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REMOVAL OF IRON FROM INDUSTRIAL MINERALS

Cel

The aim of the project is to develop more effective and economical methods of iron removal from kaolin, glass sands and ilmenite and rutile.
Techniques have been developed for removing traces of iron from quartz, kaolin and ilmenite.
The techniques presently used to remove iron from these minerals involve the use of mineral acids which are expensive, not always effective, and give rise to environmental problems.

Mineralogical investigations were carried out on the materials to determine the form and distribution of the iron and other major minerals.
Suitable microorganisms with affinity to ferric ion chelation and transport were selected and isolated.

Experiments on synthetic goethite identified 2 strains which produce acetic acid and butyric acid and a mixed acid. Leaching testwork has been carried out with chemically derived organic acids and with the fermentation broth (a molasses solution fermented by Aspergillus niger) and compared the results of conventional processes.
Tests with chemically derived organic acids on quartz gave the highest iron removal rate of 37% and while this would appear to be low the highest removal rate achieved with concentrated hydrochloric acid and sulphuric acid has been 43%.
Tests on kaolin using a mixture of citric and oxalic acid enabled the removal of +/- 40% of iron from the kaolin samples.
Leaching of the ilmenite sample has been carried out using oxalic acid. After 12 days it wasapparent that oxalic acid was effective at dissolving iron. After 35 days around 30% of the iron had been dissolved.
The organic acid produced by Aspergillus niger, contained citric and oxalic acids at ratio of approximately 3:1. Testwork on the quartz sample at a range of temperatures and at pulp densities of up to 30% (weight for weight) gave a maximum iron removal of 36%.

Tests on the biological treatment of effluents showed that methanogenic bacteria in the sludge can decompose oxalates to carbon dioxide and methane (+/- 66% reduction). Heterotrophic sulphate reducing bacteria caused the reduction of sulphate to sulphide (between 20% and 80%) and the sulphides of iron and other metals were precipitated in the presence of the hydrogen sulphide anion.
Bulk samples (100 kg) of the raw materials (namely kaolin for ceramic use, glass sands and titania for pigments) will be collected. Data on all of the samples will be assembled to include geological setting, mineralogy and chemical analysis. The data will be assessed and interpreted. The samples will be given to BRGM and NTUA for characterization. The samples will then be distributed to the organizations who will be working on them. This work will be carried out by MIRO and the Industrial Associates as minor subcontractors to MIRO, and the samples will be representative of materials from their industrial sites.

The materials will be subjected to detailed chemical and mineralogical characterization with specific attention to the occurrence of iron compounds and their distribution and association with other minerals. Complimentary techniques of investigation will be used which could include mineral separations, surface microscopy, raman spectroscopy, laser mass analysis, differential thermal analysis etc.

Biological work will include selection and isolation of suitable fungi and bacteria, cultivation of appropriate strains in suitable nutrients and separation of the fermentation fluids. The work will start on cultures which are currently available. Contact will also be made with other organisations for the acquisition of additional cultures.

Leaching experiments will be carried out with bacterial fermentation fluids (organic acids). The experiments will aim to study the kinetics of iron removal and the effects of temperature, concentration, pulp density, ore granulometry and mineralogy, and agitation rates. Materials will be characterized after leaching to assess their potential uses. Attention will be given to the degree of whiteness which can be achieved.
Different strains will be used and experiments will be performed on batches and in perfusion devices using noncontinuous, semicontinuous and continuous culture. Solubilization of ferric iron form oxyhydroxides by enzymatic reduction and transformation into soluble ferrous iron, and solubilization by the production of siderophores will be examined. Main factors to optimize yield and kinetics will be examined.
The minerals will be leached with organic acids and microbially reproduced acids, in shake flasks, percolation trays and/or columns. Microbially assisted chemical precipitation and neutralization testwork will be carried out with microaerophilic and anaerobic systems, to remove the excess inorganic or organic acids and to precipitate and retain the iron.

Preliminary chemical leaching tests with ascorbic, oxalic, citric and tannic acids and glucose will be carried out, to select the most efficient system on which to perform more systematic tests. Systematic iron extraction tests will be completed under various operating parameters such as pH, time and temperature, with assessment of the degree of whiteness of the resulting mineral.

All of the participants, including the MIRO Indstrial Associates, will participate in joint meetings and cooperate in the development of an optimal flowsheet for each mineral. Joint preliminary basic engineering design and cost evaluations will be carried out. An assessment will also be made of the process effluent disposal. The design basis for a continuous pilot trial of the selected process will be developed.

Temat(-y)

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Zaproszenie do składania wniosków

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System finansowania

CSC - Cost-sharing contracts

Koordynator

Mineral Industry Research Organisation
Wkład UE
Brak danych
Adres
Expert House 6 Sandford Street
WS13 6QA Lichfield
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