Uranyl ions can interact with amino-ligands and polymers such aschitin and chit(}san by compleX('l1ion and adsorption. Thb reaction can be ,tfteeted by certain circumstances, such ,L<; a direct exposure to visible light. to give photoreactions. Among the main photoreduction mechanism.~, sensitised photoactivation (SP) and charge transfer to mass (CTTM) are thought to explain the various responses obtained under several experimental conditions, where the nature of the ligand and the aerobic or anaerobic media arc all changed. It seems that a preliminary complexation of uranium by ligand is required to optimise the reduction rate. The pH of the solution is significantly affected by the photoreaction, depending on the experimental procedure, and a precipitate appears after a duration. Elemental analysis and infra-red studies enable the structure ofthe precipitates to be determined as dihydrated uranate forms.