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In the present investigation, a study was carried out on the use of microorganisms for the bioextraction of metallic species contained in the filtered tails, the main solid residue of the acid nickel extracting process. The developed study shows that fungus Trichoderma harzianum Rifai (A-34) has the ability to degrade multiple compounds. From the mycelial mass obtained, the incubation of the fungus was carried out under adequate temperature and agitation conditions, for a period of 24 hours. The biological reducing agent (ARB) produced by the fungus TrichodermaharzianumRifai (A-34) contains organic acids. Among this acids, citric acid (C6H8O7) has the higher concentration, which is more effective as a leaching agent. The effect of temperature was evaluated during the bioextraction process at 25 and 50 ℃ in 40g of filtered glue for 20 days. The content of metallic species in the leached liquor obtained from the bioextraction experiments in the tailings process is higher than the ARB concentration of 100 % at a temperature of 50°C, due to the increase in temperature, which causes the decrease in pH by modifying the activity of the ions in the solution, making the medium more acidic, thus favoring leachability in the filtered tailings under study. [ABSTRACT FROM AUTHOR]

Introduction: Most of the ethyl alcohol produced is from sugar sources, molasses, but this is becoming more and more sought after due to the increase in biotechnological productions, so it is necessary to study other sources of sugar substrates and/or their mixtures. Objective: To carry out a preliminary study in the alcoholic fermentation stage of the use of filter juice mixture, molasses and syrup. Materials and Methods: A simple trellis-type design of experiments was carried out, performing the preparation of culture media, some as a base and the rest are combinations of them. Up to 100% of sugars in total reducing agents (ART) of the substrates are taken into account. The response variable is alcoholic percentage. Results and Discussion: The fermented musts had percentages between 5.22 and 5.50. The highest was reached in experiments four and five, where the substrates molasses and syrup were used, 5.48 and 5.50 % respectively. On the other hand, when using the juice from the filters (experiments one, two and three), the lowest levels of alcoholic concentration in the medium were obtained, values that differ from those reached in other fermentation studies. Conclusions: The use of syrup in fermentation allows a better utilization of cane that should not be destined for sugar production, given its low quality. In the study, the highest alcoholic percentage is reached when this stream is used as substrate. [ABSTRACT FROM AUTHOR]

The main objective of this research study was to examine the conversion of sugarcane straw into a biocoal that can be used as a fuel and reducing agent in direct reduction processes of iron ore. Washing, roasting, and carbonization pretreatments were developed to improve physical-chemical properties. Sugarcane straw was washed with water, roasted at 270°C for 20 minutes, and carbonized at 600°C for 90 minutes. The biocoal obtained had 66.54% fixed carbon and 34.33 MJ/kg of higher heating value (measured on a dry basis), resembling a mineral coal. In addition, the product was friable, hydrophobic, and resistant to biodegradation. It is concluded that sugarcane-derived biocoal has adequate characteristics for its use as a fuel and reducing agent in the steel industry, improving the valorization of sugarcane straw. [ABSTRACT FROM AUTHOR]

Nowadays to obtain 99mTc solid radiotracers new porous supports are currently used, for instance sediments from rivers with a high content of aluminosilicates were labeled with 99mTc. In the present work a methodology for labeling of silica sand with 99mTcO4- as a prospective solid radiotracer was developed. Labeling of the previously treated and untreated silica sand was carried out using variable concentrations of chloride and stannous fluoride as reducing agents and different labeling times. The influence of the pre-treatment stage of the sand on the obtained Tc retention yields was evaluated. The changes in the composition of the silica sand after its previous treatment could be verified from the Scanning Electron Microscopy (SEM-EDS). The results suggested the use of previously treated silica sand and stannous fluoride as a reducing agent, modifications were proposed to the initial methodology of previous treatment of the sand. It was possible to confirm from the SEM-EDS technique that the increase in the percentage of retention of Tc in the sand after its treatment is mainly due to the observed changes in its chemical composition and structure. It was possible to obtain a 99mTc solid radiotracer on support of silica sand with a retention yield of 74%. [ABSTRACT FROM AUTHOR]

