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Aim of study: To document for the first-time the biocultural knowledge related to the use, nomenclature, and classification of wild mushrooms by the Mazatec culture, cradle of the ethnomycology. Area of study: Municipality of Eloxochitlán de Flores Magón and communities of San José Buena Vista and Agua Ancha, belonging to the state of Oaxaca, in southern Mexico. Materials and methods: A total of 291 interviews were performed by using numerical ethnomycological methods, during the rainy seasons, between 2017 and 2021. Based on the knowledge of local experts, fungal specimens with biocultural relevance were collected. Socio-demographic information, knowledge of wild mushrooms and their usages, local nomenclature, culinary uses, and transmission of traditional knowledge were documented. Main results: Paradoxically, this is the first ethnomycological study that addresses a complete study of fungi with biocultural importance in the ethnic group where ethnomycology emerged as a discipline. Previous studies related to mushrooms with Mazatec people focused exclusively on entheogenic mushrooms leaving aside paramount issues related to traditional mycological knowledge of the fungal local resources, including their edibility and cultural relevance. All interviewees consumed mushrooms, indicating high levels of mycophilia. Twenty-seven species, all of them having a native Mazatec name, were identified. Species of Pleurotus, Auricularia, Cantharellus, and Schizophyllum spp. showed the highest cultural value indexes. Research highlights: Ethnomycological knowledge of Mazatec culture is prolific and related to local natural resources cosmovision, beliefs and traditions. Mycological knowledge is currently preserved among Mazatec people and it is still transmitted to new generations despite strong transculturation processes.

Studies have been carried out of the drivers involved in the shift to the archaeal-dominated culture currently observed in industrial biooxidation cultures during the BIOX leaching of gold-bearing sulphidic refractory ores. Experiments were carried out in a 7 litre stirred and aerated reactor operated under a draw-and-fill regime wherein 750 ml of the culture was removed daily and replaced with nutrient medium 0K and pyrite/arsenopyrite mineral concentrate such that a 20% solids loading was maintained. The reactor was maintained at 45 degrees C and pH 1.2 with the addition of lime when required. The culture comprised L. ferriphilum (50%), A. caldus (46%), A. cupricumulans (3%) and a small proportion of other archaea. Monitoring was carried out of redox potential, pH and temperature, and ferrous iron activity and DNA extraction and speciation analysis was undertaken. The results showed that the iron oxidation achieved at pH 1.0 for the industrially evolved culture supplemented with yeast extract resulted in a similar iron oxidation rate to that of the bacterial dominated culture. Conversely, the unsupplemented industrial culture showed reduced iron oxidation rates. Operation at low pH gave an increase in the proportion of archaeal species. Following the elevation of operating temperature to 48 degrees, increased iron leaching was observed at pH 1.0 than at higher pH values investigated for the evolved laboratory maintained culture., Studies have been carried out of the drivers involved in the shift to the archaeal-dominated culture currently observed in industrial biooxidation cultures during the BIOX leaching of gold-bearing sulphidic refractory ores. Experiments were carried out in a 7 litre stirred and aerated reactor operated under a draw-and-fill regime wherein 750 ml of the culture was removed daily and replaced with nutrient medium 0K and pyrite/arsenopyrite mineral concentrate such that a 20% solids loading was maintained. The reactor was maintained at 45 degrees C and pH 1.2 with the addition of lime when required. The culture comprised L. ferriphilum (50%), A. caldus (46%), A. cupricumulans (3%) and a small proportion of other archaea. Monitoring was carried out of redox potential, pH and temperature, and ferrous iron activity and DNA extraction and speciation analysis was undertaken. The results showed that the iron oxidation achieved at pH 1.0 for the industrially evolved culture supplemented with yeast extract resulted in a similar iron oxidation rate to that of the bacterial dominated culture. Conversely, the unsupplemented industrial culture showed reduced iron oxidation rates. Operation at low pH gave an increase in the proportion of archaeal species. Following the elevation of operating temperature to 48 degrees, increased iron leaching was observed at pH 1.0 than at higher pH values investigated for the evolved laboratory maintained culture.

Studies have been carried out of the effect of surfactant addition on microbial growth, ability for ferrous iron oxidation and chalcopyrite bioleaching using a mixed thermophilic microbial culture (dominant in Metallosphaera hakonensis). The non-ionic surfactants Tween 20, Tween 80, Plurafac LF 120, Plurafac LF 600, and Lutensol XL 90 were tested at concentrations of 5, 10 and 20 mg/l. It was found that the addition of 5 and 10 mg/l Tween 20 showed no negative effect on microbial ferrous iron oxidation and chalcopyrite bioleaching, and its presence was seen to reduce the initial leaching lag time. Microbial ferrous iron oxidation was inhibited in the presence of 10 mg/l Plurafac LF 120 while there was partial inhibition in the system containing 10 mg/l Lutensol XL 90. Plurafac LF 600 at 5 and 10 mg/l and Tween 80 at 10 mg/l inhibited microbial growth completely. In all cases, attachment of the thermophilic microorganisms to the concentrate surface was reduced in the presence of surfactant. However, the corresponding pH, redox potential and copper recovery data indicates that the relative lack of attachment of the microorganisms did not prevent bioleaching activity., Studies have been carried out of the effect of surfactant addition on microbial growth, ability for ferrous iron oxidation and chalcopyrite bioleaching using a mixed thermophilic microbial culture (dominant in Metallosphaera hakonensis). The non-ionic surfactants Tween 20, Tween 80, Plurafac LF 120, Plurafac LF 600, and Lutensol XL 90 were tested at concentrations of 5, 10 and 20 mg/l. It was found that the addition of 5 and 10 mg/l Tween 20 showed no negative effect on microbial ferrous iron oxidation and chalcopyrite bioleaching, and its presence was seen to reduce the initial leaching lag time. Microbial ferrous iron oxidation was inhibited in the presence of 10 mg/l Plurafac LF 120 while there was partial inhibition in the system containing 10 mg/l Lutensol XL 90. Plurafac LF 600 at 5 and 10 mg/l and Tween 80 at 10 mg/l inhibited microbial growth completely. In all cases, attachment of the thermophilic microorganisms to the concentrate surface was reduced in the presence of surfactant. However, the corresponding pH, redox potential and copper recovery data indicates that the relative lack of attachment of the microorganisms did not prevent bioleaching activity.

Discussion is presented of laboratory scale tests on the selective recovery of copper from pyrolysed PCBs. The pyrolysed PCBs were reacted with two different bioleaching solutions containing mixed mesophilic microbial consortia and a synthetic chemical solution for comparative purposes. The influence of char pre-treatment, reactor type, working temperature, and the origin of leaching solution on the dissolution of the zero valent copper was studied. It was found that the type of reactor had a more pronounced effect than the origin of bacterial solution in bringing copper in solution. Characterisation of the leached char confirmed the importance of the pre-treatment step. Other than ferric iron concentration and temperature, the leaching efficiency and kinetics were largely influenced by the bacterial activity. The fact that copper was brought into solution by ferric iron at starting concentrations well below the stoichiometric requirement, implies bacterial regeneration of the ferric iron and its cycling in the system. (Authors.), Discussion is presented of laboratory scale tests on the selective recovery of copper from pyrolysed PCBs. The pyrolysed PCBs were reacted with two different bioleaching solutions containing mixed mesophilic microbial consortia and a synthetic chemical solution for comparative purposes. The influence of char pre-treatment, reactor type, working temperature, and the origin of leaching solution on the dissolution of the zero valent copper was studied. It was found that the type of reactor had a more pronounced effect than the origin of bacterial solution in bringing copper in solution. Characterisation of the leached char confirmed the importance of the pre-treatment step. Other than ferric iron concentration and temperature, the leaching efficiency and kinetics were largely influenced by the bacterial activity. The fact that copper was brought into solution by ferric iron at starting concentrations well below the stoichiometric requirement, implies bacterial regeneration of the ferric iron and its cycling in the system. (Authors.)

