Abstract A MnO 2 –ZnO heterojunction was synthesized using a simple precipitation method. The as-synthesized MnO 2 –ZnO was characterized and employed as a photocatalyst for the degradation of reactive yellow (RY) and rhodamine B (RhB) dyes in aqueous medium. XRD confirmed that the prepared composite consists of tetragonal MnO 2 and hexagonal wurtzite ZnO phases with an average crystallite size of approximately 26 nm. SEM images revealed that rod-like ZnO particles were embedded within porous MnO 2 clusters, forming a heterogeneous structure with improved dispersion and reduced agglomeration. The photocatalytic performance of MnO 2 –ZnO was significantly enhanced compared with pristine MnO 2 . About 93 % of reactive yellow and 82 % of rhodamine B were degraded within 180 min in the presence of MnO 2 –ZnO as a photocatalyst. The degradation followed pseudo-first-order kinetics, and the rate constants decreased with increasing initial dye concentration due to reduced light penetration and competition for active sites. The superior photocatalytic performance is attributed to the heterojunction interface between MnO 2 and ZnO, which facilitates efficient separation of photogenerated electron–hole pairs and promotes the formation of reactive hydroxyl radicals. These findings demonstrate that MnO 2 –ZnO can be used as a catalyst for the remediation of dye-contaminated wastewater under sunlight irradiation.
Rafique et al. (Thu,) studied this question.