DESINFECT WATER THOUGHT THE LIGHT

[maria angelica sassone]

Disinfect water without any chemicals, so organic, fast and effective, with only the sunlight. This is a dream for many, especially those who live in the developing countries are very limited access to purified drinking water. A multidisciplinary team of researchers has succeeded in this challenge from a former technology for disinfecting water using photocatalysts, but only using ultraviolet light. The system is optimized with the use of visible light, more abundant, and can disinfect even in the dark.

- Image: Angel Chests -

It was already known that the incidence of ultraviolet light (UV) high-intensity has a bactericidal effect. So some systems disinfection water for hikers and mountaineers integrate this technology. On this basis, groups of researchers had developed UV-activated photocatalyst for water disinfection, especially when traditional methods were not feasible. These systems benefit from the organic category, since they are not involved in potentially polluting chemicals. However, were not efficient in terms of utilization of sunlight, since ultraviolet radiation that feed accounts for only 5% of the spectrum compared to 46% of the visible, as specified by the researchers.

Attack bacteria

The developed system consists of titanium oxide fibers to which nitrogen is introduced to absorb visible light. The titanium oxide doped with nitrogen (name given to the technique used in this field as it moves impurities to a material to change its behavior) is capable by itself of eliminating bacteria, but not efficiently. However, this group of researchers has added palladium the fiber surface, an aspect that increases the performance of disinfection.

The positive charges react with water and create radicals capable of attacking bacteria

To test its effectiveness, experts in materials science from the University of Illinois placed the photocatalyst in a solution containing a high concentration of "E. coli", with a halogen lamp focused at different time intervals. Within an hour, the photocatalyst was able to reduce bacterial concentration of 10 million cells to one in a volume of 10,000 liters. The experiment was also performed in the dark and found the disinfecting power of the photocatalyst in the absence of light. To do this, it shone on the fibers for 10 hours in a day exposure simulation, and then stored in the dark. After 24 hours, the photocatalyst was still operating, and eliminating bacteria in the absence of light.

The fotocatalizadores traditional stop working almost instantly when the light goes off, but new devices are in business for many hours, even after only a few minutes of illumination. When light shines on the titanium oxide material with nitrogen and palladium creates positive and negative charges (electrons). The positive charges react with water and create radicals capable of attacking bacteria. Palladium kidnaps the electrons and prevents them from neutralizing the positive charges, thereby increasing the power of the process.

When the light turns off, the palladium particles gradually release its stored charge, which reacts again with water and creates more active agents. Thus, the photocatalyst disinfected with high efficiency during the day and works at night and even during periods of power outage. As a bonus, given the rapid disinfection of the system, this photocatalyst is able to clean large volumes of water.

Water Security

Illnesses associated with consumption of contaminated water is a major cause of mortality in developing countries, especially among children. It is estimated that over 80% of the disorders found in these countries are related to consumption of unsafe water. Diarrhea, malaria, parasites or hepatitis A are among the causes of biological contamination by bacteria, parasites or viruses. In addition, other chemical pollution associated with industrial discharges, which can cause acute poisoning, but also diseases in the medium and long term.

Therefore it is vital to control pollution and quality through comprehensive water purification and sanitation, and proper management of water resources to ensure adequate safety in drinking water. The development and implementation of water disinfection systems based on the use of natural resources such as sunlight is a major breakthrough in purified water, especially in developing countries where access to other energy sources or chemicals is very limited.

It is estimated that over 2,500 million people live without a proper water sanitation. This year, to celebrate World Water Day on 22 March, was released from institutions the slogan "Clean Water for a Healthy World", which outlines the close relationship between both concepts and claims that water is life and lives depend on the quality of water consumed.

OPTION ONE WITHOUT CHEMICALS

- Image: Esteban Leon -

Photocatalysts are teams that apply the photocatalytic process, also called photonic catalysis, based on the properties of titanium dioxide. Photocatalysis is an electron transfer process using titanium dioxide activated by light, far ultraviolet, for the treatment of contaminated water. The biocidal effect represents a revolution for water disinfection, since it is based on physical processes rather than traditional chemical chlorine, which is exempt.

These systems, which involve the direct application of a process known for decades, now enhanced by integrating the light source visible, instead of the ultraviolet as well as a storage system that allows gradual discharge the water disinfecting system the dark. Traditional methods disinfection involve the use of chemicals such as chlorine, heat (boiling) or filtration or a combination of these