Mechanism and kinetics study of Mg²⁺ removal from wet‐process phosphoric acid by Sinco‐430 resin

Abstract

The reaction mechanism and kinetics of Sinco-430 cation exchange resin removing Mg 2+ from wet-process phosphoric acid (WPA) were studied. Fourier transform infrared and X-ray photoelectron spectroscopy analyses revealed that the main functional group of the resin that combined with Mg 2+ ions was -SO 3 H. To investigate the most suitable conditions for Mg 2+ removal, the operating parameters that could affect Mg 2+ removal were studied. The results demonstrated that under optimal conditions (T = 50 C, solid to liquid mass ratio = 0.3, and P 2 O 5 content = 20 wt.%) the reaction reached equilibrium in 8 min and Mg 2+ removal rate reached 59.09%. The kinetic model and activation energy of the reaction were second-order and 19.11 kJ/mol according to kinetic analysis, respectively. The diffusion model of Mg 2+ removal was determined as pore diffusion according to the comparison of three different diffusion models. H 3 PO 4 was recovered using deionized water and Mg 2+ was removed from the loading resin with 20 wt.% H 2 SO 4 . In addition, after eight loading/regeneration cycles, the Mg 2+ removal ability of the Sinco-430 resin remained the same. The Mg 2+ removal rate in a fixed-bed reactor was 98.83%, higher than that obtained in a continuous stirred-tank reactor.