Aqueous liquid membrane systems for sulfur dioxide separation

Sulfur dioxide removal from an industrial effluent gas stream is receiving particular interest because of its detrimental effect on environment. This research study is an attempt towards the development of an 'environmentally sound and cost-effective' liquid membrane technology for SO{dollar}sb2{dollar} separation. A key step in the successful commercialization of a liquid membrane separation process is selection of the carrier that yields high permeant rates across the medium (or membrane).; Identification of suitable water soluble carriers was investigated using a flat type membrane contactor. Several salts of mono- and poly-protic acids: formate, acetate, adipate and citrate are shown to function as superior carrier agents compared to sulfite--the additive used in conventional regenerable processes. The observed enhancement in SO{dollar}sb2{dollar} flux across the weak acid reagent films relative to reagent-free films is ascribed to the 'dynamic role' played by these conjugate acid/base pairs as "carriers" for H{dollar}sp+{dollar} ion transport across the film. A simple theory was used to identify a set of weak-acids that optimize SO{dollar}sb2{dollar} transport. A weak acid with a pK close to the arithmetic mean of the pH values at the two faces of the liquid film was shown to provide maximum enhancement in SO{dollar}sb2{dollar} flux.; Sodium salts of poly-protic acids with closely spaced pKs (citrate and tetra carboxylate) are proved to be strong candidate carrier agents for SO{dollar}sb2{dollar} separation due to their ability to transport protons in more than one conjugate acid/base form. In addition, these reagents are shown to exhibit good performance even under varied SO{dollar}sb2{dollar} feed flue gas partial pressures. Also, experimental measurements were made for SO{dollar}sb2{dollar} removal rates across sodium citrate solutions using a hollow fiber contained liquid membrane module to test the scale-up potential of the process. Removal rates as high as 90% were obtained with these modules.