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By H. J. Garcia

Biodegradation of cyanide by microorganisms isolated from solids previously exposed to cyanide has been investigated. Initial sodium cyanide concentration was 300 ppm at pH 10.5. The kinetics of biodegradation were found to be first order with respect to cyanide concentration, and the overall reaction rate constant is k = 0.102 day-1. The activation energy and the frequency factor were determined to be { A }Ea = 5.45 Kcal/mol and A = 1.28 x 10-2 sec-1, respectively. Based on these values, thermodynamic properties of an intermediate activated complex were assessed. All tests resulted in cyanide concentrations less than 0.1 ppm in about 35 days at 250C, whereas at 350C the time of biodegradation to reach this cyanide level was 30 days. Kinetic data were also established to relate biodegradation to amount of inoculum. The maximum theoretically-attainable rate, Vm , and the optimum amount of inoculum, K , were determined to be 4.8 x 10-4 M NaCN/day and 7.5 % of amount of inoculum. With respect to the mechanism of biodegradation, cyanide was shown to decompose to carbonate, bicarbonate and ammonia. Titrimetric analyses revealed concentrations of 5.6 x 10-3, 4.8 x 10-3 M, and 70.2 ppm for carbonate, bicarbonate and ammonia, respectively. The average cell population was determined to be 3.75 x 108 cells/mL.

Jan 1, 1994

By Luciano B. Oliveira, Luis G. C. Marques, Sergio N. Monteiro, Marcos V. M. Fagundes

"Biodiesel production is normally associated with large plantations of oily vegetables such as soybean and colza, in large rural areas. However, in the municipal limits of the city of Rio de Janeiro, southeast of Brazil, biodiesel is being produced from wastes commonly generated by typical urban activities such as sewage sludge, discarded fat from meat markets and post-used cooking oils. In the present work, the experience of producing biodiesel from urban wastes in Rio de Janeiro is assessed. The type of precursor materials, equipments and logistics are presented. The environmental and economical advantages as well as the drawbacks are discussed.IntroductionThe interest for a liquid fuel that could substitute those obtained from petroleum started more than one hundred years ago when Rudolph Diesel tested his no-spark internal combustion engine, impelled by compression, with peanut oil. By that time, petroleum was beginning to be extracted in large scale and no one was concerned with the future environmental problems and its eventual depletion. In the last century, the successful association of petroleum based fuels with the automotive industry was an almost insurmountable obstacle to any attempt to use nonmineral oils [1]. In addition to the greater efficiency and, by then, lower price of the diesel from petroleum, the use of plain vegetable oils introduced undesirable carbon deposits and reduced the engine lifetime. Today, the situation is reverse. The continuous increase in the price of petroleum and, above all, its contribution to climate changes are strongly motivating the use of biofuels to replace those obtained from fossil fuels such as petroleum, natural gas and coal [2].In the case of the common petroleum derived diesel, many countries are now engaged in large scale substitution programs. The USA should produce more than 700 million litters of biodiesel, while the European Community is expected too produce around 6.5 billion litters in 2008. In Brazil, the federal biodiesel program imposed a minimum of 2% addition to the common diesel. This would demand a production of 800 million litters in 2008 [3]. The Brazilian biodiesel is made from a diversified source of vegetables mainly castor bean, African palm and soybean. The main producers are agrobusiness firms located in large rural areas of the Brazilian hinterland [4]."

Jan 1, 2008

By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By Muhammad Abid, Kh. .. S. Karimov

