Gemini ionic liquid modified nacre-like reduced graphene oxide click membranes for ReO4-/TcO4-removal

99Technetium (99Tc), as a kind of dangerous radioactive isotopes, captured from groundwater is an extremely urgent problem. A functionalize graphene oxide flexible membrane (GO-C6) was successfully obtained using thiol-ene click reaction, where C--C bond of graphene network can further to connect to the gemini ionic liquids. The click membranes modified by Gemini C4 IL, Gemini Ph IL or Gemini C6 IL exhibited different adsorption capacity for ReO4- /TcO4-, where it enhanced with the increase of number of the alkyl chains C1, C4, C6 in the corresponding structure of GO-Ph, GO-C4, GO-C6. The maximum adsorption capacity of GO-C6 at pH 3, pH 4, pH 6 and pH 10 was evaluated as 269.17 mg g-1, 246.36 mg g-1, 252.55 mg g-1, and 238.67 mg g-1, respectively. In addition, the stable removal efficiency was verified through regenerative and selective experiment in the presence of competing anions, including Cl-, SO42-, NO3-, and PO43-in certain nuclear waste. The ion exchange reaction between ReO4- /TcO4- and Cl- on the imidazolium modified GO membranes played dominant role in the adsorption mechanism. In short, reduced graphene oxide click membranes modified by gemini ionic liquid showed good application prospects in removal of radioactive 99Tc.

Automated summary

This study successfully obtained a functionalized graphene oxide flexible membrane through thiol-ene click reaction, where the connection between the graphene network and gemini ionic liquids enhanced the adsorption capacity. The membrane showed increased adsorption capacity for halogens and actinides with the increase of alkyl chain numbers. The stable removal efficiency of the membrane for various anions in nuclear waste was verified through competitive experiments.