Purification of Wet-Process Phosphoric Acid via Donnan Dialysis with a Perfluorinated Sulfonic Acid Cation-Exchange Membrane
Qin Zhong,
Tao Luo,
Zhengjuan Yan,
Lin Yang,
Zhiye Zhang,
Xinlong Wang
Affiliations
Qin Zhong
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
Tao Luo
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
Zhengjuan Yan
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
Lin Yang
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
Zhiye Zhang
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
Xinlong Wang
Ministry of Education’s Research Centre for Comprehensive Utilization and Clean Process Engineering of Phosphorus Resources, School of Chemical Engineering, Sichuan University, Chengdu 610065, China
This work reports the application of an electromembrane process, Donnan dialysis (DD), for the purification of so-called wet-process phosphoric acid (WPA). Nitric acid is used as the stripping solution to remove metallic cations (mostly Fe3+, Al3+, and Mg2+) that are harmful to the further processing of WPA. The paper first presents a set of experimental data on the measurements of the metallic cation fluxes through a perfluorinated sulfonic acid cation-exchange membrane. Not only WPA, but also synthetic phosphoric acid solutions with mixed metallic cations (MPA) and with a single metallic cation (SPA) were studied. This confrontation confirms (1) that the order of metallic cations fluxes is Mg2+ > Al3+ > Fe3+; (2) that, compared with MPA, the purification effect of WPA causes only negligible change; (3) that, by comparing the DD processes with SPA and MPA solutions, the reason for the low transmembrane fluxes of Fe3+ and Al3+ could be explained by the large ionic charge and large hydrated ion radius. Furthermore, by analyzing the ion composition of membranes equilibrated in SPA solutions, we conclude that the forms of cations in the membrane are most likely Fe3+, Al3+, and Mg2+.
