Cristiani Cinzia, Bellotto Maurizio, Dotelli Giovanni, Gallo Stampino Paola, Latorrata Saverio, Finocchio Elisabetta
Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy.
OPIGEO, SrL, Via dell'Industria 13, 36040 Grisignano di Zocco, Italy.
Polymers (Basel). 2022 Jan 26;14(3):485. doi: 10.3390/polym14030485.
This study is a starting point for the development of an efficient method for rare earths (REs) and transition metals (TMs) recovery from waste electrical and electronic equipment (WEEE) via a hydrometallurgical process. The capture and release capability of mineral clays (STx) and activated carbons (AC), pristine and modified (STx-L6 and AC-L6) with a linear penta-ethylene-hexamine (L6), towards solutions representative of the process, are assessed in the lab-scale. The solids were contacted with synthetic mono- and bi-ionic solutions containing Ni(II) and La(III) in a liquid/solid adsorption process. Contacting experiments were carried out at room temperature for 90 min by fixing a La concentration at 19 mM and varying the Ni one in the range of 19-100 mM. The four solids were able to capture Ni(II) and La(III), both in single- and bi-ionic solutions; however, the presence of the polyamine always results in a large improvement in the capture capability of the pristine sorbents. For all the four solids, capture behaviour is ascribable to an adsorption or ion-sorbent interaction process, because no formation of aquo- and hydroxy-Ni or La can be formed. The polyamine, able to capture Ni ions via coordination, allowed to differentiate ion capture behaviour, thus bypassing the direct competition between Ni and La ions for the capture sites found in the pristine solids. Release values in the 30-100% range were found upon one-step treatment with concentrated HNO solution. However, also, in this case, different metals recovery was found depending on both the sorbent and the ions, suggesting a possible selective recovery.
本研究是开发一种通过湿法冶金工艺从废弃电子电气设备（WEEE）中回收稀土（REs）和过渡金属（TMs）的高效方法的起点。在实验室规模下，评估了矿物粘土（STx）和活性炭（AC）以及用线性五乙烯六胺（L6）改性的原始和改性（STx-L6和AC-L6）对该工艺代表性溶液的捕获和释放能力。在液/固吸附过程中，将固体与含有Ni(II)和La(III)的合成单离子和双离子溶液接触。在室温下进行90分钟的接触实验，将La浓度固定为19 mM，并将Ni浓度在19 - 100 mM范围内变化。这四种固体在单离子和双离子溶液中都能够捕获Ni(II)和La(III)；然而，多胺的存在总是会使原始吸附剂的捕获能力有很大提高。对于所有四种固体，捕获行为可归因于吸附或离子 - 吸附剂相互作用过程，因为不会形成水合和羟基 - Ni或La。能够通过配位捕获Ni离子的多胺可以区分离子捕获行为，从而绕过了原始固体中Ni和La离子对捕获位点的直接竞争。在用浓HNO溶液一步处理后，释放值在30 - 100%范围内。然而，在这种情况下，也发现根据吸附剂和离子的不同，金属回收率不同，这表明可能实现选择性回收。
