Removal of diatrizoate with catalytically active membranes incorporating microbially produced palladium nanoparticles

There is an increasing concern about the fate of iodinated contrast media (ICM) in the environment. Limited removal efficiencies of currently applied techniques such as advanced oxidation processes require more performant strategies. The aim of this study was to establish an innovative degradation process for diatrizoate, a highly recalcitrant ICM, by using biogenic Pd nanoparticles as free suspension or immobilized in polyvinylidene fluoride (PVDF) and polysulfone (PSf) membranes. As measured by HPLC-UV, the removal of 20 mg L⁻¹ diatrizoate by a 10 mg L⁻¹ Pd suspension was completed after 4 h at a pH of 10. LC-MS analysis provided evidence for the sequential hydrodeiodination of diatrizoate. Pd did not lose its activity after incorporation in the PVDF and PSf matrix and the highest activity (k_cat = 30.0 ± 0.4 h⁻¹ L g⁻¹ Pd) was obtained with a casting solution of 10% PSf and 500 mg L⁻¹ Pd. Subsequently, water containing 20 mg L⁻¹ diatrizoate was treated in a membrane contactor, in which the water was supplied at one side of the membrane while hydrogen was provided at the other side. In a fed batch configuration, a removal efficiency of 77% after a time period of 48 h was obtained. This work showed that membrane contactors with encapsulated biogenic nanoparticles can be instrumental for treatment of water contaminated with diatrizoate.