Density functional theory investigation of Cs, Co and Ag separation by functionalised graphene membrane

This work simulates radionuclides enrichment and separation from radioactive wastewater through functionalised porous graphene oxide (PGO) with a six-membered ring hole structure and hydroxyl (-OH) functional groups, using density functional theory (DFT). Cs, Ag, and Co in particular are selected for theoretical simulations in order to better understand the separation mechanism from the radioactive wastewater. The results demonstrate that, except for Co, the adsorption energy of nuclides on PGO membranes is higher than on perfect graphene membranes, and that the adsorption of Ag shifts from physisorption to chemisorption. Cs has a higher energy barrier than Co or Ag. It cannot permeate the PGO membrane and only concentrates on the surface. The separation of Cs from other nuclides using a PGO membranes is attributed mainly to the strong electronic coupling between hydroxyl functional groups and Cs. It is found, in addition, that the adsorption performance of the PGO membranes for Co and Ag decreases with increasing temperature, but has relatively stable adsorption for Cs. These research results demonstrate that a PGO membrane containing six-membered ring holes can effectively screen Cs from radioactive wastewater.