Volume 10, Issue 5
August 1988, pages 401-483
pp 401-401 August 1988
pp 403-410 August 1988
Uranium is the basic raw material for a nuclear energy programme. Uranium ore is processed in India by the well-known method of sulphuric acid, ion-exchange concentration and its final precipitation as magnesium diuranate—‘yellow cake’. We have established a process for uranium recovery from the tailings of copper concentrators which also enables recovery of small amounts of copper, nickel and molybdenum present in the uranium ore. Another major activity of this centre has been the exploitation of mineral-rich beach sands to produce ilmenite, rutile, zircon and monazite. Downstream industries have also been established for chemical processing of these minerals. Production of niobium from low-grade ores and beryllium from beryl ore is also being carried out on a moderate scale.
pp 411-422 August 1988
Galvanic interaction between electrically conducting minerals may affect the mineral surface and influence their flotabilities. The metallographic examinations as well as hardness measurements have been made with grinding media. Rest potential, combination potential, galvanic current and polarization studies were made to understand the probable electrochemical interaction between grinding media and chalcopyrite. The galvanic contact lowered the flotability of chalcopyrite. AES and ESCA indicated that galvanic coupling of chalcopyrite with grinding media resulted in the formation of oxy-hydroxide species of iron on the chalcopyrite surface. Scanning electron microscopy was used to study the surface morphological changes on the grinding media due to galvanic interaction with chalcopyrite.
pp 423-433 August 1988
High molecular weight polyacrylamides were synthesized and successfully modified to contain up to 8·3% hydroxamate functional groups. The selective flocculation tests carried out on 1:1 iron oxide/kaolin mixtures using parent polyacrylamide, polyacrylic acid and the modified polyacrylamide, confirm the possibility of enhancing selectivity through introduction of iron chelating functional groups in commercially available polymers. Starting with a feed grade of 35% iron, 92% recovery with acceptable grade of 60% iron has been achieved using the modified polyacrylamide.
pp 435-442 August 1988
Batch flotation experiments were carried out using two coal samples to study the behaviour of each size and the density fractions in coal flotation. Different size fractions obtained from sizing of concentrates and tailing were subjected to float and sink analysis using organic liquids. The distribution curve technique was adopted to evaluate the performance of flotation. The results show that selectivity of flotation decreases with decrease in particle size. The specific gravity of separation is influenced more by the level of the frother dosage than by the collector dosage. The specific gravity of separation increases with increase in flotation time. The maximum value attained at infinite flotation time increases with decrease in particle size but the rate at which it is reached decreases.
pp 443-452 August 1988
Depending on their non-stoichiometry, sulphides are classified as n-type or p-type semiconductors. Adsorption of dyes from aqueous and non-aqueous solutions has been made use of to study the surface characteristics of solid adsorbents. Their use in flotation as collectors or depressants is also reported. Adsorption of anionic tartrazine on CdS-doped Ag2S shows a lower value compared to undoped Ag2S. The dye adsorption characteristics on these sulphides has been explained on the basis of their defect-structures.
pp 453-460 August 1988
The beneficiation of apatite from low grade magnetite-apatite ore was studied. Wet magnetic separation followed by flotation was found effective. The effects of different grinds, pH, depressants and collectors at varying dosages were investigated. Various process parameters were optimized and the rougher concentrate was cleaned thrice for improvement in the apatite grade. Sodium silicate as depressant, sodium oleate as collector and pine oil as frother, at a pH of 7–7·5 (natural pH), for apatite flotation were found effective. The general flowsheet of the process was developed.
pp 461-465 August 1988
A study was carried out to develop strains ofThiobacillus ferrooxidans ATCC 19859 tolerant to higher levels of heavy metal ions. Strains ofT. ferrooxidans capable of growing in Cu2+ (30 g/L) and Zn2+ (60 g/L) have been obtained. The ability of strains tolerant to either copper or zinc to grow in medium containing both the metals has been examined. The copper-tolerant strain (25 g/L) grows better in the medium containing both metals (Cu2+ 25 g/L and Zn2+ 40 g/L) compared to the zinc-tolerant strain (40 g/L).
pp 467-470 August 1988
Tests were carried out on a 76 mm heavy medium cyclone-treating coal. The results show that the specific gravity of separation of coal is influenced not only by the specific gravity of the feed medium but also by the magnetite to coal ratio in the feed slurry.
pp 471-475 August 1988
High gradient magnetic separation has proved to be a successful method for removing micron size colouring bodies from china clays. Clays from Chotanagpur, Bihar have been beneficiated to improve its brightness. The effect of field, flow rate and dispersing agents has been studied on both the run of mine (rom) clay and the washed clay. Significant improvement in the brightness of clay has been obtained.
pp 477-478 August 1988
A yeastRhodotorula glutinis repeatedly isolated from microbial copper leaching system increased the iron oxidation rate and the copper extraction efficiency of the process. It is proved that yeast could produce hydroxamate type chelating compounds, the practical implications of which are discussed.
pp 479-483 August 1988
Manganese can be easily leached from chemically inert manganese ore by aqueous solutions of SO2. Total manganese dissolution occurs at 650 rpm, 0·2% solid, 426µm, pH=1 and 310 K in only 6–8 min. The rate data for managanese fits the equation: 1 − 2/3α − (1 −α)2/3=kt. Diffusion through the siliceous layer appears to be rate-controlling.
Volume 42 | Issue 6
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