Capillary-Driven Dehydration of Heavy Oil Emulsions via Ropes

Conventional dehydration of heavy oil to meet pipeline specifications (<1% water) relies on complex, energy-intensive industrial processes. In contrast, this work demonstrates that a single sulfated cotton rope can achieve efficient, passive dehydration of heavy oil through tailored capillary action. Sulfation endowed the ropes with superhydrophilicity and underwater superoleophobicity, enabling selective water extraction while repelling the viscous oil. The dehydration efficiency was governed by the sulfation degree of the rope and the initial water content of the emulsion. Quantitative analysis revealed that ropes with a higher degree of substitution (DS) achieved significantly faster dehydration; for instance, a 10% water emulsion was completely dehydrated within 1 h using a high-DS rope, while a 30% emulsion needs 4 h. The process, characterized by distinct kinetic stages, is attributed to the synergistic effects of promoted droplet coalescence by the sulfated groups and rapid capillary transport. Furthermore, the ropes demonstrated excellent reusability after simple solvent cleaning, maintaining high performance over multiple cycles. This approach provides a sustainable and efficient pathway for heavy oil dehydration with near-zero external energy input.