Ionization‐engineered two‐dimensional confined channels in GO membranes for highly efficient OH⁻ separation

Abstract

OH− sieving membranes provide a valuable means for treating alkaline effluents but their development presents several challenges. In this study, the concept of ionization engineering is applied to two‐dimensional (2D) laminated membranes to facilitate OH− separation. This concept is demonstrated through the stacking of the self‐designed sulfonated graphene oxide (SGO) nanosheets to fabricate 2D membranes. The SGO membranes enhance synergistically the OH− dialysis coefficients and separation factors when treating simulated NaOH/Na2WO4 alkaline wastewater, compared with the performance of 2D GO membranes and commonly adopted polymeric cation exchange membranes. Furthermore, the separation factor achieved by the SGO membranes is considerably higher than that of most of the existing alkali recovery membranes. Results of molecular dynamics simulations indicate that the high efficiency of OH− separation in the 2D SGO confined channels is attributable to dehydration effects and intensified electrostatic repulsion. Overall, this research provides an alternative strategy for achieving rapid OH− sieving through the ionization of 2D confined channels.

Efficient acid/alkali recovery enabled by only one negatively charged microporous polymer membrane

“…The and of SPX membranes with varied thicknesses were in the range of 2.34 × 10 −3 –9.74 × 10 −3 m h −1 and 346–649, respectively. A comparison made on and with reported membranes, as shown in Figure 5C, SPPO‐based membranes, 49–51 PVA‐based membranes, 24 two‐dimensional sulfonated graphene oxide membranes, 52 and other hybrid membranes, 24,53–57 showed that the microporous SPX membrane balanced well with the OH − dialysis coefficient and OH − /WO 4 2− selectivity. For instance, the PVA‐MIDA hybrid membrane exhibited a very high OH − dialysis coefficient of 0.022 m h −1 but a low OH − /WO 4 2− selectivity of 33 54 .…”