Effect of amino acid additives in ammonia solution on SO2 absorption and ammonia escape using bubbling reactor for membrane contactor applications

Abstract

Controlling the SO2 emissions is crucial because they result in several environmental problems and affect human health. Several techniques have been proposed for controlling SO2 emissions. Limestone or lime-based absorbents are widely used for SO2 removal. However, their low solubility limits their applications. Ammonia solution has attracted attention owing to its higher SO2 removal efficiency. However, owing to its high volatility, it has the propensity to escape, which can cause secondary environmental pollution. Therefore, we investigated the effect of six amino acid additives to improve the SO2 absorption performance and inhibit the ammonia escape in aqueous ammonia solution. The surface tension and theoretical breakthrough pressure of the amino acid-containing ammonia solutions was investigated to evaluate their applicability to a membrane contactor process. L-histidine (His) exhibited the best performance. Therefore, the effect of His concentration, inlet SO2 concentration, and absorption temperature on SO2 absorption performance was explored. The 13C nuclear magnetic resonance (NMR) and 1H NMR analyses were used to study the SO2 absorption mechanism. This study provides a strategy for preparing an eco-friendly and highly efficient SO2 absorbent that can overcome the disadvantage of current ammonia solutions for the removal of low-concentration SO2 from industrial gas emissions for the membrane contactor process application.