Distribution of Linear Alkylbenzene Sulfonate between Fabric and Liquor in Simulated Detergent Liquors

Adsorption characteristics of cotton, 65–35 polyester/cotton, and 100% polyester fabrics were measured by liquid scintillation counting using C ¹⁴ -labeled linear alkylbenzene sulfonate (LAS) as the surfactant. A detergent liquor composed of surfactant, builder, silicate, and hardness ions were used to simulate actual detergent formulations. The effects of water hardness, builder level, temperature, pH, and sulfate and silicate levels on the distribution of LAS between the fabric and the liquor phase were examined. A considerable portion of LAS was found to be adsorbed on the fabrics depending upon the kind of fabric. For a given fabric, hardness ion and builder level are determining factors for adsorption. Detergent builders influence the degree of surfactant adsorption depending on their ability to complex Ca ⁺⁺ and Mg ⁺⁺ . Permanent-press finishes were found to cause LAS adsorption to increase relative to corresponding unfinished fabrics. The rate of LAS adsorption under agitation was determined. The amount adsorbed was found to be linear against the logarithm of time. Adsorption “isotherms” were generated for 15-minute data.