Pickering emulsions of ZIF-67 with excellent H₂S scavenging capability and other characteristics

The growing demand for energy and declining oil reservoir accessibility necessitate innovative oilfield technologies. Pickering emulsions, stabilized by nanoparticles (NPs), offer a promising route to enhance emulsion stability. Among potential stabilizers, ZIF-67 NPs present an attractive option due to their high surface area and chemical reactivity. However, studies on ZIF-67-stabilized Pickering emulsions remain limited. More importantly, the application of any Pickering emulsion, regardless of the stabilizing NPs, for H₂S mitigation has not yet been explored, to the best of our knowledge. Therefore, this study formulates diesel-in-water Pickering emulsions using ZIF-67 NPs and Tween 40, aiming to enhance both emulsion stability and H₂S scavenging capability. Emulsions were prepared with 0.5 wt% Tween 40, 0.15 wt% antifoam, and varying ZIF-67 concentrations (0.1–1.5 wt%). The synthesized ZIF-67 was characterized by XRD, FTIR, SEM, TEM, HRTEM, EDS, and TGA, while the Pickering emulsion properties were evaluated through long-term stability, zeta potential, droplet size distribution, dynamic interfacial tension, optical microscopy, and rheology. The findings of this study revealed that the Pickering emulsion stability improved at low NP loadings, but declined at higher concentrations due to aggregation. Rheological data, on the other hand, revealed shear-thinning behavior at 1.5 wt%, with increased viscosity and network formation. Additionally, H₂S scavenging tests showed that ZIF-67 emulsions achieved exceptional breakthrough capacities, reaching 9207.7 mg/L (671.53 mg/g ZIF-67) at 1.5 wt%, significantly outperforming all known commercial scavengers, to the best of our knowledge. Post-scavenging FTIR and XRD analyses confirmed the formation of Co-S bonds, sulfur–oxygen intermediates, and amorphous or mixed cobalt sulfide species, supporting a chemisorption mechanism.To the best of our knowledge, this is the first study on ZIF-67-based Pickering emulsions for H₂S mitigation. The system offers dual functionality (enhanced emulsion stability and efficient H₂S removal), highlighting its potential for oilfield applications.