Studies have been carried out of the effect of a combination of contaminants on ferrous iron oxidation activity in a two-stage biological iron oxidation and jarosite precipitation process at room temperature. The contaminants investigated were typical for nickel limonite effluents and for mineral sulphide bioleaching scenarios (5 g/l Mg, 2 g/l Al, 0.4 g/l Mn, 0.2 g/l Co, 0.05 g/l F and 0.05 g/l As). The fate of the contaminants was also studied. The performance of the system was evaluated based on iron oxidation and precipitation rate and efficiency, solution pH, redox, total suspended solids, and biomass concentration in the absence and presence of contaminants. Results showed that the contaminants slightly decreased iron oxidation rate and efficiency, and increased iron precipitation. Solution pH and cell concentration in the reactors were not notably affected by the contaminants. The presence of contaminants only marginally increased the co-precipitation of Cu and Ni with Fe which mainly precipitated as jarosite. Of the contaminants, F, As and Mg precipitated partially in the process, whereas the precipitation of Al, Cl, Co and Mn was very low. A. ferrooxidans and L. ferriphilum were detected in the continuous stirred tank reactors in the absence of contaminants, whereas L. ferriphilum was the only species detected after the introduction of the contaminants., Studies have been carried out of the effect of a combination of contaminants on ferrous iron oxidation activity in a two-stage biological iron oxidation and jarosite precipitation process at room temperature. The contaminants investigated were typical for nickel limonite effluents and for mineral sulphide bioleaching scenarios (5 g/l Mg, 2 g/l Al, 0.4 g/l Mn, 0.2 g/l Co, 0.05 g/l F and 0.05 g/l As). The fate of the contaminants was also studied. The performance of the system was evaluated based on iron oxidation and precipitation rate and efficiency, solution pH, redox, total suspended solids, and biomass concentration in the absence and presence of contaminants. Results showed that the contaminants slightly decreased iron oxidation rate and efficiency, and increased iron precipitation. Solution pH and cell concentration in the reactors were not notably affected by the contaminants. The presence of contaminants only marginally increased the co-precipitation of Cu and Ni with Fe which mainly precipitated as jarosite. Of the contaminants, F, As and Mg precipitated partially in the process, whereas the precipitation of Al, Cl, Co and Mn was very low. A. ferrooxidans and L. ferriphilum were detected in the continuous stirred tank reactors in the absence of contaminants, whereas L. ferriphilum was the only species detected after the introduction of the contaminants.

Spent printed circuit boards comminuted to 750 microns were bioleached in a double-stage continuous bioreactor to study the recovery of Fe, Cu, Ni, Zn, Pb, and Co. The first stage of the bioreactor was a bubble column in which an acidophilic consortium of Leptospirillum ferriphilum and Sulphobacillus benefaciens was used to oxidise iron(II) into iron(III) to produce an acidic ferric solution at 1 g/l Fe3+. This solution was then used to leach the metals contained in PCBs under mechanical stirring in the second stage of the bioreactor. It was found that in the first 400 h the average value of the redox potential in the second stage was much lower than that in the outlet from the first stage and Cu dissolution yield was below 1%, whereas yields of the other metals were relatively high (Fe 75%, Zn 33%, Ni 55% and Co 73%); after 400 h a significant increase in dissolution yield was observed (79%, 76%, 78% and 82%, respectively) while Pb dissolution yield remained constant at 7%. It is concluded that that solid/liquid ratio strongly influences bacterial activity, due to the expected toxicity of PCBs on micro-organisms., Spent printed circuit boards comminuted to 750 microns were bioleached in a double-stage continuous bioreactor to study the recovery of Fe, Cu, Ni, Zn, Pb, and Co. The first stage of the bioreactor was a bubble column in which an acidophilic consortium of Leptospirillum ferriphilum and Sulphobacillus benefaciens was used to oxidise iron(II) into iron(III) to produce an acidic ferric solution at 1 g/l Fe3+. This solution was then used to leach the metals contained in PCBs under mechanical stirring in the second stage of the bioreactor. It was found that in the first 400 h the average value of the redox potential in the second stage was much lower than that in the outlet from the first stage and Cu dissolution yield was below 1%, whereas yields of the other metals were relatively high (Fe 75%, Zn 33%, Ni 55% and Co 73%); after 400 h a significant increase in dissolution yield was observed (79%, 76%, 78% and 82%, respectively) while Pb dissolution yield remained constant at 7%. It is concluded that that solid/liquid ratio strongly influences bacterial activity, due to the expected toxicity of PCBs on micro-organisms.

Three case studies are presented from a project which combines biohydrometallurgy and bionanotechnology to give new nanomaterials biorefined from wastes for low-carbon energy, green chemistry and environmental applications. The main aim of the project is to show that wastes can be upgraded into value products via microbial activity, and that the cost and CO2 burdens of transport can be minimised by locally based conversion of wastes. The case studies discuss: recycling of platinum group metals from road dusts, waste acids and mining wastes; the production of ZnS quantum dots from waste H2S; and biorefining of rare earth metals, uranium and thorium for re-use., Three case studies are presented from a project which combines biohydrometallurgy and bionanotechnology to give new nanomaterials biorefined from wastes for low-carbon energy, green chemistry and environmental applications. The main aim of the project is to show that wastes can be upgraded into value products via microbial activity, and that the cost and CO2 burdens of transport can be minimised by locally based conversion of wastes. The case studies discuss: recycling of platinum group metals from road dusts, waste acids and mining wastes; the production of ZnS quantum dots from waste H2S; and biorefining of rare earth metals, uranium and thorium for re-use.

The leaching agents studied were culture broths of Y. lipolytica and B. licheniformis. The rock samples used were from the caldera structure of the Ampasabitika intrusion in Madagascar and contained (by weight) 54% kaolin-group minerals, 9.5% smectite, 0.6% goethite, 0.5% boehmite, 0.2% haematite, 20.1% sanidine, 14.8% microcline, and 0.3% quartz. Poly-gamma-glutamic acid (PGA) and low molecular weight carbon acids (LMWA) were used as leaching reagents and batch leaching tests were performed as triplicates using the microbial broth. Tests were carried out for each lixiviant at temperatures of 4, 22 and 40 degrees C at concentrations of leaching agent of 2, 5, and 7 g/l and pulp concentrations of 5, 17.5, and 30 wt%. Results showed that REE were leached in the first 24 hours, with larger amounts of REE mobilised with higher concentrations of PGA. Batches with higher pulp concentrations had a lower REE extraction level. It is suggested that the ratio between REE in the samples and the amount of chelating groups should be taken into account., The leaching agents studied were culture broths of Y. lipolytica and B. licheniformis. The rock samples used were from the caldera structure of the Ampasabitika intrusion in Madagascar and contained (by weight) 54% kaolin-group minerals, 9.5% smectite, 0.6% goethite, 0.5% boehmite, 0.2% haematite, 20.1% sanidine, 14.8% microcline, and 0.3% quartz. Poly-gamma-glutamic acid (PGA) and low molecular weight carbon acids (LMWA) were used as leaching reagents and batch leaching tests were performed as triplicates using the microbial broth. Tests were carried out for each lixiviant at temperatures of 4, 22 and 40 degrees C at concentrations of leaching agent of 2, 5, and 7 g/l and pulp concentrations of 5, 17.5, and 30 wt%. Results showed that REE were leached in the first 24 hours, with larger amounts of REE mobilised with higher concentrations of PGA. Batches with higher pulp concentrations had a lower REE extraction level. It is suggested that the ratio between REE in the samples and the amount of chelating groups should be taken into account.

Studies have been carried out to compare the effect of chloride on bacterial growth, iron oxidation activity and bioleaching performance at mesophilic and moderate thermophilic temperatures for chalcopyrite and sphalerite-containing ores. Sulphobacillus thermosulphidooxidans and Leptospirillum ferriphilum were used. It was found that the exposure to elevated NaCl concentration affected cell growth and eventual iron oxidation rate in both strains, with Sb. thermosulphidooxidans having better tolerance to NaCl than L. ferriphilum. The minimum inhibitory concentrations of NaCl were 325 mM and 525 mM for L. ferriphilum and Sb. thermosulphidooxidans, respectively. For copper-containing sulphide minerals, bioleaching by Sb. thermosulphidooxidans in the presence of 200 mM was similar to bioleaching performance in the absence of NaCl. However, in the presence of NaCl, bioleaching by L. ferriphilum reduced by 50 %. For zinc-containing ores. It was found that NaCl significantly inhibited bioleaching by both bacteria. It is concluded that Sb. thermosulphidooxidans can be useful for bioleaching of ores in saline environments due to its high tolerance to chloride, but it is vital to consider that the effect of NaCl to bioleaching can also be mineral-specific., Studies have been carried out to compare the effect of chloride on bacterial growth, iron oxidation activity and bioleaching performance at mesophilic and moderate thermophilic temperatures for chalcopyrite and sphalerite-containing ores. Sulphobacillus thermosulphidooxidans and Leptospirillum ferriphilum were used. It was found that the exposure to elevated NaCl concentration affected cell growth and eventual iron oxidation rate in both strains, with Sb. thermosulphidooxidans having better tolerance to NaCl than L. ferriphilum. The minimum inhibitory concentrations of NaCl were 325 mM and 525 mM for L. ferriphilum and Sb. thermosulphidooxidans, respectively. For copper-containing sulphide minerals, bioleaching by Sb. thermosulphidooxidans in the presence of 200 mM was similar to bioleaching performance in the absence of NaCl. However, in the presence of NaCl, bioleaching by L. ferriphilum reduced by 50 %. For zinc-containing ores. It was found that NaCl significantly inhibited bioleaching by both bacteria. It is concluded that Sb. thermosulphidooxidans can be useful for bioleaching of ores in saline environments due to its high tolerance to chloride, but it is vital to consider that the effect of NaCl to bioleaching can also be mineral-specific.

