Enhanced CO2 Storage in Saline Formations via Dual-Function Amine-Functionalized SiO2 Nanoparticles: Coupled Control of Solubility and Interfacial Tension

Abstract

Enhancing CO2 solubility while reducing CO2-brine interfacial tension (IFT) is a key factor for improving the efficiency of geological CO2 storage in saline aquifers. This study systematically investigated the combined effects of pressure (6.21–13.79 MPa), salinity (10,000–43,000 ppm), and amine-functionalized SiO2 nanoparticle concentration (100–1500 ppm) on CO2 solubility and CO2-brine IFT at 60 °C using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). CO2 solubility was measured using the volumetric expansion method, while IFT was determined using the pendant-drop technique. Quadratic regression models exhibited excellent predictive performance for both responses. Increasing pressure enhanced CO2 solubility and reduced IFT, whereas increasing salinity decreased CO2 solubility and increased IFT. The addition of amine-functionalized SiO2 nanoparticles significantly improved both responses. Under the optimum conditions (12.07 MPa, 25,577 ppm salinity, and 930 ppm nanoparticles), CO2 solubility increased from 1.28 ± 0.06 to 1.86 ± 0.09 mol kg–1 (45% increase), while IFT decreased from 24.94 ± 0.77 to 16.05 ± 0.22 mN m–1 (36% reduction) compared with the base brine system. The experimental data showed excellent repeatability, with coefficients of variation below 5%, and uncertainty analysis confirmed the reliability of the measurement procedures. These findings demonstrate that amine-functionalized SiO2 nanoparticles can simultaneously enhance CO2 dissolution and reduce CO2-brine IFT, offering a promising strategy for improving CO2 injectivity, storage capacity, and long-term storage security in saline aquifers.