Pretreatment of membrane separation of glyphosate mother liquor using a precipitation method

During the nanofiltration membrane separation of glyphosate mother liquor, a precipitation method was employed to remove HPO32 −, which is often the cause of membrane fouling and blockage. Such removal reduces the speed of membrane flux attenuation. The purpose of the present study was to investigate the effects of precipitant quantity and type, pH value, stirring time and speed, and standing time, on the removal of HPO32 −. In addition, the membrane flux separated by the nanofiltration membrane of the mother liquor post-pretreatment, was tested. Results indicated that when the initial pH was 9, the following pretreatment procedure resulted in the removal of more than 60% of the HPO32 − from the glyphosate mother liquor: the addition of 0.24 mol/L AlCl3·6H2O, stirring at 300 r/min for 30 s and 100 r/min for 2.5 min, followed by standing for 30 min. This pretreatment–precipitation method can markedly enhance the nanofiltration membrane flux in the mother liquor and reduce the membrane flux attenuation, which facilitates nanofiltration membrane separation of the glyphosate mother liquor.