Degradation of diclofenac sodium with low concentration from aqueous milieu through polydopamine-chitosan modified magnetic adsorbent-assisted photo-Fenton process

Given the widespread occurrence of low-concentration diclofenac sodium (DCFS) in the aquatic milieu, the development of an efficient and economical purification method is essential. Magnetic polydopamine-chitosan modified adsorbent (MPDA-CS) was successfully prepared by coating polydopamine-chitosan onto Fe 3 O 4 nanoparticles in this study. The favorable adsorption performance towards DCFS was well demonstrated by regulating the solution to various pH values and initial concentrations of DCFS. Furthermore, the convincing fitting of pseudo-second-order model and intraparticle diffusion model suggested that the dominance of chemical processes and intraparticle diffusion. The specific adsorption mechanism was presumed to be the interaction between MPDA-CS and DCFS molecules, including electrostatic attraction, hydrogen bonding and aromatic stacking. Through regulating standing time in acidic solution, the integrated homogeneous and heterogeneous photo-Fenton system was employed to degrade adsorbed DCFS through dissolved and surfaced Fe(II)/Fe(III) of MPDA-CS, which achieved the waste utilization of dissolved iron ions with excellent degradation efficiency of 96.38% in 40 min. The adsorption-degradation efficiency of DCFS decreased slightly by 2.2% during the initial three cycles. This work presents an energy-efficient method for removing low-concentration DCFS by drawing on the strengths of adsorption and degradation.