Caryocar brasiliense Cambess (pequi) is the fruit of the pequizeiro tree found in the Brazilian Cerrado (savanna). Supercritical fluids have been used to effectively extract bioactive chemicals. In light of the paucity of research on the supercritical extraction of pequi, in this study, experimental tests were conducted on the extraction of pequi almond oil using supercritical CO_2; the optimal extraction conditions were determined, and the fatty acids and active compounds in the oil were characterized. The experiments were conducted using the Box–Behnken experimental design of a three-variable system: pressure (15, 20, and 25 MPa), temperature (303.15, 318.15, and 333.15 K), and flow rate (2, 3, and 5 g.min⁻¹). The optimal extraction conditions were 318.15 K, 25 MPa, and 5.0 g.min⁻¹, which yielded 27.6 wt% of oil. The experimental kinetic curves were described using a second-order quadratic model (based on the Sovová model), which demonstrated a satisfactory correspondence with the kinetic curves. Significant amounts of squalene, stigmasterol, oleic fatty acids, and palmitic fatty acids were detected in pequi almond oil.

Nanoparticle applications, such as iron oxides, have advanced in recent years and offer numerous advantages. These include ease of synthesis, magnetism, low toxicity, high adsorption capacity, and affordability. Their magnetic properties make them a promising choice as adsorbents for drugs, pollutants, dyes, oils, and microplastics, simplifying material transport and facilitating recovery from the environment. Water treatment using nanostructured iron oxides is a promising approach for efficient oil removal due to its operational simplicity, low cost, and high oxide removal and recovery efficiency. Since the international use of fuels involves transportation by sea, road, rail or pipeline, and potential spills of these fuels into the environment are difficult to remediate, this study aimed to confirm the effectiveness of the remediation process by adsorbing Brazilian commercial diesel (B8) containing 8% biodiesel and pure biodiesel (B100) on the adsorbent iron oxide, magnetite (Fe3O4). The study investigated the adsorption potential of biodiesel and diesel on iron oxide using Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). The results indicate that biodiesel has a greater affinity for iron oxide compared to diesel. Specifically, magnetite exhibited a maximum adsorption capacity of 25.65% for biodiesel on a solid mass basis. When present with diesel, magnetite adsorbed 16.08% relative to its own mass. The adsorbent can potentially be used for the treatment of fuel-contaminated water.