Anyone who thinks amalgams are limited to tooth fillings is missing something: Amalgams, which are alloys of mercury and other metals, have been used for over 2500 years in the production of jewelry and for the extraction of metals like silver and gold in mining operations.
These days, the inverse process is of greater interest: the removal of mercury from wastewater by amalgamation with precious metals in the form of nanoparticles. Kseniia Katok and colleagues have now reported new insights in the journal Angewandte Chemie: if the diameter of silver nanoparticles is made even smaller, significantly more mercury can be extracted relative to the amount of silver used.In the conventional process, two silver atoms react with one mercury ion, which carries a twofold positive charge, to produce two silver ions, which go into solution, and a neutral mercury atom, which is taken up by the metallic silver particles. The stoichiometric ratio of mercury to silver is thus 1:2.
The researchers at the University of Brighton (UK) and colleagues in Kazakhstan, France and Japan have now determined that the stoichiometry of the reaction changes if the diameter of the silver nanoparticles drops below a critical 32 nm.
This effect, known as “hyperstoichiometry” depends on the size of the nanoparticles. With particles that have a diameter around 10 nm, the ratio can reach between 1.1:1 and 1.7:1, depending on the mercury counterion. In these cases, the reaction is clearly occurring differently than it does with silver particles of “normal” size. The researchers postulate that the initially produced silver ions are absorbed into the silver nanoparticles and, under the catalytic influence of the tiny silver nanoparticles, are “recycled” back to elemental silver by the negatively charged counterions of the mercury salts, which in these experiments were nitrate or acetate.It has often been observed that very small nanoparticles have a higher catalytic activity than larger ones because their surface properties dominate over their bulk properties. The hyperstoichiometric effect suggests new approaches for the purification of runoff as well as catalysis.
To produce the necessary extremely small silver nanoparticles, the scientists equipped a silicon dioxide surface with individual silicon hydride (-SiH) groups. These are able to reduce silver ions to neutral silver atoms, which are bound to the surface and probably act as nucleation sites for the further aggregation of silver. The density of SiH groups and reaction time can be used to control the size of the particles. In contrast to conventional processes, this requires no stabilizers, which stick to the silver nanoparticles and alter their physical and chemical properties.About the Author
Title: Hyperstoichiometric Interaction Between Silver and Mercury at the Nanoscale
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201106776
Dr Kseniia Katok | Angewandte Chemie
Researchers find new mutation in the leptin gene
24.06.2019 | Texas Biomedical Research Institute
Straight to the heart
24.06.2019 | Max-Delbrück-Centrum für Molekulare Medizin in der Helmholtz-Gemeinschaft
From June 25th to 27th 2019, the Fraunhofer Institute for Digital Media Technology IDMT in Ilmenau (Germany) will be presenting a new solution for acoustic quality inspection allowing contact-free, non-destructive testing of manufactured parts and components. The method which has reached Technology Readiness Level 6 already, is currently being successfully tested in practical use together with a number of industrial partners.
Reducing machine downtime, manufacturing defects, and excessive scrap
The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.
Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...
The well-known representation of chemical elements is just one example of how objects can be arranged and classified
The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...
Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.
Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...
Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.
The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
24.06.2019 | Agricultural and Forestry Science
24.06.2019 | Life Sciences
24.06.2019 | Medical Engineering