The water transport through GOMs was tested via vacuum filtration. Figure shows the water flux values for membranes prepared using two methods. It becomes clear that for both preparation methods, the water flux decreases following the trend Mg 2+ -M/S-GO < Ca 2+ -M/S-GO < Na + -M/S-GO < K + -M/S-GO. It is thus rational to plot the water flux against the hydrated diameter (D H ) of the respective cations as they follow the exact opposite trend of D H, Mg > D H, Ca > D H, Na > D H, K . It may be noted that as discussed in the next section the ionic diameter of the ions does not rationally resembles the water flux trend.