Method development for the quantification of selected early rare earth elements
| dc.contributor.advisor | Purcell, W. | |
| dc.contributor.advisor | Venter, J. A. | |
| dc.contributor.author | Xaba, Sibongile Mamusa | |
| dc.date.accessioned | 2015-09-03T09:46:19Z | |
| dc.date.available | 2015-09-03T09:46:19Z | |
| dc.date.issued | 2015-01 | |
| dc.description.abstract | English: The aim of this study was to develop an analytical procedure to accurately quantify the early REE (La, Ce and Nd) in pure REE metal, in inorganic compounds as well as in a mixture containing all three elements and finally in organometallic complexes. The study involved the use of different inorganic acids such as H2SO4, HNO3 and HCI as dissolution reagents and determination of their influence on the La, Ce and Nd recoveries. Both bench top and microwave dissolution were used in this study. Different analytical techniques such as inductively coupled plasma optical emission spectrometry (ICP-OES), CHNS-micro analyser and infrared spectroscopy (IR) were used to characterise and quantify the REE in the different samples. Validation parameters such as accuracy, precision, linearity, sensitivity, etc., using ICP-OES analysis were also evaluated (Chapter 4) to determine the suitability of the digestion and quantifying methods for REE analyses. Analytical lines (wavelengths) were carefully selected to minimize or prevent any spectral overlap with the other rare earth elements investigated in this study. Secondly, the acid matrix was strictly matched throughout the analytical process to ensure accurate analytical measurements and well controlled experimental conditions. Bench top dissolution with 98 % H2SO4, 65 % HNO3 or 32 % HCI yielded excellent La and Nd recoveries from the pure REE metal, inorganic compounds as well as in a mixture containing all three elements, ranging from 97.9(5) to 100.6(1) %. Ce recovery in the pure metal only ranged from 81.37(9) to 95.30(8) %. Microwave assisted acid digestion was employed to improve the recovery of Ce metal. The Ce recoveries improved to 96.5 and 99.6 % after microwave digestion. The efficiency of the acids in dissolving and recovering Ce in the pure metal sample was in the order HCI < HNO3 < H2SO4. Excellent metal recoveries for the synthesised organometallic complexes ranging from 98.0(2) to 103.6(4) % for acac, imda and nta were obtained for the different organometallic complexes. ([Ln(dap)(NO3)3] Ln = La, Ce) yielded metal recoveries ranging from 88.1(5) to 95.5(3) % using bench top dissolution. The metal recoveries of TPPO complexes ranged between 98.45(5) and 99.4(2) % after microwave digestion. The method validation done in Section 5.8 was considered satisfactory. All calibration curves showed good linearity with excellent r2 values which range between 0.9997 to 1 and fairly constant slopes. The elemental LODs ranged between 0.0030 - 0.0188 ppm and LOQ between 0.0289 - 0.1881 ppm in the different acid matrices used in this study. It can be concluded that the La, Ce and Nd analyses in pure REE metal, inorganic compounds and organometallic complexes were successful and the results met most of the guidelines within acceptable criteria as set out in ISO 17025. The successful metal recoveries in acac, imda, nta and TPPO complexes were also due to the fact that these complexes have been crystallographically characterised and their chemical structures are well known, whereas the metal-dap complexes has not yet been fully characterised. Characterisation of synthesised organometallic complexes and ligands using IR also played a huge role in illustrating the possible coordination of the metal and ligands. The IR spectra were analysed by simple comparisons of the stretching frequencies between the unreacted samples and the reaction products. The shifting to low or high wavenumbers and disappearance or appearance of peaks was used as a measure for the possible formation of a new product. | en_ZA |
