Lewis Acid Behavior of Cationic Complexes of Palladium(II) and Platinum(II): Some Examples of Catalytic Applications

The behavior of a variety of cationic diphosphine complexes of Pd(II) and Pt(II) as Lewis acid catalysts is reviewed. The reactions considered are the Baeyer–Villiger oxidation of ketones, the acetalization of aldehydes and ketones and the Diels–Alder reaction in both their regular and enantioselective version.     

Separation of Palladium(II) and Platinum(IV) by Bulk Liquid Membranes during Electrodialysis

Abstract

The process of PdCl₄ ^2? and PtCl₆ ^2? separation extracting from binary hydrochloric mixtures as well as palladium(II) extraction from individual solutions by bulk liquid membranes containing diphenylthiourea and di‐o‐tolylthiourea in 1,2‐dichloroethane is studied at galvanostatic electrodialysis. The effects of the current density, the composition of the liquid membrane and of aqueous solutions on the rate of the metal transport are determined. It is shown that an effective separation of Pt(IV) from Pd(II) is achieved in the presence of an excess of the carrier. Maximum separation factor β_Pt/Pd of 380 is obtained in 1 hour of electrodialysis under optimal conditions. The transport of platinum(IV) is supposed to occur in the form of ionic associates (PdL₄Cl)₂PtCl₆. Platinum(IV) concentration and composition of the strip solution do not exert a considerable influence on the separation factor.     

Chlorinative Cyclization of 1,6‐Enynes by Enantioselective Palladium(II)/Palladium(IV) Catalysis

A novel asymmetric catalysis via a palladium(II)/palladium(IV) cycle has been developed by utilizing a chiral spiro bis(isoxazoline) ligand (SPRIX). Intramolecular chlorinative cyclization of 1,6‐enynes catalyzed by a palladium‐SPRIX complex proceeded enantioselectively to afford α‐methylene‐γ‐lactone derivatives.     

叔胺萃取分离钴(II)、铁(II)

研究了不必预先氧化二价铁,直接用叔胺从氯化物溶液中萃取分离钴(II)、铁(II)的新方法. 考察了不同改性剂对叔胺萃取钴(II)、铁(II)的影响以及各种因素对钴(II)、铁(II)萃取、洗涤及反萃的影响. 提出了用叔胺萃取分离钴(II)、铁(II)的最佳工艺参数.     

Reduction of nitroaromatics with poly(vinylpyridine) complexes of palladium(II) and platinum(II)

Palladium(II) and platinum(II) anchored to 2- and 4-vinylpyridine polymers of different molecular weights were used for the dihydrogen reduction of various nitroaromatics and benzaldehyde in ethanol at 50°C. Palladium(II) complexes were far more effective than their platinum(II) analogues and the activity decreased with increasing molecular weights of the polymers. The nitroaromatics were selectively and almost completely reduced to the corresponding anilines. During reduction, the orange palladium(II) complexes changed to voluminous green precipitates, which could be used repeatedly and preserved for a long time without any loss of activity. A rate equation of the type: rate = K[Cat] [H₂] has been derived and a reduction mechanism has been proposed on the basis of experimental results and kinetic data.     

Adsorption of Hg(II) Ions by 3-Mercaptopropyltriethoxysilane Modified Mesoporous Silica Based on Multiwalled Carbon Nanotubes: Equilibrium,Kinetic, and Thermodynamic Studies

In this study, 3-mercaptopropyltriethoxysilane (MPTS) modified mesoporous silica based on multiwalled carbon nanotubes (MWCNTs@mSiO₂-MPTS) was successfully prepared. The adsorption material was characterized and used for adsorbing Hg(II) ions from aqueous solution. The equilibrium data conformed better to the Langmuir isotherm with maximum adsorption capacity calculated 349.65 mg/g at 40ºC. The kinetics analysis revealed the adsorption process fitted well with the pseudo-second-order kinetic model. The thermodynamic parameters indicated the adsorption process was spontaneous and endothermic. All results obtained suggested that MWCNTs@mSiO₂-MPTS may be employed as an efficient material for the adsorption or preconcentration of Hg(II) ions from aqueous solution.     

