Base metal recovery from glycine leach solutions using ion exchange or solvent extraction

Potgieter, Gian Viljoen (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.

Thesis

ENGLISH SUMMARY: Technological advances lead to a reduced life span of electronic equipment. This leads to large quantities of electronic waste being produced. The recovery of metals from electronic waste has both an environmental and economical drive. Various hydrometallurgical routes have been proposed for this purpose, but most of them use multiple lixiviants for base and precious metal leaching stages. Glycine in alkaline solutions has been proposed as an alternative lixiviant as it can leach both base and precious metals at varying operating conditions. This reduces the need for washing stages between leaching steps and thus the loss of reagents. Limited research has been done on the recovery of copper from these glycine pregnant leach solutions (PLS). This study investigates the use of solvent extraction or ion exchange to isolate and concentrate copper from the glycine PLS. The primary objectives of the study included to investigate the effect of key operating variable such as pH, reagent concentration and extractant functional group on the recovery of copper. A flowsheet was developed for the isolation and concentration of copper from the glycine PLS using solvent extraction. A synthetic PLS was produced which contained 10g/L copper, 1.5g/L lead and 1.1g/L zinc. pH values ranging from 8 to 11 were evaluated and solvent concentrations between 5 and 20%. LIX-84I was found to be highly selective for copper at the conditions tested. No co-extraction of any other metals was found. Increasing the pH of the aqueous phase improved the recovery of copper from 64 to 86% in a single stage with a 20% solution of LIX-84I. Increasing the solvent concentration from 5 to 20% at a pH of 10 showed an almost linear increase in the recovery from 17% with a 5% LIX-84I concentration to 64% with a 20% LIX-84I concentration. Equilibrium isotherms were drawn for 5, 10 and 20% LIX-84I concentrations and showed that 80% copper recovery is possible with 2 stages from a PLS containing 10g/L of copper at a A:O ratio of 2:1. 2M sulphuric acid can successfully strip 100% of the copper from a loaded organic phase with O:A ratios of up to 4:1, resulting in a final copper concentration of 27g/L in the concentrated electrolyte. The fate of glycine during the solvent extraction was tested using UV-VIS and it was confirmed that no glycine was co-extracted to the organic phase. Copper recovery from glycine leach liquors was proven to be ineffective using commercially available ion exchangers. Both the iminodiacetic acid resins tested, S930Plus and TP207, showed no selectivity for copper over lead or zinc at the conditions that were tested. The separation factors found were 0.03 and 0.02 for copper over lead and zinc respectively with S930Plus, for TP207 the values were 0.04 and 0.02 for copper over lead and zinc respectively. S930Plus had equilibrium resin concentration of 11.7g/L copper, 9.1g/L lead and 6.7g/L zinc, and TP207 showed equilibrium concentrations of 16.1g/L copper, 10.5g/L lead and 7.8g/L zinc. Column elution tests showed that all the metals are removed at a similar rate indicating that split elution would not be an option for the purification of copper. The concentrations found in the eluate were 5.5g/L copper, 4.7g/L lead and 3.2g/L zinc from S930Plus and 8g/L copper, 6.2/L lead and 5.2g/L zinc from TP207. The bis-picolylamine resin tested, TP220, showed separation factors of 1.67 and 1.40 for copper over lead and zinc respectively, these values are relatively close to 1 and effective separation of the metals was not achieved, the equilibrium concentrations were, 6.1g/L for copper, 0.9g/L lead and 0.8g/L zinc.

