Removal of Metal Ions in Phosphoric Acid by Electro-Electrodialysis with Cross-Linked Anion-Exchange Membranes

Abstract

There are numerous metallic impurities in wet phosphoric acid, which causes striking negative effects on industrial phosphoric acid production. In this study, the purification behavior of metallic impurities (Fe, Mg, Ca) from a wet phosphoric acid solution employing the electro-electrodialysis (EED) technology was investigated. The cross-linked polysulfone anion-exchange membranes (AEMs) for EED were prepared using N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA) to achieve simultaneous cross-linking and quaternization without any cross-linkers or catalysts. The performance of the resulting membranes can be determined using quaternization reagents. When the molar ratio of trimethylamine/TMHDA/chloromethylated polysulfone is 3:1:1, the cross-linked membrane CQAPSU-3-1 exhibits lower water swelling and membrane area resistance than the non-cross-linked membrane. The low membrane area resistance of CQAPSU-3-1 with long alkyl chains is obtained due to the hydrophilic–hydrophobic microphase separation structure formed by TMHDA. EED experiments with different initial phosphoric acid concentrations of 0.52 and 1.07 M were conducted to evaluate the phosphoric acid purification of different AEMs. The results show that the EED experiments were more suitable for the purification of wet phosphoric acid solution at low concentrations. It was found that the phosphoric acid concentration in the anode compartment could be increased from 0.52 to 1.04 M. Through optimization, with an initial acid concentration of 0.52 M, CQAPSU-3-1 exhibits an enhanced metallic impurity removal ratio of higher than 72.0%, the current efficiency of more than 90%, and energy consumption of 0.48 kWh/kg. Therefore, CQAPSU-3-1 exhibits much higher purification efficiency than other membranes at a low initial phosphoric acid concentration, suggesting its potential in phosphoric acid purification application.

CFD Modeling of Liquid–Liquid Batch-Stirred Tank at High Organic to Aqueous Phase Ratios

“…Due to this, these toxic heavy metals are necessary to separate from phosphoric acid before being used in the manufacturing process of fertilizers. Much research has been carried out to separate heavy metals using techniques such as electro-electrodialysis, nanofiltration, adsorption, extraction, etc. ,− Certain heavy metals, such as uranium, molybdenum, vanadium, etc., are valuable in addition to being hazardous. Uranium is primarily used as fuel for nuclear energy production, which produces power in several nations, including the United States, France, United Kingdom, France, India, China, and others .…”