Preparation of water-in-diesel oil nano-emulsion using nonionic surfactants with enhanced stability and flow properties

摘要

Formation of water-in-diesel oil (w/o) nano-emulsion has been achieved by a low-energy emulsification method by stabilizing a new combination of nonionic sorbitan esters surfactants, that is PEG20-sorbitan monostearate and sorbitan monooleate in mixed proportions. Different combinations of the surfactants (T6+S8) have been tested and the best possible combination of mixed surfactants is found at a surfactants ratio of 35:65 (wt/wt) for T6:S8 at hydrophile-lipophile balance (HLB)=8.01, which resulted in smaller droplet size of 44.87nm. A phase diagram study is performed to identify the zones of formation of transparent, translucent, and opaque emulsions (44nmdroplet size700nm). The mechanism responsible for the instability of emulsion is explained by Ostwald ripening, with inference describing a decrease in particle size with the Ostwald ripening rate. In case of nano-emulsion of droplet size 64.28nm, the Oswald ripening rate is found as 0.0874x10(-27)m(3)s(-1). Comparison of Ostwald ripening rate with other sets of surfactants obtained by different authors showed the lowest rate among them, indicative of enhanced stability. A rheological study of the tested set of nano-emulsions depicts the Newtonian behavior (1.0371n1.0826) over a wider range of shear rates (10-1000s(-1)) at different temperatures (25-40 degrees C).