AFRIKAANSE OPSOMMING: Die vinnige tempo waarteen tegnologie ontwikkel veroorsaak dat die lewensduur van elektroniese toerusting aansienlik afgeneem het. Dit lei tot groot hoeveelhede elektroniese afval wat geproduseer word. Herwinning van metale van elektroniese afval bied voordele uit ʼn omgewingsimpak sowel as ekonomiese oogpunt. Verskeie hidrometallurgiese roetes is voorgestel vir die behandeling van elektroniese afvanl, maar die meerderheid gebruik veelvuldige logingsmiddels om basis- en edelmetale te loog. Glisien in alkaliese oplossings is voorgestel as ʼn alternatiewe logingsmiddel aangesien dit beide basis- en edelmetale kan loog by verskillende toestande. Dit elimineer die vereiste wasprosesse tussen logings en die gepaardgaande verlies van reagense. Daar is nog nie voldoende navorsing gedoen op die herwinning van koper uit glisien logingsoplossings nie. Die huidige studie ondersoek die gebruik van vloeistof-vloeistof ekstraksie en ioon uitruiling om koper te isoleer en konsentreer uit glisien loginsoplossings. Die hoof doelwitte van die studie was om die effek van sleutel veranderlikes soos pH, reagens konsentrasie en funksionele groep op die herwinning van koper uit die logingsoplossings te ondersoek. ʼn Vloeidiagram vir die herwinning van koper met behulp van vloeistof-vloeistof ekstraksie is ook ontwikkel. ʼn Sintetiese logingsoplossing met 10g/L koper, 1.5g/L lood en 1.1g/L sink is geproduseer vir eksperimentele toetswerk. pH waardes tussen 8 tot 11 is ondersoek tesame met LIX-84I ekstraheermiddel konsentrasies tussen 5 en 20%. LIX-84I was hoogs selektief vir koper by alle toestande wat getoets is. Geen mede-ekstraksie van enige ander metaal is gevind nie. Verhoging van die pH waardes het gelei tot hoër ekstraksie van koper; die ekstraksie het toegeneem van 64% tot 86% in ʼn enkele ekstraksie stadium met ʼn toename in pH waardes van 10 tot 11. Ekstraksie het van 17% na 64% toegeneem met die verhoging van die ekstraheermiddel konsentrasie van 5 na 20%. Ewewig isoterme is ontwikkel vir 5, 10 en 20% LIX-84I konsentrasies en dit het gewys dat 80% van die koper in ʼn 10 g/L Cu oplossing herwin kon word in 2 ewewigstadia by ʼn waterige tot organiese verhouding van 2:1. Alle koper kan in ʼn enkele stadium uit die organiese fase verwyder word met 2 M H2SO4 by ʼn waterige tot organiese verhouding van 1:4; dit gee aanleiding tot ʼn finale koper konsentrasie van 27 g/L in die gekonsentreerde elektrolitiese oplossing. Die glisien in die waterige oplossing word nie geëkstraheer deur LIX-84I nie;dit is bevestig met behulp van ʼn ninhidrien toets. Koper herwinning met behulp van ioon-uitruiling was nie effektief nie. Beide iminodiasetiese suur (IDS) harse, naamlik S930 en TP207, het geen selektiwiteit vir koper oor die ander metale gewys nie. Die skeidingsfaktore was 0.03 en 0.02 vir koper oor lood en sink, onderskeidelik, vir S930, en 0.04 en 0.02 vir lood en sink met TP207. S930 het ʼn ewewigskonsentrasie van 11.7 g/L getoon vir koper, 9.1 g/L vir lood en 6.7 g/L vir sink. TP207 se ewewigskonsentrasies was 16.1 g/L vir koper, 10.5 g/L vir lood en 7.8 g/L vir sink. Kolomtoetse het gewys dat alle metale teen dieselfde spoed van die harse verwyder word wat toon dat selektiewe verwydering nie ʼn opsie is nie. Die hoogste konsentrasies wat gevind was in die finale suuroplossing was 5.5g/L vir koper, 4.7g/L vir lood en 3.2g/L vir sink met S930, en 8g/L vir koper, 6.2g/L vir lood en 5.2g/L vir sink met TP207. TP220, wat ʼn bis-pikolielamien hars is, het skeidingsfaktore van 1.67 en 1.40 vir koper oor lood en sink, onderskeidelik, getoon. Die waardes is naby aan 1 wat toon dat geen onderskeid gemaak word deur die hars vir verskillende metale nie. Die ewewigskonsentrasies op die hars was 6.1g/L vir koper, 0.9g/L vir lood en 0.8g/L vir sink.

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