Development and testing of alginate/CNporphyrin bead as a self-initiated Fenton photocatalyst for highly efficient atrazine removal.

Fenton reaction has been widely used for efficient treatment of organic wastewater. However, its applications are limited by such key factors as pH < 3. In this study, we developed, tested, and optimized an alginate/CNporphyrin bead (CNpor-SA) as a recyclable photocatalyst in a photocatalysis-self-Fenton process to overcome these limitations. Porphyrin-modified CN (CNpor) was used as the HO donator, while Fe(III) nodes served as the Fenton reagent. The as-prepared floating alginate/CNpor bead utilized the light source as a driving force for the catalysis. Under visible light irradiation for 6 h, the model pollutant atrazine was degraded by 70.96 % by the optimized photocatalyst (named as CNpor-SA-Fe1Ca5), demonstrating better photocatalytic performance than alginate/CN beads. This improvement was attributed to the higher HO yield from CNpor. The alginate/CNpor bead showed better photocatalytic activity even after several consecutive cycles and could easily be recovered for reuse. Furthermore, Fe(III)/Ca(II) bimetallic alginate bead exhibited better photocatalytic activity and a higher content of •OH radicals than the Ca(II) monometallic alginate beads, due to the ability of Fe(III) nodes to serve as a Fenton reagent. The influences of light sources, and commonly existing matters (namely SO, Cl, CO, NO, and humic acid) were investigated. Moreover, the alginate/CNpor bead demonstrated good photocatalytic performance in a simulated natural environment without the addition of extra HO, with an atrazine removal percentage of up to 96.3 % after 3-h irradiation. These findings indicated the great potential of alginate/CNpor bead in practical applications.