Resin-supported palladium nanoparticles as recyclable catalyst for the hydrodechlorination of chloroarenes and polychlorinated biphenyls

Proof-of-concept studies of novel protocols for producing highly pure 48V from a 48Cr/48V generator

The quest to improve the quality of nuclear data, such as half-lives, transition yields, and reaction cross-sections, is a shared endeavor among various areas of nuclear science. ⁴⁸V is a vanadium isotope for which experimental data on neutron reaction cross-sections is needed. However, traditional isotope production techniques cannot produce ⁴⁸V with high enough isotopic purity for some of these measurements. "Isotope harvesting" at the Facility for Rare Isotope Beams (FRIB) is a new isotope production technique that could potentially yield ⁴⁸V with the necessary purity for such studies. In this case, ⁴⁸Cr would be collected and allowed to generate ⁴⁸V that can be separated from undecayed ⁴⁸Cr to yield highly pure ⁴⁸V. Thus, any protocol for producing pure ⁴⁸V via isotope harvesting would involve utilizing a separation technique that can effectively separate ⁴⁸Cr and ⁴⁸V. In this study, the radiotracers ⁵¹Cr and ⁴⁸V were used to develop possible radiochemical separation methodologies, which can be translated to obtain high purity ⁴⁸V via this novel isotope production method. The developed protocols utilize either ion exchange or extraction chromatographic resins. Separations of ⁵¹Cr and ⁴⁸V with AG 1-X8 anion exchange resin respectively resulted in recoveries of 95.6(26)% and 96.2(12)% with radionuclidic purities of 92(2)% and 99(1)%. An even more effective Cr and V separation was obtained with an extraction chromatographic resin (TRU resin) and 10 M HNO₃ loading solution. Here, ⁵¹Cr and ⁴⁸V respectively had recoveries of 94.1(28)% and 96.2(13)% with high radionuclidic purities (100(2)% and 100(1)%) in small volumes (8.81(8) mL and 5.39(16) mL). This study suggests that, to maximize the yield and isotopic purity of ⁴⁸V, the best production protocol would involve utilizing two separations with TRU resin and 10 M HNO₃ to isolate ⁴⁸Cr and purify the generated ⁴⁸V.

Palladium nanoparticles dispersed on functionalized macadamia nutshell biomass for formic acid-mediated removal of chromium(VI) from aqueous solution

Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction analysis confirmed the formation of Pd on the modified MNS surface and suggested an estimated crystallite size of 5.0 nm. The supported nanoparticles exhibited catalytic activity in formic acid-mediated Cr(VI) reduction and showed promising stability with consecutive reuse. These findings set the stage for advanced studies into performance optimization.