Surface properties and coffee drop formation of natural surfactant: a case study of Albizia procera

Abstract Saponins are natural surfactants that are readily biodegradable, generally non-toxic to humans and environmentally friendly. In this work, the surface properties, coffee ring effect and characterisation of the extract of Albizia procera pod were studied. It showed good washing power and good soil or dirt dispersion and cleaned effectively at low surface tension. The extract is equivalent to commercial detergents, making it a viable biosurfactant. In addition to the critical micelle concentration, there is a lower concentration at which the surface tension curves flatten out. We have named this concentration “Minor Critical Micelle Concentration”. The surfactant also reduces the coffee ring effect of a drying droplet and provides a reasonably uniform distribution of suspended particles. This effect can be used to estimate the critical micelle concentration. The Fourier transform infrared spectrum of the extract shows the presence of the functional groups –OH, C–H, C=C and C–O–C, which are also found in saponins.