The objective of this work was to explore the mechanisms participated in uranium sorption by PICB and CB. Afterwards, contribution of involved mechanisms determined quantitatively. For this purpose, supplementary methods including desorption, chemical modification and PIXE combined with RBS were employed. The observed U(VI) sorption capacity improved by 1.28 times from 141.89 mg/g (CB) to 181.83 mg/g (PICB). The subsequently desorption% of U(VI) by Distilled Water (DW), NH4NO3 and EDTA from U loaded sorbents indicated a minor role for physical adsorption (5.41% for CB and 5.98% for PICB), while ion-exchange and complexation with 51.23% and 38.51% for CB and 44.65% and 40.62% for PICB were the dominant mechanisms, respectively. Specific blockage of functional groups revealed that hydroxyl accompanied by amine in both free and protonated forms, groups played an important role in U(VI) binding to the PICB, whereas protonated amine performed crucial function for the CB. PIXE and RBS analyses showed that ion-exchange mechanism contribution related to the amounts of U (VI) sorbed onto the PICB via light metals replacement was 51.34% which confirmed the compatibility of desorption method. In conclusion, the present study indicated that the uranium sorption mechanism was complicated included ion-exchange along with complexation as the main mechanisms, whereas the other mechanisms such as physical adsorption participated partly. (C) 2017 Elsevier B.V. All rights reserved.