Tag Archives: Water Treatment Solutions

Chlorine dioxide as a disinfectant

description of chlorine dioxide as a disinfectant

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Chlorine dioxide is mainly used as a bleach. As a disinfectant it is effective even at low concentrations, because of its unique qualities.

Figure 1: sir Humphrey Day discovered chlorine dioxide in 1814.

When was chlorine dioxide discovered?
Chlorine dioxide was discovered in 1814 by Sir Humphrey Davy. He produced the gas by pouring sulphuric acid (H2SO3) on potassium chlorate (KClO3). Than he replaced sulphuric acid by hypochlorous acid (HOCl). In the last few years this reaction has also been used to produce large quantities of chlorine dioxide. Sodium chlorate (NaClO3) was used instead of potassium chlorate.
2NaClO3 + 4HCl ® 2ClO2 + Cl2 + 2NaCl + 2H2O

What are the characteristics of chlorine dioxide ?
Chlorine dioxide (ClO2) is a synthetic, green-yellowish gas with a chlorine-like, irritating odor. Chlorine dioxide is a neutral chlorine compound. Chlorine dioxide is very different from elementary chlorine, both in its chemical structure as in its behavior. Chlorine dioxide is a small, volatile and very strong molecule. In diluted, watery solutions chlorine dioxide is a free radical. At high concentrations it reacts strongly with reducing agents. Chlorine dioxide is an unstable gas that dissociates into chlorine gas (Cl2), oxygen gas (O2) and heat. When chlorine dioxide is photo-oxidized by sunlight, it falls apart. The end-products of chlorine dioxide reactions are chloride (Cl-), chlorite (ClO-) and chlorate (ClO3-).

At –59°C, solid chlorine dioxide becomes a reddish liquid. At 11°C chlorine dioxide turns into gas.
Chlorine dioxide is 2,4 times denser than air. As a liquid chlorine dioxide has a bigger density than water.

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Copper-silver ionization as a disinfectant

description of water copper-silver ionization as a disinfectant

Source: Copper-silver ionization as a disinfectant

Metals such as copper and silver can be used for water disinfection, if they are ionized.

When was the disinfection mechanism of copper and silver discovered?

Archeological excavations show, that people have been using copper for more than 11.000 years and have been using silver for more than 5000 years. Copper can be easily extracted and processed. More dan 7000 years ago people developed a copper extraction mechanism for copper ores. The Roman empire gained most of its copper from Cyprus, the isle that gave copper its name.
Nowadays copper is mainly extracted form ores, such as cuprite (CuO2), tenorite (CuO), malachite (CuO3·Cu(OH)2), chalcocite (Cu2S), covelite (CuS) and bornite (Cu6FeS4). Large deposits of copper ores have been found throughout the US, Chili, Zambia, Zaïre, peru and Canada.

Silver can be obtained from pure deposits, from silver ores such as argenite (Ag2S) and horn silver (AgCl) and combined with ore deposites that contain lead, gold or copper.

Both copper and silver have been applied for centuries because of their biocidal mechanism. The Vickings used copper strings on their ships to prevent the growth of algae and shells. Modern ships still use the same technology.

Most anti-fouling paints contain copper, reducing the number of marine species growing on the walls of ships. Because of this measure, ships can reach their destination faster.

Nomads used silver coins to improve drinking water quality. Well water containing copper and silver coins is very bright, due to the biocidal affect of these metals.

Since 1869 various publications have appeared on disinfection properties of silver. Some European and Russian villages have been using silver for drinking water treatment for many years.
Copper-silver ionization was developed in both Europe and the United States in the 1950’s.

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