About one in six people in the world do not have access to water and one in three do not have adequate sanitation. There is much work being done around the world. There are two problems. One is water purification and the other is desalination.
The current best method for desalination is reverse osmosis, which uses semipermeable membranes to filter salt from the water. The issue with this type of process is the energy required to produce the filtration process. Key elements in desalination is forcing the sea water through a membrane. As pointed out in Reference 1, one third of the electric energy consumption in the Almeria province of Spain is used by the desalination process. The cost of the plant and the process for purifying water makes it too expensive for agricultural applications. The question is what else can be employed to purify the water.
The other issue is that the methods of purification of water includes chlorination, filtration, UV exposure, and employing ozone gas. These methods are costly and require a source of material/filters. These are consumables, which require a continuous supply material. For the remote areas of the world this becomes a very difficult task. There are also other contaminants that do not have an easy solution. On world-wide contaminant is arsenic. This does not have a traditional, easy solution.
Work at Rice University developed nano-iron particles that can be introduced into the water supply that has arsenic contamination. The iron particles bind with the arsenic. By employing a strong magnet, the iron-arsenic particles can be removed from the water supply. It works, but requires a strong magnet to remove the particles. This, in turn, requires a source of power.
In reference 1, the application of multiwall nanotubes can be used to capture waterborne bacteria. Experiments have demonstrated that magnets can be employed to remove the MWNT that have attracted bacteria but not the water itself.
Graphene can be employed as a filtration element. Graphene is thin, so that water flow through the material should not require the energy of the current desalination processes.
Nanosilver and nanocopper are also important. Reference 2 has a new concept called the drinkable book. The concept uses pages of the book that are impregnated with the nanosilver or nanocopper. A page is torn from the book and used as a funnel/filter. Water poured into the funnel will remove 99.9% of the impurities. When the container is filled with drinkable water, the page is discarded. A new page is torn from the book for the next container.
These are only the start of methods to increase the world’s drinkable water. The application of nanotechnology to solves critical problems is slowly developing. More applications should be coming in the near future.