Dissolution of Soap Scum by Surfactants. Part III. Effect of Chelant Type on Equilibrium Solubility and Dissolution Rate of Calcium and Magnesium Soap Scums in Various Surfactant Systems

Abstract

Soap scum can be effectively removed by using an appropriate surfactant with a chelating agent at a high solution pH. The equilibrium solubilities and dissolution rates of two model soap scums [calcium stearate and magnesium stearate: Ca(C 18 ) 2 and Mg(C 18 ) 2 ] were investigated in aqueous solutions containing three different types of surfactants [methyl ester sulfonate (MES) as an anionic surfactant; alcohol ethoxylate (EO9) as a nonionic surfactant; and dimethyldodecylamine oxide (DDAO) as an amphoteric surfactant] in the presence of different biodegradable chelants: trisodium ethylenediamine disuccinic acid (Na 3 EDDS) and tetrasodium glutamate diacetic acid (Na 4 GLDA) compared with disodium ethylenediamine tetraacetate (Na 2 EDTA), a chelant with poor biodegradability. The highest equilibrium solubility and dissolution rate of either soap scum were observed at high pH in the DDAO system with Na 4 GLDA. In addition, the calcium soap scum had a similar to higher equilibrium solubility and a higher dissolution rate constant as compared with the magnesium soap scum.

Sulfonated methyl esters, linear alkylbenzene sulfonates and their mixed solutions: Micellization and effect of Ca2+ ions

“…The sulfonated methyl esters (SME), known also as α-sulfo fatty acid methyl ester sulfonates (α-MES), sodium salts ( Fig. 1a), exhibit a series of useful properties, which make them attractive for various applications [1][2][3][4][5]: excellent biodegradation; excellent water hardness stability that allows them to be formulated in hard-water regions; very good ability to dissolve calcium-soap scum; excellent skin compatibility that makes them potentially very good for hand dishwashing formulations and body care products; very good wetting power; good detergent power, and very low viscosity of their aqueous solutions (at concentrations comparable with those of other surfactants), which makes them easy to handle and pump.…”

Solubility of ionic surfactants below their Krafft point in mixed micellar solutions: Phase diagrams for methyl ester sulfonates and nonionic cosurfactants

“…MES have excellent biodegradability and biocompatibility [5] and have been promoted as alternatives to the petroleum-based surfactants [6][7][8][9]. The sulfonated methyl esters have attractive properties for various applications [10][11][12][13][14][15][16]: very good wetting and detergent powers with low viscosity of their aqueous solutions; suitable for cleaning formulations, such as phosphate-free detergent powders; excellent water hardness stability allows them to be used in hard-water regions; very good ability to dissolve calcium-soap scum; excellent skin compatibility that makes them potentially very good for hand dishwashing formulations and body care products; viscous formulations, in mixture with nanoparticles. The recent studies on the rheological behavior of mixed MES and betaine solutions [17] and on the oil drop deposition on solid surfaces [18] have shown a possible wide application for shampoo systems.…”