"In this study, design and investigation of biogas digester consisting of methane tank with built-in solar collector to utilize solar energy for the heating of the slurry prepared from the dung and heat exchanger is designed, developed and tested. The digester was laboratory type and consists of cylindrical metallic tank of size of 0.5 m in diameter; 1 m in height and 200 liters in volume. The surface of the digester from outside was covered by thermo insulated material a glass wool, except of south side (in northern hemisphere). This side played the role of built-in collector and was blackened to increase absorption of solar irradiation and covered under 45o by glass. In the blackened side of the digester on the different heights it was installed metallic pipes for the inlet and outlet of the air, connected with heat exchanger installed inside of the digester. The heat exchanger was fixed in the level above of the inlet pipe. The horizontal plane reflector concentrates solar beams to blackened side of the digester. In the winter period, it was found that the retention time of this digester is shorter on 15% and produced biogas volume is larger on 20% with respect of ordinary biogas digester. This digester is used for the demonstrative purposes and as a teaching aid presently and base on the results it may be used for the construction of large volume digesters for use in the farms, especially located in the remote and mountain areas where the climate in the winter period is cold. Introduction At present many experts around the world have focused their efforts to energy crises because energy is one of the most important factors for the development of the society. It is known that consuming energy is proportional to quality or standard of life. There is a close relationship between energy consumption and the Gross National Product (GNP). It is obvious that for further development of the country additional sources of energy is required, which are cheap, safe and environmentally compatible with respect to the action on possible wastes. Utilization of renewable energy is one route to help in solving the above mentioned problems. In particular, biogas as a source of renewable energy is produced by biotechnology and used wide on residential scale [1]. The biogas was produced for the very first time in 1814 by Deivy from organic wastes. In 1900 production of biogas was started in Bombay (India) [2, 3]. Biogas consists of 55-70% methane (CH4) and around of 27-44% carbon dioxide (CO2) and less than 1% H2 and H2S. At present biogas is used widely in some countries for lighting, machines, and vehicles, generators, cooking and heating. Biogas generation is suitable for small to large scale operation and at present is realized in a number of developed and developing countries as USA, Hungary, China, India etc. Since 1990s biogas projects construction in China has developed steadily by the end of 1998, there were altogether 6.88 million household biogas digesters [4]. In Russia biogas digesters are used for processing of hard dung into biogas [5]. Over the last few years the very first biogas digesters were constructed in Tajikistan as well [6,7] and it was found that the digesters can work with sufficiently high efficiency in mountain areas as well ."

Jan 1, 2008

By S. J. Ojolo, B. E. Ebiobi, J. A. Kehinde

"Anaerobic digestion is being taken seriously because of increasing concerns about the environmental hazards of wastes. The production of biogas, as an alternative source of energy was investigated in a designed and fabricated 200litre biogas reactor. The digester was operated on a batch-fed basis, and the feed stock was cassava waste which is readily available in Nigerian farms. The main aim was to explore other renewable sources as a means of less dependence on fossil fuels. A total of 1.94dm3/60kg waste of biogas was produced in 40 days of hydraulic retention time (HRT) with the average yield of 0.048dm3/day. The gas burned with a bluish colour indicating presence of methane (CH4). Temperature during the period of experiment varied between 27 and 330C. The pH of the slurry after the experiments averaged 3.21.1. INTRODUCTIONAnaerobic digestion and biogas production are promising means of achieving multiple environmental benefits and producing an energy carrier from renewable resources (Borjesson and Berglund, 2005).Biogas is one of the by-products of anaerobic decomposition of organic matter by microorganisms, mainly bacterial, a process referred to as anaerobic digestion.Biogas is produced by the process of anaerobic digestion of organic material by anaerobes. Biogas can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digester.Biogas, also called digester gas typically refers to methane produced by the fermentation of organic matter including manure, wastewater, sludge, municipal solid waste or any other biodegradable feedstock under anaerobic conditions. The content of biogas varies with the material being decomposed, and the environmental conditions involved. The gas generally composes of methane, carbon dioxide, nitrogen, hydrogen, and hydrogen sulphide (Anunputtikul and Rodtong, 2004). Potentially, all organic waste materials contain adequate quantities of the materials essential for the growth and metabolism of the anaerobic bacterial in biogas production."

