Enhancing the permeation selectivity of sodium alginate membrane by incorporating attapulgite nanorods for ethanol dehydration

Abstract

Hybrid membranes for ethanol dehydration were fabricated by blending sodium alginate with natural hydrophilic attapulgite nanorods, which contained plentiful selective channels and hydrophilic –OH groups. With the incorporation of attapulgite nanorods, the crystallinity of hybrid membranes was gradually decreased and the content of non-freezable water in hybrid membranes was increased, facilitating the solution-diffusion process of water molecules by forming hydration layers along the nanorods. The water uptake of hybrid membranes was ∼10% higher than the pristine alginate membrane while the swelling degree in feed solution was only increased by ∼1%, exhibiting good structural stability in ethanol dehydration. The optimum separation performance with a permeate flux of 1356 g m⁻² h⁻¹ and a separation factor of 2030 for dehydration of a 90/10 wt% ethanol/water feed was achieved using the hybrid membrane with 2 wt% of attapulgite nanorods. Moreover, the influences of feed temperature and feed composition on separation performance were investigated.