Demulsification and Coalescence Technology: Principles and Applications for Efficient Oil-Water Separation

In industrial wastewater treatment, petroleum extraction, machining, and related sectors, emulsified oil presents a frequent and persistent challenge. These are oils dispersed in water as microscopic droplets (typically 0.1–10 μm in diameter) , forming a stable, homogeneous mixture that is difficult to separate. This "oil-in-water" state not only complicates treatment processes and increases environmental compliance pressures but also leads to the loss of recoverable oil resources.

So, how can we achieve efficient and economical separation of emulsified oil?The answer lies in demulsification and coalescence technology—it has emerged as a key solution to this pervasive industrial problem.

Understanding Emulsified Oils and Separation Challenges

Emulsified oils are generally categorized into two types: mechanical emulsification and chemical emulsification.

Mechanical Emulsification: Caused by intense physical shear forces during the process such as pumping, mixing, or agitation.

Chemical Emulsification: Occurring when surfactants or emulsifying agents are present, forming a stable interfacial film around oil droplets that prevents coalescence and phase separation.

Due to the extremely high stability of emulsified oils, traditional methods such as settling, centrifugation, and filtration often have limited effectiveness. In such cases, chemical or physical demulsification methods must be employed to disrupt their equilibrium state.

Principle of Demulsification and Coalescence Technology

Demulsification and coalescence technology is a highly efficient separation method that combines materials science and fluid mechanics. Its core lies in using fiber materials with specific functions to achieve oil-water separation through a two-step strategy of "demulsification first, then coalescence".

1.Demulsification Stage:

A composite membrane composed of both hydrophilic and oleophobic bifunctional materials is used. When the emulsion flows through, the aqueous phase is attracted to the hydrophilic portion, while the oil phase is retained. The original interfacial membrane is disrupted, and the emulsion state is broken.

2.Coalescing Stage:

The released tiny oil droplets then interact with the hydrophilic and oleophobic fibers in the membrane. They collide and merge on the micro-surfaces of these fibers, gradually coalescing into larger droplets. This process is called "coarse-grained coalescence." When the oil droplets are large enough, they float to the surface due to buoyancy, thus achieving separation.

Types of Emulsified Oil Separation Membranes

Depending on the emulsion characteristics—such as oil-to-water ratio and emulsification mechanism—emulsified oil separation membranes are optimized into two primary configurations:

Oil-in-Water (O/W) Separation Membranes: Designed for wastewater with low oil content (e.g., industrial wastewater, oily stormwater).

Water-in-Oil (W/O) Separation Membranes: Used for oily wastewater with trace water (e.g., lubricant dehydration, fuel purification).

Though material composition and pore architecture may differ, both membrane types operate on the same core principle: synergistic demulsification followed by efficient coalescence.

Practical Application: Case Example

Our company’s ZJYS-XX Oil-Water Separator is specifically engineered to treat mechanically emulsified oils. Through multi-stage demulsification and coalescence filter elements, it achieves efficient, continuous, and automatic oil-water separation. This technology is already deployed across maritime, petrochemical, and precision machining industries, delivering consistent performance and reduced operational footprint.

Technological Advantages and Future Outlook

Demulsification and coalescence technology offers several distinct benefits:

• Chemical-free operation, supporting sustainable and environmentally benign processing

• Low energy consumption and operational costs

• High separation efficiency and throughput

• Adaptability to varying feed conditions and emulsion types

With the development of new materials (such as graphene and nanofibers) and intelligent control technologies, demulsification and coalescence technology will become even more precise. Future systems may even feature emulsion-type recognition and self-optimizing operation, positioning demulsification and coalescence as a cornerstone technology in advanced industrial fluid management.

Conclusion

Emulsified oil treatment is no longer an insurmountable barrier to industrial sustainability. Through ingenious material design and structural optimization, demulsification and coalescence technology makes the seemingly impossible "oil-water separation" simple and efficient. This innovation stands as a testament to the convergence of materials science and environmental engineering, and an important support for the future development of green industry.

To explore how this technology can be tailored to your specific application, please contact our engineering team for a technical consultation.Follow us for more insights into industrial environmental protection and separation technologies!