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Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The equilibrium distribution coefficients of 42 elements [Li(I), Na(I), K(I), Rb(I), Cs(I), Sc(III), Ti(IV), V(IV), V(V), Mn(II), Fe(III), Ni(II), Zn(II), Al(III), Ga(III), As(V), Y(III), Zr(IV), Nb(V), Mo(VI), Cd(II), In(III), Sn(IV), Sb(V), Ta(V), W(VI), Pb(II), Bi(III), La(III), Ce(III), Th(IV), U(VI), Co(II), Ag(I), Ge(IV),Mg(II), Sr(II), Ba(II), Tb(III), Yb(III), Cr(III) and Cu(II)] on Bio Rad AG MP-50 macroporous cation exchange resin in varying citric acid – nitric acid mixtures were successfully determined. The equilibrium distribution coefficients of these selected elements were determined in 0.1 M and 0.25 M citric acid at various concentrations of nitric acid, namely, 0.2 M, 0.5 M, and 1.0M, respectively. Two component [Mo(VI)-Y(III); Zr(IV)-La(III) and As(V)-Zn(II)] and three component [Nb(V)-Ta(V)-V(V)] elemental separations on a 10 ml AG MP-50 resin column were successfully determined to illustrate how the results of the above equilibrium distribution coefficients can be utilised. From the equilibrium distribution coefficients obtained for magnesium(II) and sodium(I), a proposal was put forward to modify the current sodium-22 production performed at iThemba LABS. While the results did not predict a possible separation between the two elements, a theory concerning the use of citric acid in the production was proven not to hold under the chosen conditions. / AFRIKAANSE OPSOMMING: Die ewewig verdelingskoëffisiënte van 42 elemente [Li(I), Na(I), K(I), Rb(I), Cs(I), Sc(III), Ti(IV), V(IV), V(V), Mn(II), Fe(III), Ni(II), Zn(II), Al(III), Ga(III), As(V), Y(III), Zr(IV), Nb(V), Mo(VI), Cd(II), In(III), Sn(IV), Sb(V), Ta(V), W(VI), Pb(II), Bi(III), La(III), Ce(III), Th(IV), U(VI), Co(II), Ag(I), Ge(IV),Mg(II), Sr(II), Ba(II), Tb(III), Yb(III), Cr(III) en Cu(II)] is op Bio Rad se AG MP-50 makroporeuse kationiese uitruilerhars in verskillende sitroensuur – salpetersuur mengsels met sukses bepaal. Die verdelingskoëffisiënte is in 0.1 M en 0.25 M sitroensuur met verskillende konsentrasies van salpetersuur (0.2 M, 0.5 M en 1.0 M) bepaal. Twee-komponent [Mo(VI)-Y(III); Zr(IV)-La(III) en As(V)-Zn(II)] en drie-komponent [Nb(V)-Ta(V)-V(V)] skeidings op ’n 10 ml AG MP-50 harskolom is suksesvol bepaal om te demonstreer hoe die verdelingskoëffisiëntresultate gebruik kan word. As ’n uitvloeisel van die verdelingskoëffisiëntresultate vir Mg(II) en Na(I), is ’n voorstel ingedien om die huidige natrium-22 produksiemetode, tans in gebruik by iThemba LABS, te modifiseer. Die resultate het nie ’n skeiding tussen die twee elemente voorspel nie, maar het bewys dat ’n teorie oor die gebruik van sitroensuur in die produksie nie heeltemal korrek was onder die huidige toestande nie.

Ion chromatography coupled with a conductivity detector was used to investigate the analysis of Cr(III) and Cr(VI) in aqueous samples. An IC methodology for Cr(III) was developed using a cation column and an eluent containing tartaric acid, ethylenediamine, and acetonitrile at pH 2.9. The detection limit of this method can reach 0.1 ppm level with good precision. Several operational parameters were evaluated during the regular use of the method. Comparison of the IC method with AA method showed good agreement between the two methods. The anion exchange column was used for Cr(VI) determination. The best results were obtained with an eluent containing sodium gluconate, borate buffer, glycerin, and acetonitrile. The retention time for the Cr207 2 - sample was 11 min. and the calibration curve was linear between 1.0 and 100 ppm.

Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Bibliography: leaves 243-258.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017. / Certain resins used in ion-exchange separation techniques have become very expensive. Although ion-exchange is an economical method to soften water it is important to keep the cost low during the process. Any exorbitant costs will make a process unattractive and eventually obsolete. Bio-Rad AG MP-50 macroporous resin (supplied by Bio-Rad Laboratories, Ltd.) at present costs approximately R20000 (twenty thousand rand) for 500 g compared to Amberlyst 15 R840.00 for 500 mL and Dowex Marathon MSC R312.34 macroporous resin for 500 mL (both supplied by Dow, Rohm and Haas Co). This motivated the research to determine by a comparative study if there is any difference in the efficiency and effectiveness in the quantitative analysis of trace elements when these resins are used. The following elements will be used to determine distribution coefficients for the elements on these resins: Mn, Fe(III), Co, Ni, Cu, Zn, Al, Ag, Cd, In, Ga, Tl, Pb and Bi in 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 4.0 M nitric acid solutions. Another question is whether there is a difference or a preference when selecting either a microporous or a macroporous resin for the ion-exchange separation. Determination of distribution coefficients for 46 elements had been done by Strelow (Strelow F. W., 1984) in nitric acid on Bio-Rad AG 50W-X8. The results obtained in this study will be compared with the distribution coefficients obtained by Strelow. The Bio-Rad, Amberlyst and Dowex resins were stirred for approximately 30 minutes in deionised water and then packed in a column. Impurities in the resin column were eluted with 5 M HCl and the resin was then rinsed with deionised water to remove the acid. Thereafter the resins was rinsed out of the column with deionised water, filtered off and then dried under vacuum in an oven at 60 0C for approximately 24 hours. Stock solutions of the elements were prepared as 0.1 M solutions and then diluted with deionised water to obtain solutions having the respective concentrations of 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 M. Quadruplicate reference standards of each element were prepared. Distribution coefficients of the elements on each resin were determined as described by Strelow (Strelow F. W., Distribution coefficients and ion exchange behaviour of some chloride complex forming elements with Bio Rad AG50W - X8 cation exchange resin in mixed Nitric-Hydrochloric acid solutions, 1989). From the distribution coefficients, obtained from the ICP-OES data, a selectivity series for the 14 elements, mentioned above, was arranged in the decreasing order for each resin’s affinity for the elements. The distribution coefficients also give an indication whether the elements can be quantitatively separated by the cation exchangers in nitric acid media. Elution curves for some elements were done to establish the experimental conditions for quantitative separations of the elements by column cation exchange chromatography.

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Ion exchange resins have been used for retrieving radiocaesium from aqueous waste streams since the earliest days of the nuclear power industry. The physical and chemical properties of Lewatit DN ion exchange resins encapsulated in silica fume (SF)-blended cement were investigated with the aim of producing a stable solid wasteform for possible future disposal in an underground repository. Expansive reactions involving resin swelling in the high pH pore fluid and Ca(OH)2 formation around the resin particles can be suppressed by the addition of 50-75% SF at w/c ratios of 1.400-1.71. The basis of this suppression is the pozzolanic reaction between Ca(OH)2 and SF which consumes Ca(OH)2 and lowers the pH of the pore fluid to less than 10. The total heat evolution of blended cements is similar to that of a neat Portland cement, demonstrating the exothermic nature of the pozzolanic reaction. The use of high w/c ratios in cements containing 50% SF increases the permeability of the matrix. Porosity measurements indicate that this is due to the high free water content of the paste and the relatively high porosity of SF agglomerates. Elevated curing temperatures (up to 85oC) also increase the permeability as a result of coarsening of the microstructure. Despite the inferior physical immobilisation of caesium in high SF-content cements, leach tests, sorption measurements and pore fluid analysis show that chemical retention of caesium is enhanced by blending, more so in blends containing a permanent excess of SF, due to the formation of highly sorptive silica gel and low ratio C-S-H (Ca/Si as low as 0.80). On the other hand, SF-blended cements are more susceptible to physiochemical degradation in simulated groundwater's containing MgSO4. Chemical attack by MgSO4 converts C-S-H gel and silica gel to a non-cementitious magnesium silicate hydrate (identified as sepiolite) in 50-75% SF pastes, resulting in extensive deterioration of the attacked zone.