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+.

Iranian Qara Qat fruit (redcurrant) in Arasbaran forests as the resource of anthocyanin pigments in formation of [ACN-Mg2+/Al3+/Ga3+/ Sn2+/Cr3+/Fe3+] chelation clusters

Clusters of metallic cations (Mg2+, Al3+, Ga3+, Sn2+, Cr3+ and Fe3+) jointed to anthocyanins in water media were studied for unraveling the color shifting of different complexes of these structures in the low ranges of pH. Anthocyanin jointed to metallic cation progresses the color expression range of anthocyanin in more different range of pH. In this verdict, it has been studied the metallic cations diffusing of deprotonating for the anthocyanin (B)-ring of cyanidin (Cy), delphinidin (Dp) and petunidin (Pt) in two media of gas and water, transforming flavylium cations to the blue quinonoidal bases at lower range of pH applying the infrared method by approaching Beer Lambert law for getting the physico-chemical parameters of frequency, intensity, and absorbance of the compounds, respectively. In previous investigation, it has been indicated that the important factor for enhancing the absorbance in a positive non-linear fashion due to deviating from the Beer Lambert law is the self-association of anthocyanins of cyanidin, delphinidin and petunidin of anthocyanin structures. The difference of heat of formation (∆HR) among clusters of metallic cations jointed to anthocyanins has been illustrated toward the double bonds and carbonyl groups by the chelation of (B)-ring for cyanidin, delphinidin and petunidin anthocyanins in two media of gas and water that explains the stability and color of [anthocyanin-metallic cations] cluster chelation of cyanidin (Cy), delphinidin (Dp) and petunidin (Pt) colorful pigments in a weak acidic medium. By this work we exhibited that the color of the anthocyanin chelates is an important factor for estimating the efficiency of these types of food colorants.

Experimental Model for Cu(II) and Fe(III) Sorption from Synthetic Solutions Based on Maize Stalk

This study is based to a new concept, to use maize stalk for specific sorption and recovery of Cu(II) and Fe(III) from synthetic solutions. Thus, the sorption properties of the biomass resulting from the recycling of the maize stalk that reached maturity (autumn) were studied. In the first stage, the sorption properties of the maize stalk were evaluated in batch system. Moreover, in terms of water quality improvement several key parameters that influence the sorption equilibrium were evaluated. The effect of contact time (0-120min) and cations initial concentration (investigated range: 0.05-0.4 mg/L) on biomaterial sorption capacity were assessed. Kinetic studies were performed taking into consideration the initial concentration of metallic cation. The experimental data were analyzed based on first order kinetic model, pseudo-second-kinetic model and Morris Webber kinetic model. The kinetics of sorption was in accordance with the pseudo - second - kinetic model as the correlation coefficients showed (R2=0.9940 for Cu(II) and R2=0.9999 for Fe(III)). Moreover the desorption study was evaluated with hydrochloric acid and have detected to be 63% and 89% for Cu(II) and Fe(III) when 4M HCl is used. The surface of the maize stalk loaded with Cu(II) and Fe(III) was characterized by various specific techniques such as FTIR-ATR, SEM, and TG. Experimental results revealed that cations sorption process takes place on the sorbent surface. The sorption rate of each metallic cation is controlled by the formation of chemical bonds with surface polar groups. Their presence on biomass structure, evidenced by FTIR-ATR analysis, explains the behavior of maize stalk as a weak ion exchanger acid.

Mimicking bone–metal exchanges with synthetic nanocrystalline apatites

A chemical system accounting for metallic cation exchange between blood plasma and bone mineral has been developed. After a first step ensuring Ca and P equilibria, the model has been employed to characterize U(vi) interaction with bone mineral.