Jan 1, 2008

By Nicholas S. Lynn

"A new process has been developed to bioleach refractory gold ores to expose the precious metal values using Thiobacillus ferrooxidans bacteria.The ore is hosted in a limestone rock with secondary replacement of carbonaceous and pyritic minerals. Crushing, stacking, bioleaching, rinsing and neutralization have been completed in a 45-day total time cycle. The use of sulfuric acid operation, and concentrated Thiobacillus ferrooxidans population allows the short bioleaching cycle.The ore is then processed using conventional Carbon-In-Leach Cyanide recovery techniques.ABSTRACT ONLY"

Jan 1, 1997

By B. A. Paponetti

The following report discusses the bioleaching of chalcopyrite of italian origin catalyzed by Thiobacillus ferrooxidans. The developments vcr.ius time of the main .biochemical and chemical reactions involved in the production of soiuble and insoluble species were investigated focusing on the times at which they begin and bow long they last. The precipitates were characterized both in quantity and in quality relating the rate of the process to the precipitates fonnatiom. A material. balance has been made to verify the proposed mechanism.

Jan 1, 1991

By A. Alvarez

In this work, mesophilic and thermophilic cultures have been used in the presence of silver as a catalyst. Chalcopyrite and byproducts of bioleaching were characterized in order to: a) obtain information about the kinetics control of the process, and b) explain the different behaviour observed during the mineral attack. With thermophilic microorganisms (68°C and Norris medium as nutrient) the reaction stopped at approximately 65% copper extraction, with and without Ag ion addition as a catalyst. The remaining chalcopyrite appears surrounded by hydronium jarosite (with ammonium ion in substitution in the "alkaline site"), goethite and elemental sulphur. With mesophilic cultures (35°C and 9K medium as nutrient) the reaction stopped at approximately 25% copper extraction (without Ag) and approximately. 85% extraction (with Ag). In both cases, the remaining chalcopyrite was surrounded by agglomerates of ammonium jarosite (with hydronium ion substitution in the "alkaline site") and some iron oxides and/or hydroxides.

Jan 1, 1999

By A. E. Torma

In recent years the copper industry has gained considerable economic stability. An essential part of this industrial wealth is attributable to the successful application of bio-mediated heap and dump leaching techniques in the recovery of copper from low-grade resources. This study evaluated the leachability of a chalcopyrite conlentrate using naturally occurring mixed culture of predominantly Thiobacillusferrooxidans and Thiobacillus thiooxidans. For the effects-of pulp density, the overall reaction rate constant (k) and the order of reaction (n) have been determined to be 1.93 h-1 and 1.36, respectively. Cyclic voltammetric measurements revealed that intermediate reactions are involved in the chalcopyrite oxidation. Using the Price approach, it was shown that the dissolution of chalcopyrite is solid state diffusion controlled.

Jan 1, 1992

By Carlos Eduardo Gomes de Souza, Luis G. S. Sobral, Paulo A. Medeiros da Silva, Selma G. F. Leite, Renata de B. Lima

"The use of mixed cultures of acidophilus microorganisms that act in different temperature ranges, aims at speeding up the digestion of chalcopyrite, highly refractory sulphide mineral, the major mineral in the flotation concentrate of Caraíba Mining Co., with an attractive processing cost. The concentrate under consideration contains mainly chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents of, approximately, 70 and 30%, respectively. It was observed in this study, the performance of consortium of mesophiles, moderate and extreme thermophile microorganisms, in the oxidation of the aforementioned sulphides minerals, evaluating operational parameters such as pH of the leaching solution, the reaction temperature and redox potential, with consequent extraction of 80% of the concentrate copper content within 60 days of bioleaching. Such high copper extraction was achieved in column bioleaching tests.INTRODUCTIONThe solubilization of metals by the application of microorganisms from the mineral ores and the subsequent recovery of metals from solution are referred to as bioleaching (Rohwerder, T et al, 2003). This is an economical method for the recovery of metals from minerals; especially lowgrade ores, overburden, and waste from current mining operations which requires moderate capital investment with operating cost (Watling, 2006).Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes such as concentration and smelting. Those physicochemical metal extraction processes generate sulphur dioxide, a toxic emission that is increasingly the target of regulatory legislation (Stott et al., 2000; Olson et al., 2003). Bioleaching of chalcopyrite is the key industry target. The main problem hindering commercial application of chalcopyrite bioleaching is the slow dissolution rate (Fu et al, 2008).Dissolution of acid-soluble sulphide minerals such as sphalerite, and to a lesser extent chalcopyrite, occurs by a combination of ferric iron and proton attack via the polysulphide pathway (Rohwerder et al., 2003)."

