Complementary membrane-based processes for recovery and preconcentration of phosphate from industrial wastewater

Abstract

The feasibility of recovering phosphate from Algerian industrial wastewater was evaluated by a combination of membrane processes: nanofiltration, diananofiltration and Donnan dialysis. First, the separation of phosphate from a synthetic target effluent with an ionic composition resembling that of the industrial one was tested by nanofiltration using three commercial flat sheet membranes NF270, NF90 (Dow Filmtec) and Desal 5-DK (GE Osmonics) investigating the effect of the effluent pH. The results obtained show that the NF270 membrane assures the highest transport and recovery of phosphate. Afterwards, a diananofiltration process was developed with the optimal process parameters identified. A complete recovery of phosphate was achieved with one additional step of diananofiltration. Finally, Donnan dialysis was also investigated for further purification and preconcentration of phosphate from the permeates previously obtained. The performance of four anion exchange membranes with distinct properties: Neosepta AXE01, Neosepta ACS, Ralex AMH-PES and PC200D was investigated and compared, using chloride as a “driving” counterion in a KCl containing receiver solution. It was found that the AXE01 membrane gives the highest transport and phosphate recovery, achieving a 6-fold increase of the phosphate concentration in the receiver solution, in just one Donnan dialysis step.