Browsing by Author "12839981 - Van der Westhuizen, Derik Jacobus"
Now showing items 1-20 of 22
-
Automation of membrane based solvent extraction unit for Zr and Hf separation
Meerholz, Kyle; Van der Westhuizen, Derik Jacobus; Krieg, Henning Manfred (Elsevier, 2017)In recent years, research into metal ion solvent extraction using hollow fibre membranes has grown. Current studies generally use an analogue controlled experimental setup. Although the analogue system is sufficient for ... -
Cobalt-nickel pertraction refinery to process pregnant leach solution from recycled spent catalysts. Part 1: Cobalt extraction from a binary system
Mans, Nico; Van der Westhuizen, Derik; Krieg, Henning; Bruinsma, Dolf; Cole, Peter (Taylor & Francis, 2020)Owing to the recent increase in the global demand for Co, new cobalt–nickel refinery capacity is required. While solvent extraction is one of the most important separation and purification techniques in hydrometallurgy, ... -
Comparison of extractants for the separation of TaF5 and NbF5 in different acidic media
Ungerer, M.J.; Van der Westhuizen, D.J.; Lachmann, G.; Krieg, H.M. (Elsevier, 2014)To optimise the solvent extraction (SX) of Ta and Nb, eight different extractants were investigated, including the cation exchangers di-iso-octyl-phosphinic acid (PA) and di-(2-ethylhexyl)-phosphoric acid (D2EHPA), the ... -
Comparison of ionically and ionical-covalently cross-linked polyaromatic membranes for SO2 electrolysis
Peach, Retha; Krieg, Henning M.; Krüger, Andries J.; Van der Westhuizen, Derik; Bessarabov, Dmitri (Elsevier, 2014)It has been shown that hydrogen, which can be used for energy storage, can be produced efficiently by the membrane based Hybrid Sulfur (HyS) process. During the HyS electrolysis step, SO2 and H2O are converted to H2 and ... -
Density functional theory prediction of the aqueous speciation of ZrF4 and HfF4
Jansen van Vuuren, D.B.; Krieg, H.M.; Van der Westhuizen, D.J.; Van Sittert, C.G.C.E. (SAIMM, 2018)Computational chemistry was used to make predictions regarding the stepwise hydrolysis and fluoride dissociation reactions of ZrF4 and HfF4 in aqueous solutions. Specifically, density functional theory was used to predict ... -
Density functional theory study with and without COSMO of H2SO4 reactions in an aqueous environment for metal extraction
Ungerer, Maria Johanna; Van Sittert, Cornelia Gertina Catharina Elizabeth; Van der Westhuizen, Derik Jacobus; Krieg, Henning Manfred (Wiley, 2019)In a recent study investigating the suitability of solvent extraction (SX) for the separation of Ta and Nb, it was shown that speciation data would be required to help explain the data obtained. As traditional speciation ... -
DFT modelling of tantalum pentafluoride extraction with phosphorus-based extractants – a molecular dynamics study
Ungerer, M.J.; Van Sittert, C.G.C.E.; Van der Westhuizen, D.J.; Krieg, H.M. (Elsevier, 2019)Solvent extraction (SX) is a powerful method for both the separation and extraction of metals, resulting in high purity metals. The transition metals tantalum (Ta) and niobium (Nb) are of considerable significance, for ... -
The effect of molar ratio and flow velocity on the surface area required for pertraction of a Zr/Hf mixture
Malan, D.; Van der Westhuizen, D.J.; Neomagus, H.W.J.P.; Krieg, H.M. (IOP, 2019)Zirconium (Zr) and hafnium (Hf) need to be separated before being used in nuclear applications. Equilibria data have shown that Hf can be selectively extracted over Zr from a sulphate medium using organophosphorus ... -
Extraction of uranium from synthetic nuclear conversion plant waste
Potgieter, M.; Van der Westhuizen, D.J.; Krieg, H.M.; Barry, J.C. (Taylor & Francis, 2019)The nuclear conversion plant operated at Necsa in the past resulted in the formation of a large amount of waste material containing ~ 50% U, which has reuse potential if the recovery thereof can be achieved. The waste ... -
Feasibility of electro-reduction of U(VI) in oxalic acid using an electrolytic CEM-separated cell
Potgieter, M.; Van der Spoel Badenhorst, W.D.; Van der Westhuizen, D.J.; Krieg, H.M. (Springer, 2020)The feasibility of electrolytic stripping of U(VI) using an electrolytic separation cell with anode and cathode compartments, separated by a cation exchange membrane (CEM), was investigated as a possible final step in a ... -
The hafnium-selective extraction from a zirconium(hafnium) heptafluoride ammonium solution using organophosphorus-based extractants
Conradie, Elizabeth Wilhelmina; Van der Westhuizen, Derik Jacobus; Krieg, Henning Manfred; Nel, Johann Theodorus (Taylor & Francis, 2018)The suitability of the organophosphorus-based extractants, DiOPA, Ionquest 801 and D2EHPA was evaluated for the selective extraction of Zr and Hf from an (NH4)3Zr(Hf)F7 acidic solution using both dispersive and pertraction ... -
Mechanistic study of hafnium and zirconium extraction with organophosphorus extractants
Vermaak, V.; Krieg, H.M.; De Beer, L.; Van der Westhuizen, D. (Taylor & Francis, 2018)Research on the purification of Zr has increased in the last few decades and although effective processes have been developed, little is known about the mechanism of Hf and Zr extraction; particularly, at low acid ... -
Molecular modelling of tantalum fluoride in sulphuric acid medium: a DFT study
Ungerer, M.J.; Van der Westhuizen, D.J.; Krieg, H.M.; Van Sittert, C.G.C.E. (Elsevier, 2019)During the solvent extraction (SX) experiments of tantalum (Ta) and niobium (Nb), the aqueous phase consisted of tantalum- and niobium penta-fluoride (Ta(Nb)F5), water (H2O) and sulphuric acid (H2SO4), which was contacted ... -
Molecular modelling of tantalum in an aqueous phase
Ungerer, M.J.; Van Sittert, C.G.C.E.; Van der Westhuizen, D.J.; Krieg, H.M. (SAIMM, 2017)The transition metals tantalum (Ta) and niobium (Nb) are of significant importance, for example in the nuclear energy sector where they are used as cladding materials, as well as in capacitors and specialized materials. For ... -
Molecular modelling of tantalum penta-halides during hydrolysis and oxidation reactions
Ungerer, M.J.; Van Sittert, C.G.C.E.; Van der Westhuizen, D.J.; Krieg, H.M. (Elsevier, 2016)The transition metals tantalum (Ta) and niobium (Nb), which are usually found together in nature, have similar chemical and physical properties, making their separation challenging. There are various methods available for ... -
Molecular modelling of the hydrolysis of tantalum and niobium pentafluoride
Ungerer, Marietjie J.; Van der Westhuizen, Derik J.; Krieg, Henning M.; Van Sittert, Cornelia G.C.E. (Trans Tech Publications, 2014)Tantalum (Ta) and niobium (Nb) are two metals with similar chemical and physical properties and are found together in nature. One form of Ta is tantalum pentafluoride, which is stable in reducing environments, is corrosive ... -
Recovery of uranium from nuclear conversion plant waste
Potgieter, M.; Van der Westhuizen, D.J.; Krieg, H.M.; Barry, J.C. (SAIMM, 2017)The ammonium diuranate (ADU) conversion process that was operated at the Nuclear Energy Corporation of South Africa (Necsa) in the past generated a significant amount of waste containing high concentrations of uranium, ... -
The separation of zirconium and hafnium from (NH4)3Zr(Hf)F7 using amine-based extractants
Conradie, E.W.; Van der Westhuizen, D.J.; Krieg, H.M.; Nel, J.T. (SAIMM, 2016)The suitability of the amine-based extractants Alamine 336, Aliquat 336 and Uniquat 2280 (10 wt%) for the selective extraction of zirconium (Zr) and hafnium (Hf) from a (NH4)3Zr(Hf)F7 solution was investigated. The ... -
Solvent extraction and separation of hafnium from zirconium using Ionquest 801
De Beer, L.; Van der Westhuizen, D.J.; Krieg, H.M. (SAIMM, 2016)The solvent extraction (SX) characteristics of Ionquest 801 were investigated to determine if the selective extraction of hafnium (Hf) over zirconium (Zr) is possible. Firstly, Ionquest 801 was screened for its suitability ... -
The time dependent solvent extraction of Ta and Nb
Van der Westhuizen, Derik J.; De Beer, Leon; Ungerer, Marietjie J.; Krieg, Henning M. (Trans Tech Publications, 2014)The suitability of Liquid-liquid extraction (LLE) for the selective extraction of chemically similar tantalum (Ta) and niobium (Nb) mixtures was investigated by determining the influence of the acid concentration, extractant ...