Selective U(VI) removal using phosphorous-doped graphitic carbon

Development of materials for selective recovery of uranium (U) from contaminated water and sea water is necessary to solve the issues related to sources of U(VI) for nuclear energy and alleviating the environmental pollution. Phosphorous-doped Graphitic (P-Gc) material, synthesized under microwave irradiation (450 W, 40 s) has been utilized as potential adsorbent material for U removal in ppm level from contaminated water selectively at room temperature (RT). The influence of various environmental conditions (e.g. pH, contact time, ionic strength, and temperature) on U(VI) adsorption was investigated by batch method. Maximum Adsorption capacity (QM) was found 1186 mg g−1 from Langmuir fit and this could be due to high specific surface area of P-Gc (1635 m2/g) and the presence of phosphate functionalities (3.18 atomic wt% P according to XPS) on the adsorbent surface. The results of kinetic and thermodynamic studies revealed that the adsorption was a spontaneous and exothermic chemical process and the adsorption process could be better fitted by a pseudo-second order model, suggesting a chemisorption over physisorption. The adsorption of U(VI) on P-Gc was a multilayer uptake in lower concentration range of U(VI) and monolayer in higher concentration range of U(VI). The material has been reused for five cycles with almost no change in the efficiency which is very important for the wastewater treatment. 90 % of the adsorbed uranium was regenerated from P-Gc by simple acid treatment. Hence, P-Gc has a great promise in the quest to development of metal free adsorbent for uranium removal at RT.