bacterial oxidation as a pretreatment step for the extraction of gold from arsenical gold sulphide concentrates offers potentially significant economic advantages over oxidative pretreatment alternatives. In this study the bacterial oxidation of an extremely refractory gold sulphide concentrate, from Olympias, Greece, is examined. Leaching tests were conducted in air-stirred pachuca reactors in order to determine the effect of pulp density on the degree of pyrite and arsenopyrite oxidation. Cyanidation tests were conducted in order to determine the degree of gold and silver liberation in relation to the degree of each sulphide phase oxidised and to the cyanide consumed. Mathematical analysis of the leaching data allowed the gold distribution in each sulphide mineral phase to be estimated and the gold recoveries according to the degree of each mineral oxidised predicted.Presented on: Minerals Engineerin

Mineralogical characteristics and treatment of refractory gold ores

Δημοσίευση σε επιστημονικό περιοδικόSummarization: Refractory gold ores and concentrates are characterised by low gold recoveries and high cyanide consumptions when subjected to direct cyanide leaching. Therefore an oxidation pretreatment step is required before cyanidation that will break up the sulphide lattice and render gold particles accessible to cyanide ions. The main three options for the treatment of refractory ores and concentrates include the traditional oxidation roasting, the modern pressure oxidation and the bacterial oxidation which is still at an advanced experimental stage. The present work focuses on the mineralogical factors influencing the refractoriness of gold, the main characteristics and developments of each process and provides economic comparative data from various operations worldwide. Environmental considerations are also briefly discussed.Presented on: Minerals Engineerin