Ecological and economic comparative evaluation of plasmochemical and ultraviolet destruction of the anionic surfactants

Abstract

Among the huge number of pollutants in aquatic ecosystems, surfactants can be singled out. Among them, the largest number used in everyday life and in various industries are anionic surfactants. It should also be noted their negative impact on wastewater treatment processes and, more importantly, on the environment. One of the approaches aimed at reducing the negative impact of surfactants on water systems is the introduction of reliable and effective methods of wastewater treatment from surfactants. The current environmental situation dictates the need for deep (destructive) treatment of wastewater from pollutants, regardless of the volume of wastewater discharged into reservoirs, to comply with their content of the MPC. Today, the most advanced among the destructive methods are methods based on innovative oxidative processes that allow the complete decomposition of pollutants or convert them into forms capable of further biodegradation. The essence of these technologies is the oxidation of toxicants by highly reactive particles of activated oxygen, which due to various processing methods, are generated directly in the reaction system. Of particular interest are technologies in which highly active particles of activated oxygen are formed directly during processing and do not require the use of additional chemical reagents (oxidants, catalysts). Among them are the action of vacuum (λ<200 nm) ultraviolet radiation (VUV) and various electric discharge methods.However, the large-scale application of these processes for the treatment of wastewater is still limited in particular by the fact that the mechanisms of decomposition of surfactants using these processes are insufficiently studied. The complexity of studying the efficiency of oxidative destruction of surfactants is due to the multi-stage oxidation process, the formation of mixtures of various intermediate products, the composition of which is not fully established. The toxicity of surfactant degradation products is also unknown, which is an important criterion for water purification. Another determining criterion of efficiency for the operation of treatment plants is their efficiency.The aim of the article is to conduct a comparative assessment of the environmental friendliness and cost-effectiveness of plasma-chemical and ultraviolet destruction of anionic surfactants.Еcological and economic comparative evaluation of plasma chemical and ultraviolet destruction of anionic surfactants was carried out by using as an example an aqueous solution of sodium dodecyl sulfate CH3(CH2)11OSO3Na ("Serva") with a concentration of 10 mg/dm3.As a result of experiments and calculations, it was found that VUV radiation does not lead to the formation of toxic degradation products when purifying water from anionic surfactants. When using corona discharge, toxic decomposition products can be formed in sodium dodecyl sulfate solutions, which cause chronic toxicity of the solution. Comparison of the values of specific energy consumption showed a much higher efficiency of the UV lamp DRB-20 in the destruction of anionic surfactants in comparison with the positive corona discharge, as the magnitude of specific energy consumption for the lamp is 3.67´10-4 kW∙h/dm3, and for the plasma generator - 4,4´10-3 kW∙h/dm3. It is also shown that in terms of chemical efficiency, water purification from anionic surfactants is more effective when using VUV radiation than positive corona discharge, because this value for VUV is almost 18 times higher than the same indicator when using a plasma generator.Due to the high need for the introduction of new efficient, cost-effective and safe methods of water purification from surfactants in further studies it is planned to increase the efficiency of surfactant destruction in aqueous solutions through the use of transition metal catalysts (TiO2). This approach will help to increase the concentration of reactive oxygen species, namely hydroxyl radicals and achieve a much better and faster effect of purification of aqueous solutions from surfactants or other contaminants.