Photodegradation of the iodinated X-ray contract medium iopromide using combined oxidants of S₂O₈²⁻ and H₂O₂ promoted by UV irradiation promoted by UV irradiation

In the present study, the degradation of the iodinated X-ray contract medium (ICM) iopromide in aqueous solution by the combined oxidants of S₂O₈²⁻ and H₂O₂ with UV irradiation has been investigated. All experiments were carried out on a laboratory scale set-up. The effects of various parameters including different wavelengths of UV irradiation, numbers of UV lamps, and initial solution pH on the degradation efficiency have been evaluated. In addition, the presence of certain organic matters such as glucose and humic acid on the influence of the process performance was also assessed. Experimental results show that the wavelength of 254 nm exhibits best decay of ICM among the three tested wavelengths (254, 300 and 350 nm). ICM photo-decay rate linearly increases with the number ofUV lamps. For the effect of solution pH, optimum performance was observed to be pH=4.34. Additionally, the sequential addition of S₂O₈²⁻ and H₂O₂ was also studied and the degradation efficiency was ranked in the following order: UV/S₂O₈²⁻/H₂O₂>UV/H₂O₂+S₂O₈²⁻> UV/S₂O₈²⁻+H₂O₂. Furthermore, test results indicate that ICM photodecay rate by UV/S₂O₈²⁻/H₂O₂ process is significantly inhibited in the presence of glucose or/and humic acid, suggesting certain pre-treatment measures should be taken to abate their negative effect upon real application.