Classification and Properties of Green Surfactants

Green surfactants, also known as eco-friendly surfactants or biodegradable surfactants, address the severe harms caused by traditional surfactants to human health and ecosystems during production and use. Adding surfactants to detergents enhances solubility and cleaning power, but their toxicity can irritate skin. Extensive use poses ecological risks; for instance, sodium alkylbenzene sulfonate (ABS) has poor biodegradability, leading to foam overflow in urban sewers and rivers; phosphate-containing surfactants cause eutrophication in water bodies; and the production of linear alkylbenzene sulfonate (LAS) generates sulfur dioxide and sulfur trioxide, while fatty alcohol ethoxylate sulfate (AES) products contain dioxane substances that are hard to biodegrade, posing significant environmental hazards.

To meet growing health demands and ensure sustainable human environments, developing green surfactants that are minimally toxic to humans and non-polluting to ecosystems is imperative.

Classification and Properties of Green Surfactants

Green surfactants refer to surfactants processed from natural or renewable resources, with low irritation to humans and easy biodegradability. Based on dissociation in water, green surfactants are divided into nonionic and ionic types. Ionic green surfactants are further classified by their active ions into cationic, anionic, and zwitterionic.

Green surfactants are derived from natural or renewable resources, featuring naturalness, mildness, and low irritation. Like traditional surfactants, they have hydrophilic and hydrophobic groups. Compared to conventional ones, green surfactants offer high-efficiency detergency, excellent compatibility, and good environmental compatibility, exhibiting superior emulsification, detergency, solubilization, wetting, solubility, and stability.

Additionally, each type of green surfactant has unique properties; for example, α-sulfo fatty acid ester salts (MES) show surface activity at low concentrations and hard water resistance, while monoalkyl phosphates (MAP) provide excellent foaming, emulsification, antistatic properties, and skin affinity. Common green surfactants include α-sulfo fatty acid methyl ester (MES), alkyl polyglucosides (APG), glucamides (APA), alcohol ether carboxylates (AEC), monoalkyl phosphates (MAP), and alkyl glucamides (MEGA).

Properties, Applications, and Current Status of Several Green Surfactants

Green surfactants possess naturalness, mildness, and low irritation. They feature hydrophilic and hydrophobic groups like traditional surfactants but surpass them in high-efficiency detergency, compatibility, and environmental compatibility, with excellent emulsification, detergency, solubilization, wetting, solubility, and stability.

Alkyl Polyglucosides (APG)

Alkyl polyglucosides (APG) are a new generation of environmentally friendly green surfactants, synthesized from natural or renewable raw materials like glucose from starch and fatty alcohols, yielding nonionic alkyl polyglycosides. They exhibit excellent foaming, low human irritation, easy biodegradability, low surface tension, good detergency, rich and fine foam, strong compatibility with any surfactant type for obvious synergistic effects, broad-spectrum antimicrobial activity, easy dilution without cloud point or gelation, user-friendliness, and strong alkali and salt resistance.

APG raw materials—oral glucose and fatty alcohols—are non-toxic and non-irritating, positioning them as replacements for traditional surfactants with broad application prospects. They are widely used in pesticide intermediates, detergents, cosmetics, food, medicine, firefighting, textiles, printing and dyeing, petroleum, and other industries.

Recent research highlights APG’s high biodegradability and low aquatic toxicity, making them ideal for enhanced oil recovery and other sustainable applications.

Fatty Acid Methyl Ester Sulfonates (MES)

MES represent a new generation of green surfactants, with research spanning half a century. Major detergent companies have invested heavily, praising MES for superior performance. Based on natural renewable resources, they are biodegradable and environmentally friendly. MES are mild, with lower irritation and toxicity to humans than LAS, comparable to AS and AES. They have no oral toxicity and are practically non-toxic to aquatic life. They offer good detergency, maintaining performance in cold and hard water, surpassing LAS and AS—especially in hard water, addressing LAS’s key weakness. Phosphorus-free, they outperform LAS without alkali or sodium tripolyphosphate, ideal for phosphorus-free/low-phosphorus eco-detergents.

Despite advantages, MES production has hovered around 20,000 tons annually, limited by production and formulation issues: deep color, easy hydrolysis during bleaching to poor-performing byproducts like disodium salts, poor thermal stability in alkaline aqueous conditions, and formulation difficulties.

Current studies focus on MES for enhanced chemical tasks, emphasizing functional groups for better performance in various environments.

Biodegradable Gemini Surfactants

Gemini surfactants feature a special molecular structure. Monomeric surfactants typically have one hydrophobic chain and one hydrophilic group, while Gemini surfactants have two (or three) hydrophobic chains, two hydrophilic groups, and a linker (near the hydrophilic groups), which can be hydrophilic or hydrophobic. Compared to monomers, Gemini surfactants boast superior properties: high surface activity; low Krafft point and good water solubility; higher efficiency in reducing water surface tension; stronger synergies in compounding with monomers; excellent calcium soap dispersion; stronger oil/water interfacial tension reduction; enhanced oil solubilization; and lower skin irritation.

Gemini surfactants excel among new products, but high costs limit industrialization to only two products currently.

Emerging trends include bio-based and ester-based Gemini surfactants for improved biodegradability, antimicrobial activity, and applications in personal care and environmental remediation.

For more on related products, visit Surfactants. Questions? Contact us. In summary, green surfactants like APG, MES, and biodegradable surfactants such as Gemini types continue to advance sustainability in industries, offering eco-friendly surfactants with minimal environmental impact.

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