Deciphering Acetaminophen Degradation Using Novel Microporous Beads Reactor Activate Persulfate Process with Minimum Iron Leachate for Sustainable Treatment

Abstract

This first-attempt study used novel catalyst to activate persulfate (PS) with chitosan-stabilized zero-valent iron formed in microporous bead reactor for long-term acetaminophen (APAP) removal. As thermal conductivity of the metal was higher than that of organic polymer-chitosan, abundant micro-pores were formed in the proximity of zero-valence iron via heating and dehydration. Thus, the entire bead could be considered to be a “microporous reactor”. SEM, FTIR and XRD results indicated that APAP degradation was mainly taken place in such intra particulate micro pores rather than in suspended aqueous phase. This could effectively suppress the leaching of iron ions. As zero-valent iron was stably protected not to be corrosively attenuated, the catalyst exhibited persistently stable catalytic activity. Here, catalyst dosage, PS concentration, initial pH, and initial concentration of APAP were optimized for maximal performance of treatment. The optimal removal efficiency of APAP (98.5%) was achieved within 35 min with 2 mM PS and 2.0 g/L catalyst at neutral pH, and the iron leaching ratio was only 0.55%. Moreover, as metal leaching capability was not significantly altered, the catalyst could be used for long-term operation. Quenching experiment revealed that SO4·− seemed to be the predominant active species dealing with APAP oxidation. In addition, two plausible routes of competitive reactions for APAP degradation were proposed via identification of degraded intermediates. As electroactive electron shuttles 1,4-dihydroxyl benzene was generated as intermediates to stimulate oxidation, APAP degradation would be more electrochemically favorable for promising efficiency.