A detailed characterization of an iron oxy/hydroxide(gossan type) bearing refractory gold/silver ore was performed with a new diagnostic approach for the development of a pretreatment process prior to cyanide leaching...A detailed characterization of an iron oxy/hydroxide(gossan type) bearing refractory gold/silver ore was performed with a new diagnostic approach for the development of a pretreatment process prior to cyanide leaching. Gold was observed to be present as native and electrum(6-24 μm in size) and associated with limonite, goethite and lepidocrocite within calcite and quartz matrix. Mineral liberation analysis(MLA) showed that electrum is found as free grains and in association with beudantite, limonite/goethite and quartz. Silver was mainly present as acanthite(Ag2S) and electrum and as inclusions within beudantite phase in the ore. The cyanide leaching tests showed that the extractions of gold and silver from the ore(d80: 50 μm) were limited to 76% and 23%, respectively, over a leaching period of 24 h. Diagnostic leaching tests coupled with the detailed mineralogical analysis of the ore suggest that the refractory gold and silver are mainly associated within iron oxide mineral phases such as limonite/goethite and jarosite-beudantite, which can be decomposed in alkaline solutions. Based on these characterizations, alkaline pretreatment of ore in potassium hydroxide solution was performed prior to cyanidation, which improved significantly the extraction of silver and gold up to 87% Ag and 90% Au. These findings suggest that alkaline leaching can be used as a new diagnostic approach to characterize the refractoriness of iron oxy/hydroxide bearing gold/silver ore and as a pretreatment method to overcome the refractoriness.展开更多
Water hyacinth is a raw material for long-term sustainable production of cellulosics ethanol. In this study, the acid pretreatment and enzymatic hydrolysis were used to evaluate to produce more sugar, to be fermented ...Water hyacinth is a raw material for long-term sustainable production of cellulosics ethanol. In this study, the acid pretreatment and enzymatic hydrolysis were used to evaluate to produce more sugar, to be fermented to ethanol. Separated hydrolysis and fermentation （SHF） studies were carried out to produce ethanol from water hyacinth leaves. Dilute sulfuric acid pretreatment and enzymatic hydrolysis were conducted to select the optimum pretreatment conditions. The optimum pretreatment conditions included T = 135 ℃, t = 30 min, and sulfuric acid concentration = 0.1 M. The residue was enzymatically hydrolyzed using the mixture of enzymes cellulase, xylanase and pectinase. The maximum enzymatic saccharification of cellulosic material （76.8%） was achieved. SHF by mono-culture of Saccharomyces cerevisiae KM1195 achieved the highest yields of ethanol. Furthermore, ethanol production was accomplished with the co-culture ofS. cerevisiae TISTR5048 and Candida tropicalis TISTR5045 which produced the highest increase in ethanol Yield. In this case, the ethanol concentration of 3.42 （g/L）, percentage of the theoretical ethanol yield of 99.9%, the ethanol yield of 0.27 g/g and the productivity of 0.22 g/L/h were obtained. This suggested that mild acid pretreatment and co-cultureare promising methods to improve enzymatic hydrolysis and ethanol production from water hyacinth.展开更多
Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for qu...Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for quality of water in natural river or industrial waste water. Although the only method for selective detection for Cr （VI） ion is diphenylcarbazide, of which pretreatment spends long time according to the regulat^ons by the Ministry of Environment, Japan. Herein we develop a new and simple pretreatment for the job site and suitable for education and attempt to apply for analysis of the soil in Tama River actually.展开更多
基金Project(8300)supported by the Research Foundation of Karadeniz Technical University,Turkey
文摘A detailed characterization of an iron oxy/hydroxide(gossan type) bearing refractory gold/silver ore was performed with a new diagnostic approach for the development of a pretreatment process prior to cyanide leaching. Gold was observed to be present as native and electrum(6-24 μm in size) and associated with limonite, goethite and lepidocrocite within calcite and quartz matrix. Mineral liberation analysis(MLA) showed that electrum is found as free grains and in association with beudantite, limonite/goethite and quartz. Silver was mainly present as acanthite(Ag2S) and electrum and as inclusions within beudantite phase in the ore. The cyanide leaching tests showed that the extractions of gold and silver from the ore(d80: 50 μm) were limited to 76% and 23%, respectively, over a leaching period of 24 h. Diagnostic leaching tests coupled with the detailed mineralogical analysis of the ore suggest that the refractory gold and silver are mainly associated within iron oxide mineral phases such as limonite/goethite and jarosite-beudantite, which can be decomposed in alkaline solutions. Based on these characterizations, alkaline pretreatment of ore in potassium hydroxide solution was performed prior to cyanidation, which improved significantly the extraction of silver and gold up to 87% Ag and 90% Au. These findings suggest that alkaline leaching can be used as a new diagnostic approach to characterize the refractoriness of iron oxy/hydroxide bearing gold/silver ore and as a pretreatment method to overcome the refractoriness.
文摘Water hyacinth is a raw material for long-term sustainable production of cellulosics ethanol. In this study, the acid pretreatment and enzymatic hydrolysis were used to evaluate to produce more sugar, to be fermented to ethanol. Separated hydrolysis and fermentation （SHF） studies were carried out to produce ethanol from water hyacinth leaves. Dilute sulfuric acid pretreatment and enzymatic hydrolysis were conducted to select the optimum pretreatment conditions. The optimum pretreatment conditions included T = 135 ℃, t = 30 min, and sulfuric acid concentration = 0.1 M. The residue was enzymatically hydrolyzed using the mixture of enzymes cellulase, xylanase and pectinase. The maximum enzymatic saccharification of cellulosic material （76.8%） was achieved. SHF by mono-culture of Saccharomyces cerevisiae KM1195 achieved the highest yields of ethanol. Furthermore, ethanol production was accomplished with the co-culture ofS. cerevisiae TISTR5048 and Candida tropicalis TISTR5045 which produced the highest increase in ethanol Yield. In this case, the ethanol concentration of 3.42 （g/L）, percentage of the theoretical ethanol yield of 99.9%, the ethanol yield of 0.27 g/g and the productivity of 0.22 g/L/h were obtained. This suggested that mild acid pretreatment and co-cultureare promising methods to improve enzymatic hydrolysis and ethanol production from water hyacinth.
文摘Compounds containing Cr （VI） ion are widely used for chemical industry, paints, dyes, and other applications. Because of commonly known toxicity of Cr （VI） ion, Cr （VI） is one of the important check items for quality of water in natural river or industrial waste water. Although the only method for selective detection for Cr （VI） ion is diphenylcarbazide, of which pretreatment spends long time according to the regulat^ons by the Ministry of Environment, Japan. Herein we develop a new and simple pretreatment for the job site and suitable for education and attempt to apply for analysis of the soil in Tama River actually.
