Influence of size and surface charge on the adsorption behaviour of silicon dioxide nanoparticles on sand particles

The use of silicon dioxide (SiO2) nanoparticles as additives and filter materials in the oil and gas industry for mitigating sand control and fines migration problems has garnered significant attention in recent years. Despite the growing interest, the effect of size and surface charge on the adsorption behaviour of silicon dioxide nanoparticles on sand particles remains inadequately studied. This study aimed to address this knowledge gap by investigating the influence of size and surface charge on the adsorption isotherm of silicon dioxide nanoparticles onto sand particles. The SiO2 nanoparticles were synthesized using the sol-gel method into three different sizes (30, 70, and 120 nm), effectively providing different reactive surface areas, which were confirmed through the use of Dynamic Light Scattering (DLS) and Brunauer-Emmett-Teller (BET). The surface charge of the silicon dioxide was altered by functionalizing into a negatively charged carboxyl group and a positively charged quaternary ammonium group which was confirmed using Fourier-transform infrared (FTIR) spectroscopy and zeta potential. Ultraviolet-visible (UV-vis) spectroscopy was used to determine the concentration of adsorbed nanoparticles in solutions with different ionic strength and electrolyte type. Data analysis involved regression models, ANOVA, and t-tests. The adsorption isotherm was best fitted by the Langmuir model, indicating monolayer adsorption. The result indicates that SiO2 size, SiO2 concentration, and SiO2 charge levels significantly affect adsorption behaviour, whereas electrolyte type and electrolyte concentration do not have a significant effect. Smaller nanoparticles exhibited higher adsorption capacity, and positively charged nano particles displayed greater affinity for adsorption. The presence of electrolyte and its concentration although statistically insignificant, had a negative impact on the electrostatic interactions. This study provides insights into the effect of size and surface charge on nanoparticle adsorption of nanoparticles onto sand particles, contributing to the field of sand control and fines migration.