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Nanoparticles and Surfactants Complex Effects on Water Evaporation

Behnejhad Takleh, Katayoun | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51090 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Bastani, Dariush; Jvadi, Aliyar
  7. Abstract:
  8. Interest in the study of evaporation of liquid droplets is associated with a variety of practical applications, ranging from fuel burning and intensification of heat and mass transfer processes to formation of nanostructures. The study of the evaporation of liquid droplets is a fundamental problem, and it is the subject of a large number of works. However, in droplet evaporation processes, there are still many fundamental issues requiring more in-depth studies. In this study, the effect of the presence of hydrophilic silica nanoparticles and cationic (CTAB), anionic (SDS) and nonionic (TX-100) surfactants separately and in combination on the evaporation rate of water in a pendant droplet with a constant surface area using a Profile Analysis Tensiometer (PAT) in the presence of calcium chloride adsorbent has been investigated. The results showed that pure surfactant solutions of CTAB, TX-100 and SDS based on the concentration of surfactant in the solution, 3-51%, 27-56% and 11-53%, respectively, has increased the evaporation of the base water fluid in comparison with pure water under the same conditions. Also, addition of 0.5 to 2 weight percent of silica nanoparticles to water causes a 17 to 27% increase in the evaporation of the base water fluid from the droplet. The effect of surfactant on evaporation can be attributed to the reduction of surface tension in the interface of solution-air and thus reduce the energy needed for evaporation. For silica nanoparticles, also Increase evaporation rate can be attributed to two factors including drop surface morphology and high surface to volume ratio of silica nanoparticles. By investigating the system containing silica nanoparticles and cationic surfactant CTAB, found that surfactant molecules stick to the surface of the nanoparticle and greatly increase the surface activity of the silica nanoparticles. This factor increases the evaporation of the system in low concentrations of surfactants. However, in high concentrations of surfactants, due to spatial repulsion between the complexes, it decreases the evaporation rate. In the system containing anionic silica nanoparticles and SDS surfactant, the electrostatic repulsion force between silica nanoparticles and SDS molecules improves the efficiency of surfactants. Unlike anionic surfactant SDS, the effect of nanoparticle on surface tension is insignificant in non-ionic TX-100 surfactant systems that are inductively anionic. In general, the presence of cationic surfactant CTAB has the highest evaporation rate and the presence of non-ionic surfactant TX-100 yields the lowest evaporation rate for water along with silica nanoparticles
  9. Keywords:
  10. Evaporation ; Nanoparticles ; Surfactants ; Surface Tension ; Pendant-Drop Method

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