Removal of aniline from waste streams using a combined adsorption and catalytic oxidation approach

The focus of the work described was the development of a solid catalytic adsorbent material capable of being regenerated, with the ability of adsorbing aniline from aqueous solution and the subsequent catalytic oxidation of the adsorbed aniline. Initially, an H-ZSM-5 zeolite was loaded with copper via an ion-exchange process to enhance its catalytic activity. Experimental results indicated an aniline adsorption level of ca. 37-42 mg/g for each of the unmodified H-ZSM-5, the 0.5 w/w% Cu-ZSM-5 or the 1.4 w/w% Cu-ZSM-5 zeolites. The Langmuir adsorption model was applicable to all aniline-on-zeolite adsorption processes, with the level of aniline adsorbed being largely unaffected by a change in temperature. The kinetics of the adsorption processes, indicated that the maximum uptake of aniline occurred within 50 min of contact. Assessment of the aqueous stability of the exchanged copper on the ZSM-5 zeolites indicated minimum copper leaching within the pH range 5-11, thus providing a stable working pH range for both the 0.5 w/w% and 1.4 w/w% Cu-ZSM-5 adsorbent materials. Catalytic oxidation studies on the adsorbed aniline indicated that the presence of copper in the zeolites significantly enhanced the degradation of aniline to predominantly carbon dioxide, water and nitrogen, with the production of significantly smaller levels of nitrogen oxide, benzene and nitrogen dioxide.