Fe0/C-bentonite alginate beads and oyster shell fixed-bed column combined process to continuously remove N-acetyl-p-aminophenol in persulfate system

In this study, the ion-gelation method was applied to fabricate novel Fe–carbon–bentonite–alginate beads (Fe 0 /C-BABs). Fe 0 /C-BABs could effectively control Fe release during persulfate (PS) activation in N -acetyl- p -aminophenol (APAP) oxidation. A novel two-stage approach that combined Fe 0 /C-BABs and an oyster-shell-filled bed (OSFB) column was developed to address the low pH and high Fe concentration of the effluent of the traditional PS process. The application of the Fe 0 /C-BABs and OSFB column regulated pH levels and Fe release during the advanced oxidation of APAP. The characteristics of Fe 0 /C-BABs were also investigated through scanning electron microscopy, energy dispersive spectrometry, and Fourier transform infrared spectroscopy. The long-term operation performance of Fe 0 /C-BABs in a continuous fixed-bed reactor under simultaneous PS and APAP feeding was also evaluated. The effects of initial PS concentration, pH, fixed-bed weight, in-flow rate, and dissolved oxygen (DO) were investigated. Under selected conditions, 86.3% efficiency was achieved during the first stage of APAP degradation (effluent pH of 3.05, Fe contents: 106.25   mg   L −1 ). Water quality improved after the effluent was passed through the OSFB column (effluent pH of 6.32, Fe contents: 21.43   mg   L −1 ). Moreover, this study analyzed the free radicals and intermediates produced during APAP degradation to identify the possible routes of APAP degradation.