Tubular bag membrane for simple diffusion dialysis

Tubular bag membrane, designed from bionic aspect, is with a tortuous and long flowing channel in a dual-layer structure, which looks like an intestine in belly. The tubular bag membrane is in a large surface area with high packing density. Herein, one tubular bag membrane is prepared from polyvinyl alcohol (PVA), and the other tubular bag is prepared from PVA and quaternized poly (2,6-dimethyl-1,4-phenylene oxide) (QPPO). The bag has an effective area of 1261-1296 cm2, a channel length of 128 cm, and a volume of 650-675 mL. The tubular bag is immersed in a matrix solution to separate H2SO4/FeSO4 solution through a batch or semi-continuous diffusion dialysis (DD) process.Batch DD process shows an improved acid recovery ratio (RH) of 62.7% and a Fe2+ rejection ratio (& eta;Fe) of 90.5% after 2 h. As for the semi-continuous DD process, the RH of 82.1% and & eta;Fe of 90.6% are obtained after 6 h when the acid feed flows in bag PVA at 0.7 L m- 2 h-1. In addition, acid with concentration of 1.66 mol ?L- 1 can be recovered when water flows in bag QPPO/PVA at 1.6 L m- 2 h-1. The tubular bag in DD process shows the advantages of simple structure, low weight, sufficient mass transfer and high separation ability. Hence, the tubular bag has strong potential to be applied in a large amount of matrix solution such as feed storage tank or salt lake.