Study On High Temperature Concentration Of Glyphosate Mother Liquor Using Nanofiltration Membrane And Crystallization Process

In this paper, nanofiltration membrane was applied to concentrate glyphosate mother liquor, and the crystallization conditions of glyphosate mother liquor concentrated were studied. The conditions of concentration at high temperature and cooling crystallization were optimized, the better technological parameters were got, those can provide some suggestion to industrial applications.Glyphosate mother liquor was separated with selected acidproof and high temperature resistance nanofiltration membrane, the effects of different temperatures, operating pressure and feed flowrate on membrane flux and retention rate were studied, membrane stability was investigated. The results showed that membrane flux increased with the increase of temperatures, operating pressure and feed flowrate; retention rate increased with the increase of operating pressure and feed flowrate, slightly decreased with the increase of temperatures; under the condition of 60℃,1.6 MPa and feed flowrate O.6m3h-1, membrane flux of different concentration feed solution was 50-70L/(m3-h), retention rate reached a stable level of 97.5—98.0%.The mechanism of nanofiltration membrane fouling and membrane fouling control were studied and analyzed. In this experimental system, resistance of nanofiltration membrane mainly consisted of four aspects:membrane itself, concentration polarization, gel layer and membrane pore adsorbed stain. Resistance distribution is respectively as follows:membrane resistance is 42.4%, concentration polarization resistance is 31.7%, gel layer is 20.6%, pore stain resistance is 5.24%of total resistance.Solubility curve was drawn through determining glyphosate solubility in different temperatures, the results were compared with the cooperation company and MONSANTO, and it showed that the outcome got by my LAB was more reliable. Ultra-solubility curve and solubility curve were drawn in one figure, so the metastable zone can be determined, it can help to control the crystallization conditions.The experimental conditions composed by cooling curve, stirring rate, the introduction of crystal seed and impurities, and the influence of these conditions on parameters including particle size distribution, crystal shape, packing density were studied. The result showed that cooling rate had great influence on the process of crystallization, fast cooling rate can lead to flocculent crystal which were adverse to improve the packing density, the optimize cooling curve was better. Fast stirring rate can made more small particles, so we should use the fewer stirring rate as we can in the context of control, the introduction of crystal seed can improve the crystal uniformity so crystal seed should be introduced at the right time, there were less influence of formaldehyde and formic acid whose concentration was 0.5% on glyphosate crystal shape and packing density, so the influence of this condition on glyphosate cooling crystallization can be excluded.