The present study focuses on the synthesis of silicon dioxide nanoparticles (SiO2) using a green method, incorporating buckthorn leaves extract and potassium metasilicate (K2SiO3) as the precursor. A comprehensive characterization of the prepared nanoparticles was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and dynamic light scattering (DLS). The results confirmed the purity of the SiO2 nanoparticles and exhibited a range of diverse functional groups on their surface. Furthermore, the average size and surface area of the nanoparticles were determined to be 35.8 nm and 246 m2.g-1, respectively. These well-characterized SiO2 nanoparticles were employed as an effective adsorbent for the removal of bromophenol blue dye from aqueous solutions in a batch mode adsorption unit, under varying operating conditions. The factors considered for evaluating the efficiency of SiO2 nanoparticles as an adsorption media included pH, contact time, agitation speed, dye concentration, temperature, and the quantity of nanomaterial utilized. Experimental findings demonstrated a remarkable removal efficiency of 96% for bromophenol blue dye at an initial concentration of 100 ppm in the contaminated solution. Interestingly, the percentage removal exhibited an inverse relationship with dye concentration and temperature, while being directly proportional to other factors. Overall, the green-synthesized silicon dioxide nanoparticles proved to be a promising adsorbent for the effective removal of bromophenol blue dye from aqueous environments. The findings highlight the potential application of these nanoparticles in wastewater treatment and pollution mitigation, offering a sustainable and eco-friendly solution for environmental challenges