A dissertation submitted to the Faculty of Engineering, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree
of Master of Science in Engineering. / Laboratory experimentation were conducted to investigate the regeneration and
recycling of nitric acid during leaching in froth (LIF) processing of Gamsberg zinc
sulphide concentrate.
Two experiments were performed in a mechanically stirred batch reactor at 80-
90°C to determine the leaching kinetics of the zinc sulphide concentrate. 93 to
97% of zinc was extracted into spent zinc sulphate electrolyte containing 30 to 40g/1
nitric acid during 40 to 60 minutes of leaching without regeneration of nitric acid.
Between 60.72. and 97.79% of the consumed nitric acid was regenerated after 45
minutes of batch L/F experiments carried out at 80·90oC and 50kPa. The results
show that the degree of nitric acid regeneration is inversely proportional to the
concentration of nitric acid in the leaching solution. Zinc extraction ranged between
56.31 and 78.37% whilst 40.29 to 50.99% of the initial sulphide sulphur was
oxidised to elemental sulphur. In the continuous L/F experiments conducted at 80-
90°C and 100·200kPa, the degree of nitric acid regeneration varied from 33.63 to
97.22%. Overall zinc extraction was about 62% whilst 47% of the sulphide sulphur
reported as elemental sulphur after 60 minutes of processing.
A five-stage L/F processing of the concentrate was carried out in which the flotation
phenomenon was used for selective separation of the floatable fraction from the nonfloatable
fraction. About 40 to 80% of the consumed nitric acid was regenerated,
88.94% of zinc was extracted whilst 55.65% of the sulphide sulphur reported is
elemental sulphur after 77 minutes of processing. The recoveries of zinc and
elemental sulphur increased to over 92% and 58% respectively when the leach
residue was subsequently leached in the batch reactor. / Andrew Chakane 2019
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/27822 |
| Date | January 1997 |
| Creators | Obeng, Daniel Philip |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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