| dc.description.abstract | Afrikaans: Die doel van hierdie studie was om ‘n analitiese metode te ontwikkel wat die vroeë skaarse-aardmetale (REE) in suiwer metaliese, anorganiese verbindings, in mengsels van die drie aardmetaal (La, Ce en Nd) asook in organometaalverbindings akkuraat te kwantifiseer. Drie verskillende anorganiese sure, H2SO4, HNO3 en HCl is as oplosmiddels gebruik en hulle invloed op die opbrengs van La, Ce en Nd ns die verskillende chemise verbindings is bepaal. Bankskaal bereiding sowel as ‘n mikrogolf is gebruik om monsters kwantatitief op te los. Verskillende analitiese tegnieke is gebruik om die nuut-bereide verbidings te karateriseer asook te kwantifiseer. Dit sluit onder andere optiese-emissie spektroskopie met behulp van induktief-gekoppelde plasma (ICP-OES), CHNS-mikro analise en infra-rooi spektroskopie (IR) in. Akkuraatheid, presisie, lineariteit, sensitiwiteit ens., deur middel van ICP-OES is geëvalueer (Hoofstuk 4) om die geskiktheid van die oplos- en kwantifiseringsmetodes vir die skaars-aardmetale te bepaal. Die golflengtes vir die drie elemente is baie noukeurig gekies om enige oorvleueling met mekaar of ander metale se spektrums te beperk of total te verhoed. Tweedens is die suurmatriks gedurende die analitiese proses noukeuring dieselfde gehou om akkurate analitiese metings en goed-gekontroleerde eksperimentele toestande te handhaaf. Die verskillende monsters is op bankskaal met behulp van 98% H2SO4, 65% HNO3 en 32% HCl opgelos en voortreflike resultate is vir La en Nd as suiwer elemente asook die anorganiese verbindings en die mengsel van die drie elemente verkry met opbrengste wat gewissel het tussen 97.9(5) % en 100.6(1) %. Die Ce-opbrengs tydens die studie vir die suiwer Ce metaal het tussen 81.37(9) % en 95.30(8) % gevarieer. Mikrogolf is vervolgens gebruik om die oplosproses te prober verbeter en die opbrengs het na 96.5 % en 99.6 % verhoog. Die doeltreffendheid van die sure in die oplos van die Ce metaal was in die volgende volgorde: HCl < HNO3 < H2SO4. Baie goeie opbrengste is gevind vir die nuut bereide organometaalverbindings en het tussen 98.0(2) % tot 103.6(4) % vir acac, imda en nta gevarieer. Kleinskaalbereidings van [Ln(dap)(NO3)3] (Ln = La, Ce) het metaalherwinning van 88.1(5) % en 95.5(3) % gelewer terwyl TPPO-verbindings opbrengste tussen 98.45(5) % en 99.4(2) % na mikrogolfvertering gelewer het. Metode validering aan die hand van ISO 17025 in Paragraaf 5.8 dui op aanvaarbare valderingsparameters. Die kalibrasiekurwes toon almal goeie lineariteit met goeie r2 waardes wat tussen 0.9997 en 1 varieer, en redelike konstante hellings. Die waarnemingslimiete in die verskillende suur-matrikse varieer tussen 0.0030 en 0.0188 dpm terwyl die kwantifiseringslimiete tussen 0.0289 en 0.1881 dpm varieer. Opsommend word die herwinning van La, Ce en Nd in die suiwer skaars-aardmetaal (REE), anorganiese verbindings en organometaalverbindings as uiters suksesvol beskou en die resultate voldoen grootliks aan die riglyne soos in ISO 17025 aangediu. Die suksesvolle metaal-opbrengs in die acac, imda, nta en TPPO verbindings kan deels toegeskryf word aan die feit dat die verbindings reeds deur vorige studies kristallografies gekarateriseer is en dat hulle chemiese strukture (empiriese formules) bekend is. Die metaal-dap verbinding daarenteen is nog tot op hede nie ten volle gekarateriseer nie. Die karakterisering van die ligande en die nuut-bereide organometaalverbindings met behulp van infrarooi spektroskopie het ‘n groot rol in die karakterisering en odentifikasie van die bereide produkte gespeel. Vergelykings van die strekkingsfrekwensies van die ongekoördineerde ligande en die bereide komplekse is as maatstaf gebruik. ‘n Verskuiwing na ‘n hoër of laer energie of die laer golfgetal of die verdwying of verskyning van pieke is gebruik vir bevestiging van die sulksevolle bereiding van die nuwe produk. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/1147 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Cerium | en_ZA |
| dc.subject | Neodymium | en_ZA |
| dc.subject | Dissertation (MSc. (Chemistry))--University of the Free State, 2015 | en_ZA |
| dc.subject | Lanthanum compounds | en_ZA |
| dc.subject | Lanthanum | en_ZA |
| dc.subject | Quantitative analysis | en_ZA |
| dc.subject | Qualitative analysis | en_ZA |
| dc.subject | Accuracy | en_ZA |
| dc.subject | Recovery | en_ZA |
| dc.title | Method development for the quantification of selected early rare earth elements | en_ZA |
| dc.type | Dissertation | en_ZA |