The photo is sourced from rscf.ru
Textile and pharmaceutical businesses produce chemical waste that is hazardous to the environment. These include aromatic hydrocarbons (benzene, naphthalene), which must be decomposed into non-toxic compounds, such as water and carbon dioxide, in order to improve environmental safety. As a rule, such reactions are carried out using singlet oxygen, whose molecule has higher energy than ordinary oxygen. Thanks to this energy, singlet oxygen interacts more actively with organic substances and oxidizes them more strongly, causing them to break down. Singlet oxygen can also be used to oxidize sulfides formed during the production of petroleum products into sulfoxides, which constitute part of many pharmaceutical drugs.
Today, singlet oxygen is mainly obtained using ultraviolet lamps and metal catalysts, but this method poses hazards to many aquatic organisms (including phytoplankton, which fish feed on). A safer way to obtain singlet oxygen has been proposed by the scientists from the Ivanovo State University of Chemistry and Technology. The authors synthesized six photocatalysts – compounds that generate singlet oxygen under the influence of visible light (sunlight or LED lamps). For that purpose, the scientists used boron bromide and the organic reagent phthalonitrile, which is obtained from oil fractions. Using these substances, the scientists produced a red-pink colorant, which later interacted with derivatives of aromatic carboxylic acids and phenol to form photocatalysts.
The authors tested the efficiency of singlet oxygen formation by photocatalysts from ordinary oxygen through dissolving them in ethyl alcohol and placing them under an LED lamp for 16 hours. The experiment showed that photocatalysts exposed to light converted ordinary oxygen into singlet oxygen with an efficiency of 49% to 62%. As a point of comparison, catalysts based on titanium and tungsten compounds provide a conversion efficiency of about 30%.
The new photocatalysts could be used at treatment facilities to convert ordinary oxygen into singlet oxygen under low-power light from LED lamps. Singlet oxygen will, in its turn, decompose drug intermediates and aromatic hydrocarbons into water and carbon dioxide. This solution will reduce the cost of the treatment process, as LED lamps are on average 65–70 times cheaper than ultraviolet lamps.
“We plan to test photocatalysts with various chemical structures and test them in pairs with other substances that decompose pollutants, such as titanium dioxide, carbon nitride and graphene. This will allow us not only to improve the properties of the photocatalysts currently in use, but also to develop new ones and thereby advance the technologies for the decomposition of toxic chemical compounds in water,” Roman Skvortsov, candidate of chemical sciences, is quoted as saying by the Russian Science Foundation.
