Advanced Ionic Liquid as a Sustainable Demulsifier for Crude Oil Emulsions

This study evaluated an in-house-synthesized hydrocarbon-based ionic liquid (HBIL) for its potential as an environmentally friendly demulsifier for crude oil emulsions, specifically targeting applications in produced water treatment. The emulsions were formulated from different light oil and water blends, and the HBIL was tested using a bottle test method across a range of dosages (100–1000 ppm) and temperatures (25–90 °C) to assess its demulsification efficiency (DE). Additionally, the influence of monovalent salts (NaCl and KCl) and varying pH levels (acidic at pH 4 and 6 and alkaline at pH 9 and 11) on the separation efficiency was investigated. Experimental results indicated that DE improved with increasing temperature, with the optimum dosage of 300 ppm achieving 98% DE at 90 °C for emulsions derived from distilled water. In the presence of salts, the DE reached 99.8% (NaCl) and 99.7% (KCl) under similar conditions. In the acidic medium, the separation efficiency of HBIL was moderate, reaching a DE of 35% (at pH 6), while under alkaline conditions (pH 11), the HBIL demonstrated a significant increase in DE, reaching up to 83.3%, suggesting that a change in the emulsion pH could impact the separation performance in produced water. The HBIL showed an effective reduction in the emulsion viscosity, indicating its ability to adsorb and displace emulsifying agents. Images from the optical microscopic analysis illustrated the demulsification process stages, while interfacial viscoelasticity measurements provided insights into the adsorption kinetics and structural growth of asphaltenes at the oil–water interface. Interfacial tension values of various HBIL dosages remained within 18.15–21.55 mN/m, with the lowest value achieved at 300 ppm of HBIL. These findings suggest that HBIL holds promise as an alternative to conventional chemical demulsifiers, providing an efficient and potentially sustainable solution for produced water treatment in the petroleum industry.