Chemical filtration of Cr (VI) with electrospun chitosan nanofiber membranes

• Electrospun chitosan nanofiber/PET composite membranes were fabricated.
• Membranes were fine-tuned with micron pore size and cross-linked.
• Chemical filtration behavior of Cr (VI) was uncovered with membrane stacks.
• Single-pass dynamic adsorption capacity exceeded static adsorption.
• Dose–response model presented good interpretation of Cr (VI) sorption.

Chitosan nanofibers (average diameter of 75 nm) were electrospun on polyester (PET) scrim to form composite nanofiber membranes with controlled pore size. The membranes were then stacked as a membrane bed for chemical filtration of Cr (VI) of 1–5 mg/L. The performance of the bed with respect to loading capacity at breakthrough, bed saturation and utilization efficiency were carefully investigated. The results showed that while these three parameters were dependent on pH, flow rate, flow distribution and packed pattern of the membrane, the latter two were less affected by feed Cr (VI) concentration and bed length. The maximum bed loading capacity for 1 mg/L Cr (VI) filtration at breakthrough was found to be 16.5 mg-chromium/g-chitosan, higher than the static adsorption capacity of 11.0 mg-chromium/g-chitosan using nanofiber mats, indicating the membranes’ better potential for dynamic adsorption. The minimum bed length required to avoid breakthrough was determined to be three layers of stacked membranes with nanofiber deposition density of 1 g/m2 by applying bed depth service time (BDST) model.