Carbon nanospheres decorated Fe3O4@SiO2@chitosan as new demulsifier for water-in-crude oil emulsion separation and magnetic collector for oil spills

The occurrence of water-in-crude oil emulsions during petroleum production is a critical operational challenge, leading to equipment corrosion and reduced processing efficiency. Simultaneously, accidental oil spills pose serious hazards that necessitate efficient remediation strategies. To address the two issues, novel magnetic demulsifiers based on carbon nanospheres (CNs) coated with chitosan and silica were hydrothermally synthesized, and characterized using various spectroscopic techniques. The prepared demulsifiers designated as Fe3O4@CNs, Fe3O4@SiO₂@CNs, Fe3O4@CS@CNs, and Fe3O4@SiO₂@CS@CNs were engineered to synergistically integrate magnetic responsiveness, surface activity, and interfacial affinity for both oil and water phases. Magnetization saturation measurements confirmed their suitability for magnetic recovery. Surface chemistry analysis revealed that the demulsifiers possess a negative surface charge within the investigated pH range (4–8). The incorporation of chitosan and silica effectively tuned their wettability characteristics, rendering them efficient breakers for W/O emulsion and magnetic collectors for oil spills. The prepared demulsifiers significantly reduced the dynamic interfacial tension (IFT) of water/oil systems within the initial seconds after demulsifier injection. They can achieve 100% DE (demulsion efficiency) at relatively low dosages (600–800 ppm), temperatures of 50–70 °C, pH 4–7, and settling times of 30–35 min. Moreover, the demulsifiers demonstrated excellent reusability for at least eight cycles. Under saline conditions, DEs reached 86.6% for Fe₃O₄@CNs and 97.3% for Fe₃O₄@SiO₂@CS@CNs. The prepared demulsifiers show rapid and effective magnetic collection for oil spills from oily wastewater. Overall, the developed magnetically recoverable and environmentally friendly demulsifiers provide an efficient solution for breaking W/O emulsions and absorber for oil spills.