jats:sec<jats:label />jats:pMembranes were produced from fine (∼10 nm) alumina fibres, by dispersing them in liquid and using controlled sedimentation to produce two types of membrane – one a duplex structure (layers of well‐dispersed fibres and micro‐bundles) and the other entirely micro‐bundles. Incorporation of silica, via a sol‐gel route, produced “hybrid” forms. Filtration and separation efficiencies were assessed using two ionic dyes of similar molecular weight, but opposite charge. Successful separation of these is attributed to surface electrical effects within nano‐pores. Hybrid duplex membranes give an excellent combination of fine scale filtration efficiency and high permeability.</jats:p></jats:sec>