Obtaining an industrial level is done with pyrometallurgical techniques, such as roasting. Currently, rhenium manufacturing comes from the roasting of polymetallic sulphides from previous operational processes, such as flotation. However, due to the environmental drawbacks of roasting sulfides, the application of new processes, such as carbonated reduction roasting, is sought [1]. This has the purpose of obtaining a calcite with high content of rhenium and with low operating costs. Expecting to achieve good environmental responses, ie without releasing pollutant gases into the atmosphere, such as SO2 (Sulfur Anhydride). Operationally the toasting with carbothermal reduction, uses a sulfur capture agent such as CaO (Calcium Oxide), CaCO3 (Calcium Carbonate) or Na2CO3 (Sodium Carbonate) and a reducing agent such as C (Carbon); preventing the release of SO2 (Sulfur Anhydride) into the atmosphere [2]. The objective of this work is to use carbonaceous reduction to retain the rhenium in the calcite. This goal is achieved through an exhaustive study of the operational variables of roasting, such as temperatures, times, molar ratios of C (Carbon) and CaO (Oxide of Calcium) with respect to the Rhenium. Emphasizing that when the best recoveries of Re are achieved, optimal operational conditions are obtained respectively. Trials of toasting with carbothermic reduction applied to molybdenum-copper - rhenium sulfhide minerals. Based on this, they plotted: temperature variation, evaluated from 300 °C to 600 °C, variation of times from 10, 20, 30, 45, 60 to 90 min. For a constant molar ratio of CaO and C with respect to the element to Re (Re: CaO: C), equal to 1: 0.5: 1. It is important to note that for roasting with carbothermal reduction the variables of temperatures, times and molar ratios must be analyzed together. Concluding that according to these variations the optimal operational conditions were determined as: molar ratio of 1: 0.5: 1 with respect to Re (rhenium), working temperature corresponding to 400 ° C and an optimal roasting time of 30 minutes. Obtaining recoveries with values of 90% of Re (rhenium) in the calcine. [ABSTRACT FROM AUTHOR]

In the barium salts production process, the carbothermic reduction stage (barite transformation into barium sulfide) is the most complex, due to the high consumption of the reducing agent (coal), low conversion rate and the high temperatures at which the process occurs. The objective of this work was to study the carbothermic reduction process of briquettes formed by a mixture of barite and coke coal concentrate. The isothermal tests were conducted under air atmosphere at 900, 1100 and 1300°C during 0.25, 0.50, 1.00 and 2.00 h. The calcines produced were characterized by X-ray diffraction and Scanning electron microscopy. The results indicated that it is possible to obtain conversions greater than 80% in 0.25 h for all temperatures under study. Additionally, it was detected that the conversion rate decreases with higher carbothermic reduction times. This is related with the depletion of coal, which promotes the conversion of barium sulfide into barium sulfate. [ABSTRACT FROM AUTHOR]

In this work, the results of recovering gold from ammoniacal thiosulfate solutions through cementing and electrodeposition were studied and analyzed. In cementation, the kinetic aspects of gold precipitation were analyzed using zinc and aluminum powder as cementing agents. The variations in the concentrations of the reducing agents, copper and gold as a function of time were analyzed to evaluate the influence of the previous deoxygenation and the activation energy was determined. The gold recoveries were greater than 98% for both reducers. The results showed that zinc is better cement, since aluminum, despite having a higher reaction speed, destroys thiosulfate. The highest consumption of zinc and aluminum was due to the deposition of copper, a ratio was observed (1: 1) and (2: 5) respectively. In zinc cementation, the gold concentrations were taken as a function of time for different reaction temperatures, the linearized form of the Arrenius equation was graphed to obtain the activation energy (Ea) which was found to be 15.43 KJ / mol. This value responds to a diffusive control for the reaction, and is similar to that found for processes with prior deoxygenation. This would indicate that, unlike the cementation of gold from cyanide solutions, the deoxygenation of these solutions would not be necessary. The experimental data of the electrolysis were adjusted to a model C = f (t) with R2 greater than 0.94. This allowed the calculation of the gold mass transfer coefficient (0.80 x10-6 m/s). This result is in the same order as that obtained by other authors for the electrodeposition of gold of cyanized solutions, (1.3x10-6 m / s) for a fluid velocity of 4.80x10-3 m / s. A final recovery of gold was obtained (92.1%) and copper co-precipitation was confirmed. [ABSTRACT FROM AUTHOR]

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The objective of this work was to optimize the levels of oxidant/reducer substances to improve the technological behaviour of flours. Combinations of azodicarbonamide and ascorbic acid with a reducing agent as sodium bisulfite were used. Experiences in bread-making were made determining the dough consistency at the end of mixing and the specific volume of bread. Also, the bread score and the texture score were obtained trough sensorial evaluation. The results indicated that in the case of simultaneous use of azodicarbonamide and low levels of sodium bisulfite produce a softening of the dough with a decrease in specific volume of bread. This does not occur when the reducing agent is added at levels close to 100ppm. The simultaneous use of ascorbic acid and sodium bisulfite, at intermediate levels, produces a very significant beneficial effect, so its use is highly recommended. [ABSTRACT FROM AUTHOR]