Recent studies in adsorption of Pb(II), Zn(II) and Co(II) using conventional and modified materials:a review

ABSTRACT

Heavy metal contamination and its detrimental effects on human health and environment have been a worldwide concern. Over the years, various technologies have been adapted to tackle this problem. Adsorption is still considered to be one of the most feasible and cost-effective methods for treating wastewater contaminated with heavy metals. Adsorbents such as activated carbon, clay, zeolites and silica have been studied extensively in the past. Modification of these conventional adsorbents and the synthesis of nonconventional adsorbents such as nanocomposites and metal organic frameworks (MOF’s) have been the main focus of study in recent times. This review article attempts to present a detailed account of various adsorbents and their removal efficiencies for the treatment of wastewater contaminated with lead(II), zinc(II) and cobalt(II) in the current decade. Influence of various parameters, adsorption isotherms and kinetics best described for their removal have also been reviewed in detail. It is observed that most of the adsorbents followed pseudo second order kinetics suggestive of a chemisorption process. After conducting a thorough review of more than 120 recently published papers, it can be inferred that nanomaterials and nanocomposites have shown excellent adsorption capacity for removal of these heavy metals.     

Diatom Biosilica Doped with Palladium(II) Chloride Nanoparticles as New Efficient Photocatalysts for Methyl Orange Degradation

A new catalyst based on biosilica doped with palladium(II) chloride nanoparticles was prepared and tested for efficient degradation of methyl orange (MO) in water solution under UV light excitation. The obtained photocatalyst was characterized by X-ray diffraction, TEM and N₂ adsorption/desorption isotherms. The photocatalytic degradation process was studied as a function of pH of the solution, temperature, UV irradiation time, and MO initial concentration. The possibilities of recycling and durability of the prepared photocatalysts were also tested. Products of photocatalytic degradation were identified by liquid chromatography–mass spectrometry analyses. The photocatalyst exhibited excellent photodegradation activity toward MO degradation under UV light irradiation. Rapid photocatalytic degradation was found to take place within one minute with an efficiency of 85% reaching over 98% after 75 min. The proposed mechanism of photodegradation is based on the assumption that both HO^• and O₂^•− radicals, as strongly oxidizing species that can participate in the dye degradation reaction, are generated by the attacks of photons emitted from diatom biosilica (photonic scattering effect) under the influence of UV light excitation. The degradation efficiency significantly increases as the intensity of photons emitted from biosilica is enhanced by palladium(II) chloride nanoparticles immobilized on biosilica (synergetic photonic scattering effect).     

Palladium(II) extraction from concentrated chloride media: Reactions involving thioamide derivatives

This work focuses on the detailed study of the palladium(II) extraction reactions by N-methyl-N-phenyl-octanthioamide (MPHTA) and N-methyl-N-cyclohexyl-octanthioamide (MCHTA) in toluene, since their ability to efficiently and selectively recover Pd(II) from a wide range of HCl concentrations is already known. Equilibrium data are presented and discussed, and further complemented by information depicted from UV–visible and NMR spectra. The determined apparent molar volumes show that MPHTA is monomeric, and MCHTA exhibits a slight tendency to aggregate. The Pd(II) extraction reactions by MPHTA and MCHTA are equivalent until 4.5 M HCl, passing through the formation of inner-sphere complexes with the metal ion.     

脲基苯乙炔4-′(对甲基苯基)-6-苯基-2,2′-二联吡啶铂(II)络合物的合成

本文通过异氰酸酰化反应合成了含有脲基的苯乙炔新型配体及以它作为辅助配体的4′-(对甲基苯基)-6-苯基-2,2′-二联吡啶铂(II)络合物,初步研究了铂(II)络合物的光物理性质,发现由于脲基的存在,当浓度大于3.32×10-5mol/L时铂(II)络合物能够发生分子间簇集.     

