The utilization of cardanol, obtained from cashew nutshells, for the synthesis of renewable surfactants

Declining conventional reserves and rising energy demand are accelerating interest in chemical EOR and various other energy-process separations. To advance greener operations, this study focuses on the synthesis and characterization of a renewable (cardanol-based) surfactant focusing on promoting Green Enhanced Oil Recovery (GEOR) and its application on other fields. Advancing the use of natural surfactants in oil recovery and biofuel production is crucial for sustainable practices in the energy sector, also help drive down costs while also being more environmentally friendly. The increasing environmental concerns and the growing demand for sustainable alternatives to petroleum-based surfactants have driven the development of novel, eco-friendly surface-active agents. Bio-based surfactant derived from cardanol, a component of Cashew Nutshell Liquid (CNSL) which is an agro-industrial by-product. Cardanol, with its phenolic hydroxyl group and unsaturated aliphatic side chain, the molecular structure of a surfactant has a pronounced effect on the efficiency of their application in various processes. In this work, cardanol was sulfonated using sulfuric acid and oleum under controlled conditions to produce cardanol sulfonate, an anionic surfactant. A series of experiments were conducted to optimize sulfonation conditions, varying solvents, temperatures, and dosing times. Methanol was identified as the most suitable solvent, facilitating effective sulfonation and subsequent neutralization to yield a solid sodium cardanol sulfonate (CDS). FTIR spectroscopy confirmed the successful incorporation of sulfonate groups, with characteristic peaks observed for sulfonic acid group, phenolic O–H, and aromatic C=C stretches. The surface-active properties of the synthesized surfactant were evaluated by measuring surface tension at varying concentrations using the Wilhelmy plate method. The results indicated a significant reduction in surface tension with increasing surfactant concentration, with a clear inflection point corresponding to the Critical Micelle Concentration (CMC). The CMC of cardanol sulfonate was determined to be 0.029 g/L, which is comparable to several conventional surfactants, highlighting its efficiency in micelle formation. Overall, this research demonstrates the potential of cardanol as a sustainable raw material for the synthesis of high-performance surfactants. The study not only contributes to the advancement of green chemistry and circular economy principles but also supports the use of agricultural waste for environmentally benign industrial applications.