The present paper describes the design and operation of the first large-scale extraction and separation of metals from a complex matrix using an ionic liquid. The liquid was a deep eutectic solvent based on choline chloride. The hydrogen-bond donors were mixed to optimize solubility and fluid viscosity. It was found that the incorporation of a fine particulate dust actually decreased the viscosity of the fluid. The present paper shows that selective extraction of zinc and lead can be achieved through judicious choice of the hydrogen-bond donor and it is also shown that metals in solution can be separated using cementation with zinc powder. Electrowinning of pure zinc is demonstrated but scale-up tests suggest that the process is relatively slow and has poor current efficiency. An alternative methodology was developed to rapidly recover the zinc from solution using dilute ammonia solution. It is also shown for the first time that cementation can be efficiently carried out in ionic liquids because the recovered metal is porous and allows thick layers to be deposited.
PurposeThis paper aims to present a review carried out under DEFRA‐funded project WRT208, describing: the composition of WEEE, current treatment technologies, emerging technologies and research.Design/methodology/approachThis paper summarises the output from the first part of the project. It provides information on the composition of WEEE and an extensive survey of technologies relevant to materials recycling from WEEE. A series of further papers will be published from this research project.FindingsWEEE has been identified as one of the fastest growing sources of waste in the EU, and is estimated to be increasing by 16‐28 per cent every five years. Within each sector a complex set of heterogeneous secondary wastes is created. Although treatment requirements are complicated, the sources from any one sector possess many common characteristics. However, there exist huge variations in the nature of electronic wastes between sectors, and treatment regimes appropriate for one cannot be readily transferred to another.Research limitations/implicationsA very large number of treatment technologies are available, both established and emerging, that singly and in combination could address the specific needs of each sector. However, no single set of treatment methods can be applied universally.Originality/valueThis paper is the first part of work leading to the development of technical strategies and methodologies for reprocessing WEEE into primary and secondary products, and where possible the recovery of higher added‐value components and materials.
Discharges of coloured effluents into surface waters provide conspicuous evidence of the impact of industry on the environment. The textile industry is an obvious candidate for sources of such discharges. Conventional treatment methods appear to alleviate this situation by removing colour, however the affect on toxicity is less obvious. The objective of this study was to examine the changes in effluent toxicity during the course of two alternative wastewater treatment methods, ozonation and electrochemical oxidation, using a novel toxicity biosensor, GreenScreen EM. The biosensor is capable of measuring both general acute toxicity (cytotoxicity), and more specifically genotoxicity, that is damage to a cell's DNA structure, replication or distribution, caused by substances that may be mutagenic and/or carcinogenic. The biosensor utilises a modified strain of the brewers yeast Saccharomyces cerevisiae, incorporating a gene encoding green fluorescent protein (GFP) linked to the inducible promoter of the DNA damage responsive RAD54 gene. Upon exposure to a genotoxin, the production of GFP is up-regulated in parallel with RAD54, and the resulting cellular fluorescence provides a measure of genotoxicity. Acute toxicity is simultaneously determined by monitoring relative total growth of the cell culture during incubation. The results presented in this paper show that a reduction in colouration does not necessarily correspond to a reduction in effluent toxicity.
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