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Electrochemical deposition for the separation and recovery of metals using carbon nanotube-enabled filters†
Environmental Science: Water Research & Technology ( IF 5 ) Pub Date : 2017-10-26 00:00:00 , DOI: 10.1039/c7ew00187h
Megan P. O'Connor 1, 2, 3, 4 , Riley M. Coulthard 4, 5, 6, 7 , Desiree L. Plata 4, 5, 6, 7
Affiliation  

Rare earth and specialty elements (RESE) are functionally integral to several clean energy technologies, but there is no domestic source of virgin RESE in the United States. Manufacturing waste streams, which are relatively simple compositionally, and electronic wastes, which are chemically complex, could both serve as viable sources of secondary RESE if efficient methods existed to recover and separate these metals for reuse. Leveraging differences in RESE reduction potentials, high surface area, high conductivity carbon nanotubes (CNTs) could enable space- and solvent-efficient, selective recovery of RESE from mixed metal wastes. In this study, unaligned CNTs encapsulated in polyvinyl alcohol were used to develop an electrochemically active filter and tested for recovery of six metals or metalloids (Cu, As, Eu, Nd, Ga, and Sc) as a function of flow rate (1–5 mL min−1), pH (2–10), and voltage (0.1–3.0 V), with maximum recoveries of 86–96%, except for As, which was unretained. All metals were recovered as oxides, rather than their zero valent or reduced forms (except for Cu, which was partially reduced at low pHs). Deaeration experiments suggested electrochemical reduction of dissolved O2 and O2 derived from water splitting were jointly responsible for metal capture, where metal oxides were first formed via metal hydroxide intermediates, and this mechanism was enhanced at higher pHs. A synthetic, multi-metal waste stream of Cu and Eu was successfully separated on multiple stages with increasing voltages (97 ± 0.1% Cu and 65 ± 0.3% Eu recovery), indicating the approach might be useful for the treatment of electronic end-of-life and manufacturing derived wastes.

中文翻译:

使用支持碳纳米管的过滤器进行电化学沉积以分离和回收金属

稀土和特种元素(RESE)在功能上是几种清洁能源技术不可或缺的,但是在美国,没有国内的原始RESE来源。如果存在有效的方法来回收和分离这些金属以进行再利用,则组成相对简单的制造废物流和化学成分复杂的电子废物都可以用作次级RESE的可行来源。利用RESE还原电位,高表面积,高电导率的碳纳米管(CNT)的差异,可以从混合金属废料中高效利用空间和溶剂效率,选择性回收RESE。在这项研究中,用聚乙烯醇封装的未取向CNTs用于开发电化学活性过滤器,并测试了六种金属或准金属(Cu,As,Eu,Nd,Ga,-1),pH(2-10)和电压(0.1-3.0 V),除未保留的As以外,最大回收率为86-96%。所有金属均以氧化物形式回收,而不是以零价或还原形式(铜除外,铜在低pH值下会部分还原)被回收。脱气实验表明的电化学还原溶氧2和O 2从水分解衍生的是用于捕获金属,其中金属氧化物首先形成共同负责通过金属氢氧化物中间体,并在较高的pH值下增强了这种机理。随着电压的升高(97±0.1%的Cu和65±0.3%的Eu回收率),成功地在多个阶段成功分离了Cu和Eu的合成多金属废料流,这表明该方法可用于处理电子尾气。 -生活和制造废物。
更新日期:2017-10-26
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