Discussion is presented of an integrated comminution and bioleaching concept, whereby ultrafine grinding is used as a pre-treatment of a polymetallic concentrate (pyrrhotite, chalcopyrite, pentlandite) prior to bioleaching (at 42 degrees C) of slurry direct from a mill. Studies used a polymetallic sulphide concentrate from a Finnish nickel froth flotation processing plant. The effects of grind size and the use of peroxide and/or acid during the milling process were considered. Three continuous stirred tank reactors were used and the mesophilic culture predominantly contained Leptospirillum ferriphilum, Acidithiobacillus caldus, and Sulphobacillus benefaciens. It was found that milling under acidic, oxidising conditions to a d90 of 10 microns led to the dissolution of 97-100% of both copper and nickel at 42 degrees C at a pulp density of 10% (w/v). Acid addition in the mill gave more controlled pH in the bioreactors, leading to faster leaching of pyrrhotite. It is likely that the high copper dissolution at this temperature was facilitated by the low redox maintained as a result of rapid ferric iron consumption by the reactive pyrrhotite content of the concentrate., Discussion is presented of an integrated comminution and bioleaching concept, whereby ultrafine grinding is used as a pre-treatment of a polymetallic concentrate (pyrrhotite, chalcopyrite, pentlandite) prior to bioleaching (at 42 degrees C) of slurry direct from a mill. Studies used a polymetallic sulphide concentrate from a Finnish nickel froth flotation processing plant. The effects of grind size and the use of peroxide and/or acid during the milling process were considered. Three continuous stirred tank reactors were used and the mesophilic culture predominantly contained Leptospirillum ferriphilum, Acidithiobacillus caldus, and Sulphobacillus benefaciens. It was found that milling under acidic, oxidising conditions to a d90 of 10 microns led to the dissolution of 97-100% of both copper and nickel at 42 degrees C at a pulp density of 10% (w/v). Acid addition in the mill gave more controlled pH in the bioreactors, leading to faster leaching of pyrrhotite. It is likely that the high copper dissolution at this temperature was facilitated by the low redox maintained as a result of rapid ferric iron consumption by the reactive pyrrhotite content of the concentrate.

Bioleaching experiments with a mixed Acidithiobacillus culture were carried out in shake flasks as well as in column percolators with crushed and sieved sphalerite-rich ore from a former mine in the German Harz Mountains. An efficient sphalerite dissolution in the bioleaching assays was observed in contrast to the chemical leaching experiments. Up to 6 g/l zinc were measured in the pregnant leach solution. Total cell counting and most-probable-number cultivation congruently exhibited high cell numbers at the end of the bioleaching experiments of about one month. The redox potential was higher in the bioleaching than in the chemical control assays. The pH was adjusted to values about 2.5 to be able to compare the leaching kinetics at a similar pH for bioleaching and chemical leaching assays. The kinetics of sphalerite bioleaching showed a linear increase of the zinc concentration in solution and exhibited similar sphalerite surface related reaction rates for percolators and shake flasks. Besides zinc, up to 1 mg/l gallium as trace element was extracted. (Authors.), Bioleaching experiments with a mixed Acidithiobacillus culture were carried out in shake flasks as well as in column percolators with crushed and sieved sphalerite-rich ore from a former mine in the German Harz Mountains. An efficient sphalerite dissolution in the bioleaching assays was observed in contrast to the chemical leaching experiments. Up to 6 g/l zinc were measured in the pregnant leach solution. Total cell counting and most-probable-number cultivation congruently exhibited high cell numbers at the end of the bioleaching experiments of about one month. The redox potential was higher in the bioleaching than in the chemical control assays. The pH was adjusted to values about 2.5 to be able to compare the leaching kinetics at a similar pH for bioleaching and chemical leaching assays. The kinetics of sphalerite bioleaching showed a linear increase of the zinc concentration in solution and exhibited similar sphalerite surface related reaction rates for percolators and shake flasks. Besides zinc, up to 1 mg/l gallium as trace element was extracted. (Authors.)

Mineral extraction processes based on biohydrometallurgy can deliver environmental benefits and enhance the degree of extraction from the overall resource. While many commercial applications use solvent extraction and electro-winning for metal recovery, the use of biohydrometallurgy to remove metals from aqueous solutions has been considered from the environmental perspective through biological sulphate reduction with associated metal precipitation. Key aspects to be considered include the need to account for and prevent unintentional bioleaching reactions during disposal of waste rock and tailings, and the development of waste rock handling and restoration, rehabilitation and water resource protection at prior mine sites. Limited global resources of key metals highlight both the need to process mineral resources of decreasing grade, smaller size of deposit and increasing complexity and the ability to extract metals from secondary sources for re-use. The processing of secondary resources such as waste electrical and electronic equipment and municipal solid waste presents new challenges., Mineral extraction processes based on biohydrometallurgy can deliver environmental benefits and enhance the degree of extraction from the overall resource. While many commercial applications use solvent extraction and electro-winning for metal recovery, the use of biohydrometallurgy to remove metals from aqueous solutions has been considered from the environmental perspective through biological sulphate reduction with associated metal precipitation. Key aspects to be considered include the need to account for and prevent unintentional bioleaching reactions during disposal of waste rock and tailings, and the development of waste rock handling and restoration, rehabilitation and water resource protection at prior mine sites. Limited global resources of key metals highlight both the need to process mineral resources of decreasing grade, smaller size of deposit and increasing complexity and the ability to extract metals from secondary sources for re-use. The processing of secondary resources such as waste electrical and electronic equipment and municipal solid waste presents new challenges.

Life-cycle analysis has been carried out of the catalytic upgrading of heavy fossil oil and pyrolysis oils from dry biomasses for the production of liquid fuel. Commercial catalysts and bio-precious metal catalysts refined from secondary waste sources are compared. Economically, it was found to be more feasible to use commercial catalysts for pyrolysis oil upgrading, as the ecological impacts of upgrading with bio-precious metal neo-catalysts must be decreased. Precious metal recovery with aqua regia leachate needs further optimisation of the catalyst to oil ratio to decrease costs. However, bio-precious metal neo-catalysts are highly competitive for heavy oil upgrading, both economically and ecologically, due to their competitive 0.1% C/O requirements. Advancements in bio-precious metal neo-catalyst synthesis are required to reduce production costs, in addition to further work regarding lower pyrolysis oil to bio-catalyst ratios and CO2 balances. Liquefaction of algae and agricultural slurries, which do not need intensive drying stages, would provide an alternative comparison for bio-oil production., Life-cycle analysis has been carried out of the catalytic upgrading of heavy fossil oil and pyrolysis oils from dry biomasses for the production of liquid fuel. Commercial catalysts and bio-precious metal catalysts refined from secondary waste sources are compared. Economically, it was found to be more feasible to use commercial catalysts for pyrolysis oil upgrading, as the ecological impacts of upgrading with bio-precious metal neo-catalysts must be decreased. Precious metal recovery with aqua regia leachate needs further optimisation of the catalyst to oil ratio to decrease costs. However, bio-precious metal neo-catalysts are highly competitive for heavy oil upgrading, both economically and ecologically, due to their competitive 0.1% C/O requirements. Advancements in bio-precious metal neo-catalyst synthesis are required to reduce production costs, in addition to further work regarding lower pyrolysis oil to bio-catalyst ratios and CO2 balances. Liquefaction of algae and agricultural slurries, which do not need intensive drying stages, would provide an alternative comparison for bio-oil production.

Five halophilic bacteria (Halomonas boliviensis, Marinobacter spp, Halobacillus sp, Marinococcus sp and Halomonas eurihalina) have been studied as potential pyrite depressants in the bioflotation of Chilean copper porphyries using sea water. Micro-flotation tests were carried out in Hallimond tubes, along with hydrophobicity and adhesion experiments. It was found that Halobacillus sp and Halomonas eurihalina had a high adhesion to pyrite which correlated with the hydrophobicity of the cells. Halomonas boliviensis and Marinococcus sp also showed a significant depression of pyrite., Five halophilic bacteria (Halomonas boliviensis, Marinobacter spp, Halobacillus sp, Marinococcus sp and Halomonas eurihalina) have been studied as potential pyrite depressants in the bioflotation of Chilean copper porphyries using sea water. Micro-flotation tests were carried out in Hallimond tubes, along with hydrophobicity and adhesion experiments. It was found that Halobacillus sp and Halomonas eurihalina had a high adhesion to pyrite which correlated with the hydrophobicity of the cells. Halomonas boliviensis and Marinococcus sp also showed a significant depression of pyrite.

