No abstract

No abstract

The dissolution behaviour of a series of d- and p-block metal oxides was investigated in deep eutectic solvents, DES, to determine the effect of pH and HBD coordination strength on...

No abstract

The dissolution and subsequent selective recovery of elements from complex mixtures naturally necessitates redox chemistry. The majority of processes involve hydrometallurgical dissolution followed by selective chemical precipitation or electrochemical winning. The atom and energy efficiencies of these processes are poor, leading to a large volume of aqueous waste which needs to be treated before disposal. In this study it is demonstrated that electrocatalysis is an atom effective method of carrying out digestion and subsequently recovering elements from solution. Here deep eutectic solvents are used to simplify the speciation of solutes and to allow redox potentials to be modified compared to standard aqueous values. The redox catalyst used is iodine, as it demonstrates high solubility, fast electron transfer and the ability to oxidise most elements, including precious metals such as gold. The efficacy of this electrocatalyic method is demonstrated using three samples; Cu/Zn, Ga/As and Au/Ag/sulfidic ore.

No abstract

publisher: Elsevier articletitle: The application of deep eutectic solvent ionic liquids for environmentally-friendly dissolution and recovery of precious metals journaltitle: Minerals Engineering articlelink: http://dx.doi.org/10.1016/j.mineng.2015.09.026 content_type: article copyright: Copyright © 2015 The Authors. Published by Elsevier Ltd

A pilot study was conducted to determine the applicability of toenails as a biomarker of exposure to elevated environmental arsenic (As) levels. A total of 17 individuals were recruited for the pilot study: 8 residents living near to a former As mine, Devon, UK, forming the exposed group, plus 9 10 residents from Nottinghamshire, UK, with no anticipated As exposure who were used for comparison as a control group. All toenail samples were thoroughly washed prior to analysis and the wash solutions retained for As determination via ICP-MS to provide an indication of the background environmental As levels for each group. Total As was determined in washed toenail samples via ICP-MS following microwave assisted acid digestion. Concentrations of total As in the 15 toenails of the exposed group were elevated, ranging from 858 to 25,981 µg kg -1 (geometric mean = 5406 µg kg -1 ), compared to the control group whose toenail As concentrations ranged from 73 to 273 µg kg -1 (geometric mean = 122 µg kg -1 ). Higher levels of exogenous As contamination were present on the toenails of the exposed group (geometric mean = 506 µg kg -1 ) compared to the control group (geometric mean = 4.0 µg kg -1 ) providing evidence of higher environmental As 20 levels in the exposed group. Total As concentrations in toenail samples were positively correlated to environmental As levels (r = 0.60, p <0.001). HPLC-ICP-MS analysis of aqueous toenail extracts revealed inorganic arsenite (As III ) to be the dominant species extracted (~ 83 %) with lesser amounts of inorganic arsenate (As V ) and organic dimethylarsinate (DMA V ) at ~ 13 % and ~ 8.5 % respectively. Arsenic speciation in analysed toenail extracts from the two groups was 25 comparable. The only notable difference between groups was the presence of small amounts (<1 %) of organic methylarsonate (MA V ) in two toenail samples from the exposed group. Toenails are presented as a viable biomarker of exposure at sites with elevated environmental As, such as the former mining sites found throughout Devon and Cornwall, UK. Introduction 30Arsenic is naturally occurring and ubiquitous in the environment. Humans are exposed to As via contaminated water, food, soil and dust 1 . Chronic exposure to As is associated with increases in lung, liver, bladder and kidney cancer, skin keratoses and peripheral vascular disease 2, 3 . 35 Biological markers (biomarkers) can be utilised to make quantitative estimates of exposure to harmful substances 4 and subsequent risk of disease. There is now increasing interest in the use of human nails as a routine biomarker of As exposure. On ingestion, soluble arsenic is adsorbed from the gastro- 40 intestinal tract and distributed to all bodily systems in the blood, accumulating in many body parts, in particular the keratin rich materials such as hair and nails 5 . Arsenic is thought to accumulate in hair and nails as a result of its affinity for sulphydryl groups 6 and remains isolated from the 45 body's metabolic processes both after nail formation and througho...