ORIGINAL ARTICLE Drag Reduction by Wormlike Micelles of a Biodegradable and Non-Biodegradable Surfactants Roberta K. Rodrigues 1 · Lucas A. S. Silva 2 · Gabriel G. Vargas 3 · Bruno V. Loureiro 3 Received: 6 February 2019 / Revised: 15 July 2019 / Accepted: 26 August 2019 © 2019 AOCS Abstract This study describes the effects of wormlike micelles formed by the commercial surfactants tallowalky- lamidopropyl dimethylamine oxide (Aromox APA-TW) and oleyl methyl bis(2-hydroxyethyl) ammonium chloride (Ethoquad O/12) as drag reducers. Ethoquad O/12 is immune to degradation by heat and microorganisms. Con- versely, Aromox APA-TW is biodegradable in the environ- ment, and its susceptibility to heat-induced degradation was previously assessed. This work considers the effects of tem- perature, salt, and time on the drag-reduction capacity (in different Reynolds number) of wormlike micelles of these two surfactants. Wormlike micelles formed by Aromox APA-TW are able to reduce drag at higher temper- atures compared to wormlike micelles formed by Ethoquad O/12. However, Aromox APA-TW can degrade after being heated to 80  C and also after storage of the worm- like micelle solutions. Ethoquad O/12 does not undergo degradation after being heated or stored. These surfactants have the potential to be used as additives in industrial operations, as the wormlike micelles formed are able to reduce drag in systems with long pumping distances or recirculation, even in solutions with high salt concentra- tions (brine) and high temperatures. Keywords Quaternary ammonium surfactant  Biodegradable surfactant  Wormlike micelles  Drag reduction J Surfact Deterg (2019). Introduction Small amounts of additives (usually polymers with a high molar mass) can reduce the energy required to pump a fluid (Bailey and Koleske, 1976; Toms, 1948). This effect is com- monly called drag reduction. The phenomenon of drag reduc- tion by polymer injection was demonstrated by Toms in 1948 (Toms, 1948) when an oil containing a small amount of a high molecular weight polymer showed less resistance to flow than pure oil (Leuchtag, 1978; Shenoy, 1984). A physi- cochemical approach to drag reduction is interesting; how- ever, it is necessary to consider that little about the phenomenon is understood. Hypotheses fundamentally sug- gest that macromolecules interfere in the production, devel- opment, or transport of turbulence. The main models can be segregated according to approaches related to length, time, and energy scales (Morgan and McCormick, 1990). Polymers have been widely used as drag reducers due to their high availability and low cost, as only a tiny amount is needed to obtain high rates of drag reduction (Hoyt, 1966; Kenis, 1971; Kulicke et al., 1989). Therefore, polymers may exhibit low efficiencies in systems with fluid recirculation or long pumping distances. Thus, the technical and economic feasi- bility of using polymers as drag reducers needs to be evalu- ated in certain cases (Campolo et al., 2015). One alternative to using drag reducers in systems with long pumping distances or recirculation is to use surfactants * Roberta K. Rodrigues rkamei@esp.puc-rio.br 1 Department of Mechanical Engineering, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, RJ 22451-900, Brazil 2 Transport Phenomena Laboratory, UCL – Faculdade do Centro Leste, Serra, ES 29164-050, Brazil 3 Department of Mechanical Engineering, Technological Center, Federal University of Espírito Santo, Vitória, ES 29075-910, Brazil J Surfact Deterg (2019) J Surfact Deterg (2019) DOI 10.1002/jsde.12354