Aqueous Two-phase System Separation of Heat-Stable Salt Ions in Flue Gas Desulfurizer

Abstract

The heat-stable salts (HSS) in flue gas desulfurizer 1,4-bis-(2-hydroxypropyl)-piperazine (HPP) are separated by HPP forming an aqueous two-phase system (ATPS) with Na₂SO₄, which is the main component of HSS. In this work, SO₄^2–, NO₃^–, Cl^–, K⁺, PO₄^3– and SO₃^2– were selected to study the separation performance in the HPP+Na₂SO₄ ATPS. The results indicate that the partition coefficients of the above ions in the ATPS are related to their structures. Furthermore, the partition coefficients of anions are related to the charge numbers and salting out capacity. Simultaneously, with the increase of pH in ATPS, the partition coefficients of ions decrease first and then have no significant change. These findings provide an effective reference for the process design of separating HSS from HPP by ATPS.