Unveiling the Chemistry of Surfactants: How Soaps and Detergents Work

Liquid soaps, detergents, degreasers and disinfectants or antimicrobials all contain surfactants, a common cleaning agent. These versatile compounds play a pivotal role in removing dirt, grime, and grease from surfaces, making them essential ingredients in soaps, detergents and disinfectants. But what exactly are surfactants, and how do they achieve such remarkable cleaning prowess?

Surfactants Found in Your Home & in Industrial Cleaners

In households worldwide, a plethora of surfactants and disinfectants are within the cleaning products we use daily, each tailored to tackle specific cleaning challenges. From the ubiquitous sodium lauryl sulfates (SLS) found in liquid soaps, dish soaps and shampoos to the gentle alkyl polyglucosides (APGs) prevalent in eco-friendly cleaners, a diverse array of surfactants populate our cleaning arsenal.

Cationic surfactants (identified by their molecular structure) like benzalkonium chlorides (BACs) dominate disinfectants and fabric softeners, while nonionic surfactants such as ethoxylated alcohols excel in laundry detergents, offering excellent stain removal without compromising fabric integrity. Meanwhile, amphoteric surfactants like cocamidopropyl betaine (CAPB) strike a delicate balance, contributing to the mildness and foaming properties of personal care products. These surfactants, with their varying properties and functionalities, combine forces to deliver effective cleaning solutions tailored to our diverse household needs.

Quaternary ammonium compounds (QACs), also known as quats, are widely used as disinfectants, antiseptics, and surfactants due to their excellent antimicrobial properties and detergent action. Quaternary ammonium compounds or QACs disrupt microbial cell membranes, leading to the inactivation of bacteria, viruses, and fungi. Their surfactant properties make them effective in cleaning surfaces by lowering surface tension and facilitating the removal of dirt and grime. QACs are commonly found in household disinfectants, hand sanitizers, fabric softeners, and personal care products, making them versatile compounds in various industrial and domestic applications.

• Sodium lauryl sulfates (SLS)
• Alkyl polyglucosides (APGs)
• Benzalkonium chlorides (BACs)
• Ethoxylated alcohols
• Cocamidopropyl betaine (CAPB)
• Quaternary ammonium compounds (QACs)

Understanding Surfactants: The Building Blocks of Cleanliness

Surfactants, short for surface-active agents, are molecules with a unique structure that enables them to interact with both water and oil-based substances. At their core, surfactants consist of a hydrophobic (water-repelling) tail and a hydrophilic (water-attracting) head. This distinctive arrangement allows surfactants to bridge the gap between water and oily substances, facilitating their removal from surfaces.

At a molecular level, surfactants resemble tiny magnets, with one end attracting water molecules and the other end repelling them. This duality gives surfactants their remarkable ability to disrupt the cohesion of oil and grease, effectively lifting them away from surfaces.

The hydrophobic tail of a surfactant seeks out oily substances, such as dirt and grease, while the hydrophilic head interacts with water molecules, forming micelles—clusters of surfactant molecules surrounded by water. These micelles encapsulate the oily particles, allowing them to be dispersed and washed away.

Water and Surfactants

When liquid soaps or detergents like sodium lauryl sulfates (SLS) are applied to a surface, surfactant molecules spring into action, forming a thin layer over the dirt and grease. This layer, known as a micelle, traps the oily particles within its core, effectively isolating them from the surface.

As water is introduced, it surrounds the micelles, creating a suspension of soapy water that carries the trapped dirt and grease away. This process, known as emulsification, enables surfactants to dissolve and disperse even the toughest stains, leaving surfaces clean. The effectiveness of surfactants lies in their ability to break the bonds between oil and water molecules, allowing for effortless removal of dirt and grease.

Challenges in Wastewater Treatment with Increased Surfactants

The exponential increase in our daily reliance on cleaning and personal care products has led to a surge in surfactant usage, resulting in higher concentrations of these compounds in wastewater. This trend is not limited to households (commonly found in sodium lauryl sulfates in liquid soaps) but extends to industrial settings, where stringent cleaning and disinfecting procedures are commonplace. The widespread adoption of cleaning chemicals like quaternary ammonium compounds (QACs), benzalkonium chloride (BACs) and other disinfectants in various industries, including healthcare, hospitality, and food processing, has further exacerbated the issue.

As a result, wastewater streams now carry elevated levels of surfactants, posing significant challenges for wastewater treatment facilities. The influx of surfactants not only strains the capacity of treatment plants but also disrupts critical processes, leading to reduced treatment efficiency and increased operational costs. Addressing this growing concern requires collaborative efforts to develop sustainable practices, innovative technologies, and stringent regulations to mitigate the adverse effects of surfactants on wastewater treatment and environmental health.

Effects of Surfactants on Wastewater Treatment

Surfactants, notably sodium lauryl sulfates and quaternary ammonium compounds (e.g. benzalkonium chloride), pose significant challenges to wastewater treatment processes due to their multifaceted inhibitory effects and interactions within the treatment system.

Firstly, surfactants can disrupt biological processes by inhibiting the growth and activity of beneficial bacteria responsible for breaking down organic matter. This inhibition can lead to reduced treatment efficiency and the accumulation of organic compounds in the water. Additionally, surfactants can form stable emulsions with fats, oils, and grease (FOG), making them more difficult to separate and remove from wastewater. These emulsions can contribute to the formation of fatbergs and clog sewer systems, causing operational issues and potential environmental hazards. Moreover, certain surfactants possess antimicrobial properties, which, while effective for cleaning and disinfection purposes, can also harm the essential microbial communities involved in wastewater treatment processes.

As a result, the presence of surfactants in wastewater can compromise treatment performance, increase operational costs, and pose challenges for maintaining regulatory compliance.

Viable solutions to these inhibitory effects are now possible with Moleaer's technology, a chemical-free way to combat surfactants and solve complex wastewater treatment challenges while reducing costs.