Wet Process Phosphoric Acid Purification Using Functionalized Organic Nanofiltration Membrane

Abstract

The utilization of phosphoric acid in various sectors, e.g., food industry, is controlled by the authorized concentration limit of impurities. However, industrial phosphoric acid is contaminated with undesirable impurities (such as F, Al, Fe, Mg, etc.). Herein, this study aimed to evaluate the efficiency of the membrane purification process of pretreated industrial phosphoric acid using a premodified nanofiltration membrane. We demonstrated that the prior pretreatment steps for industrial phosphoric acid allowed the elimination of sulfate, fluorine and arsenic. Further purification of the obtained pretreated phosphoric acid using membrane cells reduced the concentrations of Cd, Al, Fe and rare earth elements by 94.81, 99.30, 99.63 and 96.67%, respectively. The membrane is functionalized by a deposit of a high molecular weight polycationic polymer of polyethyleneimines in order to produce a highly charged membrane surface to enhance the separation efficiency, selectivity and stability of the membrane. We found that the purification process relies on electrostatic repulsion between the functionalized membrane and highly charged ions, and the reduction rate of metals is a cation charge-dependent parameter. The laboratory and industrial pilot scale results showed that this process allows the production of food-grade phosphoric acid.

Remediation and recycling of inorganic acids and their green alternatives for sustainable industrial chemical processes

“…Several studies have reported the integration of NF and RO for the treatment of acidic streams polluted with metals. Puri-cation of phosphoric acid, 235,236 nitric acid used in the manufacture of picture tubes, 237 recovery of metals and acids from electroplating effluents, 238 and purication of sulfuric acid are its few uses. 239 In addition to the aforementioned applications, the combination of NF and RO has shown to be a viable treatment for pressure oxidation process effluent, a waste product from the gold mining sector.…”