Recovery of Platinum and Palladium from Chloride Solutions by a Thiodiglycolamide Derivative

The liquid-liquid extraction of platinum(IV) and palladium(II) from hydrochloric acid media was carried out using N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) in 1,2-dichloroethane (1,2-DCE). Pt(IV) is efficiently extracted from 5 M HCl onwards (%E ≥ 97%), whereas Pd(II) is quantitatively recovered from 1 to 8 M HCl solutions. Both Pt(IV) and Pd(II) can be successfully stripped from the loaded organic phases, the former with a 1 M HCl solution, the latter with 0.1 M thiourea in 1 M HCl. The maximum loading capacity of DMDCHTDGA for Pt(IV) could not be determined but it is high, since molar ratios extractant:Pt(IV) within 2 and 3 have been achieved. Data obtained from successive extraction-stripping cycles suggest a good stability profile of DMDCHTDGA towards Pt(IV) recovery. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, comparable %E for Pt(IV). The study of the influence of acidity, as well as chloride ion and DMDCHTDGA concentrations, allows a proposal for the composition of the Pt(IV) species formed upon extraction. Results obtained with binary metal ion solutions point out that Pt(IV) and Pd(II) can be efficiently separated from DMDCHTDGA loaded organic phases through sequential selective stripping.     

From Isonitriles to Unsaturated NHC Complexes of Gold,Palladium and Platinum

In a modular template synthesis, unsaturated NHC complexes of gold, palladium and platinum were synthesized from simple metal salts, isonitriles and amines with acetal or ketal groups. Upon the addition of amines with tethered acetal or ketal moieties to the metal‐activated isonitrile, first nitrogen acyclic carbene (NAC) complexes are formed. These undergo ring closure and elimination to the unsaturated NHC complexes upon addition of acid. This simple strategy opens an attractive and fast approach to NHC complexes of gold, palladium and platinum. The modular approach allows a fast modification and is well‐suited for the synthesis of unsymetrically and symmetrically substituted unsaturated NHC complexes.

     

The Solvent Extraction Performance of N,N’-Dimethyl-N,N’-Dibutylmalonamide Towards Platinum and Palladium in Chloride Media

The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide (DMDBMA) in 1,2-dichloroethane (1,2-DCE) towards platinum(IV) and palladium(II) in hydrochloric acid media was systematically evaluated. Pt(IV) extraction (%E) increases with the HCl concentration in the aqueous phases, being always higher than 72%, whereas Pd(II) extraction decreases from 65% at 1 M HCl to 22% at 8 M HCl. Several stripping agents for the two metals were tested: Pt(IV) is successfully recovered by a 1 M sodium thiosulfate solution, whereas the best result for Pd(II) was achieved with 0.1 M thiourea in 1 M HCl. The loading capacity of DMDBMA for Pt(IV) is high, and data obtained from successive extraction-stripping cycles suggest a good DMDBMA stability pattern. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, worse %E for Pt(IV). The dependence of Pt(IV) distribution coefficients on DMDBMA and chloride ion concentrations, as well as on acidity, are the basis of a proposal for the composition of Pt(IV) extracted species.     

玻璃表面的金和白金装饰

综述了玻璃表面金和白金的各种装饰方法,指出这些方法存在的问题以及发展方向。     

Adsorption of Phenol on Different Activated Carbons Prepared from Date Pits

The potential use of different activated carbons (ACs) prepared from dates pits and phosphoric acid for the removal of phenol from aqueous solutions was investigated. Date pits were converted into five different types of activated carbons by air and phosphoric acid activation. The specific surface area (BET) of the prepared ACs varied from 794 m²/g, for the phosphoric acid:date pit ratio of 5:1, to 1707 m²/g for a ratio of 2:1. Batch adsorption experiments revealed that the adsorption of phenol varied among all of the prepared ACs, where the 2:1 AC showed the highest uptake. Equilibrium pH studies showed that the phenol removal was pH dependent and the maximum phenol uptake occurred at an equilibrium pH of 3.0. Dynamics studies indicated that the initial uptake of phenol on 2:1 AC at pH 4 was rapid, where 80% of the maximum uptake was achieved during the first 30 minutes; both surface adsorption and intraparticle diffusion were involved in the adsorption process and the data followed the pseudo second-order reaction. The equilibrium adsorption data of phenol on 2:1 AC at solution pH 3 was best described by the Redlich-Peterson, Sips, and Langmuir models.     

