Browsing by Author "Krieg, H.M."
Now showing items 1-20 of 45
-
Automation of membrane based solvent extraction for Zr and Hf separation
Meerholz, Kyle (North-West University (South Africa), Potchefstroom Campus, 2015)In recent years, research into metal ion extraction using hollow fibre membranes has grown, focussing on the extraction of a wide range of metals including base, transition, and rare earth metals. This non dispersive solvent ... -
Biocatalytic resolution of substituted styrene oxides
Yeates, Charl Alan (Potchefstroom University for Christian Higher Education, 2001)Stereochemistry and chirality are arguably two of the most important subjects pertaining to the development of new pharmaceutical drugs. Since enantiomers have the potential to encompass different pharmacological effects ... -
Characterization of NaA-zeolite membranes using pervaporation
Mzinyane, Nozipho Nompumelelo (North-West University, 2005)Pervaporation has gained increasing attention as an energy saving process for separating azeotropes such as ethanol and water mixtures. Pervaporation distinguishes itself from other membrane processes in that it entails ... -
The cobalt-nickel pertraction refinery to process recycled spent catalysts leach solutions
Mans, Nico (North-West University (South Africa), 2019)Over the last two years, the cobalt (Co) price has increased considerably. The observed increase can be attributed to the increase in demand of lithium-ion batteries (LIBs) of which Co forms an integral part. As a consequence ... -
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 ... -
Computational chemistry study of zirconium monomers in low acid concentration aqueous solutions
Jansen van Vuuren, D.B.; Krieg, H.M.; Van Sittert, C.G.C.E. (IOP Publishing, 2018)Zirconium and hafnium have to be separated prior to their use in nuclear energy reactors. Therefore, a lot of research has been done on the solvent extraction of zirconium. However, most of this research involved screening ... -
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 ... -
Design and characterization of asymmetrical porous nickel membranes
Botha, Ruan (North-West University, 2006)As an alternative to organic membranes, ceramic membranes are suitable for the chemical industry due to their intrinsic thermal, chemical and mechanical stability. The centrifugal dispositioning technique has the advantage ... -
Development of an iron electrowinning process using anion exchange membranes
Van der Spoel Badenhorst, W.D. (North-West University (South Africa), 2020)Traditionally, spent leaching solutions (SLS) originating from base metal refineries are treated using (i) tailings dams, (ii) anoxic limestone drains (ALDs), or (iii) jarosite, hematite or goethite precipitation. While ... -
Development of novel PBI-blended membranes for SO2 electrolysis
Peach, Retha (North-West University (South Africa), 2019-05)In light of the increased applicability of hydrogen as a clean alternative fuel source, the demand for hydrogen and the subsequent production thereof is expected to grow significantly in the near future. From the hydrogen ... -
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 ... -
Die elektroherwinning van Fe en H2SO4 uit ’n FeSO4-logingsoplossing met behulp van anioonruilmembrane
Rossouw, Jacobus Johannes Cloete (North-West University (South Africa), 2019)The purpose of this study was to develop an economical, safe and environmentally friendly electrochemical process for the conversion and recovery of Fe and H2SO4 from a FeSO4 leaching solution. For this purpose, two basic ... -
Direct crystallisation of hydroxysodalite and MFI membranes on α-alumina supports
Van Niekerk, Anelia (North-West University, 2005)Hydroxysodalite and MFI are zeolites that consist of crystalline (tecto)aluminosilicates and silicates with specific aperture sizes. Zeolite membranes are suited for any process requiring separation on a molecular level ... -
Direct synthesis of a titania membrane on a centrifugally casted tubular ceramic support
Patterson, V.A.; Krieg, H.M.; Kriek, R.J.; Bisset, H. (Elsevier, 2006)In-house manufactured tubular ceramic supports prepared by centrifugal casting have a smooth inside surface and are ideal for thin defect-free coatings. The aim of this study was to directly coat a thin defect-free titania ... -
A dual-channel gas chromatography method for the quantitation of low and high concentrations of NF3 and CF4 to study membrane separation of the two compounds
Branken, D.J.; Le Roux, J.P.; Krieg, H.M.; Lachmann, G. (Elsevier, 2013)A dual-channel gas chromatographic method is described in this paper that can be conveniently used for quantitation of NF3/CF4 mixtures with a thermal conductivity detector (TCD) on one channel for the quantitation of ... -
The effect of feed water TDS on RO membrane rejection rates and performance
Du Toit, Philip Thomas (North-West University (South Africa)., 2023)Power generation is a major user of fresh water, which is becoming important for Eskom and South Africa due to the water-scarce status. Therefore, the water usage at a thermal power station is a key metric and reverse ... -
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 ... -
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 ... -
Gas separation of steam and hydrogen mixtures using an ?-alumina-Alumina supported NaA membrane
Moodley, Shawn (North-West University, 2007)In this study, the feasibility of a NaA zeolite membrane for the gas phase separation of steam and hydrogen mixtures was determined. The Fischer-Tropsch (FT) process, which produces high value fuels and chemicals from coal ... -
H2SO4 stability of PBI-blend membranes for SO2 electrolysis
Schoeman, H.; Krieg, H.M.; Krüger, A.J.; Chromik, A.; Krajinovic, K. (Elsevier, 2012)For hydrogen to become a serious contender for replacing fossil fuels, the manufacturing thereof has to be further investigated. One such process, the membrane based Hybrid Sulfur (HyS) process, where hydrogen is produced ...