Tubular membrane used in continuous and semi-continuous diffusion dialysis

Abstract

Tubular membrane is firstly developed from the polyvinyl alcohol based casting solution. The membrane is compact with the diameter of 1.27–1.72 cm and the length of 30–60 cm, which is like a piece of “sieve tube” or “blood vessel” from bionic aspect. The membrane can be used in the static and continuous diffusion dialysis (DD) processes to separate an acidic liquor containing HCl and glyphosate (Gly). The acidic liquor is filled or pumped into the tubular membrane, while the membrane is immersed in the matrix solution of water. The matrix solution can also be static while the acidic liquor is continuous to form a semi-continuous process.Static DD process shows that the recovery ratio (RH) can reach up to 70.2% with the Gly rejection of 95.3% after 1 h. Continuous process shows that the water osmosis coefficient (UH2O) is in the range of 1.54–3.09 × 10−4 m h−1. The RH increases from 64% to 74% as the water flow rate increases. The Gly productivity is 43–72% after precipitation from the residual liquor. Finally, semi-continuous process shows high feed flow rate of 1.86 L m−2 h−1, stable RH values of 71.1–75.5%, and high Gly productivity of 65.1–87.9%.