Treatment of glyphosate by-product phosphorus-containing waste salt by a combined ultrafiltration and nanofiltration process

The feasibility of treating glyphosate by-product phosphorus-containing waste salt by hybrid ultra-filtration-nanofiltration is investigated. The ultrafiltration removal and permeability were tested to select a suitable upstream membrane module. On this basis, the effects of subsequent condi-tions on the nanofiltration fraction of the combined process, such as permeate concentration, pH, and pressure applied to the nanofiltration, on membrane removal of total phosphorus and chloride ions. The optimal conditions were used to remove total phosphorus and retain sodium chloride. Scanning electron microscopy analysis was also performed on the nanofiltration, and the fouling was within the membrane surface pores. Results show that the upstream use of ultrafiltration can bet-ter remove impurities and relieve the pressure of nanofiltration. In the nanofiltration part, the max-imum total phosphorus removal rate of 96.28% and the minimum chloride removal rate of 46.38% can be achieved when the permeate concentration is 330 g/L, pH = 10.0 and pressure is 2.6 MPa, and the membrane flux can reach 210 L/m2 center dot h when the above results are maintained. Molecular weight cut-off of 5,000 and 150 Da for the two membranes, respectively.