Separation of acidic HCl/glyphosate liquor through diffusion dialysis and electrodialysis

摘要

Acidic HCl/glyphosate (Gly) liquor is the intermediate product during the production of glyphosate herbicide. Here the acidic liquor contains about 2.8 mol L-1 (M) HCl, 1.0 M Gly, 34 wt% other organic components and 40 wt% water. The HCl component is recovered by diffusion dialysis (DD) and subsequent electrodialysis (ED) processes, and the Gly product is precipitated at low acid concentrations. The DD process shows significant water osmosis, which can obtain the recovered HCl concentration (Cd-H) of 0.54-0.98 mol/L (M), HCl recovery ratio (R-H) of 29.2-35.9% and Gly rejection (eta(Gly)) of 96.8-98.6%. The obtained residual liquors are further separated by the ED process. The ED process shows water reverse osmosis, which can obtain Cd-H of 0.65-1.30 M, R-H of 23.8-57.2%,eta(Gly) of 74.9-97.2% and energy consumption of 1.14-10.03 kWh kg(-1). Besides, 51-59% Gly product can be precipitated in the residual solution without previous neutralization and concentration. Hence, the combination of DD and ED processes can balance the water osmosis, recover most of HCl from the acidic liquor, save energy greatly, and precipitate Gly directly. The combination of DD and ED processes may become the foundation for practical separation of the acidic liquor.