COMPOSITION AND THE RELATIVE STABILITY OF SULFUR DIOXIDE INTERACTION PRODUCTS WITH POTASSIUM AND MONOETHANOLAMMONIUM TAURATES AQUEOUS SOLUTIONS. PROLONGED-ACTION CHEMOSORBENT

Abstract

Much research attention has been paid to amino acids as an alternative to amino alcohols for capture of sulfur dioxide. Taurine (Tau) occupies a special place among amino acids. This study was stimulated by the limited literature data on the nature of the interaction of SO2 with Tau salts aqueous solutions, the composition and relative stability of the corresponding reaction products. Chrono-pH-, chrono-redox- and chrono-conductometric studies of SO2 chemisorption with potassium taurate (TauK) and monoethanolammonium (TauMEA) aqueous 0.1 M solutions were carried out in the temperature range 293–313 K to study these processes. The maxima on the differential pH-metric titration curves positions coincide with the positions of the jumps on the integral and maxima on the redox-metric titration differential curves, as well as with breaks on the conductometric curves position. Δk negative values indicate the formation of weakly dissociated particles or less mobile ions in the solutions under study that is confirmed by the data of mathematical calculations. Using a mathematical model that takes into account the law of mass action, material balance and electrical neutrality principle, SO2 – TauK – H2O solutions ion-molecular composition and ionic strength were calculated. With an increase in the chemisotption SO2 amount, the taurate anions concentration decreases due to the hydrolytic transformation into zwitter ions +NH3CH2CH2SO2O - and the sequential transformation of hydrotaurate-sulfite (4:1 and 2:1; I and II), taurate-sulfite (2:1; III), hydrotaurate-hydrosulfite (2:1; IV) and taurate-hydrosulfite (1:1; V) associates. The concentration and thermodynamic constants for the formation ionic associates I–V were calculated. TauK input into impregnated fibrous chemisorbents (IFCS) composition obtained by impregnating viscose fibers with monoethanolamine aqueous 0.25 M solutions (IFCS-0.25MEA) leads to a synergistic increase in quantity of adsorbed SO2. IFCS-0.25MEA-TauK are long-acting sulfur dioxide chemisorbents, and TauK itself serves as a promoter-modifier towards IFCS-0.25MEA preventing the MEA removal from IFCS surface by the GPS flow due to the ionic associates formation and promoting deeper HOCH2CH2NH2 «response».