The Application of surfactants in engineering

Surfactants serve as "industrial magicians" in modern engineering fields. By enabling directional alignment at interfaces (gas-liquid, liquid-liquid, solid-liquid) and altering their properties, they address numerous critical technical challenges. Below are the core applications of surfactants in several key engineering domains:

---Energy engineering

  This is one of the most widely used and economically valuable fields of surfactants.

1. improving oil recovery：

  · Three-stage oil recovery (chemical flooding): Surfactants, as the core of the flooding agent, can significantly reduce the interfacial tension between crude oil and injected water (down to the 10⁻³ mN/m level), enabling the deformation and flow of residual oil droplets "locked" in the formation capillaries to be expelled. This is the key technology for extracting 60%-70% of crude oil remaining after water flooding.   

· Emulsification viscosity reduction: For heavy and extra-heavy oil, surfactants can emulsify them into oil-in-water emulsions, reducing viscosity by hundreds to thousands of times, facilitating pipeline transportation.

  · Change the rock wettability: change the surface of the reservoir rock from oil-wetting to water-wetting, which is beneficial to water displacement of crude oil.

2. Oil and Gas Production and Gathering：

  · Fracturing/acidizing fluids: Functioning as proppant additives, they reduce interfacial tension between construction fluids and reservoir rock, facilitating rapid fluid drainage post-operation and minimizing formation damage.   

 · Demulsification and dehydration: During crude oil extraction, stable W/O emulsions form. Specialized reverse-phase demulsifiers (surfactants) are required to disrupt the interfacial film, enabling oil-water separation.

  · Clear wax preventive: The surfactant can form a polar film on the surface of pipes and tubing, inhibiting the deposition and adhesion of paraffin crystals.

3.  New energy ：

   · Fuel cell: In proton exchange membrane fuel cells, the preparation of the catalytic layer and gas diffusion layer is used to improve the dispersion of catalysts (such as platinum) and the formation of the three-phase reaction interface.   

   · lithium battery: Used as a dispersant in electrode slurry preparation to ensure uniform distribution of active material, conductive agent, and binder; also applicable as an electrolyte additive.

-----Materials and Chemical Engineering

1. synthesis of nanomaterials：

   · Template agent: In the synthesis of mesoporous materials (e.g., MCM-41, SBA-15), micelles formed by surfactant self-assembly serve as "soft templates" to precisely control the size and structure of the pores.   

      ·Morphology control agents and stabilizers: During the preparation of metal and metal oxide nanoparticles, they adsorb on specific crystal surfaces to regulate the growth direction and rate, thereby obtaining special morphologies such as nanorods, nanosheets, and nanocubes, while preventing particle aggregation.

2. Polymer and Composite Materials：

   · Emulsion polymerization: As an emulsifier, hydrophobic monomers are dispersed in water to form micelles, where the polymerization reaction occurs. This process is a core technology for producing synthetic rubber (e.g., SBR), coatings, adhesives, and other materials.

   · Composite interface modification: Surface treatment of fillers (e.g., carbon nanotubes, graphene, glass fibers) to enhance their compatibility and adhesion with the polymer matrix.

------Environment engineering 

1. Soil and Groundwater Remediation：

   ·Enhanced elution technology: Using surfactant solutions to flush contaminated soil with organic pollutants (e.g., oils, polychlorinated biphenyls (PCBs), pesticides), the solubilization and emulsification effects effectively release pollutants adsorbed on soil particles, significantly improving remediation efficiency.

2.  Effluent treatment：

   · The flotation method: as the collector and foaming agent, the hydrophobic pollutant particles adhere to the bubbles and float up to separate.

   · Defoaming and foam suppression: controlling harmful foam in industrial wastewater treatment.

-------Biomedical Engineering

1. Drug delivery system ：

  ·Carrier: Amphiphilic molecules such as phospholipids and cholesterol serve as the foundation for drug carriers like liposomes and nanomicrospheres. They can encapsulate hydrophilic or hydrophobic drugs, enabling targeted delivery, sustained release, and controlled release.

   · Solubilization: Solubilization of poorly soluble drugs (e.g., the anticancer agent paclitaxel) to enhance their bioavailability.

2.  Bioseparation：

   · Bifacial phase extraction: Utilizing surfactants and polymers to form a bifacial phase system, it gently and efficiently separates biomacromolecules such as proteins, enzymes, and nucleic acids.   

  · Cell lysis: Certain surfactants can dissolve the cell membrane, releasing intracellular products.

------Advanced Manufacturing and Microelectronics

1. precision cleaning：

   · Semiconductor wafer cleaning: In chip manufacturing, this process removes particles, organic photoresist residues, and metal ion contaminants from silicon wafer surfaces, requiring ultra-high purity and minimal metal impurities.

2.coatings, inks and coatings：

   · Wetting and leveling: Added to paints, inks, and coatings to reduce surface tension, enabling uniform spread on substrates and preventing defects such as shrinkage cavities and orange peel.   

  ·Dispersion: Maintain stable dispersion of pigments and fillers in the system to prevent sedimentation.

------- Construction engineering 

1. concrete additive：

   ·Air-entraining agent: A typical surfactant (e.g., rosin soap). It introduces a large number of uniform and stable microbubbles during concrete mixing, significantly enhancing the freeze-thaw cycle resistance of concrete. This is an essential component for high-performance concrete in cold regions.

   · Water-reducing agent: Although most of the modern high-efficiency water-reducing agents are polymers, their mechanism of action also involves surface adsorption and dispersion, which can reduce the mixing water consumption and improve the strength and durability of concrete.

Summary of Core Mechanisms

 The ability of surfactants to play pivotal roles across these diverse domains stems from their amphiphilic molecular structure and the core functionalities derived from it:

· Reducing interfacial tension: This is fundamental to all applications, including enhanced oil recovery and wetting/spread enhancement.

·Emulsification, demulsification, and foaming/desurfacing: achieved by stabilizing or disrupting the interfacial membrane (e.g., crude oil dehydration, emulsion polymerization, air flotation, concrete air entrainment).

· Solubilization: Encapsulation of insoluble substances into micelles (e.g., drug solubilization, soil elution).

· Dispersion and Aggregation: Achieved by altering the surface properties of particles (e.g., nanomaterial synthesis, pigment dispersion, wastewater flocculation).

· Formation of ordered molecular assemblies: as templates or building blocks (e.g., mesoporous materials, drug carriers).

 Future development trends focus on: greening (biobased, biodegradable surfactants), intelligence (stimulus-responsive types such as pH, temperature, and light-sensitive), high-efficiency specialization (for extreme conditions like high-temperature/high-salt reservoirs or special interface design), and the deepening of multifunctional compounding technologies.

In a word, surfactants have penetrated into the main artery of modern engineering technology, such as energy, material, environment, biomedicine, etc.