Unprecedented silver ion leaching, in the range of 0.7 ppm was seen when metallic silver was heated in water at 70 °C in presence of simple carbohydrates, such as glucose, making it a green method of silver extraction. Extraction was facilitated by the presence of anions, such as carbonate and phosphate. Studies confirm a two-step mechanism of silver release, first forming silver ions at the metal surface and later complexation of ionic silver with glucose; such complexes have been detected by mass spectrometry. Extraction leads to microscopic roughening of the surface making it Raman active with an enhancement factor of 5×108. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Pradeep Thalappil

Department Of Chemistry

Ananya Baksi

Swathi Chaudhari

Soujit Sen Gupta

EXTRACTIVE METALLURGY

glucose

Ions

Mass spectrometry

Metal ions

Metals

Silver

Enhancement factor

GREEN METHOD

Green process

METAL SURFACES

Metallic silver

SILVER EXTRACTION

Silver ions

TWO-STEP MECHANISMS

Extraction

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Angewandte Chemie - International Edition

Polytetrafluoroethylene (PTFE) is probably the most extensively used chemically inert and thermally stable polymer. We report the degradation of PTFE in water in the presence of common metals and carbohydrates resulting in polymeric fragments. About 53 mg of solid materials consisting of polymeric fragments and copper was separated from a copper vessel in 15 days when a PTFE pellet of about 920 mg was stirred with 1000 ppm glucose in 70 mL of water at 70 °C. Degradation produced fluorocarbon species in water were detected by high-resolution electrospray ionization mass spectrometry. Triboelectric charging of the PTFE surface during stirring and consequent interaction of the charged surface with the metal ions, brought to solution by carbohydrate-induced corrosion, is attributed to this phenomenon. We show that such a process can be extended to other polymers such as polypropylene. The study suggests important consequences of nanoplastics to environment and health, including impact of such chemistry to cooking. Copyright © 2019 American Chemical Society.

Fulltext

ACS Sustainable Chemistry and Engineering

Tribochemical Degradation of Polytetrafluoroethylene in Water and Generation of Nanoplastics

Extraction of silver into water occurs from its apparently inert metal surface by the simple carbohydrate glucose. Here we show that there are large synergistic effects in the extraction process, which results in ca. 45 times larger leaching with specific molecules, when used along with glucose. While glucose (1 g) alone can extract ca. 650 ppb of silver from the metal, 60 mg of it extracts ca. 30000 ppb in a combination with 200 mg of glutathione (GSH) under similar experimental conditions of 70 °C and an extraction time of 7 d, in deionized (DI) water (200 mL). This enhancement is similar when glucose is replaced with cyclodextrin (CD). This enhanced concentration of silver in solution enables the formation of the silver clusters protected with glutathione and cyclodextrin, Ag20(SG)15CD3–, in the presence of a reducing agent. A similar extraction for copper leads to excessive leaching, and typical concentrations are even higher than the solubility limit of the copper–glutathione complex. As a result, these complexes are precipitated. This synergistic extraction is observed for zinc and stainless steel as well. Enhanced extraction is a result of the formation of complexes of metals with glutathione and the consequent leaching of the complex into solution as well as the stabilization of the complex by inclusion complexation with cyclodextrin. Enhanced leaching in the presence of glucose is mostly due to simultaneous complexation with glucose as well as glutathione. The science presented may be used for the green extraction of different metals and could be a new potential top-down approach for metal cluster synthesis. This may also be useful for green and sustained leaching of minerals into water to regulate its quality. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

European Journal of Inorganic Chemistry

Synergistic Effect in Green Extraction of Noble Metals and Its Consequences

Silver, a metal with phenomenal commercial importance has been exploited in its ionic form in the field of water purification, with the objective of delivering microbially safe drinking water. Silver released at such concentrations is unrecoverable and has to be reduced to ensure sustainable utilization of the metal. We have shown that small concentrations of carbonate can effectively bring down the amount of silver ion used for microbial disinfection by half. Implementation of this finding requires constant carbonate releasing materials in natural water for an extended period. In this work, we describe a hybrid material with intrinsically high stability in water that is prepared using naturally abundant ingredients which releases carbonate constantly and in a controlled fashion. This composition in conjunction with reduced silver ion concentration delivers mircobially safe water, tested with E. coli and MS2 phage. Use of constant carbonate releasing material for antimicrobial applications can reduce the unrecoverable silver released into the environment by ∼1300 tons/year. We also show that the composition can be modified to release cations of choice without disturbing the CO32- release from the same. A sustained release of selective cations along with carbonate can supplement drinking water with the minerals of interest. © 2016 American Chemical Society.

Sparingly soluble constant carbonate releasing inert monolith for enhancement of antimicrobial silver action and sustainable utilization

We report the chemical interactions of unsupported and alumina-supported Ag7 and Ag8 clusters protected with MSA (mercaptosuccinic acid) with heavy metal ions Hg(II), Cd(II), and Pb(II) in water at different concentrations. The investigation was carried out to determine the feasibility of this interesting new class of materials called quantum clusters for water purification. These systems were studied using various spectroscopic and microscopic techniques such as ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, zeta potential measurements, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy and in detail by X-ray photoelectron spectroscopy. We observed that the metal ions interact with both the silver atoms of the clusters and the functional groups of the capping agent (MSA). The mercuric ions were reduced to metallic mercury by both supported and unsupported clusters, due to the feasibility of the redox reaction, whereas no reduction was observed for Cd(II) and Pb(II). As a result of the interaction, the luminescence of the cluster is lost which can be used to sense Hg(II). At lower concentrations, the metal ions were chemically bonded to the carboxylate groups of MSA. Absence of reduction of Hg(II) at lower concentration is due to the chemical affinity of the ligands and the lower silver content per cluster compared to the number of carboxylate groups. © 2011 American Chemical Society.

Langmuir

Investigation into the reactivity of unsupported and supported Ag 7 and Ag8 clusters with toxic metal ions

Chemistry of Materials

Structural Evolution of Silver Nanoparticles during Wet-Chemical Synthesis

Nature Communications

Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin

Physical Chemistry Chemical Physics

Recent progress in SERS biosensing

Proceedings of the National Academy of Sciences

The strange case of the earliest silver extraction by European colonists in the New World

Extraction of Silver by Glucose

Journal	Data powered by TypesetAngewandte Chemie - International Edition
Publisher	Data powered by TypesetWiley-VCH Verlag
ISSN	14337851
Open Access	No