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Acid leaching process by using glucose as reducing agent: A comparison among the efficiency of different kinds of manganiferous ores
No full textThe experimental results of a leaching process of different manganiferous ores are here reported The leaching treatment showed a satisfactory selectivity of manganese extraction in comparison of other metals such as Al, Si and Na. XRD analyses have been none on the ores before and after the leaching treatment. The experimental results showed a good technical feasibility, of the process which can use alternative feedstocks (containing carbohydrates) to treat different manganese ores. (C) 2000 published by Elsevier Science Ltd. All rights reserved
Equilibrium biosorption studies in single and multi-metal systems
No full textDifferent models were used in order to describe equilibrium data obtained by heavy metal biosorption tests. Arthrobacter sp. biomass was suspended in aqueous solution and tested as biosorbent material for copper and cadmium ions. The effects of pH on biosorption in single metal systems (copper and cadmium) and on the selectivity of biomass in two metal systems (copper-cadmium) was studied. Biosorption trials performed for each single metal (in the range 0-2 mmol/l) at different equilibrium pHs (3-6 units) showed a general positive effect of pH increase on metal specific uptake. Experimental data obtained for each metal were fitted using adsorption models including Langmuir, Freundlich and Redlich-Peterson isotherms. Biosorption tests were also carried out using binary solutions of copper and cadmium at different equilibrium pH to evaluate biomass selectivity. Modified Langmuir and Freundlich models were used to fit these equilibrium data. The biomass tested was more selective for copper ions and this selectivity changes with equilibrium PH. In both single and two metal systems, a simple procedure of model discrimination was performed to establish which of the tested models better represents the experimental behaviour. (C) 2001 Elsevier Science Ltd. All rights reserved
Surface response methodology and preliminary process analysis in the study of manganiferous ores by using whey or lactose in sulphuric acid solutions
No full textReductive leaching of manganiferous ores by glucose and H2SO4: effect of alcohols
No full textThe effect of alcohols on the dissolution of manganese, calcium, and iron from manganiferous ore is reported. The extractive process was studied in sulphuric acid solution by using glucose as reducing agent. The alcohols were employed in order to evaluate their effect on the leaching performance with and without glucose as reducing agent. Three different alcohols MeOH, EtOH, and n-BuOH, were tested in order to investigate the influence of the organic chain length on the metal dissolution during the leaching process. Two different test sequences were followed. The first one was based on the leaching of manganiferous ore by using glucose as reducing agent and a mixture of alcohol/H2O/H2SO4 as reaction media. In the second one, leaching was carried out by using glucose in the H2O/H2SO4 reaction media and after leaching, the aqueous solution was separated from the solid by filtration. Successively, alcohols were added to the leach liquor. The experimental results of Mn, Ca, and Fe dissolution obtained by using the latter procedure were compared with those obtained in the former one. In both the experimental sequences, methyl alcohol gave better results as compared to ethyl and n-butyl alcohol. MeOH showed a notable negative effect on calcium dissolution, thereby decreasing its concentration with respect to manganese and iron extraction. The effect was larger in the runs performed by alcohol addition to the leach liquor than that obtained in the mixed solvent leaching tests. The decrease in calcium dissolution caused by the presence of alcohol has been analysed and modelled. (C) 2001 Elsevier Science B.V. All rights reserved
Shrinking core model with variable activation energy: A kinetic model of manganiferous ore leaching with sulphuric acid and lactose
No full textA kinetic model of manganiferous ore dissolution varying sulphuric acid and lactose as reducing agent was developed here. The Shrinking Core Model (SCM) was modified to take into account both the variable reagent concentrations and the reaction rate change with respect to the manganese dioxide conversion: this last aspect is due to several oxidation reactions of the carbohydrates in a hot sulphuric acid medium. The effects of three factors were investigated for three ore size fractions: temperature, lactose and sulphuric acid concentrations. The application of the kinetic model to different size ore fractions with and without the particle size effect shows that the best results in data fitting were gained by applying the model separately to each particle size fraction. The influence of the particle size in the kinetic model is discussed with the support of SEM analysis and BET surface measurements before and after leaching
Biosorption of Metal ions on Arthrobacter sp.: Biomass Characterization and Biosorption Modeling
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Acid leaching of manganiferous ores by sucrose: kinetic modelling and related statistical analysis
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