Functionalized sol–gels for mercury(II) separation: a comparison of mesoporous materials prepared with and without surfactant templates

Granular silica gels 1b (7.0 mol% ligand) and 1c (17.0 mol% ligand) containing different amounts of tethered mercapto ligand HS(CH₂)₃Si(O–)₃ were prepared in one step from the co-hydrolysis of HS(CH₂)₃Si(OMe)₃ and Si(OMe)₄. Analyses of 1b revealed that it was mesoporous (pore diameter: ca. 50 Å) with a large surface area (471 m²/g). In 0.5, 5.0, 50, and 500 ppm Hg²⁺ solutions, 1b was found to have Hg²⁺ uptake capacities comparable to those of sub-micron mesoporous powders prepared with two different surfactants in the current studies. 1b and 1c removed Hg²⁺ ions to be below 5 × 10⁻⁵ ppm (the detection limit of atomic absorption) from 0.368 and 50 ppm solutions, respectively. The granular 1b and 1c are easier to prepare and handle, and may offer an alternative to sub-micron powders prepared with surfactants for Hg(II) uptake.     

Adsorption/Desorption of Hg(II) on FDU-1 Silica and FDU-1 Silica Modified with Humic Acid

Incorporation of humic acid in the FDU-1 mesoporous silica improved Hg(II) adsorption and did not destroy the ordered network, providing surface area of 500 m² g^?1, pore volume of 0.9 cm³ g^?1, and mean pore diameter of 10 nm. Carboxylic and phenolic groups increased the affinity by forming surface complexes with Hg(II). Isotherms (25.0 ± 0.1°C) were fitted to the Freundlich equation, exhibiting K_f values that increased with pH and 1/n that decreased to values < 1 with the heterogeneity of sites. Hg(II) desorption in 0.10 mol L^?1 acetic acid was lower than 10%, suggesting that chemisorption processes govern the Hg(II) removal.     

Separation and concentration processes of solutions of Co(II), Ni(II), Cr(III), Fe(III) and Mn(II) by extraction with toluene-dissolved rosin

The extraction and stripping of Co(II), Ni(II), Cr(III) and Fe(III) from aqueous solutions by rosin dissolved in toluene has been investigated. Results obtained show that rosin is better extractant than abietic or n-lauric acids under comparable conditions. From these results, and the data of Mn(II) solvent extraction studied previously under the same conditions, a separation and concentration process for these five cations in aqueous solutions has been designed. Saturated solutions of Fe(III), Cr(III), Mn(II) and finally Co(II) and Ni(II) have been obtained successively by extraction and stripping, by addition of ammonium hydroxide to obtain the appropriate pH value, and by modifying adequately the organic phase/aqueous phase volume ratio.     

硫氰酸锰及其相关衍生物的合成及化学表征

合成了金属有机配合物非线性光学晶体硫氰酸汞锰，及其相关衍生物，二二甲亚砜合硫氰酸汞锰，乙二醇一甲醚合硫氰酸汞锰，二水合二N，N－二甲基乙酰胺合硫氰酸汞锰，二水合二N－甲基－α－吡咯烷酮合硫氰酸汞锰。采用元素分析，红外光谱以及紫外－可见－近红外透央求我谱分析对其进行了化学表征。     

Fatty Imidazolines: A Novel Extractant for the Recovery of Palladium(II) from Hydrochloric Acid Solutions

The extraction of palladium(II) from hydrochloric acid solutions with a novel highly basic extractant, a mixture of homologous 1-[2-(alkanoylamino)ethyl]-2-alkyl-2-imidazolines (AAI) in toluene with 15% (v/v) of n-octanol was studied. Palladium(II) is rapidly and most effectively extracted with AAI hydrochloride at the low hydrochloric acid (chloride ions) concentration (up to 1 M) and can be completely separated from Fe(III), Cu(II), and Co(II). The palladium(II) extraction at the optimum acidity occurs via an anion-exchange mechanism with the formation of ionic associates (LH)₂PdCl₄ (K _ex = (1.5 ± 0.2) · 10⁴ at 0.5 M HCl) and is accompanied by the dimerization of palladium(II) in the organic phase with the formation of ionic associates (LH)₂Pd₂Cl₆ (K _dim = (3.9 ± 0.4) · 10^?4 at 0.5 M HCl). The anion-exchange extraction of palladium(II) at the acidity of 0.5 M HCl is temperature independent in the range 20–49°C. Complete stripping of palladium(II) can be performed using a 5% solution of thiourea in 0.1 M HCl.     