In Turkish bauxites, between 4-17% total REE are acid soluble (acetic acid), 17-42% are reducible (hydroxylammonium chloride) and 2-24% are oxidisable (hydrogen peroxide). Studies were carried out using Aspergillus sp. to produce organic acids to target the acid soluble fraction and Acidithiobacillus ferrooxidans grown on either sulphur or ferrous iron to target the reducible and oxidisable fractions. Three bauxite samples from the Mortas and Dogankuzu deposits were used for REE leaching in a two-step batch process. The samples contained cerium as the dominant REE and were classified as low-Ca (Ce associated with iron oxides), high-Ca (containing small clasts of limestone), and altered (porous with clay-rich phases and impurities). During the growth stage the pH of the Aspergillus leaching solution reached 2, which increased after the addition of bauxite and then fell to below initial pH over the 7 day test. When compared with control conditions without bauxite, the oxidative bioleaching of all three samples showed little change in reduced and total iron whereas differences in Fe composition were seen between reductive bioleaching of the uninoculated control. Both low-Ca and high-Ca samples had a greater concentration of reduced and total iron in inoculated tests, but the opposite occurred in altered samples., In Turkish bauxites, between 4-17% total REE are acid soluble (acetic acid), 17-42% are reducible (hydroxylammonium chloride) and 2-24% are oxidisable (hydrogen peroxide). Studies were carried out using Aspergillus sp. to produce organic acids to target the acid soluble fraction and Acidithiobacillus ferrooxidans grown on either sulphur or ferrous iron to target the reducible and oxidisable fractions. Three bauxite samples from the Mortas and Dogankuzu deposits were used for REE leaching in a two-step batch process. The samples contained cerium as the dominant REE and were classified as low-Ca (Ce associated with iron oxides), high-Ca (containing small clasts of limestone), and altered (porous with clay-rich phases and impurities). During the growth stage the pH of the Aspergillus leaching solution reached 2, which increased after the addition of bauxite and then fell to below initial pH over the 7 day test. When compared with control conditions without bauxite, the oxidative bioleaching of all three samples showed little change in reduced and total iron whereas differences in Fe composition were seen between reductive bioleaching of the uninoculated control. Both low-Ca and high-Ca samples had a greater concentration of reduced and total iron in inoculated tests, but the opposite occurred in altered samples.

Municipal wastewater was used to prepare microalgal biosorbents for the biosorption of indium from secondary sources. Different biosorption parameters were studied in the laboratory, including pH, contact time, initial In concentration, and presence of competing ions. The desorption of In ions adsorbed by the microalga biomass was investigated using desorbing agents HCl, HNO3, NaCl, CaCl2, and EDTA. Results showed that the biosorbent had a maximum In adsorption capacity of 0.20 mmol/g, which was observed at an initial pH value of 3. The adsorption equilibrium data were found to fit the Langmuir isotherm model, indicating that indium ions were adsorbed in monolayers onto the homogeneous active sites of the biomass surface. The kinetics data showed that biosorption attained equilibrium within 30 minutes. Cu, Zn, Sn, Al, and Fe did not show a negative effect on In removal efficiencies, and indium selectivity was observed over Zn and Cu. It was found that the biosorbent could be regenerated using 0.1 M HCl solution, with up to 85% In recovery., Municipal wastewater was used to prepare microalgal biosorbents for the biosorption of indium from secondary sources. Different biosorption parameters were studied in the laboratory, including pH, contact time, initial In concentration, and presence of competing ions. The desorption of In ions adsorbed by the microalga biomass was investigated using desorbing agents HCl, HNO3, NaCl, CaCl2, and EDTA. Results showed that the biosorbent had a maximum In adsorption capacity of 0.20 mmol/g, which was observed at an initial pH value of 3. The adsorption equilibrium data were found to fit the Langmuir isotherm model, indicating that indium ions were adsorbed in monolayers onto the homogeneous active sites of the biomass surface. The kinetics data showed that biosorption attained equilibrium within 30 minutes. Cu, Zn, Sn, Al, and Fe did not show a negative effect on In removal efficiencies, and indium selectivity was observed over Zn and Cu. It was found that the biosorbent could be regenerated using 0.1 M HCl solution, with up to 85% In recovery.

Ore samples from the Platreef deposit in the Bushveld Complex (South Africa) have been used in feasibility tests on oxidative and reductive bioleaching by acidophilic cultures under aerobic and anaerobic conditions in shake flasks or serum bottles and stirred tank bioreactors. The samples included drill core sections which spanned zones of pristine and weathered ore. After bioleaching, the residues were subjected to chemical extraction using saturated sodium chloride solution supplemented with nitric acid. The results suggest that oxidative and reductive bioleaching are a promising processing option for the pretreatment of PGE ores, depending on the degree of weathering of the ore and the acidophilic microorganisms used., Ore samples from the Platreef deposit in the Bushveld Complex (South Africa) have been used in feasibility tests on oxidative and reductive bioleaching by acidophilic cultures under aerobic and anaerobic conditions in shake flasks or serum bottles and stirred tank bioreactors. The samples included drill core sections which spanned zones of pristine and weathered ore. After bioleaching, the residues were subjected to chemical extraction using saturated sodium chloride solution supplemented with nitric acid. The results suggest that oxidative and reductive bioleaching are a promising processing option for the pretreatment of PGE ores, depending on the degree of weathering of the ore and the acidophilic microorganisms used.

A two-stage system is proposed in which a polymetallic sulphide concentrate is partially leached in a mesophile reactor to recover the majority of the metal from labile minerals, before being transferred to a thermophile reactor to dissolve the remaining metal, and all the copper from the recalcitrant sulphides. Tests were carried out using a nickel-copper concentrate (with a d10=9 microns, d50=41 microns and d90=140 microns) of around 3.9% Cu and 9.2% Ni. Further tests were carried out after re-grinding to a p80 of 20 microns, giving resulting Cu and Ni concentrations of 4.0% and 6.9%, respectively. Different combinations of jacketed continuous stirred tank reactors were used (at 42 degrees or 78 degrees C and pulp densities varying from 5% to 20%). Reactors were aerated with CO2-enriched air (at around 2%) at 0.5 vvm, and soluble Ni, Cu and Fe as well as redox and pH were monitored daily. It was found that the mesophile front end reduced the solids loading going into the thermophile back end, and improved overall system stability. Higher pulp densities could be processed in the coupled system than could be tolerated by the thermophile system in isolation. Reducing the p80 of the concentrate improved solids tolerance of the system as a whole., A two-stage system is proposed in which a polymetallic sulphide concentrate is partially leached in a mesophile reactor to recover the majority of the metal from labile minerals, before being transferred to a thermophile reactor to dissolve the remaining metal, and all the copper from the recalcitrant sulphides. Tests were carried out using a nickel-copper concentrate (with a d10=9 microns, d50=41 microns and d90=140 microns) of around 3.9% Cu and 9.2% Ni. Further tests were carried out after re-grinding to a p80 of 20 microns, giving resulting Cu and Ni concentrations of 4.0% and 6.9%, respectively. Different combinations of jacketed continuous stirred tank reactors were used (at 42 degrees or 78 degrees C and pulp densities varying from 5% to 20%). Reactors were aerated with CO2-enriched air (at around 2%) at 0.5 vvm, and soluble Ni, Cu and Fe as well as redox and pH were monitored daily. It was found that the mesophile front end reduced the solids loading going into the thermophile back end, and improved overall system stability. Higher pulp densities could be processed in the coupled system than could be tolerated by the thermophile system in isolation. Reducing the p80 of the concentrate improved solids tolerance of the system as a whole.

A continuous-flow, low pH biofilm sulphidogenic bioreactor inoculated with indigenous microbial communities has been developed for treating mine impacted water. The inoculum came from an anaerobic sediment in the acidic Azufire River in northern Chile. The sulphidogenic system (2.3 litres) was operated as a continuous flow mode unit for 99 days at 30 degrees C and fed with water of pH 2.1, with Zn 0.5 mM and Fe 2 mM. The bioreactor pH was initially 4.5 and was increased in stages to 6.0. The results show that zinc concentrations in liquors draining the bioreactor were below the detection level in most of the samples analysed. By progressively increasing the glycerol concentration, it was possible to increase the removal of iron (70% of the total present), though more acetic acid (from 1 to 5 mM) was generated. Analysis of the microbial populations showed that they changed with varying operation parameters, and a known acetogenic sulphidogen (Desulphoporosinus acididurans) became more dominant. The sulphidogenic bioreactor unit was found to be robust with low complexity engineering., A continuous-flow, low pH biofilm sulphidogenic bioreactor inoculated with indigenous microbial communities has been developed for treating mine impacted water. The inoculum came from an anaerobic sediment in the acidic Azufire River in northern Chile. The sulphidogenic system (2.3 litres) was operated as a continuous flow mode unit for 99 days at 30 degrees C and fed with water of pH 2.1, with Zn 0.5 mM and Fe 2 mM. The bioreactor pH was initially 4.5 and was increased in stages to 6.0. The results show that zinc concentrations in liquors draining the bioreactor were below the detection level in most of the samples analysed. By progressively increasing the glycerol concentration, it was possible to increase the removal of iron (70% of the total present), though more acetic acid (from 1 to 5 mM) was generated. Analysis of the microbial populations showed that they changed with varying operation parameters, and a known acetogenic sulphidogen (Desulphoporosinus acididurans) became more dominant. The sulphidogenic bioreactor unit was found to be robust with low complexity engineering.

