Removal of Fe(III)/Al(III)/Mg(II) by phosphonic group functionalized resin in wet-process phosphoric acid: Mechanism and intrinsic selectivity

The removal of iron ions (Fe(III)), aluminum ions (Al(III)), and magnesium ions (Mg(II)) in phosphoric acid -(H3PO4) solution is vital for the production of -H3PO4 and supply of phosphate fertilizer. However, the mechanism and intrinsic selectivity for removal of Fe(III), Al(III), and Mg(II) from wet- process phosphoric acid ( WPA) by phosphonic group (PO3H2) functionalized MTS9500 are still unclear. In this work, the removal mechanisms were determined via combined analysis of FT-IR, XPS, molecular dynamics (MD), and quantum chemistry (QC) simulations based on density functional theory (DFT). The metal-removal kinetics and isotherms were further studied to confirm the removal mechanisms. The results indicate that Fe(III), Al(III), and Mg(II) interact with the -PO3H2 functional groups in MTS9500 resin with sorption energies of -126.22 kJ center dot mol(-1), -42.82 kJ center dot mol(-1), and -12.94 kJ center dot mol(-1), respectively. Moreover, the intrinsic selectivities of the resin for Fe(III), Al(III), and Mg(II) removal were quantified by the selectivity coefficient (S-i/j). The S-Fe( III)/Al(III), S-Fe( III)/Mg(II) and S-Al( III)/Mg(II) are 18.2, 55.1 and 3.02, respectively. This work replenishes sorption theory that can be used in the recycling of electronic waste treatment acid, sewage treatments, hydrometallurgy, and purification of WPA in industry.

Automated summary

In this study, the mechanisms and intrinsic selectivity for the removal of Fe(III), Al(III), and Mg(II) from phosphoric acid solution were investigated. The results showed that the interactions between Fe(III), Al(III), and Mg(II) ions and the phosphonic group functionalized MTS9500 resin were determined, and the intrinsic selectivities of the resin for Fe(III), Al(III), and Mg(II) removal were quantified. This research provides valuable insights for the treatment of electronic waste, sewage, hydrometallurgy, and purification of phosphoric acid in industry.