Selective recovery of palladium using an innovative functional polymer containing phosphine oxide

A new method for incorporating polyethyleneimine (PEI) in algal beads: High stability as sorbent for palladium recovery and supported catalyst for nitrophenol hydrogenation

“…Pd(II) could bind to carboxyl groups by coordination and to protonated amine groups through electrostatic attraction/ion exchange (with anionic chlorocomplexes). When the sorption occurs through ligand exchange mechanisms, a low pH will lead to a decrease of sorption capacity due to the competition between the protonation and the Pd coordination [33], while in the case of electrostatic attraction, a low pH is usually required to positively charge the amine groups: protonated amine groups bind anionic complexes. It should be noted that, in this study, the concentration of HCl in the initial solutions diluted from stock solution was around 0.09 M, leading to predominant formation of chloro-palladium complexes (PdCl 4 2− , 96%; PdCl 3 − , 3-4%) throughout the pH range.…”

Batch sorption and fixed-bed elution for Pd recovery using stable amine-functionalized melamine sponge

“…The percentage of PdCl 4 2− increased from 63% at pH 2-97% at pH 1 and the sorption capacity increased from 87 mg g − 1 at pH 2-127 mg g − 1 at pH 1. Ricoux et al (2015) also reported an increase in Pd(II) sorption capacity onto functionalized polymer with increasing pH. They concluded that Pd(II) sorption mainly involved ligand exchange mechanisms; the decreasing pH resulted in protonation of amine groups and thus limited the coordination of Pd(II).…”

A Comparison of Palladium Sorption Using Polyethylenimine Impregnated Alginate-Based and Carrageenan-Based Algal Beads

“…When the pH eq is lower than 4, the maximum binding for both beads is observed at pH 1 with a sorption capacity of 0.88 ± 0.03 mmol g −1 for LD/PEI and 1.37 ± 0.02 mmol g −1 for CC/PEI beads. Ricoux et al [45] reported that a decrease of pH (below 4) reduced the amount of palladium sorbed on functionalized macroreticular Amberlite XAD resins with sulfur and nitrogen ligands. In their case, the Pd binding was mainly attributed to a coordination mechanism; the competition from protons for the active binding sites when decreasing the solution pH would reduce the coordination between Pd(II) and the above ligands.…”

“…Figure 6 shows that with the increasing concentration of the salts, the sorption capacity decreases, regardless of the sorbent. The addition of NO 3 − and Cl − may influence Pd(II) sorption through different mechanisms [45], depending on the main functional groups on the sorbents and the speciation of Pd(II):…”