Dissolution Study of Salt of Long Chain Fatty Acids (Soap Scum) in Surfactant Solutions. Part II: Kinetics of Dissolution

Abstract

A study of the dissolution kinetics of soap scum, calcium octadecanoate (Ca(C 18 ) 2 ), by aqueous solutions was carried out by measuring the rate of dissolution of Ca(C 18 ) 2 using a flow cell apparatus. These solutions contained three different types of surfactants: dimethyldodecylamine oxide (DDAO), sodium dodecyl sulfate (SDS), or octyl polyglycoside (C 8 APG), in the presence of a chelating agent, disodium ethylenediaminetetraacetate (Na 2 EDTA). The resulting rate of dissolution corresponds well with the equilibrium solubility obtained in the part I of this series even though the dissolution is rate limited (far from equilibrium). High rates of Ca(C 18 ) 2 dissolution are achieved in solutions of zwitterionic DDAO or nonionic C 8 APG with Na 2 EDTA at high pH. From rate analysis, the Ca(C 18 ) 2 dissolution was found to be surfacereaction limited rather than limited by solution processes or wettability.

Dissolution of Soap Scum by Surfactant. Part II: Effects of NaCl and Added Chelant on Equilibrium Solubility and Dissolution Rate of Calcium Soap Scum in Amphoteric Surfactant Solutions

“…The use of an amphoteric surfactant (dimethyldodecylamine oxide, DDAO) with a Na 2 EDTA chelating agent at high pH gave the highest solubilities of both studied soap scums. The dissolution rate of soap scum was shown to follow first order kinetics in one of our previous studies [5] of different surfactant systems that studied in Part I [4] of this work or in this study.…”

“…An effective soap scum cleaning system requires both the dissociation of calcium ions from soap scum and the formation of mixed micelles of the free fatty acids dissociated from soap scum with an added surfactant [3]. The dissolution rate of soap scum was shown to follow first order kinetics in one of our previous studies [5] of different surfactant systems that studied in Part I [4] of this work or in this study. The synergism in mixed micelle formation of the free fatty acids and added surfactant depends on the surfactant structure and pH, so different types of added surfactants affect the dissolution of calcium soap scum [3].…”

“…Figure 1 shows the experimental configuration of the flow cell apparatus used in this study to determine the dissolution rates of calcium soap scum Ca(C 18 ) 2 under different conditions as developed in our previous work [5]. The DDAO solutions were freshly prepared 1 day before use.…”

“…The average data from at least triplicate measurements had less than 1 % variance. Figure 1 shows the experimental configuration of the flow cell apparatus used in this study to determine the dissolution rates of calcium soap scum Ca(C 18 ) 2 under different conditions as developed in our previous work [5]. A quantity of 0.05 g of the synthesized calcium soap scum sample was placed in between two 0.22-lm nylon membranes of a filter cartridge (Whatman, 1980-002).…”

Preparation and structural analysis of a comb‐like polymer through functional monomer design

“…Therefore, the mutual repulsions of these groups force the chain to stretch out resulting in a densely packed arrangement of polymer chains. [ 41–43 ] Finally, the polymer chains presented the shape of comb‐like in an aqueous solution. The optimal result is obtained via comparing the viscosities of the polymer under different conditions.…”