Abstract:
Soap scum can be removed by using an appropriate surfactant with a chelating agent. However, ethylenediaminetetraacetic acid (EDTA), one of the most widely used chelating agents has low biodegradability and is suspected to be toxic to aquatic life. The purpose of this research was to investigate an approach to dissolve different types of soap scum by using different surfactants with various biodegradable chelating agents. The solubilities of two soap scum (calcium stearate, Ca(C₁₈)₂ and magnesium stearate, Mg(C₁₈)₂) were investigated at various solution pHs (from 4 to 11) and different types of surfactants: methyl ester sulfonate (MES) as an anionic surfactant, alcohol ethoxylate with 9 ethylene oxide groups (EO9) as a nonionic surfactant, and dimethyldodecylamine oxice (DDAO) as an amphoteric surfactant in the presence of different biodegradable chelating agents: ethylenediaminedisuccinic acid (EDDS) and glutamatediacetic acid (GLDA). The highest equilibrium solubility of any soap scum was observed at a pH of 11 with DDAO and GLDA. In addition, the calcium soap scum system had higher equilibrium solubility than the magnesium soap scum system.
