Biomass-derived surfactant to improve salt tolerance potential of ZnO nanofluid for wettability alteration and surface adsorption in porous media

This study investigates the preparation and characterization of two distinct nanofluids (NF1 and NF2) with varying particle sizes (500 nm and 700 nm respectively), focusing on the impact of salinity and natural surfactants on their stability and interaction with porous media. Single-step nanofluid synthesis was employed to minimize agglomeration and enhance dispersion. The nanofluids were subjected to different salinity conditions (6000 and 17,000 ppm) to explore their adsorption behavior and stability in the presence of sand, simulating subsurface environments. The role of natural surfactant was explored by introducing them at three different concentrations (0.1, 0.2, and 0.3 wt%), and their influence on nanofluid behavior was analyzed through UV–Vis spectroscopy. Contact angle measurements were performed to assess wettability changes, and electrical conductivity studies were conducted to examine ionic interactions within the system. NF1 demonstrated better salt tolerance than NF2, retaining higher absorbance values even at elevated salinity (17,000 ppm NaCl). The addition of a biomass-derived natural surfactant substantially improved nanofluid stability and adsorption behavior, especially beyond the critical micelle concentration, by enhancing nanoparticle dispersion in saline environments. In addition, NF1 showed a greater increase in absorbance with increasing surfactant concentration compared to NF2, reflecting stronger surfactant-nanoparticle interactions and reduced aggregation. The findings demonstrate that incorporation of natural surfactants significantly enhances nanofluid stability, reduces aggregation, and improves performance in saline environments. This work provides new insights into the potential of sustainable, biomass-derived surfactants for stabilizing nanofluids in high-salinity conditions, offering a more eco-friendly approach for applications in enhanced oil recovery, environmental remediation, and other fluid-based technologies. • ZnO nanofluids (500 nm and 700 nm) were synthesized via a single-step method and tested in saline conditions. • Smaller particles (NF1) showed better stability and higher zeta potential than larger ones (NF2). • Natural surfactant improved nanofluid dispersion and adsorption, especially above CMC. • NF1 enhanced water-wetness and showed higher conductivity under all conditions. • Findings support potential use in EOR, CO 2 storage, and geothermal systems.