Synthesis of magnetite nanoparticles and their potential application in transition and platinum group metal ion extraction

Vatta, Laura Lisa (2007-03)

Dissertation (PhD) -- University of Stellenbosch, 2007.

Thesis

ENGLISH ABSTRACT: This thesis comprises of the following main sections: Synthesis of magnetite nanoparticles Parameters that are potentially important for the industrial-scale synthesis of magnetite nanoparticles were investigated in a factorial design experiment. It was found that the Fe(III):Fe(II) ratio specifically should be controlled in an industrial environment while small variations in the iron and ammonia solution concentrations do not significantly affect precipitate properties. These parameters were incorporated into a study on the large-scale synthesis of 8 - 12 nm magnetite particles using high pressure impinging stream reactors. The magnetite material was synthesised at rates of between 30 g min- 1 at 200 kPa and 50 g min- 1 at 500 kPa. Applications of magnetite nanoparticles in transition metal ion extraction The use of magnetite, a magnetic liquid and the extractants Aliquat 336 and methyl isobutyl ketone incorporated into a magnetic liquid were investigated in the extraction of Co(II) from a model [Co(SCN)4f system. The magnetically modified systems were found to compare favourably with or extract more [Co(SCN)4f than the conventional extractant systems as a result of the added potential for anion extraction by the cationic magnetite surface in acidic media. Commercial solvent extractants (Cyanex 272, D2EHPA and LIX 984N) incorporated into a magnetic liquid showed an increased rate of phase separation after solvent extraction when using an externally applied magnetic field as compared to a non-magnetic system. Applications of magnetite nanoparticles in platinum group metal ion extraction Magnetite nanoparticles coated with silica and functionalised with diethylenetriamine were shown to be capable of selective Pd(II) extraction over Cu(II) (at pH< 4) as well as showing an improved resistance of up to 80 % as compared to bare magnetite in acidic media. Degradation of ion exchanger material of up to 55 % was observed when the ion exchanger was used in four successive recovery cycles and under harsh desorption conditions. Alternative desorbents should decrease this iron dissolution.

AFRIKAANSE OPSOMMING: Die verhandeling bevat die volgende hooftema's: Sintese van magnetiet nanopartikels Die belangrikste proses eienskappe vir die industriele skaal sintese van magnetiet nanopartikels is ondersoek deur gebruik te maak van 'n faktoriale ekperimentele ontwerp benadering. Die Fe(III):Fe(II) verhouding is van kritiese belang en moet noukeurig gekontroleer word in die industriele skaal sintese, terwyl klein variasies in die magnetiet en ammoniak oplossing konsentrasies nie 'n waameembare invloed op die presipitasie eienskappe van die nanopartikels het nie. Die resultate van die ondersoek is in ag geneem tydens die grootskaalse sintese van 8 - 12 nm magnetiet partikels met behulp van 'n hoedruk stroomreaktor. Die magnetiet nanopartikels is gesintetiseer met vloeitempo's tussen 30 g min- 1 by 200 kPa en 50 g min- 1 by 500 kPa. Gebruik van magnetiet nanopartikels in oorgangsmetaal ioon ekstraksie Magnetiet, magnetiese vloeistof, en die gemodifiseerde magnetiese vloeistof bestaan uit die ekstraktant Aliquat 336 en metiel isobutiel ketoon, was gebruik om die ekstraksie van Co(II) uit die model [Co(SCN)4f systeem te ondersoek. Die gemodifiseered magnetiese vloeistof stelsel vergelyk gunstig, of ekstraheer meer [Co(SCN)4f, as konvensionele ekstraksie. Dit is waarskynlik as gevolg van die affiniteit vir anioon ekstraksie deur die katiooniese magnetiet oppervlakte in 'n suur medium. Met die toevoeging van kommersiele ekstraheer middels (Cyanex 272, D2EHPA en LIX 984N) word die faseskeiding van die magnetiese vloeistof na die ekstraksie onder die invloed van 'n eksteme magnetiese veld verhoog in vergelyking met die nie-magnetiese sisteme. Gebruike van magnetiet nanopartikels in platinum groep metal ioon ekstraksie Deur die silika bedekte magnetiet nanopartikels te funksionaliseer met di-etileentriamien toon die nanopartikels 'n selektiewe ekstrasie vir Pd(II) oor Cu(II) by 'n pH< 4. Verder vertoon die nanopartikels 'n verhoogde weerstand teen degradasie in 'n suur medium van tot 80 %. Onder desorpsie kondisies toon die funksionele nanopartikels 'n degradasie van tot 55 % na vier agtereenvolgende desorpsie siklusse. Die gebruik van altematiewe desorpsie materiaal kan die degradasie van die magnetiet verder venninder.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/50746
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