This paper describes the crystal interphase impact of ZnFe 2 O 4 –Ag in the photodegradation of Rhodamine B. Prepared ZnFe 2 O 4 nanoparticles (NPs) were deposited with Ag NPs to offer ZnFe 2 O 4 –Ag (0–2.5%). An X-ray diffraction peak corresponding to the Ag NPs was detected if the particle content reached about 2.0%, observing multiple crystalline interphases in HR-TEM. Magnetic saturation (Ms) was increased ∼160% times for ZnFe 2 O 4 –Ag (7.25 to 18.71 emu/g) and ZnFe 2 O 4 (9.62 to 25.09 emu/g) if the temperature is lowered from 298 to 5.0 K; while for Fe 3 O 4 (91.09 to 96.19 emu/g), the Ms increment was just about 5.6%. After analyzing the DFT–Density of State, a decrease of bandgap energy for ZnFe 2 O 4 –Ag 6 from the influence of the size of Ag cluster was seen. Quantum yield (Φ) was 0.60 for ZnFe 2 O 4 , 0.25 for ZnFe 2 O 4 –Ag (1.0%), 0.70 for ZnFe 2 O 4 –Ag (1.5%), 0.66 for ZnFe 2 O 4 –Ag (2.0%), and 0.66 for ZnFe 2 O 4 –Ag (2.5%), showing that the disposition of Ag NPs (1.5–2.5%) increases the Φ to >0.60. The samples were used to photo-oxidize RhB under visible light assisted by photopowered Langmuir adsorption. The degradation follows first-order kinetics ( k = 5.5 × 10 –3 min –1 ), resulting in a greater k = 2.0 × 10 –3 min –1 for ZnFe 2 O 4 –Ag than for ZnFe 2 O 4 (or Fe 3 O 4 , k = 1.1 × 10 –3 min –1 ). DFT-total energy was used to analyze the intermediates formed from the RhB oxidation. Finally, the ZnFe 2 O 4 –Ag exhibits good antibacterial behavior because of the presence of Zn and the Ag components.