Jan 1, 2008

By D. Morin

A general study of gold refractory arsenopyrite-pyrite concentrate bioleaching has been carried out including two continuous bioleach testworks at different sizes, namely one at a laboratory scale with a 100 I unit at a 2 kg/d dry solid flowrate and the other at a pilot scale at a 100 kg/d dry solid flowrate. Both tests show a 80% bioleaching of arsenopyrite in about four days of treatment and with the same kinetic. Pyrrhotite is attacked at the earlier stage of the bioleaching but pyrite remains unaffected. The weak potential of oxidation associated with the decomposition of arsenopyrite and the abundance of arsenite leads to a high grade of elemental sulfur in the bioresidue which consumes the major part of the cyanide during the gold recovery. Furthermore. the arsenite and ferrous produced in solution have to be oxidized to obtain a stable precipitate in the waste products and as outlined in previous works of other authors on this subject the addition of iron to obtain a Fe/As molar ratio at least above 3 is necessary. The agitation equipment used in the pilot unit allowed an optimization study calculation for scaling-up the design and power requirements of an industrial installation. For the pretreatment of a gold refractory As high-graded concentrate the reagent cost has the greatest part in the operating cost of the biooxidation step due to the necessary retreatment of the biosolution. In that conditions the power cost is quite marginal. actually it is significant for the treatment of pure pyrite.

Jan 1, 1991

By E. G. Noble

The potential for using heterotrophic microorganisms to solubilize manganese from low-grade domestic ores is being assessed at the Reno Research. center, U.S. Bureau of Mines. More than 90 pct of the manganese has been extracted from a variety of oxide ores in shake-flask tests using molasses as a source of .. nutrients for the microorganisms. It has also been demonstrated that high recoveries of manganese can be obtained from a domestic wad ore using column bioleaching. 'l'he isolation and identification of organisms responsible for manganese extraction is discussed, as are the mechanisms responsible for manganese solubilization.

Jan 1, 1991

By Vijaya Thangavelu

Biological leaching of low-grade nickel laterite is based on a non-traditional leaching of oxide minerals using heterotrophic micro-organisms. The organisms solubilise metals by excreting organic acids; these acids then form complexes with heavy metals. High salinity of water supplies and soils in the vicinity of nickel laterite ore bodies is a major abiotic stress to fungi and represents a major challenge in the application of bioleaching process in-situ. Salinity exposes fungi cells to Na+ toxicity and osmotic stress. This study examined the salt tolerance development of Aspergillus foetidus based on gradual acclimatization of organism, its salt threshold and the salinity effect on its metabolism. The biological leaching of weathered saprolite ore with the resulting halotolerant organism under saline conditions was assessed. It was observed that salinity stress affected the organism?s growth and energy utilization

Jan 1, 2006

By Michael L. Free

Bacterial oxidation of an arsenopyritic gold-ore .concentrate was carried out with continuous-flow .operation in 14-liter, mechanically agitated reactors. Samples from the slurry reactors were separated into solid and liquid fractions and analyzed separately to determine the electrochemical rates of sulfide conversion by the bacteria and the rates of direct bacterial oxidation of sulfide. The rates of the individual mechanisms are compared to the overall rates of biooxidation in the continuous-flow slurry reactors. The results show that the commonly hypothesize4 direct and indirect mechanisms of biooxidation both play a significant role in the bacterial oxidation of sulfide ores.

