Hardness tolerance of anionic surfactants in the presence of nonionic surfactants

Dispersion and solubilization characteristics of calcium salts of anionic surfactants in the presence of various nonionic surfactants, such as TX-100 and some polyethylene oxide-polypropylene oxide-polyethylene oxide (EO/PO/EO) triblock copolymers were investigated by turbidimetry. For comparison, such systems were also studied in the presence of polyethylene oxides (PEOs). The calcium salts of anionic surfactants are insoluble in water and thus produce turbidity. They become soluble in the presence of nonionic surfactants. The addition of nonionic surfactants greatly enhances the solubility of Ca-salts of anionic surfactants. The triblock copolymers are more effective at increasing hardness tolerance than polyethylene oxide. An increase in the PEO chain of nonionic surfactants has a pronounced effect on the hardness tolerance of anionic surfactants. Mixed micelle formation is responsible for increased hardness tolerance in anionic surfactant solutions when a nonionic surfactant is added.