Extraction and recovery of naphthenic acids from heavy crude oil using magnetically treated nanobubble water

Naphthenic acids (NAs) are among the most significant corrosive and environmentally persistent constituents in high-acid crude oils, posing major challenges in production, transportation, and refining processes. This study introduces an efficient ammonia-assisted extraction process utilizing magnetically treated nanobubble water (MTNW) for the simultaneous extraction and recovery of naphthenic acids from a high-TAN Iranian heavy crude oil (TAN = 1.34 mg KOH g⁻¹). Multistage liquid–liquid extraction was conducted under near-static conditions following brief initial dispersion, with the effect of magnetic conditioning systematically evaluated. The process integrates liquid–liquid extraction, gravity phase separation, acid regeneration, and product recovery. Extraction performance was quantified by total acid number (TAN) measurements, while the recovered naphthenic acids were thoroughly characterized using FT-IR spectroscopy and GC–MS analysis. A single extraction stage reduced the TAN from 1.34 to 0.22 mg KOH g⁻¹, achieving 83.5% acid removal. Three consecutive stages further lowered the TAN to 0.027 ± 0.004 mg KOH g⁻¹, corresponding to an overall deacidification efficiency of 98.0 ± 1.2%. Gravimetric recovery of the naphthenic acids reached 91.4 ± 3.8%. FT-IR and GC–MS analyses confirmed the successful isolation of petroleum-derived naphthenic acids, predominantly monocyclic and bicyclic species, with preservation of their characteristic molecular structures. The remarkable deacidification performance under low-energy, near-static conditions highlight the substantial role of nanobubbles in overcoming mass transfer limitations at the oil–water interface. Comparative experiments demonstrated that nanobubbles were the primary driver of enhanced extraction efficiency, while magnetic conditioning provided a modest but reproducible supplementary benefit. The proposed MTNW-based process offers a simple, energy-efficient, and scalable approach for the simultaneous deacidification of heavy crude oils and valorization of naphthenic acids, laying a strong foundation for continuous and pilot-scale applications.