The degradation of the antibiotics discharged into water and wastewater has become a challenge in environmental engineering. A new Z-scheme nanocomposite was designed, synthesized, and characterized for photooxidative degradation of the binary antibiotics (doxycycline and tetracycline) in aqueous solution simultaneously. Firstly, the proposed nanocomposite was created from dendric fibrous nano-silica (KCC-1), as support, improved with Ti(VI)-salen, as organometallic complex, and its structural and morphological properties were investigated. The band-gap energy achieved from the Tauc equation was in good accordance with the calculated one by the Gaussian software. Analysis of the band structure was used to deduce the probable Z-scheme heterojunction mechanism for the proposed photocatalyst. The photodegradation procedure was studied in terms of pH (2.0–6.0), catalyst amount (1.5–7.5 mg.mL–1), concentration of H2O2 (0–0.08% w/v), and irradiation time (5–25 min) under UV light. In optimal conditions, employing the simplex non-linear optimization algorithm, the photodegradation of doxycycline and tetracycline showed efficiencies higher than 95%. Optimal circumstances leading to the maximum simultaneous removal of doxycycline and tetracycline were discovered as pH of 3.6, catalyst dose of 6 mg.mL–1, H2O2 amount of 0.06%w/v, and irradiation time of 16 min. Under the optimal circumstances, the kinetics data for investigated antibiotics were fitted employing a pseudo-first-order model. The nanocomposite could successfully remove doxycycline and tetracycline contaminations. Regarding the high degradation efficiency as well as fast kinetics, the observations suggest that the proposed photocatalyst has a significant capability of reducing antibiotic pollutants.

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