Carbon-based building blocks for alcohol dehydration membranes with disorder-enhanced water permeability

Graphene oxide (GO) thin films have demonstrated outstanding water permeability and excellent selectivity towards organic molecules and inorganic salts, unlocking a new exciting direction in the development of nanofiltration, desalination and pervaporation membranes. However, there are still high concerns about their stability at basic pH and under cross-flow conditions. The stabilization of graphene oxide can be achieved by thermal or chemical reduction; but stacked layers of reduced GO tend to form ordered and compact graphite-like structures, thus preventing their application as molecular separation membranes. In this work, a humic acid-like biopolymer (HAL), extracted from organic compost with a yield of ∼20%, was used to fabricate composite GO-HAL membranes. The HAL brings a high degree of disorder to the membrane structure, with the benefit of an increased water permeation rate. Upon thermal stabilization, the membrane with a biopolymer loading of 30% presented an ideal water/ethanol selectivity of 45 and a water permeance that is 33% higher than the pristine graphene oxide membrane. The enhanced water permeability along with the good water/ethanol selectivity makes the GO-HAL membranes promising devices for alcohol dehydration technologies.