Abstract:
This work studied the effect of ions present as hardness in tap water, i.e. calcium, magnesium, hydrogen carbonate and hydrogen sulfate ions, on the foaming properties of three surfactant systems. The first system consisted of sodium dodecyl sulfate and coconut oil sodium soap. In the second system, a nonionic surfactant (C12-C15 alcohol with 7 moles of ethylene oxide) was additionally introduced to the first system. The third system consisted of all surfactants used in the second system together with an added co-surfactant (diethylene glycol mono-butyl ether). The results showed that a minute amount of hydrogen carbonate ions enhances defoaming in the presence of calcium and magnesium ions, the major components of hardness in tap water. Unexpectedly, hydrogen sulfate ions showed a foam-destabilizing effect. However, in the first and third systems, hydrogen carbonate ions have a greater defoaming effect than hydrogen sulfate ions. Among the three systems, the second system showed the highest foam stability whereas the first system showed the lowest.
