On-site Regeneration of Acetaminophen Loaded Zeolite Granules by Applying Gaseous Ozone Based Oxidation Process

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The wide application of pesticides, pharmaceuticals and personal care products cause an increasing contamination of aquatic systems. Adsorption by zeolites is a promising process to remove target organic micro-pollutants (OMPs) selectively from water bodies. In order to have a sustainable adsorption process, restoring the adsorption capacity of the exhausted zeolites is necessary.
In this research, the gaseous O3 based process was applied to regenerate the column packed with acetaminophen (ACE) loaded zeolite granules. The aim of this study was to investigate the regeneration performance by using the gaseous O3 based process and the feasibility of its long-term operation. An initial concentration 200mgL^-1 of ACE was used for the zeolite granules adsorption process. After 120 hours of loading, the gaseous O3 based process was applied to regenerate the ACE loaded zeolite granules. It was found that an ideal ACE degradation rate of 80 -100% was obtained by drying the zeolite granules before the regeneration. While when the drained bed (without drying process) was applied, the ACE degradation rates were below 35% for both the gaseous O3 and the gaseous O3/H2O2 processes. The water content of zeolite granules was the main limiting factor that affected the regeneration performance. A higher ACE degradation rate was obtained with lower water content. It was also found that adding H2O2 to the process enhanced the ACE degradation rate for the zeolite granules with the same water content. Nevertheless, the highest ACE degradation rate was achieved when the water content was 0% without adding H2O2. Regarding the long-term regeneration, three cycles of regeneration were conducted to investigate the feasibility of long-term regeneration by using the gaseous O3 process in dried bed. The effect of ozone on zeolite surface characteristics and the accumulation of intermediates had minor influences on the adsorption capacity restoration. Compared to the fresh zeolite, owing to the incomplete regeneration of the adsorbed ACE in the inner part of zeolite, the used zeolite granules lost 25% of the adsorption capacity in the long-term operation. Therefore, it is feasible to use gaseous O3 process in dried bed to regenerate ACE-loaded zeolite granules from the long-term operation perspectives.