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article imageEssential Science: Making dirty water drinkable

By Tim Sandle     Aug 1, 2016 in Science
In many parts of the world water is not fit for people to drink. Technologies to render dirty water drinkable are limited by size and cost. Now a lower cost solution is on the horizon, based on graphene.
Graphene, in its various forms, has been heralded as the wonder material of our age. Graphene is a form of carbon and it has properties that are remarkable and very useful. For instance, the material is light yet very strong (being composed of a just one-atom layer in terms of thickness); moreover, it is transparent, flexible, and highly conductive to both heat and electricity.
Making a superlattice with patterns of hydrogenated graphene is the first step in making the materia...
Making a superlattice with patterns of hydrogenated graphene is the first step in making the material suitable for organic chemistry. The process was developed in the Rice University lab of chemist James Tour.
Tour Lab/Rice University
Applications being developed include next generation electronic devices and fold-away computer screens. Super-fast electronics are promised through the incorporation of graphene into semi-conductors. Semiconductors are the basis of all modern electronic devices and their properties are based on the ability to switch the current running through them on and off.
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In the domestic and business sphere, graphene provides the basis for a type of ‘smart’ wallpaper, capable of generating electricity from the light from a lamp. Imagine the possibility in the average family home – creating your own electricity just by having the lights on. To add to this, graphene could become the basis of a new generation of faster, lighter aircraft. The research is examining the potential of graphene reinforced aluminum matrix nanocomposites.
Outside of the white heat of technology, graphene is being examined for its use in healthcare and as part of global development. These two spheres combine with the new consideration of using graphene oxide to render dirty water clean and drinkable.
Graphene oxide is produced by oxidation of graphite. It is similar to another material that has been around for a number of years, called graphite oxide. However, while graphite oxide is a multilayer system; graphene oxide is a dispersion that is only made up of a few layers of flakes in an ultra-thin monolayer. One of the advantages of the gaphene oxide is its easy dispersible in water and other organic solvents.
For this application, graphene oxide sheets are incorporated into nanocellulose foam within a laboratory setting as the bacteria are cultured. The graphene oxide is added in the form of flakes. This is being worked on by scientists at Washington University in St. Louis. The method requires linking bacteria-produced cellulose together with chemically constructed graphene oxide to form a bi-layered biofoam. This is a relatively simple process. In addition, the biofoam is very light and it can be produced at a low cost.
Before It's News (@beforeitsnews) tweeted: "Global Game-Changer: Graphene Biofoam Purifies Dirty Water Quickly Using Sunlight." The Centre for Environmental Change & Human Resilience (@CECHR_UoD) posted: "Solar Powered Graphene Evaporator Zaps Dirty Water…With Bacteria?!?"
The resultant bi-layer structure is made up to a light-absorbing graphene oxide filled nanocellulose positioned at the top and the nanocellulose located at the bottom. When the device is suspended on water, the water moves the top surface where evaporation takes place. Water moves up because the cellulose at the bottom acts like a sponge and draws water up to the graphene oxide located at the top of the structure. Here light is radiated and is converted into heat because of the graphene oxide which accelerates the evaporation. The water collected from the evaporation process is filtered, clean and drinkable.
The water produced is both purified (in terms that most chemical impurities and microorganisms are removed) and desalinated (where the removal of salt make the water suitable for people to drink.)
Speaking with Controlled Environments magazine, lead researcher Professor Srikanth Singamaneni commented: “We hope that for countries where there is ample sunlight, such as India, you’ll be able to take some dirty water, evaporate it using our material, and collect fresh water.”
The research has been published in the journal Advanced Materials. The research paper is titled “Bilayered Biofoam for Highly Efficient Solar Steam Generation.”
This article is part of Digital Journal's regular Essential Science columns. Each week we explore a topical and important scientific issue. Last week we looked at a new warning about cancer risks relating to drinking alcohol. The week before we considered how bacteria are being used to create a new generation of nanoelectric materials, which could aid next generation electronic devices.
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