Purpose Pharmaceutical contaminants, including antibiotics, present in the environment, especially water resources, are a main concern for human and environmental health due to their stability and non-degradability. Accordingly, the purpose of this study was to investigate the photocatalytic removal of penicillin G antibiotic from simulated wastewater using a photocatalytic process [UV/ZnO] in an isotherm and kinetic study. Methods In the current research, the ZnO nanoparticles [ZnO NPs] were initially characterized by scanning electron microscope [SEM] and X-ray diffraction [XRD]. Then, its efficiency was investigated in the photocatalytic degradation process of penicillin G. The evaluated parameters in the adsorption process penicillin G antibiotic were pH [1-5], penicillin G concentration [10-30 mgL(-1)], NP dosage [0.5-4.5 gL(-1)] and contact time [5 to 200 min]. Then, the effect of pH [3, 5, 7, 9, 11, and], penicillin G concentration [10-30 mgL(-1)], NP dosage [0.01-1.5 gL(-1)] and contact time [5 to 200 min] in the photocatalytic degradation (UV/ZnO) was studied. The residual penicillin G concentration was measured using a spectrophotometery at a wavelength of 283 nm. Results The results indicated that the penicillin G removal efficiency of photocatalytic process [UV/ZnO] using ZnO was 74.65% at the concentration of 10 mgL(-1), the pH value of 5, the ZnO NP dosage of 0.1 gL(-1) and the contact time of 180 min, as well as the kinetics of degradation followed the pseudo-first-order kinetic model. Conclusion It can be concluded that the use of this process is appropriate an effective for the removal of the antibiotic pollutants.