New Heterocyclic Dithioether Ligands for Highly Selective Separation and Recovery of Pd(II) from Acidic Leach Liquors of Spent Automobile Catalyst

Closed-loop process for selective leaching and recovery of palladium from spent auto-exhaust catalysts using iodotrihalide ionic liquids

The recovery of palladium from spent auto-exhaust catalysts (SAE-catalysts) is of great significance for resource sustainability. Herein, we proposed an efficient closed-loop leaching and recovery method for palladium from SAE-catalysts using iodotrihalide ionic liquids (ILs). Recovery design was explored aimed at green leaching and process simplification. Iodotrihalide ILs exhibited exceptional performance in terms of leaching efficiency (99.1%), selectivity (selectivity > 6.8 ×103) and reusability (over 6 cycles). The mechanism study revealed that excellent leaching performance was attributed to the redox and complexation. Additionally, the chemical reaction-controlled model was best suited to describe the leaching process. Notably, under the optimal conditions determined by the response surface methodology, a high-purity Pd(II) solution (purity > 99.8%) was obtained. More significantly, it was ideal for practical applications due to the low-viscosity (36.0 cP), mild (55 °C) and one-step leaching and recovery. In conclusion, this work provides an eco-friendly method for recovering palladium from SAE-catalysts with its non-high corrosiveness and low environmental impact.

Recovery of Pd(II) from Hydrochloric Acid Medium by Solvent Extraction-Direct Electrodeposition Using Hydrophilic/Hydrophobic ILs

Mixed [C₈bet]Br/[C₄mim][NTf₂] ionic liquids were used as a new extraction system to extract Pd(II) from multimetal-ion solutions. The separation factors K _Pd/M (M: Cu, Fe, Ni, Zn, Co) are greater than 10³. Thiourea was found to be an effective stripping agent. After three cycles, the recovery efficiency was higher than 91.0%. Direct electrodeposition of palladium from the mixed ionic liquid phase was also studied. The Pd(II) complex in [C₈bet]Br/[C₄mim][NTf₂] system was studied by cyclic voltammetry at 348 K. The results indicate the existence of three types of Pd(II) complex in the [C₈bet]Br/[C₄mim][NTf₂] system, leading to three reductive waves. The reduction of Pd(II) to Pd(0) in this system is irreversible. A uniform black coating was obtained by constant-potential deposition at -1.7 V on a nickel foil, confirmed to be palladium metal by energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy analyses. After three cycles of continuous extraction-electrodeposition, over 90.0% of palladium was recovered.

NIS-promoted intermolecular bis-sulfenylation of allenamides via a two-step radical process: synthesis of 1,3-dithioethers

The first report of NIS-promoted two-step radical addition of thiols to allenamides to provide an efficient route for accessing 1,3-dithioethers.

Extraction of Pd(ii) and Pt(ii) from aqueous hydrochloric acid with 1,3-diaminocalix[4]arene: switching of the extraction selectivity by using different extraction modes

1,3-Diaminocalix[4]arene shows extraction ability toward Pd(ii) and Pt(ii), the selectivity of which can be switched by changing the concentrations of H⁺ and Cl⁻ in the aqueous phase.

Optimization of adsorption configuration by DFT calculation for design of adsorbent: A case study of palladium ion-imprinted polymers

Trial-and-error method is widely used to seek an efficient adsorbent, although it is time- and money-consuming. Rationally design of functional materials via theoretical calculation is an emerging and appealing strategy in material science. However, exploiting of theoretical calculation for assistance of adsorbent design is rarely to be attempted despite it is usually utilized to explore the adsorption mechanism. In this work, density functional theory (DFT) calculation is exploited to design an adsorbent with high adsorption capacity and selectivity. The well-known palladium ion-imprinted polymer (IIP) was used as a model adsorbent. Then, three types of given adsorption configurations (a-Pd-IIP, b-Pd-IIP and c-Pd-IIP) were optimized. Further, their adsorption energies were calculated by DFT, which were -13.978 eV for b-Pd-IIP, -8.764 eV for a-Pd-IIP and -3.587 eV for c-Pd-IIP, respectively. The correlation coefficient (R²) between the theoretical adsorption energy and the experimental adsorption capacity reached to as high as 0.985. In addition, the dynamics and selectivity experimental results further consolidated the tendency of the calculation result. All these results demonstrate that the adsorption energy derived from DFT calculations is an important factor in guiding the design of IIPs.