Environmental Impact Assessment of Nanofluids Containing Mixtures of Surfactants And Silica Nanoparticles

Due to the widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable, causing a toxic effect to biota and/or wastewater treatment processes. Because of concerns about the environmental impact of nanofluids, the study of the fate and environmental impact, hazards and toxicity of nanoparticles is beginning. However, the interactions between nanoparticles and surfactants as well as the biodegradability in mixtures have been little studied until now. In this work the environmental impact of nanofluids containing mixtures of surfactants and silica nanoparticles were evaluated. The systems studied were hydrophilic silica nanoparticles (size 7 and 12 nm), a non-ionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The aerobic ultimate biodegradation and interfacial and adsorption properties of surfactants, nanoparticles and mixtures during the biodegradation process were also evaluated. Aerobic biodegradability was determined by measurements of dissolved organic carbon for solutions with variable concentrations of surfactants and nanoparticles. The ultimate biodegradation was studied below and above the CMC of the individual surfactants. Interfacial and adsorption properties of surfactants solutions containing nanoparticles are influenced by the addition of silica particles. It was determined that silica nanoparticles reduced the capability of non-ionic surfactants to decrease the surface tension. Thus, silica NP promoted a considerable increase of their CMC, whereas the effect was the opposite in case of anionic surfactants. The increasing concentration of surfactant and nanoparticles in the test medium causes a decrease in the maximum levels of mineralization reached for both types of surfactants. The presence of silica nanoparticles in the medium reduces the biodegradability of binary mixtures non-ionic-anionic- surfactants solutions, being this effect more intense for larger nanoparticles. These results could be taken into account to model the behavior of nanofluids in aquatic environments and to select appropriate nanofluids containing nanoparticles and surfactants with low environmental impact.

SURFACTANTS FOR NON-FREEZING LIQUIDS

Исследованы свойства водных растворов смесей поверхностно-активных веществ, для их дальнейшего использования в качестве основных компонентов при создании экологически безопасных не спиртовых стеклоомывающих жидкостей. The properties of aqueous solutions of mixtures of surfactants for their further use as the main components in the creation of environmentally safe non-alcoholic glass-washing liquids are studied.

Adsorption capacity of binary surfactants mixtures at solution/air and solution/mineral material interfaces

The adsorption capacity on the interphase surfaces of solution / air and solution / mineral material of binary mixtures of anionic (alkylbenzenesulfonic acid and its sodium salt (ABSCNa)) and nonionic surfactants (Tween-80) was studied. It has been established that the adsorption interaction of binary mixtures of surfactants with the surface of quartz and dolomite is affected by the presence of potential-determining ions that activate the surface of mineral materials, the charge and hydration of the anionic antagonists, the nature of the intermolecular interactions between the surfactant-components of the mixture. It was shown that the ABSCNa / Tween-80 mixture, characterized by low adsorption capacity to the mineral materials under study and absence of interaction between the surfactant components of the mixture, has a maximum oil displacement capacity from the surface of dolomite and quartz.

Swollen micelles and alcohol–surfactant co-adsorption: structures and mechanisms from liquid- and solid-state 1H–1H NMR spectroscopy

Mixtures of surfactants and medium-chained alcohols display an anomalous phase behaviour, with the formation of swollen micelles in mid-range surfactant concentrations. Such alcohols also affect the aggregation and adsorption behaviour of surfactants at solid–liquid interfaces.