Capture mechanism of la and Cu ions in mixed solutions by clay and organoclay

In this work, Ca-montmorillonite (STx), natural and modified (STx-L6) with a linear penta-ethylene-hexamine (L6), were tested as sorbents in a liquid/solid process for La and Cu capture in bionic model solutions. Twelve La/Cu ratios in solution were set and analyzed with the final target of investigating the capture mechanisms when both Cu and La are present. The liquid phase was characterized via inductively coupled plasmaoptical emission spectroscopy (ICP-OES), while the solids were studied by means of X-ray powder diffraction (XRPD). No direct competition between Cu and La ions for the capture sites was found but rather the modification of the acidâ'base condition of the solution and the related equilibria due to aquo- A nd hydroxycopper complexes formation. Cu complexes are responsible for pH modification and the related influence on the capture of La ions. Three distinct mechanisms were identified to be active in the capture process, i.e., ion exchange, surface adsorption, and coordination of the metal by the polyamine, when present. Only La is involved in the ionic exchange process, since no Cu was captured by pristine clays, while only Cu is coordinated to the polyamine, in view of its preferential interaction with amino groups. The different capture mechanisms are responsible for the higher efficiency of the organoclay, with respect to the pristine one. This study lays the groundwork for the development of an efficient method for rare earths (REs) and precious metal recovery from waste electrical and electronical equipment (WEEE) by a liquid/solid process

Tecnologie di recupero e separazione di terre rare: stato dell’arte e prospettive

Entro il 2015 la domanda globale di terre rare potrebbe raggiungere la cifra di 210000 t/anno [1] e, dal momento che la Cina detiene il 50% delle riserve mondiali, per poter soddisfare la domanda, la produzione annua non-cinese dovrebbe aggirarsi tra le 45000 e le 70000 t. Date, quindi, la criticità e la strategicità di questi materiali, nel testo si proporrà la raccolta dei RAEE ed il recupero delle terre rare in essi contenuti come contributo alla soluzione del problema, si riassumeranno i benefici che il recupero apporterebbe alla sostenibilità e all’economia e ci si focalizzerà, tramite analisi bibliografica critica, sulle tecnologie di separazione attualmente disponibili. Global demand for rare earths could reach the value of 210000 t/year by 2015 [1]. From the moment that China holds 50% of world reserves, non-Chinese annual production is expected to reach values between 45000 t and 70000 t in order to meet demand. To face the criticality and the key role of these materials, WEEE collection and recovery of contained rare earths will be proposed as a contribution to the solution of the problem. The work will summarize the benefits that the recovery could bring to sustainability and to economics and will focus on the separation technologies, through a critically literature review

Capture and release mechanism of la ions by new polyamine-based organoclays: A model system for rare-earths recovery in urban mining process

Uptake and release capability of a new organoclay material were assessed with the final goal to evaluate its applicability in recovering REs from solutions. Capture and release capability have been tested towards a La ions model solution, and interaction mechanism and reactions, active in both capture and release processes, were related to the nature of the organoclay and the operating process parameters. The studied system, polyamine-based organoclay, is able to capture and release La ions with high efficiency. Capture involves three distinct mechanisms: ion exchange reaction with interlayer cations, surface adsorption, and finally, coordination by the polyamine. 2.5 mmol/g of amino-groups in a linear ethylene-amine based organoclay are enough to remove all the lanthanum ions in solution when contacted with containing 0.48 mmol/gclay, i.e. 2600 ppm/clay. 12 coordinating sites are needed for each lanthanum ion. Finally, the organic part of the sorbent solid is highly stable, being unmodified upon many cycles of use. The release step is greatly pH dependent, and the optimised pH is equal to 1. Under these conditions, release efficiencies are always higher than 80 %. Appling multiple steps and intermediate re-basification, very high and reproducible global efficiencies (up to 90 %) are reached

Capture mechanism of la and Cu ions in mixed solutions by clay and organoclay

In this work, Ca-montmorillonite (STx), natural and modified (STx-L6) with a linear penta-ethylene-hexamine (L6), were tested as sorbents in a liquid/solid process for La and Cu capture in bionic model solutions. Twelve La/Cu ratios in solution were set and analyzed with the final target of investigating the capture mechanisms when both Cu and La are present. The liquid phase was characterized via inductively coupled plasmaoptical emission spectroscopy (ICP-OES), while the solids were studied by means of X-ray powder diffraction (XRPD). No direct competition between Cu and La ions for the capture sites was found but rather the modification of the acid\ue2'base condition of the solution and the related equilibria due to aquo- A nd hydroxycopper complexes formation. Cu complexes are responsible for pH modification and the related influence on the capture of La ions. Three distinct mechanisms were identified to be active in the capture process, i.e., ion exchange, surface adsorption, and coordination of the metal by the polyamine, when present. Only La is involved in the ionic exchange process, since no Cu was captured by pristine clays, while only Cu is coordinated to the polyamine, in view of its preferential interaction with amino groups. The different capture mechanisms are responsible for the higher efficiency of the organoclay, with respect to the pristine one. This study lays the groundwork for the development of an efficient method for rare earths (REs) and precious metal recovery from waste electrical and electronical equipment (WEEE) by a liquid/solid process