Influence of rhamnolipids, anionic surfactants, and Al2O3 nanoparticles on the viscosity of distilled water-based fluids: A comparative experimental study

This experimental study examines the effect of different surfactants—sodium lauryl sulfate (SLS), sodium dodecyl sulfate (SDS), and bio-surfactant rhamnolipids (RHL)—on the viscosity of distilled water (DW) with varying concentrations of aluminium oxide (Al₂O₃) nanoparticles (NPs). Al₂O₃ NPs were used in concentrations ranging from 0.02 to 0.5 wt%, while surfactant concentrations ranged from 2000 to 4000 ppm for SDS and SLS and from 200 to 600 ppm for RHL. Viscometric experiments revealed that the type and concentration of surfactants, along with the NP loading, influenced the viscosity of nanofluids (NFs). NFs without surfactant exhibited consistently higher viscosities compared with DW with surfactant alone. At 0.5 wt% Al₂O₃, NF viscosity was 17% higher than SDS and RHL and 9% higher than SLS. Interestingly, in DW with both surfactant and NPs, viscosity initially decreased with increasing Al₂O₃ concentration, followed by a rapid increase after 0.1 wt%. These results offer insights into the interaction between surfactants and NPs, relevant for industries requiring precise viscosity control, such as pharmaceuticals, cosmetics, and environmental applications.