Surface tension and foam behaviour of aqueous solutions of blends of three alkanolamines, as a function of temperature

We have determined the equilibrium surface tension for aqueous solutions of three alkanolamines composed of 32.5 mass% N-methyldiethanolamine (MDEA) and 12.5 mass% diethanolamine (DEA) with the addition of 2, 4, 6, 8, and 10 mass% of 2-amino-2-methyl-1-propanol (AMP), at 303.15, 308.15, 313.15, 318.15, 323.15, 328.15, 333.15, 338.15, and 343.15 K. We have also determined experimentally the foaming properties for the same aqueous solutions of three alkanolamines as in the surface tension study, at 303.15, 313.15, 323.15, 333.15, and 343.15 K. In order to elucidate the effect of the concentration of AMP on the two studied properties we have also determined experimentally the foamability of the aqueous system of two alkanolamines composed of 32.5 mass% MDEA + 12.5 mass% DEA, at 303.15, 313.15, 323.15, 333.15, and 343.15 K, and for the two binary systems composed of DEA + water and MDEA + water, at concentrations of 10, 20, 30, 40, and 50 mass% of the alkanolamine, at 313.15, 323.15, 333.15, and 343.15 K. In the temperature range studied, the experimental surface tension values of the aqueous blends of three alkanolamines decrease linearly both as the AMP concentration increases and as the temperature increases. The surface tension results for the aqueous solutions of blends of three alkanolamines were correlated simultaneously as a function of temperature and AMP concentration. The foamability results for the quaternary systems reveal that the high surface activity of AMP allows it to act favorably as antifoaming agent in the concentration range of 4–10 mass%, at 303.15, 313.15, and 323.15 K. The experimental behaviour of the different studied systems show that the high surface activity of AMP leads to low surface tension, large surface adsorption, large limiting elasticity, and very low foamability for aqueous systems with one, two or three alkanolamines in which it is present as a component.