The uptake mechanism of palladium ions into Prussian-blue nanoparticles in a nitric acid solution toward application for the recycling of precious metals from electronic and nuclear wastes

Abstract

The uptake mechanism of palladium ions into Prussian-blue nanoparticles in a nitric acid solution was investigated via high-resolution TEM, ICP-AES, powder XRD, and UV-Vis-NIR spectroscopy in combination with first principles calculations.

The uptake characteristics of Prussian-blue nanoparticles for rare metal ions for recycling of precious metals from nuclear and electronic wastes

“…For Pd ion (right hand), the theoretical spectra of the Pd ion substituted with Fe 2+ (c) well explain the experimental spectral change (red shift) when compared to the spectra of the Pd ion substituted with Fe 3+ (d). This is consistent with the previous results obtained using CASTEP 24 . For Rh ion (right-middle hand), comparison in theoretical spectra between before (b) and after (c, d) Rh substitution indicates that spectra (d) obtained for Rh substituted with Fe 3+ reasonably explain the experimental spectral change after Rh sorption test.…”

“…Here, the inset shows the unit cell of PB crystal structure. The XRD pattern (black) shows that the pristine PBNPs have a face centered cubic (FCC) structure (space group: ), which is consistent with the previous results obtained using high-resolution transmission electron microscope 24 . Table 2 summarizes the lattice constant and crystallite size of the PBNPs before and after 24 h PGMs/Mo sorption test, which were estimated by fitting the (200) diffraction peak with pseudo-Voigt function and by using the Scherrer equation 47 with a constant of 1.5, respectively.…”

“…PB precipitates thus formed were rinsed with ultrapure water after centrifugation (3000 rpm), which was performed for five times. Thereafter, PBNPs were dried at 75 °C for 12 h and thereafter kept in the vacuum desiccator for 3 h. We already confirmed the structural and physicochemical characteristics of PBNPs used in the present work elsewhere 24 .…”

“…Table 1 summarizes the sorption efficiency of PGM/Mo ions, the elution efficiency of Fe ion from PBNPs, the substitution efficiency of PGMs/Mo with Fe when incorporated into PBNPs, and the estimated amount of PGM/Mo recovery per 1 g PBNPs after 24 h sorption test. Since we already unraveled the uptake mechanism for Pd ion exhibiting the highest sorption and elution efficiencies 24 , we mainly discuss the mechanism for Ru, Rh, and Mo ions in relation to the results of Table 1 .…”

“…More recently, we have investigated the uptake mechanism of Pd (one of the most important elements in industry such as catalyst) ion into PB nanoparticles (PBNPs) in a nitric acid solution, and revealed that the Pd 2+ ion is incorporated into PBNPs by substitution with Fe 2+ ion of the PB framework with maintaining the crystal structure before and after Pd sorption, and the substitution efficiency was estimated to be 87% per PB unit cell 24 . This implies that 0.30 g Pd can be recovered by using 1 g PB with a chemical form of KFe(III)[Fe(II)(CN) 6 ].…”