氯霉素在活性炭上的吸附平衡与动力学

为去除水体中残留的氯霉素,采用生物相容性佳的活性炭作吸附剂,测定了25,30,35℃下氯霉素在自制活性炭上的吸附平衡与动力学,并与商用竹炭作对比。结果表明高比表面积活性炭是去除水体中残留氯霉素的高效吸附剂,活性炭的吸附容量随着吸附剂比表面积和孔容的增大而增大,但随温度从25,30到35℃升高而减小,自制高比表面积活性炭的吸附容量达到3种市售活性炭样品吸附容量的10倍以上;Freundlich吸附等温线方程可较好地描述氯霉素在活性炭上的吸附平衡,准二级方程是用来描述氯霉素在活性炭上吸附的合适动力学模型,并通过拟合得到了其动力学参数。随着温度的升高吸附容量逐渐减小。本研究为活性炭对水体中残留氯霉素的吸附处理提供了科学依据。     

大孔强酸树脂吸附硫脲金

研究了D072大孔强酸性阳离子交换树脂从硫脲[Tu=CS(NH2)2]浸金液中吸附Au(Tu)2+的性能和机理. 结果表明，pH=2.0时，树脂对Au(Tu)2+有优良的吸附性能，金的交换容量为78.95 mg/g (Au/干树脂)，吸附的硫脲金可用乙醇-硫酸水溶液洗脱，洗脱率可达96.5%. D072树脂对Au(Tu)2+的吸附符合Langmuir吸附模型.     

Adsorption Characteristics of Acetaldehyde on Activated Carbons Prepared from Corn-Based Biomass Precursor

The ACs (R-1/2 and R-1/4) having two different textual and chemical properties are prepared from corn-based biomass precursor and evaluated together with a wood-based activated carbon (WAC) at room temperature using a gas chromatograph. The results obtained from the correlation studies indicate that the pore size distribution (below 8 Å) and the relatively lower energetic heterogeneity of ACs on acetaldehyde adsorption are considerable factors rather than that of a specific surface area and surface chemistry. The adsorption equilibrium of ACs is well correlated with the Sips equation. The pseudo second-order equation was better in describing the ACs' adsorption kinetic of acetaldehyde.     

Adsorption of 1,2-Dichlorobenzene from the Aqueous Phase onto Activated Carbons and Modified Carbon Nanotubes

This study aimed to describe the adsorption process of ortho-dichlorobenzene (o-DCB) onto activated carbons (ACs) and modified carbon nanotubes (CNTs) from the aqueous phase. The starting material NC_7000 carbon nanotubes were modified by chlorination (NC_C) and then by the introduction of hydroxyl groups (NC_C_B). The concentration of o-DCB in solutions was performed by UV-VIS spectrophotometry. After adsorption, the activated carbons were regenerated by extraction with organic solvents such as acetone, methanol, ethanol, and 1-propanol; the carbon nanotubes were regenerated by methanol. The degree of adsorbate recovery was determined by gas chromatography (GC) with flame ionization detection, using ethylbenzene as an internal standard. The equilibrium isotherm data of adsorption were satisfactorily fitted by the Langmuir equations. The results indicate that carbon adsorbents are effective porous materials for removing o-DCB from the aqueous phase. Additionally, activated carbons are more regenerative adsorbents than carbon nanotubes. The recoveries of o-DCB from ACs were in the range of 76–85%, whereas the recoveries from CNTs were in the range of 23–46%. Modifications of CNTs affect the improvement of their adsorption properties towards o-DCB compared to unmodified CNTs. However, the introduction of new functional groups on carbon nanotube surfaces makes the regeneration process less effective.     

酸性硫脲浸金液中金的富集研究

研究了D072大孔强酸性阳离子交换树脂从硫脲[Tu=CS(NH2)2]浸金液中吸附Au(Tu)2^ 的性能和机理。结果表明：在pH=2.0时,树脂对Au(Tu)2^ 有优良的吸附性能,1gD072大孔强酸性阳离子交换树脂金的交换容量为78．95mg,吸附的硫脲金可用乙醇-硫酸水溶液洗脱,洗脱率可达96．5％。D072树脂对Au(Tu)2^ 的吸附符合Langmuir吸附模型。     

Adsorption of Silver and Gold Ions from their Aqueous Solutions using a Magnetic Chelating Resin Derived from a Blend of Bisthiourea/Thiourea/Glutaraldehyde

A magnetic chelating resin was obtained from copolymerization of a blend of bisthiourea/thiourea/glutaraldehyde in the presence of magnetite (Fe₃O₄). The uptake of Ag(I) and Au(III) by the resin using batch and column techniques was studied. The maximum uptake capacity showed 6.2 and 5.78 mmol/g for Ag(I) and Au(III), respectively. Breakthrough curves showed critical bed height values of 0.03 cm and 0.04 cm for Ag(I) and Au(III), respectively, indicating the higher affinity of resin to Ag(I) relative to Au(III). Regeneration of the resins was achieved using acidified thiourea at efficiency of 98% over five cycles with no appreciable change in durability. The investigated resin was found to be able to remove 13 different metal ions from a real wastewater matrix at efficiency of 91%.     

Adsorption Equilibrium and Fixed Bed Adsorption of Aniline onto Polymeric Resin and Activated Carbons

The adsorption of aniline on several adsorbents including resin Sepabeads SP206 and activated carbons Jacobi and Norit, has been studied. The influence of temperature in the adsorption capacity was obtained by batch method. Langmuir and Bi-Langmuir were the best models to represent the equilibrium sorption isotherm of aniline in the resin and the activated carbons, respectively. