Experimental screening and optimization of various dispersants for stable Fe2O3 nanoparticle suspensions

Muhammad Jawad Khan, Muhammad Jawad Khan, Syahrir Ridha, Numair Ahmad Siddique, Mian Umer Shafiq, Ali Samer Muhsan, Muhammad Umair Shahid, Muhammad Mohsin Yousufi

Energy Geoscience, 2026

Full text Open access: Gold Metadata (CSL-JSON)
DOI 10.1016/j.engeos.2026.100633
Data confidence 70 medium
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Abstract

Iron oxide nanoparticles are widely recognized for their magnetic properties; however, their dispersion stability in subsurface-relevant nanofluid systems can be affected by aggregation under high-ionic-strength reservoir conditions. Ensuring colloidal stability is therefore critical, yet selecting a suitable dispersant and formulation conditions remains challenging. This study establishes a dual-screening framework for identifying Fe 2 O 3 nanofluid systems with improved dispersion stability under controlled laboratory conditions. Four dispersants, including SDS, CTAB, Tween-80, and PVP, were comparatively evaluated by varying both dispersant chemistry and concentration. Stability was assessed using absorbance-based extractability index, sedimentation testing, Zeta potential measurement, Turbiscan analysis at elevated temperatures, and rheological characterization. Among the dispersants tested, PVP showed the most favorable overall stability, achieving the highest extractability index and dispersion stability index. During the 14-day static evaluation in saline media, minor to moderate visible sedimentation was observed, while macroscopic phase separation was not detected. During the 24-hour Turbiscan assessment at 80 °C, the optimized PVP-Fe 2 O 3 nanofluid showed Turbiscan stability index ( TSI ) of 19.59 in NaCl brine and 21.80 in synthetic reservoir brine, compared with 10.18 in deionized water. These values indicate a stronger but gradual destabilization response in saline media, but no abrupt aggregation or macroscopic phase separation during the test. Zeta potential analysis indicated that electrostatic repulsion alone could not account for the stability trend, particularly for PVP, whose improved stability was likely attributable to polymer-related steric effects. Rheological analysis showed Newtonian behavior at 30, 60, and 90 °C, with viscosity decreasing with increasing temperature. The results highlight the importance of considering both dispersant chemistry and concentration when screening Fe 2 O 3 nanofluid formulations, and serve as a foundation for further evaluation of porous-medium flow under representative geological storage conditions.