Affiliation:
1. CAS Key Laboratory of Design and Assembly of Functional Nanostructures and Fujian Key Laboratory of Nanomaterials Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian 350002 P. R. China.
2. College of Geography and Oceanography Minjiang University Fuzhou Fujian 350108 P. R. China.
3. Fujian Research Center for Rare Earth Engineering Technology Xiamen Institute of Rare Earth Materials Haixi Institute Chinese Academy of Sciences Xiamen 361021 P. R. China
4. Jiangxi Province Key Laboratory of Cleaner Production of Rare Earths Ganjiang Innovation Academy Chinese Academy of Sciences Ganzhou Jiangxi 341000 P. R. China
Abstract
AbstractAiming at the problems of the graphene oxide (GO) membrane‘s water swelling and low ion selectivity, a two‐step reduction method was designed to prepare the interlayer positive charge modified two‐step reduced graphene oxide (TS‐rGO) membrane. Modified stable polyamino molecules onto GO, such as ethylenediamine (EDA), piperazine (PIP) and melamine (MA), provided the membrane interlayer with positive charge to enhance ion selectivity and maintained the stability of the interlayer channel at the same time. The moderate reduced graphene oxide (RGO) membrane was obtained by two‐step reduction process of hydrothermal reduction and heat treatment reduction, which enhanced the stability in water environment and increased the water flux. The permeability of TS‐rGO membrane, represented by PIP‐rGO, to monovalent metal ions (K+, Na+, Li+) was similar to that of GO membrane, but its rejection effect on trivalent metal ion (the penetration rate of La3+ is as low as 4.65×10−5 mol m−2 h−1.) was enhanced by nearly two orders of magnitude. The TS‐rGO membrane could have high ion selectivity, high low‐valent ion permeability, and high water flux simultaneously. In the process of ion permeation, due to the successful modification of interlayer positive charge, the charge effect and size effect synergistically improve the ion selectivity of TS‐rGO membrane.