Enhancing purification of an azo dye solution in nanosized zero-valent iron-ZnO photocatalyst system using subsequent semibatch packed-bed reactor

In this work, simultaneous synthesis-immobilization of nano zero-valent iron (reductive catalyst) and nano ZnO (photocatalyst) on perlite as a suitable bed (nZVI-P and nZnO-P) was done. Three processes (reduction, oxidation, and reduction-oxidation) were evaluated for removal of azo dye C.I. acid orange 7 (AO7) from aqueous solution in a semibatch packed-bed reactor. Our results show that AO7 was successfully removed, synchronously in terms of its total color and total organic carbon, using integrated innovative technology by coupling the reduction system (nZVI-P) with the photodegradation process (nZnO-P). Thus, the coupling provided a superior solution for dye wastewater treatment. The kinetic results confirmed the pseudo-first-order model for the Re-Ox process in all initial concentrations of the dye on the basis of P.