An assessment of old and current mine tailings in Finland has shown that they have economic potential, with the metallic value being hundreds of millions of euros. Samples of acidic waters from the Pyhasalmi mine were analysed for bioleaching microorganisms and then used in bioleaching experiments using pyrite and pyrrhotite tailings from four Finnish mines. A high bacterial and fungal diversity was found in the mine water: Acidithiobacillus and Leptospirillum dominated the mine water 240 m below the surface, Leptospirillum dominated at 500 m below the surface, and Ferrovum and Metallibacter were dominant at 600 m below the surface. The bioleaching experiments showed that three of the tailings samples had rapid decrease of pH and increase of redox-potential, suggesting sulphide mineral dissolution, and resulting in iron oxidation and sulphuric acid production. For Tailing 4, no major pH decrease or redox-potential increase was observed, even though the material contained several wt% of pyrrhotite. Zn yields for Tailings 1 were 85% in 5 days, with low Ni and Co. Tailings 2 had a Zn yield of 100% in 18 days, and Tailing 3 had a Zn yield of 78% in 32 days., An assessment of old and current mine tailings in Finland has shown that they have economic potential, with the metallic value being hundreds of millions of euros. Samples of acidic waters from the Pyhasalmi mine were analysed for bioleaching microorganisms and then used in bioleaching experiments using pyrite and pyrrhotite tailings from four Finnish mines. A high bacterial and fungal diversity was found in the mine water: Acidithiobacillus and Leptospirillum dominated the mine water 240 m below the surface, Leptospirillum dominated at 500 m below the surface, and Ferrovum and Metallibacter were dominant at 600 m below the surface. The bioleaching experiments showed that three of the tailings samples had rapid decrease of pH and increase of redox-potential, suggesting sulphide mineral dissolution, and resulting in iron oxidation and sulphuric acid production. For Tailing 4, no major pH decrease or redox-potential increase was observed, even though the material contained several wt% of pyrrhotite. Zn yields for Tailings 1 were 85% in 5 days, with low Ni and Co. Tailings 2 had a Zn yield of 100% in 18 days, and Tailing 3 had a Zn yield of 78% in 32 days.

The Barroca Grande tailings disposal facility at the Panasqueira Sn-W sulphide mine (Portugal) contains over 8 000 000 m3 of mine wastes. The tailings contain recoverable grades of tungsten, while the As and Cd content has produced acid mine drainage which has contaminated local soils and water. A microbial consortium enriched from the mine site was used in bioleaching tests of a composite sample from Panasqueira and Neves Corvo mines. The experiment was conducted for 65 days using 250 ml flasks with 50 ml of DSMS670 medium and a solids percentage of 11.5% plus/minus 0.5. The results showed that although there was no bioleaching of W, the microorganisms removed most of the As (96%) and Cd (58%) pollutants., The Barroca Grande tailings disposal facility at the Panasqueira Sn-W sulphide mine (Portugal) contains over 8 000 000 m3 of mine wastes. The tailings contain recoverable grades of tungsten, while the As and Cd content has produced acid mine drainage which has contaminated local soils and water. A microbial consortium enriched from the mine site was used in bioleaching tests of a composite sample from Panasqueira and Neves Corvo mines. The experiment was conducted for 65 days using 250 ml flasks with 50 ml of DSMS670 medium and a solids percentage of 11.5% plus/minus 0.5. The results showed that although there was no bioleaching of W, the microorganisms removed most of the As (96%) and Cd (58%) pollutants.

Studies have been carried out of a new method to extract copper, nickel, cobalt, and zinc from low-grade flotation tailings by biological pretreatment prior to gold and copper recovery by cyanide-free chloride leaching. Bioloeaching experiments showed that the highest redox potentials and metal extractions of Ni, Co, Zn, and Fe, (90%, 60%, 86%, and 67%, respectively) were gained at 5% and 7.5% solid concentrations. Cu and Au remained in the final residue, which was used as feed material in the chloride leaching. The effect of particle size was studied using as-received (150 micrometre) and ground (26 micrometre) samples. In all chloride leaching experiments, the highest extractions of metals were gained with the microbiologically pretreated material. The highest Cu (98%) and Au (63%) extractions were gained at pH 1, 150 micrometre particle size and 72 hours leaching time. The maximum dissolution of Ni, Co and Zn (99%, 80% and 90%, respectively) were achieved at pH 1.8, 26 micrometre particle size and leaching time of 24 hours. Extractions of Ni, Co and Zn were up to 50% higher with ground material than with the as-received material. It is concluded that bacterial pretreatment can improve chloride leaching., Studies have been carried out of a new method to extract copper, nickel, cobalt, and zinc from low-grade flotation tailings by biological pretreatment prior to gold and copper recovery by cyanide-free chloride leaching. Bioloeaching experiments showed that the highest redox potentials and metal extractions of Ni, Co, Zn, and Fe, (90%, 60%, 86%, and 67%, respectively) were gained at 5% and 7.5% solid concentrations. Cu and Au remained in the final residue, which was used as feed material in the chloride leaching. The effect of particle size was studied using as-received (150 micrometre) and ground (26 micrometre) samples. In all chloride leaching experiments, the highest extractions of metals were gained with the microbiologically pretreated material. The highest Cu (98%) and Au (63%) extractions were gained at pH 1, 150 micrometre particle size and 72 hours leaching time. The maximum dissolution of Ni, Co and Zn (99%, 80% and 90%, respectively) were achieved at pH 1.8, 26 micrometre particle size and leaching time of 24 hours. Extractions of Ni, Co and Zn were up to 50% higher with ground material than with the as-received material. It is concluded that bacterial pretreatment can improve chloride leaching.

Studies have been carried out to show the potential of pyrite-bearing waste rock samples, in an unsaturated system that resembles a waste rock pile, as a potential system of characterising waste material for acid rock drainage formation. The two pyritic samples, low- and high-sulphur metapelite, were milled and wet sieved and characterised using three biokinetic approaches: slurry batch test (BT), batch test with coated beads (BT-CB) and flow-through column test with coated beads (FT-CB). Solution redox potential, pH and iron were analysed. A mixed mesophilic culture was used, consisting of Leptospirillum ferriphilum, Acidithiobacillus caldus and archaea (Ferroplasma acidiphilum and Acidiplasma cupricumulans). In the tests using coated beads, microbial activity on the mineral surface was measured using calorimetry and SEM observations of microbial colonisation. The unsaturated, flow through biokinetic column test was found to be more suitable than the batch biokinetic tests as it showed depletion of readily acid neutralising minerals early in the experimental run. The establishment of a well colonised mineral surface was observed with the progression of the column test, with increasing microbial activity associated with increasing mineral colonisation within 30 days., Studies have been carried out to show the potential of pyrite-bearing waste rock samples, in an unsaturated system that resembles a waste rock pile, as a potential system of characterising waste material for acid rock drainage formation. The two pyritic samples, low- and high-sulphur metapelite, were milled and wet sieved and characterised using three biokinetic approaches: slurry batch test (BT), batch test with coated beads (BT-CB) and flow-through column test with coated beads (FT-CB). Solution redox potential, pH and iron were analysed. A mixed mesophilic culture was used, consisting of Leptospirillum ferriphilum, Acidithiobacillus caldus and archaea (Ferroplasma acidiphilum and Acidiplasma cupricumulans). In the tests using coated beads, microbial activity on the mineral surface was measured using calorimetry and SEM observations of microbial colonisation. The unsaturated, flow through biokinetic column test was found to be more suitable than the batch biokinetic tests as it showed depletion of readily acid neutralising minerals early in the experimental run. The establishment of a well colonised mineral surface was observed with the progression of the column test, with increasing microbial activity associated with increasing mineral colonisation within 30 days.