Jan 1, 1991

By Yasuo Kudo, Wu, Hayato Sato, Hiroshi Nakazawa, Shouming

"In order to recover copper from a waste nickel condenser powder, bioleaching experiments were carried out using Thiobacillus ferrooxidans in a shaking flask. The content of nickel and copper in the waste nickel condenser powder in this study were 8.0% and 3.5%. X ray analysis showed the peak of barium titanate. In the preliminary study using metal nickel and copper powders , the dissolutions of nickel and especially copper were accelerated with the addition of ferric iron in the bioleaching of nickel and copper powders while not in the absence of ferric iron. Ferric iron oxidizes both metals, and Thiobacillusferrooxidans oxidizes ferrous iron resulting from the oxidation of metals, whereby the dissolutions of metals proceeds. The dissolution rates of nickel and copper increased with increase in the concentration of ferric iron in the bioleaching of the waste nickel condenser powder.1. IntroductionNickel condensers rejected from manufacturing plants are crushed and landfilled. Waste nickel condensers contain nickel and copper and could be considered as nickel and copper ores. Since the capacity of landfills is diminishing, it is required to recycle metals of waste nickel condensers in order to reduce the amount of wastes landfilled. Conventionally, metals in the waste were recovered by dry metallurgy after the incineration.Nickel has been refined by solvent extraction - electrowinning method (SX-EW method). Recently the amount of copper refined by SX-EW method has increased (Takahashi, et al. 1994). This method is cleaner and consumes less energy than conventional methods. Nickel dissolved well in acid solutions, but copper is not. If copper is leached efficiently from a waste nickel condenser powder, SX-EW method will be applied to recover copper from them"

Jan 1, 2000

By Jorge Alberto Soares Tenório, Denise Crocce Romano Espinosa, Solange Kazue Utimura, Amilton Barbosa Botelho, Carlos Gonzalo Alvarez Rosario

In this study, the recycling of waste materials is interesting in the environmental aspect to reduce the amount of waste in land fill and attenuate the pollution of groundwater, air and soil due to the liberation of dangerous elements. Recycling materials is an important issue once it represents a potential source of valuable metals. Waste printed wired boards (PWBs) as a principal part of Waste Electrical and Electronic Equipment (WEEE) and it is a fast growing stream with complex composition. The composite materials from PWBs are ceramic, polymers and metals. Biohydrometallurgical route may offer possibilities to recycle PWBs from discarded computers with the order to recover copper. The extraction of copper from PWBs by bioleaching processeswas studied using a mixed culture of acidophilic bacteria fromacid mine drainage (AMD) and the bacteria Acidithiobacillus ferrooxidans (A. ferrooxidans). The bioleaching experiments were performed in shaker flasks at temperature 30 °C and 170 rpmwith 10% (v/v) inoculum and pulp density of 35 g/L. Themetals concentration was determined by energy dispersiveX-ray Fluorescence (XRF). The results showed that the maximum copper recovery from PWBs using A. ferrooxidans was approximately 89% and with a mixed culture of bacteria from AMD the copper recovery was 92%.

Mar 1, 2017

By D. J. Adams

Cyanide heap leaching is the predominant technology used in processing low-grade gold ores. During closure ora heap leach operation, residual cyanide must be removed from the process and waste solutions, as well as the heap. Biological cyanide oxidation is a proven, economical technology for destroying cyanide in process and waste waters and spent heaps; The use of biological cyanide degradation eliminates the need for toxic or corrosive chemical oxidizers and has- been implemented at full scale at treatment costs usually <$0.50/1,000 gal. The Applied Biosciences biological cyanide destruction (BCND?) process has been demonstrated to effectively treat cyanide, concentrations up to 350 mg/L. Treated process solutions and wastewaters also contained other contaminants such as arsenic, copper, iron, silver. selenium, mercury, nitrate and zinc, much of which was removed in the cyanide degradation process. Under optimal conditions, microorganisms can rapidly oxidize free cyanide in some process solutions from over 250 mg/L down to 0.1 mg/L in 4 to 5 hr. Cyanide is degraded to ammonia and carbon dioxide, with 50%ofthe cyanide carbon liberated as C02. In general, carbon tank based bioreactors degrade cyanide at significantly higher rates than process or wastewater pond configured treatments, which usually degrade cyanide-more rapidly than in heap treatments. Investigation of cell-free enzyme preparations as an alternative to live microbial cyanide degradation shows promise. Advantages of enzymes over live microbes for cyanide degradation include: (I) the ability to tolerate and degrade higher cyanide concentrations (> I ;000 mg/L), (2) nutrients to support live microbial cells are not required, (3) the effects of other toxic contaminants, such as metals, found in mining waters-are eliminated and (4) the potential for greatly increased kinetics.

