71% of the surface of the earth is covered by water, but all the water only 0.01% can be used directly for human.According to statistics, 663 million people around the world about to live in a country where no drinking water supply, a lot of people need to walk for hours to get clean water.
Africa one third population lack of drinking water, nearly half of the population infected by drinking unclean water.In order to solve the problem of water shortage, some coastal countries have started developing seawater desalination system. but many developing countries cannot afford water shortage resulting huge cost.
now, the solution of these problems a new dawn.DT jun, I would like to introduce today is a low cost to effective desalination technologies -- graphene oxide membrane filtration technology. the latest research results were published in the Nature Nanotechnology ".
the new technology was born in the world's top graphene research institutions - the university of Manchester in the national institute for graphene ".The institute has been a Nobel Prize winner - that is the well-known "father" of graphene Andre Geim (Andre Geim).
for excellence in graphene materials research, Andre geim and his colleague Konstantin carbon (Konstantin Novoselov) won the 2010 Nobel Prize in physics. Andre geim is also one of the corresponding author of this paper.
" the father of graphene "professor Andre geim (pictured above), who teaches at the university of Manchester institute of physics, and the university of Manchester, one of the national institute of graphene led in his career, geim published more than 150 top article, many of which were published in nature and the journal science.Maybe we in the "father" of graphene know little, but for is often referred to as the "miracle material graphene," believe that most people are familiar.
graphene is carbon allotropes, is currently the world's most thin (about one over two hundred thousand of a human hair), maximum strength (maximum strength steel 200 times), the light quality, electrical and thermal conductivity, the best transmission of light (white light transmittance up to 97.7%) and electronic transmission is the most excellent (electronic transmission speed in graphene is hundreds of times of transmission speed in silicon) of the new material. therefore, graphene in almost every industry has potential application prospect.
however, graphene after fame, not quickly into People's Daily life. truly limit is widely used in graphene is its hard to industrialized mass production. on the other hand, using techniques such as chemical vapor deposition (CVD) method is difficult to produce a large amount of single layer and performance of graphene;On the other hand, the production cost is too high.
however, the derivatives of graphene - graphene oxide - can through simple oxidation produced in the laboratory.In ink or some solution, scientists have used some basal material or porous materials for synthesis of graphene oxide, and then use it for membrane system.Considering the flexibility and cost of graphene oxide, graphene oxide more potential advantages than single-layer graphene.
all in all, the unique properties of graphene oxide thin film make it a filter or desalination field the best candidate for the film. at the university of Manchester scientists now shows the how to graphene oxide thin films used for efficient filtration system, desalination has achieved substantial breakthrough.
the research team, said the film not only can be used for desalination, and tunable pore size to filter more types of ions.If the scalable membrane aperture uniform could atomic other aperture , this will be a major breakthrough, it will be to improve the efficiency of desalination technology open a new door.
in fact, this is not the first time the graphene oxide film in the" off ".Prior to that, this material has been filtering in the separation of gas and ion, and other fields has made great progress.
before, according to a study at the university of Manchester, graphene oxide film immersed into the water, they will happen some deformation, make the membrane pore size bigger, therefore smaller ions will be as the water flow through the membrane, and large ions or molecules will be cut off, it played the role of a certain degree of filtering.
now, the university of Manchester research team's latest research results, according to the these graphene oxide thin film has been further optimization, avoid the aperture caused by the expansion when water flows through a film.
the most important of all, this time they can precise control of graphene oxide thin film aperture size, this can effectively prevent unwanted ions. using the graphene membrane filtered water to drink, and more safety.
there is no doubt that the result is of great practical significance. on the other hand, according to the UN sustainable development "target", in 2030, the world everyone can get basic freshwater resources, however the situation is not optimistic.
on the other hand, climate change is also put people at the edge of the water security threats, drought, flood, melting glaciers will lead to the shortage of fresh water resources.Go down for a long time, these factors will further affect food production, health care, energy and industry.The lack of freshwater resources has brought nots allow to ignore the threat to human.
the United Nations predicts that arrived in 2025, the world will have 14% of the population is facing the threat of water shortages.This technology is expected to innovation worldwide water filtration technology, especially for those who can't afford to set up a country of large-scale desalination plants is extremely advantageous.
according to the results of this research, the people can on-demand design graphene oxide thin film aperture, to achieve "on-demand filter". with plenty of water on earth, the sea is our abundant water resources library, if we can make the film in a large-scale system used for seawater desalination, fresh water crisis can be well solved.
at present, many developed countries invest heavily in seawater desalination technology, so the technology is in a critical period of development.
however, this kind of graphene membrane system to be commercially viable may also need a period of time.The researchers of the ultimate goal is to build an efficient filtration of industrial wastewater and water purification plant. the main challenges are the following three points:
first, in the industry, to production on a large scale, cheap and stable, sustainable work in bad environment of graphene oxide thin film system must also consider the film system how to organic matter, salt resistance, corrosion and biological materials;
second, researchers how to production on a large scale the graphene oxide film, and has a wide range of industrial applications and they face a huge challenge;
third, in the production of graphene films will inevitably produce defects, such as membrane caused by uneven holes, these holes is extremely unfavorable to the filtration and separation.
appendix: the principle behind
usually, graphene oxide thin film of water permeability resistance small, can be used for filtering and separating, proton conductor, energy storage and conversion, etc.However, they in the ionic sieve and desalination technology is limited by 0.9 nm seepage threshold, namely diameter less than 0.9 nm hydrated ion can through this film, is greater than 0.9 nm ions can be effective filtering.
theory proves that the 0.9 nm threshold is the layer of graphene oxide thin film system by spacing (d, about 1.35 nm).Usually, graphene oxide film in water easy to expand, to achieve a smaller layer spacing has a considerable challenge.There is evidence that d layer spacing within the scope of 0.64 to 0.98 nano graphene oxide thin film system can of common salt hydrate ions effectively filtering.
based on these findings, the researchers found a way, of the university of Manchester (on both sides of the graphene oxide thin film is introduced into the epoxy resin) can effectively control the expansion of the aperture.Confirmed by experiments, with their method can make graphene oxide thin film filter for sodium chloride ion rate is as high as 97%, which means that the membrane system can effectively filter common salt ions.
it can be a landmark achievements in the research area.