The presence of base metals, especially copper, in PCB waste compromises biohydrometallurgical extraction as it can have toxic effects on the microbes. Studies have been carried out of a process in which a mesophilic Leptospirillum ferriphilum-dominated culture was adapted to 1 g/l copper (Cu2+) and subsequently exposed to increasing concentrations of metals including Cu2+, Al3+, Ni2+ and Zn2+ at concentrations representative of PCB composition (0%, 11%, 18% and 27%). The results showed that adaptation to 1 g/l Cu2+ mitigated microbial inhibition completely at Cu2+ concentrations up to 1.92 g/l. However, exposure to Cu2+ concentrations associated with 11%, 18% and 27% PCB metal loadings was found to correspond with increasing lag time linked to the onset of ferrous iron oxidation as well as a reduction in ferrous iron oxidation rate at 27% metal loading. The ternary combination of Al3+, Zn2+ and Ni2+ was found to have negligible impact on microbial activity, but exposure to Al3+, Zn2+ and Ni2+ coupled with Cu2+ was found to be comparable to results obtained with Cu2+ in isolation. It is suggested that adaptation to a higher Cu2+ concentration may significantly improve microbial tolerance and mitigate inhibition., The presence of base metals, especially copper, in PCB waste compromises biohydrometallurgical extraction as it can have toxic effects on the microbes. Studies have been carried out of a process in which a mesophilic Leptospirillum ferriphilum-dominated culture was adapted to 1 g/l copper (Cu2+) and subsequently exposed to increasing concentrations of metals including Cu2+, Al3+, Ni2+ and Zn2+ at concentrations representative of PCB composition (0%, 11%, 18% and 27%). The results showed that adaptation to 1 g/l Cu2+ mitigated microbial inhibition completely at Cu2+ concentrations up to 1.92 g/l. However, exposure to Cu2+ concentrations associated with 11%, 18% and 27% PCB metal loadings was found to correspond with increasing lag time linked to the onset of ferrous iron oxidation as well as a reduction in ferrous iron oxidation rate at 27% metal loading. The ternary combination of Al3+, Zn2+ and Ni2+ was found to have negligible impact on microbial activity, but exposure to Al3+, Zn2+ and Ni2+ coupled with Cu2+ was found to be comparable to results obtained with Cu2+ in isolation. It is suggested that adaptation to a higher Cu2+ concentration may significantly improve microbial tolerance and mitigate inhibition.

The EU-funded IntMet research project aims to establish technologies for on-site recovery of metals from low grade, complex and polymetallic ores and concentrates. Laboratory-scale bioleaching tests have been carried out for the recovery of Cu and Zn from four different polymetallic ores at both moderate thermophilic and thermophilic conditions. Tests were carried out at 45 and 70 degrees C in a continuously operated four-stage reactor system with a volume of 3 l in the first stage reactor and 1 l in consecutive reactors. Larger-scale tests were also carried out in a 60 l first stage reactor and 3 secondary reactors of 20 l each. Nutrients were added at concentrations of 1 g/l (NH4)2SO4, 0.2 g/l MgSO4, and 0.5 g/l K2HPO4 and the air supply was enriched with 0.3% CO2. The reactors were agitated with impeller speeds of 450 rpm at the laboratory scale and 220 rpm in the mini-plant. Tests suggested that optimal conditions are: temperature of 45 degrees C, feed solids concentration of 15%, a 6 day retention time across 4 reactors in series, and a particle size of d80=20 microns., The EU-funded IntMet research project aims to establish technologies for on-site recovery of metals from low grade, complex and polymetallic ores and concentrates. Laboratory-scale bioleaching tests have been carried out for the recovery of Cu and Zn from four different polymetallic ores at both moderate thermophilic and thermophilic conditions. Tests were carried out at 45 and 70 degrees C in a continuously operated four-stage reactor system with a volume of 3 l in the first stage reactor and 1 l in consecutive reactors. Larger-scale tests were also carried out in a 60 l first stage reactor and 3 secondary reactors of 20 l each. Nutrients were added at concentrations of 1 g/l (NH4)2SO4, 0.2 g/l MgSO4, and 0.5 g/l K2HPO4 and the air supply was enriched with 0.3% CO2. The reactors were agitated with impeller speeds of 450 rpm at the laboratory scale and 220 rpm in the mini-plant. Tests suggested that optimal conditions are: temperature of 45 degrees C, feed solids concentration of 15%, a 6 day retention time across 4 reactors in series, and a particle size of d80=20 microns.

Studies have been carried out of the solubilisation of lateritic nickel ores by the action of heterotrophic bacteria Bacillus subtilis. A sample of Brazilian lateritic nickel ore was used in which goethite was the primary Ni mineral, and the ore contained 1% NiO (0.85 % Ni). Bioleaching batch experiments demonstrated that about 8% Ni (0.7 mg Ni/ g ore) were solubilised by the B. subtilis after 7 days. Pre-treating the ore by microwave heating was found to increase the bioextraction to 26% Ni (2.3 mg Ni/ g ore)., Studies have been carried out of the solubilisation of lateritic nickel ores by the action of heterotrophic bacteria Bacillus subtilis. A sample of Brazilian lateritic nickel ore was used in which goethite was the primary Ni mineral, and the ore contained 1% NiO (0.85 % Ni). Bioleaching batch experiments demonstrated that about 8% Ni (0.7 mg Ni/ g ore) were solubilised by the B. subtilis after 7 days. Pre-treating the ore by microwave heating was found to increase the bioextraction to 26% Ni (2.3 mg Ni/ g ore).

The demand for CO2 was investigated during bioleaching of sulphidic materials in a stirred tank reactor using a bacterial consortium which included Leptospirillum ferriphilum, Acidithiobacillus caldus and Sulphobacillus. Batch tests were carried out in 2 litre reactors at 10% w/w solid load using a copper concentrate from flotation of a black shale organic-rich ore in which the carbonates dissolve in acidic conditions to produce CO2. The results showed that Fe oxidation (and thus microbial activity) was delayed when air was injected without CO2-supplementation, and that CO2-supplementation improved leaching kinetics. A methodology to determine gas/liquid transfer components and to asses CO2 limitations in the system showed that the microorganisms were not only sensitive to the transfer rate of CO2 from the gas to the liquid phase, but also to the availability of CO2 in solution., The demand for CO2 was investigated during bioleaching of sulphidic materials in a stirred tank reactor using a bacterial consortium which included Leptospirillum ferriphilum, Acidithiobacillus caldus and Sulphobacillus. Batch tests were carried out in 2 litre reactors at 10% w/w solid load using a copper concentrate from flotation of a black shale organic-rich ore in which the carbonates dissolve in acidic conditions to produce CO2. The results showed that Fe oxidation (and thus microbial activity) was delayed when air was injected without CO2-supplementation, and that CO2-supplementation improved leaching kinetics. A methodology to determine gas/liquid transfer components and to asses CO2 limitations in the system showed that the microorganisms were not only sensitive to the transfer rate of CO2 from the gas to the liquid phase, but also to the availability of CO2 in solution.

The effects of elevated pressures of 1, 10 and 20 bar above atmospheric pressure on the biooxidation of a low-grade gold ore was evaluated in a continuously-stirred reactor. The ore, from a deposit in Eastern Finland, contained 92.6% silicates, 4.7% pyrite and 1.6% pyrrhotite as the main phases. The average gold content was 3.5 g/t, contained in inclusions in the pyrite and the silicates, with a fine particle size of up to 15 microns. Experiments were carried out in a 2 L continuously stirred pressure reactor operated in batch mode at 25-29 degrees C and pulp density of 10% using an initial pH of 1.8. An enrichment culture containing Acidithiobacillus, Ferrimicrobium and Sulfobacillus sp. was used, and results showed that this oxidised the low-grade ore even at +20 bar. Iron oxidation rate was highest at +1 bar and decreased with increasing pressure., The effects of elevated pressures of 1, 10 and 20 bar above atmospheric pressure on the biooxidation of a low-grade gold ore was evaluated in a continuously-stirred reactor. The ore, from a deposit in Eastern Finland, contained 92.6% silicates, 4.7% pyrite and 1.6% pyrrhotite as the main phases. The average gold content was 3.5 g/t, contained in inclusions in the pyrite and the silicates, with a fine particle size of up to 15 microns. Experiments were carried out in a 2 L continuously stirred pressure reactor operated in batch mode at 25-29 degrees C and pulp density of 10% using an initial pH of 1.8. An enrichment culture containing Acidithiobacillus, Ferrimicrobium and Sulfobacillus sp. was used, and results showed that this oxidised the low-grade ore even at +20 bar. Iron oxidation rate was highest at +1 bar and decreased with increasing pressure.

