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'Super' sand could improve water filtration
7 July 2011 | EN
Ordinary sand, like that found on beaches, can be used for the filter
Flickr/justLuc
[JAKARTA] Ordinary sand, such as that from beaches, could be used to filter dirty water using a nanotech-based technique developed by researchers.
Sand, which retains bugs and chemicals in water flowing through it, has been used as a cheap water filtration method for hundreds of years. Coarse sand filters water faster than finer sand, but produces water that is less clean.
Now, a team of scientists in Australia and the United States has come up with a way to coat ordinary coarse sand with a nanomaterial called graphite oxide — which can remove five times more impurities than ordinary sand.
The graphite oxide is suspended in a liquid, to which the sand is added. This mixture is heated to ensure the sand is covered, and then dried.
Compared with untreated sand, the coated sand removed up to five times as much mercury and dye from water. The authors wrote that its activity was similar to that of activated carbon, a porous form of carbon that has a large surface area to absorb impurities but is expensive to make.
The method for treating the sand is simple and uses cheap materials such as sulphuric acid, making the technique likely to be used in developing countries, said Mainak Majumder, co-author of the study and a mechanical engineer at Monash University, Australia.
Although the sand used in the experiment was a commercially available filtration sand, any sand could be used provided it is cleaned beforehand, Wei Gao, a co-author of the research from Rice University, United States, told SciDev.Net.
The researchers have no plans to themselves test the sand in developing countries, as they do not have access to large-scale production methods, said Wei.
Thalappil Pradeep, a prominent nanotechnologist at the Indian Institute of Technology Madras, said he has also conducted research into using a similar material to graphite oxide to improve the filtration properties of sand. He said the biggest issue is translating the technique into a product that ordinary people can use.
"The technologies have to be applied to real products. In our case, one product is undergoing field trials incorporating such materials."
The research was published in Applied Materials & Interfaces in May.
Link to abstract in Applied Materials & Interfaces
Read our Spoltight on Nanotechnology for clean water.
Comments (2)
Sreeprasad and Shihab ( IIT Madras | India )
11 July 2011
Graphite oxide (GO, also known as graphene oxide in the literature) based materials were studied for water purification applications by our group in 2009. A paper based on this work was submitted to a prominent journal in Dec. 2009 which did not find it to have ‘broad enough interest’.
In view of the practical applications, GO based materials were supported on sand. This modified manuscript was also turned down by another journal in April 2010 on split verdict. The same work was subsequently published in J. Haz. Mater. (http://www.sciencedirect.com/science/article/pii/S0304389410015268) and the paper was available online on Nov. 30, 2010. Fig. 7 of the paper gives a photograph of GO based materials on sand. An Indian patent application on this work with complete specifications of such sand for water purification was filed on Sep. 3, 2010.
A number of materials of interest to water purification can be made from GO. GO of varying degrees of oxidation are possible depending on the preparation conditions. Partly reduced GO is called reduced graphene oxide (RGO). RGO can reduce several free and complex metal ions and by this process, one gets nanoparticle-loaded GO wherein RGO has got oxidised to GO. The composites showed higher adsorption efficacy. We have demonstrated that one can bind GO/RGO/composite on sand. We have used a natural biopolymer as binder as we wanted to do the process at room temperature by green chemistry route. Various ways of functionalization of GO or sand can be used for binding. Sand is only one of the substrates.
Our other studies on chemical reactivity of graphene and use of nanomaterials for water purification can be accessed through our website, http://www.dstuns.iitm.ac.in/complete-list.php.
T. S. Sreeprasad and S. M. Maliyekkal
IIT Madras
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erich ( United States of America )
12 July 2011
This relates to heavy metal binding using the less activated biochar by producta of biofuel production.
The International Biochar Initiative now has 33 biochar affiliates around the world -- including in China, India, Japan UK, US, Australia, Korea, Canada, Italy and Israel.
Note also that the Japan Biochar Association have a very long tradition of biochar use and have been developing "modern methods" over the last thirty years. A governmental act officially acknowledged charcoal as a "soil ameliorator" back in 1988 and have completed work using Biochar as an in situ sorbent of Cd, and starting work on heavy metal radio-isotopes.
USDA, looking at heavy metals; ARS Research Turns Poultry Waste into Toxin-grabbing Char
http://www.ars.usda.gov/IS/AR/archive/jul05/char0705.htm
The in situ remediation of a vast variety of toxic agents in soils and sediments.
Biochar Sorption of Contaminants;
http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview/breakout-session-5/agriculture-forestry-soil-science-and-environment.html
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29 May 2012