Separation,Preconcentration, and Recovery of Pd(II) Ions using Newly Modified Silica Gel with Bis(3-Aminopropyl)Amine

Bis(3-aminopropyl)amine bonded silica gel (BAPA-SG) was synthesized and characterized by elemental analysis and FT-IR spectroscopy, and tested for adsorption, preconcentration, and recovery of Pd(II) ions. The effective parameters on the preconcentration of Pd(II) ions such as pH, volume, and flow rate of the Pd(II) solution, and the type and volume of eluent solution, and also matrix ions such as alkaline and heavy metals were investigated. Flame atomic absorption spectrometry was used for the determination of Pd(II) concentration. The modified silica gel could adsorb Pd(II) ions quantitatively from the solutions up to 400 mL at pH 1.0 by the flow rate of 5 mL/min. The retained Pd(II) ions could be easily eluted by using 5 mL of 1% (m/v) thiourea in 1.0 M HCl solution. The recovery of Pd(II) ions was 95 ± 2% at 95% confidence level. The analytical detection limit of Pd was found to be 0.36 µg L^?1 at the preconcentration factor of 80. Selective adsorption of Pd(II) ions over some base metal ions was also investigated. The developed method was applied to spent auto catalyst for palladium recovery, and a certified ore sample for the determination of palladium content.     

Equilibrium Studies in Adsorption of Hg(II) from Aqueous Solutions using Biocompatible Polymeric Polypyrrole-Chitosan Nanocomposite

This article deals with the adsorption of Hg(II) ions from aqueous solution on biocompatible polymeric polypyrrole-chitosan (PPy/CTN) nanocomposite. The Hg(II) uptake of PPy/CTN was quantitatively evaluated using sorption isotherms. In order to describe the isotherm mathematically, the experimental data of the removal equilibrium were correlated by either the Langmuir, Freundlich and Temkin equations. Results indicated that the Langmuir model gave a better fit to the experimental data than the other two equations. The adsorption capacity (q_max) of PPy/CTN for Hg(II) ions in terms of monolayer adsorption was 40 mg/g.     

Equilibrium and Kinetic Studies of Ni (II) Adsorption using Pineapple and Bamboo Stem Based Adsorbents

This work addresses the preparation and characterization of inexpensive adsorbents for the removal of Ni (II) from aqueous solutions. Activated carbon based adsorbents have been prepared from plant based biomass resources, namely Pineapple stem ( Ananas Comosus ) and Bamboo Stem ( Bambuseae ). Adopting phosphoric acid and heat treatment techniques, it has been observed that the bamboo stem activated charcoal (BSAC) and pineapple stem (PS) adsorbents had a BET surface area of 116 and 11.47 m ² /g, respectively. FTIR analysis indicated that various surface functional groups (such as C ≡ N stretching, stretching vibration of C = O, –CH₃ wagging and C–O stretching vibration) contribute towards Ni (II) adsorption. Batch mode adsorption experiments were conducted for these adsorbents in the range of 50–300 mg/L Ni (II) solution concentration, 2–10 pH, 15–300 min. contact time, and 0.02–0.1 g/50 mL dosage. The BSAC adsorbent has been characterized with a metal uptake and %removal of 121.72 mg/g and 92.47, respectively, which corresponds to 45% higher metal uptake than corresponding bamboo based adsorbents presented in the literature. Further experimentation with BSAC enabled to achieve activated charcoal with surface area values similar to that of the commercial activated carbon adsorbent. The bamboo adsorbent has also been evaluated to perform similar to the commercial activated carbon for the removal and recovery of Pd (II) from synthetic electroless plating solutions. Also, a conceptual cost analysis indicated and affirmed towards the potential of the BSAC adsorbents for waste water treatment applications.     

Adsorption of Ni(II) and Co(II) Using Microballoons Containing Mg-Silicate and CYANEX923 Prepared by the Emulsion Liquid Membrane System

Abstract

The Mg-silicate microballoons containing CYANEX923 were prepared by W/O/W emulsion. The diameter of obtained micro-sphere particles was ～10 µm and shell thickness was 2 µm. The adsorption of Co(II) and Ni(II) from aqueous solutions using prepared micro-sphere particles was investigated. Experiments were carried out as a function of solute concentration and temperature (25–60°C). Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Equilibrium adsorption data were analyzed using Langmuir isotherm model. The results indicated that prepared micro-sphere particles can be used as an efficient adsorbent for the removal of Ni(II) and Co(II) from aqueous solution.