The cobalt, copper, manganese and lead contents and the 206Pb/207Pb isotope ratios in pine tree rings and soils at sites close to the Nkana smelter and a roadway in the vicinity of Kitwe and at sites in a remote area were determined using inductively coupled plasma-mass spectroscopy. The copper content of the tree rings was in the range 2-40 mg/kg and was higher in the vicinity of the smelter, increasing after 1975; the cobalt content of the tree rings was in the range 0.05-0.07 mg/kg with the highest cobalt contents corresponding to maximum ore production in the mid-1970s; the manganese content of the tree rings was in the range 5-125 mg/kg with acidification through sulphur dioxide emissions indicative of increased manganese contents from the mid-1980s; and the lead content of the tree rings was 0.02-0.7 mg/kg. The isotopic composition of the tree rings and the soil (206Pb/207Pb) was in the ranges 1.16-1.34 and 1.18-1.35, respectively, and was formed by a combination of lithogenic lead, combustion of leaded petroleum, and lead in processed ores., The cobalt, copper, manganese and lead contents and the 206Pb/207Pb isotope ratios in pine tree rings and soils at sites close to the Nkana smelter and a roadway in the vicinity of Kitwe and at sites in a remote area were determined using inductively coupled plasma-mass spectroscopy. The copper content of the tree rings was in the range 2-40 mg/kg and was higher in the vicinity of the smelter, increasing after 1975; the cobalt content of the tree rings was in the range 0.05-0.07 mg/kg with the highest cobalt contents corresponding to maximum ore production in the mid-1970s; the manganese content of the tree rings was in the range 5-125 mg/kg with acidification through sulphur dioxide emissions indicative of increased manganese contents from the mid-1980s; and the lead content of the tree rings was 0.02-0.7 mg/kg. The isotopic composition of the tree rings and the soil (206Pb/207Pb) was in the ranges 1.16-1.34 and 1.18-1.35, respectively, and was formed by a combination of lithogenic lead, combustion of leaded petroleum, and lead in processed ores.

A study of the spatial distribution of exploration licences and mining areas in relation to Namibia's national parks, marine protected areas, and commercial and private conservancies, a comparison of the economic benefits derived from these activities, an investigation of the environmental research and rehabilitation activities of mining companies, and the potential adverse impacts of exploration and mining including small-scale mining are described. Mining operations, e.g. Namdeb diamond mines, Langer Heinrich uranium mine and Skorpion zinc mine, and salt works along the coast, which are currently being conducted in Namibia's protected areas and have environmental programmes to minimise the impact are discussed. An analysis of mineral-production data, turnover, tax, royalty and employment figures presented for these commodities, diamonds, uranium, zinc and salt, in the Namibian mining sector indicates that the contribution to mining royalties and taxes from mining operations in these areas was about Nam, A study of the spatial distribution of exploration licences and mining areas in relation to Namibia's national parks, marine protected areas, and commercial and private conservancies, a comparison of the economic benefits derived from these activities, an investigation of the environmental research and rehabilitation activities of mining companies, and the potential adverse impacts of exploration and mining including small-scale mining are described. Mining operations, e.g. Namdeb diamond mines, Langer Heinrich uranium mine and Skorpion zinc mine, and salt works along the coast, which are currently being conducted in Namibia's protected areas and have environmental programmes to minimise the impact are discussed. An analysis of mineral-production data, turnover, tax, royalty and employment figures presented for these commodities, diamonds, uranium, zinc and salt, in the Namibian mining sector indicates that the contribution to mining royalties and taxes from mining operations in these areas was about Nam

Samples of cassava leaves, cassava tubers and soil were collected from contaminated and uncontaminated areas of the Zambian Copperbelt mining district and the metals (copper, cobalt, zinc, lead and iron) and arsenic contents were analysed by flame or hydride-generation atomic absorption spectroscopy. The contents of copper in leaves of cassava growing on contaminated soils were up to 612 mg/kg Cu total dry weight, compared to up to 252 mg/kg Cu in cassava leaves growing on uncontaminated soils. The contents of cobalt, arsenic and zinc in leaves of cassava growing on contaminated soils were found to be higher than those from uncontaminated areas, while the contents of lead in the leaves of plants from both areas were low and did not differ significantly. The metals contents in the tubers of plants from both areas were markedly lower than those in the leaves. A dietary risk assessment of copper, lead and arsenic indicated no excessive intake of copper, but an occasional excessive intake of lead and arsenic in both contaminated and uncontaminated areas. The surfaces of leaves of cassava growing near the smelters were strongly contaminated by metalliferous dust and were considered to pose a health risk if the cassava were poorly washed., Samples of cassava leaves, cassava tubers and soil were collected from contaminated and uncontaminated areas of the Zambian Copperbelt mining district and the metals (copper, cobalt, zinc, lead and iron) and arsenic contents were analysed by flame or hydride-generation atomic absorption spectroscopy. The contents of copper in leaves of cassava growing on contaminated soils were up to 612 mg/kg Cu total dry weight, compared to up to 252 mg/kg Cu in cassava leaves growing on uncontaminated soils. The contents of cobalt, arsenic and zinc in leaves of cassava growing on contaminated soils were found to be higher than those from uncontaminated areas, while the contents of lead in the leaves of plants from both areas were low and did not differ significantly. The metals contents in the tubers of plants from both areas were markedly lower than those in the leaves. A dietary risk assessment of copper, lead and arsenic indicated no excessive intake of copper, but an occasional excessive intake of lead and arsenic in both contaminated and uncontaminated areas. The surfaces of leaves of cassava growing near the smelters were strongly contaminated by metalliferous dust and were considered to pose a health risk if the cassava were poorly washed.

The use of remote sensing of canopy spectral reflectance of two native evergreen phreatophyte tree species (Searsia lancea and Euclea sp) to distinguish Black Reef quartzite and sulphide ore body from Malmani dolomite and Ventersdorp lava at a site situated at Vaal River mining operations, North West Province, South Africa is described. Significant differences between the geologies were found for the three vegetation stress indices - normalised difference vegetation index, plant senescence reflectance index and red-edge normalised difference vegetation index - as well as for the red-edge wavelength and inflection point, and the 725/702 ratio of the first-order derivative of the reflectance data. The results of the Dunn's multiple pairwise comparisons between the three geologies and between the six landscape functional types for each test (normalised difference vegetation index, plant senescence reflectance index, normalised difference water index and red-edge normalised difference vegetation index) are presented for the two tree species. Relatively few significant differences were found between landscape functional types within geologies for all of the vegetation indices, indicating that the topography and physical landscape played a lesser role in the tree spectral reflectance than the substrate parent geology., The use of remote sensing of canopy spectral reflectance of two native evergreen phreatophyte tree species (Searsia lancea and Euclea sp) to distinguish Black Reef quartzite and sulphide ore body from Malmani dolomite and Ventersdorp lava at a site situated at Vaal River mining operations, North West Province, South Africa is described. Significant differences between the geologies were found for the three vegetation stress indices - normalised difference vegetation index, plant senescence reflectance index and red-edge normalised difference vegetation index - as well as for the red-edge wavelength and inflection point, and the 725/702 ratio of the first-order derivative of the reflectance data. The results of the Dunn's multiple pairwise comparisons between the three geologies and between the six landscape functional types for each test (normalised difference vegetation index, plant senescence reflectance index, normalised difference water index and red-edge normalised difference vegetation index) are presented for the two tree species. Relatively few significant differences were found between landscape functional types within geologies for all of the vegetation indices, indicating that the topography and physical landscape played a lesser role in the tree spectral reflectance than the substrate parent geology.

Mineral and trace-element (Cu, Pb, Zn, Cr, Ni, Co and Cd) compositions of tailing samples and surrounding arable-soil samples collected from the Kombat copper mine area, Grootfontein district, Otavi Mountainland, Namibia were studied using X-ray diffraction and flame atomic absorption spectroscopy. A sequential-leaching procedure was employed to determine the binding mechanisms of the metal retentions in soils. Copper and lead showed median-concentration values of 1 328 and 946 mg/kg, respectively, in tailings and 112 and 117 mg/kg, respectively, in farmland soils west of the tailings impoundment, the latter concentrations exceeding maximal permissible values for agricultural soils. Copper and lead were found to be relatively strongly bound to the soils with the principal binding site for these metals being the iron oxide/manganese oxide fraction., Mineral and trace-element (Cu, Pb, Zn, Cr, Ni, Co and Cd) compositions of tailing samples and surrounding arable-soil samples collected from the Kombat copper mine area, Grootfontein district, Otavi Mountainland, Namibia were studied using X-ray diffraction and flame atomic absorption spectroscopy. A sequential-leaching procedure was employed to determine the binding mechanisms of the metal retentions in soils. Copper and lead showed median-concentration values of 1 328 and 946 mg/kg, respectively, in tailings and 112 and 117 mg/kg, respectively, in farmland soils west of the tailings impoundment, the latter concentrations exceeding maximal permissible values for agricultural soils. Copper and lead were found to be relatively strongly bound to the soils with the principal binding site for these metals being the iron oxide/manganese oxide fraction.

