1. THE ISSUE: THE WATER CRISIS

Increasing water scarcity in many regions

Around 700 million people in 43 countries suffer from water scarcity today.

2.1 billion people do not have water in their homes.

3.4 million people die every year from water-born and water related diseases.

By 2025 two-thirds of the world’s population could be living under water stressed conditions.

Given that only 2.5 % of the earth’s water is fresh and the other 97.5 % of our water is salty ocean or brackish

groundwater, scientists are turning to examine the applications of desalination.

CREDIT: wwww.arts2science.org

2. CURRENT METHODS: DESALINATION

Current desalination processes have high energy, construction, and operating costs, requiring enormous water pressures and constant maintenance and monitoring of filters.

Primarily REVERSE OSMOSIS using filters / membranes

High ENERGY use

High CONSTRUCTION COSTS

High OPERATING COSTS constant MAINTENENCE & FILTER CLEANING

Other options include:

DISTILLATION (stills) not scale-able

FORWARD OSMOSIS – high costs

ELECTRICALLY CHARGED OSMOSIS -high costs

NEW MEMBRANES – developing

Desalination by the Numbers

18,426 The total number of desalination plants worldwide (as of June 30, 2015) 

More than 86.8 million cubic meters per day The global capacity of commissioned desalination plants (as of June 30, 2015)

22.9 billion US gallons The equivalent of 86.8 million cubic meters per day (as of June 30, 2015)

150 The number of countries where desalination is practiced

More than 300 million The number of people around the world who rely on desalinated water for some or all their daily needs

3. GRAPHENEAdvances in nanoscale technology suggest that a much more cost effective and environmentally friendly desalination process using graphene is possible. Graphene’s structure and innate properties make it an ideal candidate to improve the process. Graphene consists of a single atom thick layer of carbon atoms bonded in a honeycomb structure. This allows for high water permeability. Its strength allows it to withstand high water pressures.

WHAT IS GRAPHENE?

GRAPHENE IS A 2-DIMENSIONAL NETWORK OF CARBON ATOMS IN A SINGLE LAYER

THESE CARBON ATOMS ARE BOUND WITHIN THE PLANE BY 3 STRONG ATOMIC BONDS

INTO A HEXAGONAL STRUCTURE (RESEMBLING A HONEYCOMB)

IT IS A BASIC BUILDING BLOCK FOR GRAPHITIC MATERIALS OF ALL OTHER DIMENSIONALITIES.

IT CAN BE WRAPPED UP IN TO FULLERENES, ROLLED INTO NANOTUBES OR STACKED INTO 3D GRAPHITE.

CREDIT: www.hindawi.com

PROPERTIES OF GRAPHENE:

STRENGTH: 200-300 times stronger than steel

TENSILE STRENGTH: > 1 TPa

HARDER than diamond

ELECTRICAL CONDUCTIVITY: 100 times higher than copper wire

>2000S/m

FLEXIBILITY: Stretchable up to 20% of original length

DURABLE: under prolonged contact with salt water

RESISTANT: to fouling by biological materials

THE TENSILE STRENGTH OF GRAPHENE EXCEEDS 1 TPA

1 Tera pascal (TPa) = 1012 pascals (Pa)

The pascal (Pa) is the SI unit of pressure, equivalent to one newton per square meter.

CREDIT: https://twitter.com/generalelectric/status/446333123635052544?lang=en

WHO DISCOVERED GRAPHENE?

ANDRE GEIM & KONSTANTIN NOVOSELOV of UNIVERSITY OF MANCHESTER, ENGLAND discovered graphene in 2004. They essentially used scotch tape to peel layers of graphene off graphite!

IN 2010 THEY WON THE NOBEL PRIZE IN PHYSICS for ground breaking experiments with graphene.

TYPES OF GRAPHENE:

SINGLE LAYERED GRAPHENEA single atom sheet of bonded carbon atoms freely suspended or adhered to substrate.

FEW LAYER GRAPHENE / MULTILAYER GRAPHENEStacked layers of graphene

GRAPHENE OXIDEChemically modified graphene prepared by oxidation and exfoliation

GRAPHIC CREDIT: www.tiochemicals.com

4. POTENTIAL SOLUTIONS

Benefits of using graphene membranes in place of current filters include decreased energy costs (up to 50%) due to greater water flow and permeability, decreased cost of construction and less maintenance. Additionally, the flexibility graphene and graphene oxide suggest improvements and simplifications to desalination and purification processes, such as graphene oxide sieves, and single step filters that can make clean water accessible to the broader population, including areas of poverty.

LATEST RESEARCH & TECHNOLOGIES

Scientists at MIT have developed a new way to produce graphene using a chemical technique that breaks graphite into graphene sheets, optimizing the quality of graphene for desalination while decreasing the time, money, and labor involved in production. They have engineered pores of 0.8-1.6nm in the sheets to allow water molecules to pass through while stopping the passage of salt molecules. (1)

Scientists at the University of Manchester in England are developing a graphene-oxide membrane that works as a sieve. (2)

Australian scientists of the Commonwealth Scientific and Industrial Research Organization (CSIRO) have made a

new filter made from soybean-based graphene film. The filter is called Graphair and is made from a graphene film

with microscopic channels that trap pollutants while letting clean water through. The Graphair technology can grow

graphene film in regular air, making its production faster, simpler and cheaper. It transforms soybean oil, a renewable,

natural material, into graphene films in one step. (3)

Graphic representation of GRAPHENE OR GRAPHENE OXIDE MEMBRANE

POLLUTED/ SALT WATER CLEAN/ DESALINATED WATERCREDIT: https://www.sciencedirect.com/science/article/pii/S0008622317301045

BARRIERS

COST OF PRODUCTION $

This is now decreasing significantly with new production methods

NANOTECHNOLOGY CHALLENGES

Hard to create pores of less than 1nanometer in graphene sheets

It can be done (MIT, 2017)

Graphene oxide membranes swelled in salt water.Applying epoxy resin prevents this (University of Manchester, 2017)

CREDIT: www.bbc.com/news/science-environment-39482342

Forecast of Desalination Costs for Medium and Large Size Projects

Source: International Desalination Association http://www.iwa-network.org/desalination-past-present-future/

Year 2016 Within 5 Years Within 20 Years

 

Cost of Water

(US$/m3)

 

0.8 – 1.2

 

0.6 – 1.0

 

0.3 – 0.5

Construction Cost

(US$/MLD)

 

1.2 – 2.2

 

1.0 – 1.8

 

0.5 – 0.9

Electrical Energy Use (kWh/m3) 

3.5 – 4.0

 

2.8 – 3.2

 

2.1 – 2.4