José Rivera Utrilla and Manuel Sánchez Polo, who are both scientists from the department of Inorganic Chemistry of the University of Granada, have designed a material that can dispose of 100 % of the halide ions such as bromide, iodide and chloride in the water used for human consumption. Under certain conditions, the presence of these ions gives the water undesired properties and, in the worst case scenario, they cause the creation of highly toxic by-products during the water purification process.
Water chlorination has played an essential role in public health, since it has protected us from infectious diseases passed on through drinking water. Likewise, ozone is another of the most powerful disinfectants currently used. Both chlorine and ozone are powerful bactericides and, although their main function is to disinfect the water, they also produce secondary by-products when they react with organic substances and other precursors that the untreated water contains.
So, for example, bromate is a by-product of the water ionisation produced when there are bromides in the water. Bromates are carcinogen agents which are very powerful at low concentrations, and when they form they are very difficult to remove. Water which is rich in iodides presents another problem. These ions react with organic matter to form compounds known as iodomethanes which cause the medicinal smell in water. This phenomenon is often attributed to plastic containers.
Extra pure water
To avoid the formation of these compounds, the researchers from Granada have obtained a low density and highly porous material that can retain the halides in natural water. The material prepared has a great porosity and a high concentration of silver atoms on its surface. The process of disposal of the halide ions from the water is due to a process of chemisorption i.e. a chemical reaction between these ions and the silver on the solid surface. This process causes the halide ions to be retained when the appropriate silver halides are formed. When the water passes through a bed full of this material, the concentration of these ions is reduced to the point of being null and void.
Scientists maintain that with this process they can obtain water with very low concentrations of these ions. Therefore, this discovery is attractive for the drug industry, which needs water with these features for its production process.
Materials Engineering
Until now, the activated carbon, which is considered to be the adsorbent par excellence, has been inefficient in disposing of these halide ions of the water. However, the effectiveness of the new material designed by the researchers from Granada is 100 %, even on an industrial scale.
Another added value is the ease and high capacity of regeneration of this material. In order for this to happen, once the material has been used to dispose of the ions of water, a diluted aqueous solution of ammonia passes through the column and causes the material to present the same adsorbent properties as at the beginning.
Currently, the Oficina de Transferencia de Resultados de Investigación ,OTRI (the University of Granada’s Research Transfer Office) promotes this discovery which is protected by a patent.
Reference:
Prof. José Rivera Utrilla. Department of Inorganic Chemistry of the University of Granada.
Telephone Numbers: 958 – 248 523 / 243 322. E-mail address: jrivera@ugr.es
