The recycling of metals from end-of-life secondary sources such as electronic waste remains a significant environmental and technological challenge currently detrimental to the development of circular economies. The complex nature of electronic waste, containing a myriad of different elemental metals, means that sophisticated yet simple separation methods need to be developed in order to recycle these valuable and often critical metal resources. In this work simple 2 primary, secondary, and tertiary amides are appraised as reagents that selectively transport gold from aqueous to organic phases in a solvent extraction experiment. While the strength of extraction of gold from single metal solutions is ordered 3 o >2 o >1 o , the 3 o and 2 o amides are ineffective at gold transport from mixed-metal solutions of concentrations representative of smartphones due to the formation of a third, dense phase. Increasing the polarity of the organic phase can negate third phase formation but at the expense of selectivity. The identities of the species that reside in the organic and third phases have been studied by a combination of slope analysis, mass spectrometry, NMR spectroscopy, and computational methods. These techniques show that protonation of the amide L occurs at the oxygen atom, resulting in the protonated dimer HL2 + which acts as a receptor for AuCl4 − to form dynamic supramolecular aggregates in the organic phase. The characterization of a tin complex in the third phase by X-ray crystallography supports these conclusions and furthermore, suggests the preference for the chelation of the proton by two amide molecules instead of the transport of hydronium into the organic phase and its subsequent use as structural template.

Understanding the composition of soil organic matter (SoM) is vital to our understanding of how soils form, evolve and respond to external stimuli. the shear complexity of SoM, an inseparable mixture of thousands of compounds hinders the determination of structure-function relationships required to explore these processes on a molecular level. Litter bags and soil hot water extracts (HWe) have frequently been used to study the transformation of labile SoM, however these are still too complex to examine beyond compound classes. in this work, a much simpler mixture, HWe buried green tea, was investigated by nuclear Magnetic Resonance (nMR) spectroscopy and fourier transform ion cyclotron Resonance Mass Spectrometry (ft-icR-MS), as a proxy for labile SoM. changes induced by the burial over 90 days in a grassland, woodland and two peatland sites, one damaged by drainage and one undergoing restoration by drain-blocking, were analysed. Major differences between the extracts were observed on the level of compound classes, molecular formulae and specific molecules. The causes of these differences are discussed with reference to abiotic and biotic processes. Despite the vastly different detection limits of NMR and MS, chemometric analysis of the data yielded identical separation of the samples. These findings provide a basis for the molecular level interrogation of labile SOM and c-cycling processes in soils. Earth's soils store a greater amount of C than both the vegetation and atmosphere combined and thus play a crucial role in the global C cycle 1. The accumulation of C is largely the result of restricted decomposition rates, which are ecosystem dependent. Three major causes for these restrictions include climate (temperature and moisture), substrate quality (chemical and physical characteristics), and the composition, abundance and activity of the soil biotia 2,3. Soil decomposition has historically been studied using litter bags, which consist of plant material of known mass enclosed in a screened container 4,5. A variety of different litter bag compositions and protocols have been used over the years, which makes a cross-study comparison practically impossible 6,7. More recently, a standardized method using green and rooibos Lipton tea bags has emerged 8 , which involves burying pairs of pre-weighed green and rooibos tea bags 15 cm apart to a depth of 8 cm. After 90 days, the tea bags are collected, dried and weighed. Using the fact that the rooibos tea decomposes slower than the green tea permits the so-called stabilization factor, S and decomposition rate, k, to be calculated from the determined weight losses. These two variables constitute the Tea Bag Index (TBI) which has been measured for different soils worldwide in order to define the relationships between soil types, decomposition rates and environmental factors 6,8-10. The tea bag decomposition rates, k, have been shown to positively correlate with those of local litter and respond in similar ways to biotic factors 7,9,11. On a molecular level soil litter d...