Hydrothermal synthesis, response surface study, and interfacial tension evaluation of modified nanotube

Abstract

Modification of pure Halloysite nanotube (pHNT) with organic and inorganic materials for various applications have been reported, but inadequately addressed in the area of enhanced oil recovery (EOR). This work for the first time employed Design-Expert Software tool to systematically modify the surface of the pHNT with Cerium and Silver nanoparticles to achieve optimum product yield; modified HNT (m-HNT). The influence of reactants on m-HNT yield were analysed via a Response Surface Methodology (RSM). Central composite design at 5-levels was deployed in determining the loading of the pHNT (1–5 g), Cerium Nitrate (Ce; 1–2 g) and Silver Nitrate (Ag; 0.5–2.5 g). The synthesis was accomplished by a Hydrothermal reflux method using a Teflon-lined Stainless-Steel Autoclave. The FTIR, FESEM, XRD and TGA were used to characterize the m-HNT. Subsequently, a spinning drop equipment was used to investigate the interfacial tension (IFT) reduction effect of the optimized m-HNT at different concentrations in comparison with the pHNT. Results have shown that the surface modification was successful after establishing improvements in terms of wave numbers, crystallography, morphology, and thermal stability in the m-HNT. In RSM analysis, the ANOVA demonstrates an adequate R2 of 99.5 %, signifying good data correlation. Thus, each of the pHNT, Ce and Ag is significant to the m-HNT yield (P < 0.05). At optimum conditions, experimental yield was found to be 92.4 % against the model predicted the yield of 94.7 %. Consequently, at this condition, the formulation of the m-HNT had reduced the IFT of the baseline brine/oil system from 9.2 ± 1.1 mN/m to a range of 0.043–0.052 mN/m at 100 to 500 ppm. Moreover, in comparison with the pHNT, about 17 to 41 % reduction effects were achieved by m-HNT at different concentrations. The study reveals that modifying the pHNT with Ce/Ag could improve its chemical properties and significantly offers good IFT reduction effect as parts of prerequisite conditions in enhanced oil recovery (EOR).