Absorption of n-butyl acetate from tannery air emissions by waste vegetable oil/water emulsions

Abstract

Tanning industries emit a huge quantity of Volatile Organic Compounds (VOCs), including hydrophilic and hydrophobic solvents. In this study, vegetable oil/water emulsions with 2 and 5 vol% of corn oil (O) or waste cooking oil (WCO) were prepared. Their potential as absorbents of n-butyl acetate (BA), in place of water, was investigated to increase the efficiency of tannery wet scrubbers. BA was selected as a representative component of hydrophobic VOC emissions derived from leather finishing processes. Static and dynamic absorption tests were performed with a BA concentration of 500 ppmv (2.6 g/m3) and a flowrate of 3.0 L/min to evaluate Henry’s law constant, absorption efficiency, absorption capacity, and saturation time of the various investigated absorbents. The feasibility of the absorbent regeneration was also studied by hot stripping with nitrogen. The results showed that Henry’s constant of BA in oil/surfactant/water or oil/water emulsions (5 vol% oil), regardless of the oil used, were significantly lower than those in water (3.6 versus 15.9 atm), and BA absorption capacity (0.84 g/L) was four times higher than the value in water. The presence of the surfactant (0.2–0.8 vol%) contributed to improving the oil/water emulsions stability without having a significant effect on BA absorption capacity. Almost complete BA desorption from the saturated emulsions was obtained by flowing hot N2 at 80°C, demonstrating the absorbent regeneration's feasibility followed by recovery and reuse. Therefore, the oil/water emulsions containing 5 vol% of WCO are efficient and sustainable absorbents of BA, with potential use in VOC emission treatment systems.