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.

Pradeep Thalappil

Department Of Chemistry

Jakka Ravindran Swathy

Chennu Sudhakar

Avula Anil Kumar

Carbonation

Disinfection

Escherichia coli

Hybrid materials

Metal ions

Microorganisms

Positive ions

Potable water

Purification

Water

Water treatment plants

Anti-microbial activity

CARBONATE MATERIALS

DRINKING WATER PURIFICATION

SUSTAINABLE RELEASE

SYNERGETIC EFFECT

Chemicals removal (water treatment)

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

ACS Sustainable Chemistry and Engineering

Decreasing mineral content in drinking water is a serious concern especially due to the proliferation of desalination technologies. We present an approach to remineralize water with essential minerals such that their concentrations are at the recommended daily dose. We accomplished this using composite materials whose composition and surface area were tuned to achieve constant release of minerals into water over a prolonged period of time. We developed a nature-mimicking tectosilicate porous composite matrix and used it as a structural framework to incorporate leachable minerals to the extent of 40% of the whole mass, which were released into the water during its functional working life. Release of not only the common macro minerals but also the vital trace minerals was possible in this work. Compacted composites of this kind have been used to create mineralization cartridges. The greenness of these composites evaluated from several sustainability metrics shows that the manufacturing process has minimum or negligible carbon emission, E-factor, and energy consumption. This methodology may be extended to encompass all the essential minerals expected to be present in water. © 2019 American Chemical Society.

Geologically Inspired Monoliths for Sustainable Release of Essential Minerals into Drinking Water

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

Angewandte Chemie - International Edition

Extraction of Silver by Glucose

Silver is an indispensable metal but its use has to be minimised for sustainable growth. Much of the silver lost during use is unrecoverable; an example being its use as an antimicrobial agent, a property known since ages. While developing methods to create an affordable drinking water purifier especially for the developing world, we discovered that 50 parts per billion (ppb) of Ag+ released continuously from silver nanoparticles confined in nanoscale cages is enough to cause antimicrobial activity in conditions of normal water. Here we show that the antibacterial and antiviral activities of Ag+ can be enhanced ∼1,000 fold, selectively, in presence of carbonate ions whose concentration was maintained below the drinking water norms. The protective layers of the organisms were affected during the carbonate-assisted antimicrobial activity. It is estimated that ∼1,300 tons of silver can be saved annually using this new way to enhance its antimicrobial activity.

Fulltext

Scientific Reports

Antimicrobial silver: An unprecedented anion effect

Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity. The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces. Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms. These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.

Proceedings of the National Academy of Sciences of the United States of America

Biopolymer-reinforced synthetic granular nanocomposites for affordable point-of-use water purification

Water is one of the essential enablers of life on earth. Beginning with the origin of the earliest form of life in seawater, it has been central to the evolution of human civilizations. Noble metals have been similarly associated with the prosperity of human civilizations through their prominent use in jewellery and medical applications. The most important reason for the use of noble metals is the minimal reactivity at the bulk scale, which can be explained by a number of concepts such as electrochemical potential, relativisitic contraction, molecular orbital theory, etc. Recently, water quality has been associated with the development index of society. A number of chemical and biological contaminants have endangered the quality of drinking water. An overview of important events during last 200 years in the area of drinking water purification is presented. Realizing the molecular nature of contamination in drinking water, significant progress has been made to utilize the chemistry of nanomaterials for water purification. This article summarizes recent efforts in the area of noble metal nanoparticle synthesis and the origin of their reactivity at the nanoscale. The application of noble metal nanoparticle based chemistry for drinking water purification is summarized for three major types of contaminants: halogenated organics including pesticides, heavy metals and microorganisms. Recent efforts for the removal, as well as ultralow concentration detection of such species, using noble metal nanoparticles are summarized. Important challenges during the commercialization of nano-based products are highlighted through a case study of pesticide removal using noble metal nanoparticles. Recent efforts in drinking water purification using other forms of nanomaterials are also summarized. The article concludes with recent investigations on the issue of nanotoxicity and its implications for the future. © 2009 Elsevier B.V. All rights reserved.

Thin Solid Films

Noble metal nanoparticles for water purification: A critical review

Silver nanoparticles can be coated on common Polyurethane (PU) foams by overnight exposure of the foams to nanoparticle solutions. Repeated washing and air-drying yields uniformly coated PU foam, which can be used as a drinking water filter where bacterial contamination of the surface water is a health risk. Nanoparticles are stable on the foam and are not washed away by water. Morphology of the foam was retained after coating. The nanoparticle binding is due to its interaction with the nitrogen atom of the PU. Online tests were conducted with a prototypical water filter. At a flow rate of 0.5 L/min, in which contact time was of the order of a second, the output count of Escherichia coli was nil when the input water had a bacterial load of 105 colony-forming units (CFU) per mL. Combined with the low cost and effectiveness in its applications, the technology may have large implications to developing countries. © 2005 Wiley Periodicals, Inc.

Biotechnology and Bioengineering

Potential of silver nanoparticle-coated polyurethane foam as an antibacterial water filter

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

Journal	Data powered by TypesetACS Sustainable Chemistry and Engineering
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	21680485
Open Access	No