Influence of the freezing and lyophilization of bacterial cellulose hydrogel on water removal from both water-in-oil and oil-in-water emulsion

Cellulose hydrogels are potential candidates to remove water from oil–water emulsions. However, their practical application has been limited by complex processing procedures and low separation rates limited by high water holding rates. Therefore, in this work, natural bacterial cellulose (BC) hydrogel with the characteristics of underwater superoleophobicity/underoil superhydrophilicity is introduced to remove water from oil-in-water and water-in-oil emulsions. Also, the influence of the treatment process of BC hydrogel on the separation rate was studied. The results showed that the separation rate of treated BC hydrogel was significantly higher than that of the original BC hydrogel, and the maximum separation flux could reach 180,000 ± 50 Lm−3 h−1 MPa−1. The mechanism has been investigated by the small-angle X-ray scattering and atomic force microscope, which was attributed to the decrease of the capability to confine water caused by the bundling of cellulose microfibrils during freezing or drying. The work might provide an alternative approach for improving the separation rate of cellulose materials for oil/water separation.