Waste Electrical and Electronic Equipment (WEEE) disposal and recovery is becoming more and more important nowadays since it can represent a crucial resource for the precious and strategic metals contained inside it. Only in the EU area 17 kg of electronic waste are produced every year by every inhabitant and among the electronic scraps, printed circuit boards are the richest in precious metals and rare earths (REs). So far, the most applied technology for the recovery of metals is the dissolution with acids followed by liquid-liquid extraction, but it has many drawbacks related to the expensive chemical agents employed and their environmental impact. Adsorption on solid sorbents represents a possible solution that, with respect to the liquid-liquid extraction, exhibits some advantages: easy separation of the two-phase system, a good recovery efficiency, short reaction time, low cost and low consumption of organic solvent. The purpose of this work is to test this emerging adsorption methodology, following the results of previous similar works and using them as a starting point. The kinetic of the process was studied first, testing the adsorption of Yttrium and Neodymium on four solid matrixes: activated carbon, montmorillonite clay and the modified versions of these materials, doped with a commercial pentaethylenhexamine (L6). In the second part the uptake and release properties of activated carbon and modified activated carbon with the polyamine are studied towards the adsorption of Neodymium and Yttrium ions. In the final phase all the data and results collected throughout all the thesis works have been combined in order to understand the mechanisms governing this technology and to provide helpful indications for a future scale-up of the process.
I rifiuti elettrici ed elettronici e il loro recupero sta diventando un argomento sempre più importante negli ultimi anni in quanto può rappresentare una risorsa cruciale per i metalli che sono contenuti in essi, considerati preziosi e strategici. Nella sola zona della UE, ogni cittadino produce in media 17 kg di rifiuti elettronici ogni anno e i circuiti elettronici rappresentano i più ricchi in metalli preziosi e Terre Rare. Ad oggi la tecnologia dominante per il recupero di questi metalli è rappresentata dalla dissoluzione con acidi seguita da estrazione liquido-liquido, ma presenta diversi svantaggi legati ai costosi agenti chimici impiegati e al loro impatto ambientale. L’assorbimento su solido rappresenta una possibile soluzione alternativa che, rispetto all’estrazione liquido-liquido, ha diversi vantaggi: facile separazione del sistema bifase, una buona efficienza di recupero, tempi di reazione brevi, basso costo e basso consumo di solventi organici. L’obiettivo di questo lavoro è di tesare questa emergente metodologia, seguendo i risultati di lavori precedenti. La cinetica del processo è studiata all’inizio testando l’assorbimento di Yttrio e Neodimio su quattro solidi: carboni attivi, argilla montmorillonite e le loro versioni modificate con una pentaetilenesammina commerciale (L6). Nella seconda parta le proprietà di cattura e rilascio dei soli carboni attivi e della loro versione modificata viene testata nei confronti di Yttrio e Neodimio. Nella ultima sezione vengono ripresi i dati di lavori simili per avere una visione più chiara dei meccanismi dominanti in questa tecnologia al fine di fornire indicazioni utili nell’ ottica di uno scale-up.
Evaluation of capture capacity on natural and modified solid sorbents towards rare earth ions
D'OTTAVIO, EUGENIO
2017/2018
Abstract
Waste Electrical and Electronic Equipment (WEEE) disposal and recovery is becoming more and more important nowadays since it can represent a crucial resource for the precious and strategic metals contained inside it. Only in the EU area 17 kg of electronic waste are produced every year by every inhabitant and among the electronic scraps, printed circuit boards are the richest in precious metals and rare earths (REs). So far, the most applied technology for the recovery of metals is the dissolution with acids followed by liquid-liquid extraction, but it has many drawbacks related to the expensive chemical agents employed and their environmental impact. Adsorption on solid sorbents represents a possible solution that, with respect to the liquid-liquid extraction, exhibits some advantages: easy separation of the two-phase system, a good recovery efficiency, short reaction time, low cost and low consumption of organic solvent. The purpose of this work is to test this emerging adsorption methodology, following the results of previous similar works and using them as a starting point. The kinetic of the process was studied first, testing the adsorption of Yttrium and Neodymium on four solid matrixes: activated carbon, montmorillonite clay and the modified versions of these materials, doped with a commercial pentaethylenhexamine (L6). In the second part the uptake and release properties of activated carbon and modified activated carbon with the polyamine are studied towards the adsorption of Neodymium and Yttrium ions. In the final phase all the data and results collected throughout all the thesis works have been combined in order to understand the mechanisms governing this technology and to provide helpful indications for a future scale-up of the process.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/137432