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D.Sc. (Chemistry) / The Phosphate Development Corporation (FOSKOR) recovers apatite from foscorite ore by a process of froth flotation. Four reagents are used viz. sodium hydroxide, water-glass, nonylphenol tetraglycol ether (EMU) and a fatty acid. The fatty acid is mainly composed of a mixture of oleic and linoleic acid in a ratio of 1,2:1. The aim of this study was to investigate the influence of the first three above-mentioned reagents on the adsorption of oleic, linoleic and linolenic acids on apatite and The Phosphate Development Corporation (FOSKOR) recovers apatite from foscorite ore by a process of froth flotation ...

The preparation and synthetic utility of various β-trialkylstannyl-α,β-unsaturated carbonyl compounds is described. In this connection, treatment of tetrahydrofuran solutions of Me₃SnLi and n-Bu₃SnLi with one equivalent of PhSCu led to the in situ formation of PhS(Me-₃Sn)CuLi 72 and PhS (n-Bu₃Sn)CuLi 73, respectively. The latter reagents readily transferred, in a conjugate sense, the trialkyl-stannyl group to α,β-unsaturated carbonyl systems. In particular, these trialkylstannylcuprate reagents efficiently transformed β-iodo enones 4 into β-trialkylstannyl-α, β-unsaturated ketones 11, a new class of organotin derivatives. Likewise, treatment of the β-iodo enones 4_with Me₃SnCu • LiBr • SMe₂ 94, prepared by the reaction of Me₃SnLi with one equivalent of Me₂S*CuBr, gave the corresponding 6-trimethylstannyl enones in good yield. Two of these β-trialkylstannyl enones, β-trimetehyl-stannyl-2-cyclohexen-l-one 70 and β-tri-n-butylstannyl-2-cyclohexen-l-one, 74 were transformed into the vinylithium reagent 111. Sequential treatment of the enones 70 and 74 with lithium diisopropylamide and tert-butyldimethylsilyl chloride in the presence of hexamethylphosphoramide gave the enol silyl ethers 110 and 108, respectively. Transmetalation of the compounds 110 and 108 was accomplished by treatment of these substances with 1.1 equivalent of an alkyllithium reagent. Reaction of the resultant vinyllithium reagent 111 with electrophilic reagents proceeded smoothly to afford the corresponding substituted 1,3-cyclohexadienes in good yield. The reaction of PhS(Me₃Sn)CuLi 72 with various a, 6-acetylenic esters is also described. The course of the reaction could be controlled experimentally so as to produce, highly stereoselectively, either the (E) - or the (Z)-β-trimethylstannyl-α, β-unsaturated esters. Treatment (THF, -78°C) of PhS (Me₃Sn)CuLi 72 with a, β-acetylenic esters in the presence of a proton source (e.g., MeOH) gave the corresponding (E)-S-trimethylstannyl-a,g-unsaturated esters in good yield. Reaction of 7_2 with α,β-acetylenic esters at slightly higher temperatures (-48°C) in the absence of a proton source resulted in the formation of the corresponding (Z)-isomers. Reaction of ethyl (Z)-3 -tosyloxyacrylate 180 with Me₃SnCu*LiBr-SMe₂ 94 and n-Bu₃SnCu•LiBr*SMe₂ 181 gave the corresponding (Z)-β-trialkylstannylacrylates. Finally, two of the β-trimethylstannyl esters, ethyl (E)-3-trimethy1stanny1-2-butenoate 163 and ethyl (Z)-3-trimethylstannyl-2-butenoate 166, were converted into the geometrically isomeric trimethylstannyl dienes 184 and 185, respectively. Both of these substances underwent rapid and complete transmetalation when treated with 1.2 equivalents of methyllithium in tetrahydrofuran. The resultant 4-lithio-l,3-pentadienes (186 , 187) reacted smoothly with a variety of electrophiles to produce the corresponding substituted dienes (192 and 193). / Science, Faculty of / Chemistry, Department of / Graduate

A dissertation submitted to the faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering November 2018 / The aim of this study is to improve the flotation of non-sulphide PGM ores from the Mimosa Mine in the Great Dyke of Zimbabwe by evaluating a variety of collector reagents that have not been tested on such material before and applying a full factorial experimental design to investigate the effects of the main primary collector, co-collector and depressant on PGM recovery and grade. The mineralogical studies by XRD revealed that the non-sulphide PGM ore had substantial amounts of gangue material, comprising of 45% quartz, 21% chabazite and 33% of magnetite. The ICP-OES analysis showed that this particular non-sulphide PGM ore is a low-grade ore with an average 4E head assays of 2.37ppm. In the preliminary flotation stage, three reagent suites made up of (i) a collector, (ii) a co-collector and (iii) a depressant i.e. (SIBX, DTP, M98B); (SIBX, C7133, M98B) and (SIBX, AM810, M98B) respectively were tested. It was observed that (SIBX, AM810, M98B) reagent suite gave the best performance with respect to both recovery and grade of the PGM concentrate from the ore. Attempts were made to optimize the dosage levels of the 3 reagents. The optimization studies revealed that 78.5% Pt and 69.3% Pd can be recovered at grades of 17.90g/t Pt and 9.44g/t Pd respectively. This represents a significant upgrade for the roughing stage from the 1.42g/t Pt and 0.85g/t Pd in the feed. These results were obtained at optimized dosages of 86g/t SIBX and 80g/t AM810, with depressant M98B at 50g/t. The observations from the experiments indicated that recovery of PGEs was on the upward trend as the dosage of hydroxamate was increasing hence the effect of the hydroxamate co-collector was further tested at higher dosages while fixing SIBX at 100g/t. The experiments were carried out using 50g/t, 60g/t, 70g/t and 80g/t hydroxamate (AM810) with the depressant M98B at 50g/t. It was observed that the Pt recovery only increased slightly with increasing hydroxamate (AM810) dosage. / E.R. 2019

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Call number: LD2668 .T4 1949 M61 / Master of Science

Call number: LD2668 .T4 1956 C38 / Master of Science

Call number: LD2668 .T4 1958 K66