ZIF-67/Bacterial cellulose (BC) membranes for the removal of dyes and oil/water separation

Bacterial cellulose (BC) is a highly attractive, sustainable biopolymer, offering superior intrinsic properties, including high mechanical strength, crystallinity, and porosity, alongside being inexpensive, non-toxic, and biodegradable. Here, we investigate the potential of BC membranes for simultaneous methylene blue (MB) dye removal and oil/water separation. To enhance separation efficiency, a layer of zeolite imidazole framework type of material (ZIF-67) was deposited onto the BC surface, and the optimal conditions (e.g., ZIF-67 dose, dye concentration, feed volume) for the resulting ZIF-67/BC composite were systematically determined. The BC membrane showed excellent durability, yielding 97.5% ± 1.1 % MB removal over 10 consecutive runs, with the percentage removal being robust against twenty-five times increase in dye concentration (from 2 to 50 ppm). While efficiency decreased significantly with larger feed volumes (from 10 to 100 ml), the ZIF-67 composite layer was the key to overcoming this. A 7.5 g/L ZIF-67 dose increased removal to 71% at the higher volume (100 mL). Furthermore, ZIF-67/BC membranes demonstrated a substantial leap in separating oil/MB/water emulsions, achieving 95% and 97% water recovery for the 50% and 5% oil in oil/MB/water emulsions, respectively, compared to 70% and 92% for BC membrane. Both membranes also retained significant dye removal capacity in complex oily feeds. This study confirms the exceptional dual-functional potential of BC and ZIF-67/BC membranes.