Ligand Design for the selective removal of metal Ions from industrial streams and wastewater

Saban, Waheed (2016-12)

Thesis (PhD)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: This thesis reports the development of new types of solvent extractants for use in the hydrometallurgical recovery of base metals, and addresses the ligand design features which are needed to control the strength, transport efficiency and selectivity of these extractants. The first section of the thesis deals with the synthesis of a new series of monocationic Schiff base ligands. The ligands are fully characterized using 1H and 13C NMR, FT-IR, mass spectrometry and elemental analysis. The extraction and bulk liquid membrane transport abilities of the ligands were evaluated by monitoring the extraction and transport of the metal ions Co(II), Ni(II), Cu(II), Zn(II),Cd(II) and Pb(II) over a 24-hour period. Palmitic acid was included in the organic phase. All ligands showed extraction of Cu(II) and Pb(II) ions, with 2 ligands being more selective towards the extraction of Cu(II) whereas the other 2 ligands extracted more Pb(II). The extraction of Pb(II) is most likely due to a synergistic effect, since palmitic acid was added throughout the organic phase. In the transport studies, only Cu(II) ions were transported. pH-isotherms for both Cu(II) and Pb(II) were also carried out for all ligands. Interestingly Pb(II) is extracted better at lower pH’s compared to Cu(II) in two cases. This study shows how these salen-type ligands, when used together with palmitic acid, show transport selectivity for Cu(II), and in the extraction studies, extraction selectivity for Cu(II) and Pb(II). Single crystals of two free ligands and two Cu(II) complexes were obtained and these were refined to acceptable levels. Extensive intramolecular and intermolecular hydrogen bonding is found in the free ligand structures. One Cu(II) complex is similar to that in the literature whilst the other Cu(II) complex is novel, with Cu(II) being four co-ordinate in a structure producing a metallocycle. The second section of this thesis describes the synthesis of several new salicylaldoxime scaffolds as well as the anchoring of substituents onto the Schiff bases in section one making them ditopic ligands. These ligands were fully characterized using 1H and 13C NMR, FT-IR, mass spectrometry and elemental microanalysis. Cu(II) was selectively extracted by all the ditopic ligands showing extraction percentages from 69% to 79%. Cu(II) and Pb(II) metal ions were transported throughout into the receiving phase by these ligands. Cu(II) complexes were synthesized using copper (II) acetate and these were characterized using FTIR and mass spectrometry. These Cu(II) complexes were then used in competitive extraction and transport studies of the anions nitrate, chloride and sulfate. Selective extraction and transport was obtained for nitrate and chloride in agreement with the Hofmeister bias. The third section of this thesis aims to investigate how four different carboxylic acids attach to aSchiff base ligand(2-((E)-(2-(2-((E)-5-tert-butyl-2-hydroxybenzylideneamino)ethylamino)ethylimino)methyl)-4-tert-butylphenol); L1before complexation to the metal ion by using NMRstudies. The extraction of both copper and lead was observed whenpalmitic and salicylic acid was used with the ligand. It was observed that the ligand palmitic acid assembly showed the highest uptake of lead ions above pH=5. An extraction experiment involvingpalmitic acid and Pb(II) only gave34% extraction.This behaviour is consistent with synergistic solvent extraction.

AFRIKAANSE OPSOMMING: Hierdie tesis reporteer die ontwikkeling van nuwe ekstraeermiddels vir die herwin van basis metale. Dit beklemtoon ligand ontwerpings besonderhede wat benodig word om die selektiwiteit en sterkte van hierdie ekstaeermiddels te beheer. Die eerste afdeling van hiedie skripsie behandel oor die sintese van ′n nuwe reeks monokationiese Schiff basis ligande. Die ligande word volledig gekaraktiriseer met gebruik van 1H en 13C KMR, FT-IR, massa spektrometrie en elementele analise. Die ekstraksie en membraan vervoer vermoёns van die ligande is ge-evalueer deur die hoeveelheid van die metale Co(II), Ni(II), Cu(II), Zn(II), Cd(II) en Pb(II) te meet na ′n periode van 24 – uur. Palmitienseer is deurgaans in die organiese fase gevoeg. Alle ligande het ekstraksie van Cu(II) and Pb(II) getoon, met twee ligande meer selektief vir Cu(II) en die ander twee meer selektief vir Pb(II). Die ekstraksie van Pb(II) is waarskynlik weens ′n sinergistiese effek, want palmitiensuur is deurgaans in die organiese fase bygevoeg. In die vervoer studie is net Cu(II) in die ontvangs fase gevind. pH-isoterme vir beide Cu(II) en Pb(II) is gedaan vir al die ligande. Dit is interessant dat Pb(II) beter as Cu(II) ge-ekstraeer word in twee gevalle. Hierdie studie toon hoe hierdie salen-tipe ligande, wanneer met palmitiensuur gebruik word, vervoer selektiwiteit vir Cu(II) toon en ekstraksie selektiwiteit vir Cu(II) en Pb(II). Enkel kristalle van twee vrye ligande en twee Cu(II) komplekse is verkry en hierdie is verfyn na aanvaarbare vlakke. Uitgebreide intramolekulêre en intermolekulêre waterstof bindings is gevind in die vrye ligand strukture. Een Cu(II) kompleks is soortgelyk aan dit wat in die literatuur voorkom terwyl die ander Cu(II) kompleks nuut is. In hierdie een is Cu(II) gebind aan vier donor atome in ′n struktuur wat ′n metaalosiklus produseer. Die tweede afdeling van hierdie skripsie beskryf die sintese van nege nuwe salisielaldoksiem steiers sowel as die ankerering van substituente aan Schiff basis ligande om hulle ditopiese ligande te maak. Hierdie ligande is volledig ge-karaktiriseer met gebruik van 1H en 13C KMR, FT-IR, massa spectrometrie en elementele mikroanalise. Cu(II) is allenlik ge-ekstra-eer deur al die ligande met waardes vanaf 69% tot 79%. Cu(II) en Pb (II) metaal ione is deurgaans na die ontvangs medium vervoer. Cu(II) komplekse is ge-sintetiseer en hierdie is deur middel van FT-IR en massa spektrometrie gekaraktiriseer. Hierdie komplekse is dan gebruik in mededingende ekstraksie en vervoer van die anione nitraat, chloride, en sulfaat. Selektiewe ekstraksie en vervoer is verkry vir nitraat en chloried wat in ooreenkoms is met die Hofmeister bias. Die derde afdeling van hierdie skripsie se doel is om te ondersoek hoe vier verskillende karboksielsure aan ′n Schiff basis heg deur van KMR gebruik te maak. Die ekstraksie van beide koper en lood is waargeneem waneer palmitiensuur en salisielsuur tesame met die ligand gebruik word. Die ligand palmitiensuur kombinasie het die hoogste opname van lood getoon bokant pH 5. ′n Ekstraksie eksperiment met net palmitiensuur en Pb(II) het ′n resultaat van 34 % ekstraksie Pb(II) getoon. Hierdie gedrag is konsektwent met sinergistiese ekstraksie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100395
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