Adsorption Equilibrium, Kinetics, Thermodynamics and Dynamic Separation of Magnesium and CalciumIons from Industrial Wastewater by New Strong Acid Cation Resin of SPVC

In the research work, the adsorption equilibrium, kinetics, thermodynamics and dynamic separation of magnesium and calcium ions from industrial wastewater by new strong acid cation resin of SPVC (sulphonated polyvinylchloride) were investigated. The sorption capacity of the studied resin was 3.78 mmol/g and 3.74 mmol/g for magnesium and calcium ions, respectively, according to Langmuir isotherm. It was found that the pseudo−first−order model was better fitted for the adsorption kinetics of magnesium and calcium ions on the resin. The dynamic separation results confirmed that the selected resin effectively separated magnesium and calcium ions from industrial wastewater in the dynamic condition. The change of the standard Gibbs free energy (G) and enthalpy (H), and entropy (S) were calculated. The obtained results confirmed that the adsorption of magnesium and calcium ions on the selected resin is endothermic.

Purification of Wet-Process Phosphoric Acid via Donnan Dialysis with a Perfluorinated Sulfonic Acid Cation-Exchange Membrane

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+.