Screening of bio-based anionic surfactants for hand dishwashing liquid detergents

Formulations of hand dishwashing liquid detergents include various ingredients to ensure effective cleaning, foaming and overall product performance, with anionic surfactants serving as the primary agents for breaking up and removing dirt and grease. The increasing demand for eco-friendly products has pressured detergent formulations to enhance sustainability and competitiveness by synthesizing surfactants from low-cost, biorenewable raw materials. This study evaluates the potential use of sulfonated fatty acids derived from rapeseed oil as anionic biobased surfactants in hand dishwashing liquids. The study primarily focused on assessing their physical and chemical properties, such as surface tension and critical micelle concentration, as well as their performance in terms of detergency, foamability, and grease emulsification and stability. The effects of co-surfactants, the choice of alkaline solutions for fatty acid neutralization, and water hardness levels on surfactant properties and performance were also examined. The presence of unsulfonated free fatty acid impurities in biobased surfactants, fixed at 15%, negatively impacted their performance. This necessitated the evaluation of various purification techniques, including vacuum filtration, high-pressure filtration, liquid-liquid extraction, centrifugation, and precipitation using calcium counterions. Centrifugation emerged as the most effective purification strategy. Since the CatSO3 test could not be used to determine the surfactant content after centrifugation, and the free fatty acid analysis was not performed on the supernatant, the main limitation of the study was the assumption that centrifugation selectively removed free fatty acids from the surfactant solution without any surfactant loss. Although the addition of betaine co-surfactant to the biobased surfactant solutions resulted in minor performance improvements, the overall effectiveness was deemed unsatisfactory for use in hand dishwashing liquid detergents.