Jan 1, 1998

By Nelson Collao I.

Loss of the organic phase from solvent extraction circuits is a major cost factor for SXEW operations. Recognized sources of loss include evaporation, entrainment, and biological degradation. The mechanisms for both entrainment and evaporative losses are well recognized. Biological degradation of the organic has not been as extensively evaluated as the other mechanisms but is a major source of loss. This paper discusses the impact of biological degradation on an operating plant, potential mechanisms for degradation, conditions under which biodegradation of plant organic can occur and plant conditions that may assist in promoting biodegradation.

Jan 1, 2003

By J. Huisman

With the introduction of ever-stricter environmental operating guidelines, capital expenditure restrictions and operational budget cutbacks, the biological method of SO2 removal becomes more and more attractive. Biological treatment of dilute flue gases is a more cost effective technology in comparison to conventional sodium hydroxide scrubbing. Although the investment costs for sodium hydroxide scrubbing is lower, the operational costs are significantly higher. In addition, the end product of the biological installation is sulfur instead of sodium sulfate; and no further wastewater treatment of the bleed from the biological installation is required since heavy metals are removed simultaneously. Another option for the treatment of SO2 containing gas at a sulfuric acid plant is the production of extra sulfuric acid of the discharged SO2 by applying an additional converter. Comparing biological treatment with this option shows much lower investment costs for the biological installation. Sulfur is produced which can be converted to sulfuric acid, so the bio-route will be more cost-effective than an additional converter. In principle, the biotechnological gas cleaning system is an integration of an absorber with a wastewater treatment facility. In the absorber, the SO2 containing gas is brought into contact with the washing water. The effluent absorber liquid contains a mixture of sulfite and sulfate that is converted into elemental sulfur. This conversion takes place in an integrated system; first, the sulfite/sulfate mixture is converted anaerobically into sulfide; secondly, the sulfide is converted aerobically into elemental sulfur. Subsequently the sulfur is separated and the water is returned to the absorber. Due to the buffer capacity of the washing water, removal efficiencies over 98% are possible. In addition to SO2 removal, it is possible to convert for example other bleeds streams such as scrubber acid or weak acid to sulfur in the same SO2 installation. Recent evaluations concluded that biological desulphurization of flue gases is not only economically attractive in comparison to convention sodium hydroxide scrubbing but also in comparison to gypsum producing systems and even seawater scrubbers. This paper describes the technological and economical viability of biological flue gas desulphurization.

Jan 1, 2005

By Tina Maniatis

Applied Biosciences has developed a biological technology for removal of arsenic, nitrate, selenium, and other metals from mining and industrial waste waters.The ABMet® technology was implemented at a closed gold mine site in Canada for removing arsenic from tailings pond water. The system included six bioreactors that began treating water in the spring of 2004. Design criteria incorporated a maximum flow of 567 L/min (150 gallons per minute) and water temperatures ranging from 10°C to 15°C. Influent arsenic concentrations range from 0.5 mg/L to 1.5 mg/L. The ABMet® technology consistently removes arsenic to below detection limits (0.02 mg/L). Data from the full scale system will be presented, as well as regulatory requirements and site specific challenges. Keywords: Arsenic, Sulfate Reduction, Metal Sulfide Precipitate, Biological Water Treatment

Jan 1, 2005