Wet Process Phosphoric Acid Purification using Nanofiltration Membrane Technology

Herein we report the purification of pre-treated industrial phosphoric acid using pre-modified nanofiltration membranes. We demonstrated that the prior pre-treatment steps of industrial phosphoric acid allow the elimination of sulphate, fluorine and arsenic. Further purification of the obtained pre-treated phosphoric acid using membrane cells reduce the concentrations of Cd, As, Al, Fe and rare earth elements by 94.47%, 82.35%, 99.40%, 99.64% and 96.67%, respectively. We found that this purification process relies on electrostatic repulsion between the membrane and highly charged ions and the reduction rate of metals is a cation charge dependent parameters. The laboratory and pilot scale results show that this process allows the production of food-grade phosphoric acid. Keywords Nanofiltration; Phosphoric acid; Membrane; Functionalization; Purification; Pilot scale