A study is presented of the stability of nonferrous metal smelting wastes in Europe and Africa and their effects on the adjacent soil environment. Slag, fly-ash and soil samples from smelting sites at Pribram, Czech Republic (primary and secondary lead), Tsumeb, Namibia (copper-lead-arsenic) and Kitwe-Nkana, Mufulira and Chambishi, Zambian Copperbelt (copper-cobalt) were studied using a range of analytical techniques as well as long-term and pH-static laboratory leaching experiments and soil mobility/bioavailability tests. For the Pribram site, the data from leaching experiments showed that higher amounts of lead are released from the primary than from the secondary lead slag and the latter material (slag from car-battery processing) is relatively stable, the released amounts of lead being low, even after long-term (12 y) interaction with water. For zinc, the concentrations released from primary lead slag were found to exceed the European Union regulatory limit for hazardous waste by about ten-fold and by more than 40-fold after 1 and 12 y of leaching, respectively. Leaching experiments carried out on slags from the Tsumeb site showed a high risk of arsenic and antimony release, with arsenates having a tendency to form efflorescence secondary minerals on the slag surfaces., A study is presented of the stability of nonferrous metal smelting wastes in Europe and Africa and their effects on the adjacent soil environment. Slag, fly-ash and soil samples from smelting sites at Pribram, Czech Republic (primary and secondary lead), Tsumeb, Namibia (copper-lead-arsenic) and Kitwe-Nkana, Mufulira and Chambishi, Zambian Copperbelt (copper-cobalt) were studied using a range of analytical techniques as well as long-term and pH-static laboratory leaching experiments and soil mobility/bioavailability tests. For the Pribram site, the data from leaching experiments showed that higher amounts of lead are released from the primary than from the secondary lead slag and the latter material (slag from car-battery processing) is relatively stable, the released amounts of lead being low, even after long-term (12 y) interaction with water. For zinc, the concentrations released from primary lead slag were found to exceed the European Union regulatory limit for hazardous waste by about ten-fold and by more than 40-fold after 1 and 12 y of leaching, respectively. Leaching experiments carried out on slags from the Tsumeb site showed a high risk of arsenic and antimony release, with arsenates having a tendency to form efflorescence secondary minerals on the slag surfaces.

Samples of pore water in the unsaturated zone and water in the saturated zone of Mine Doyon waste rock pile (sericite schist; 7 and 2 wt.% pyrite and calcite, respectively), Montreal, Quebec, Canada were collected from a site close to the pile slope and a site in the core of the pile. The concentrations of sulphate and aluminium in pore water close to the slope of the pile reached 270 and 33 g/l, respectively, while those in the central zone of the pile reached 150 and 12 g/l. The temperature and oxygen profiles indicated convective oxygen supply near the pile slope and diffusive transport of oxygen in the core. Pyrite oxidation rate data are presented using large-scale field methods and small-scale laboratory tests, namely temperature and oxygen profile, pyrite mass balance, and oxygen consumption determinations., Samples of pore water in the unsaturated zone and water in the saturated zone of Mine Doyon waste rock pile (sericite schist; 7 and 2 wt.% pyrite and calcite, respectively), Montreal, Quebec, Canada were collected from a site close to the pile slope and a site in the core of the pile. The concentrations of sulphate and aluminium in pore water close to the slope of the pile reached 270 and 33 g/l, respectively, while those in the central zone of the pile reached 150 and 12 g/l. The temperature and oxygen profiles indicated convective oxygen supply near the pile slope and diffusive transport of oxygen in the core. Pyrite oxidation rate data are presented using large-scale field methods and small-scale laboratory tests, namely temperature and oxygen profile, pyrite mass balance, and oxygen consumption determinations.

Samples were collected from a platinum tailings facility in Steelpoort, Mpumalanga, South Africa by hand auger and direct push probe drilling. The results of analyses using X-ray diffraction, X-ray fluorescence, acid-base accounting, net acid generation and reflected light microscopy, acid-leaching tests, inductively coupled plasma scans, permeameter and pumping tests and geochemical and unsaturated flow modelling indicated that alteration mineral phases formed within ten years in the tailings material. Elevated concentrations of major cations and anions were observed in the fluid discharged from the tailings (Ca, Mg, Na, Si, Cl and SO4) and in the groundwater (Ca, Mg, Na, Cl and SO4). The movement and discharge of contaminants from the tailings were predicted to occur at a rate of ca. 0.7 m/10 y into the underlying vadose zone., Samples were collected from a platinum tailings facility in Steelpoort, Mpumalanga, South Africa by hand auger and direct push probe drilling. The results of analyses using X-ray diffraction, X-ray fluorescence, acid-base accounting, net acid generation and reflected light microscopy, acid-leaching tests, inductively coupled plasma scans, permeameter and pumping tests and geochemical and unsaturated flow modelling indicated that alteration mineral phases formed within ten years in the tailings material. Elevated concentrations of major cations and anions were observed in the fluid discharged from the tailings (Ca, Mg, Na, Si, Cl and SO4) and in the groundwater (Ca, Mg, Na, Cl and SO4). The movement and discharge of contaminants from the tailings were predicted to occur at a rate of ca. 0.7 m/10 y into the underlying vadose zone.

Samples of topsoil were collected from a large zone in the vicinity of the Nkana copper smelter, from the Chingola mining area and from the Nkana-Kitwe smelting area, and a soil profile (Oxisol) 100 cm in depth was sampled close to the smelter stack. The spatial distribution of arsenic, cobalt, copper, lead and zinc indicated that the highest concentrations were downwind, i.e. northwest, of the smelter. The highest concentrations (mg/kg) in the topsoils were arsenic (255), cobalt (606), copper (27 410), lead (480) and zinc (450). Investigation of the soil profile using lead isotopic tracing and sequential extraction procedures showed that lead exhibited a downward migration with an estimated penetration rate of 1.36 cm/y and that copper also had a significant mobility. Bioaccessibility, determined using simulated gastric conditions, in the smelting area was up to 100% of total lead and arsenic, compared to 81 and 84%, respectively, in the mining area, with the bioaccessibilities of cobalt, copper and zinc being similar for the two areas. The calculated amounts of ingested materials exceeding tolerable daily intake values suggested that the ecotoxicological risks related to soil ingestion were significant for copper and cobalt., Samples of topsoil were collected from a large zone in the vicinity of the Nkana copper smelter, from the Chingola mining area and from the Nkana-Kitwe smelting area, and a soil profile (Oxisol) 100 cm in depth was sampled close to the smelter stack. The spatial distribution of arsenic, cobalt, copper, lead and zinc indicated that the highest concentrations were downwind, i.e. northwest, of the smelter. The highest concentrations (mg/kg) in the topsoils were arsenic (255), cobalt (606), copper (27 410), lead (480) and zinc (450). Investigation of the soil profile using lead isotopic tracing and sequential extraction procedures showed that lead exhibited a downward migration with an estimated penetration rate of 1.36 cm/y and that copper also had a significant mobility. Bioaccessibility, determined using simulated gastric conditions, in the smelting area was up to 100% of total lead and arsenic, compared to 81 and 84%, respectively, in the mining area, with the bioaccessibilities of cobalt, copper and zinc being similar for the two areas. The calculated amounts of ingested materials exceeding tolerable daily intake values suggested that the ecotoxicological risks related to soil ingestion were significant for copper and cobalt.

A study of the influence of land use, soil chemistry and rate of contamination on the distribution, geochemical position and mobility of thallium in forest and grassland soils affected by the Boleslaw zinc smelter at Bukowno, Olkusz district, Silesia-Krakow region, southern Poland is presented. The ability of forest soils to concentrate large quantities of thallium, if present in smelter emissions, especially within the organic layers, was demonstrated. Sequential extraction showed that soil organic matter plays an important role in thallium mobilisation. Chemical fractionation indicated that the organic horizons of forest soils contained up to 23% of labile thallium associated with the exchangeable/acid-extractable fraction. A comparison of the concentrations of thallium in the upper and bottom horizons of forest and grassland soils demonstrated strong anthropogenic contamination and vertical mobility of thallium. Thallium concentrations determined in grassland soils were significantly lower than those in forest soils., A study of the influence of land use, soil chemistry and rate of contamination on the distribution, geochemical position and mobility of thallium in forest and grassland soils affected by the Boleslaw zinc smelter at Bukowno, Olkusz district, Silesia-Krakow region, southern Poland is presented. The ability of forest soils to concentrate large quantities of thallium, if present in smelter emissions, especially within the organic layers, was demonstrated. Sequential extraction showed that soil organic matter plays an important role in thallium mobilisation. Chemical fractionation indicated that the organic horizons of forest soils contained up to 23% of labile thallium associated with the exchangeable/acid-extractable fraction. A comparison of the concentrations of thallium in the upper and bottom horizons of forest and grassland soils demonstrated strong anthropogenic contamination and vertical mobility of thallium. Thallium concentrations determined in grassland soils were significantly lower than those in forest soils.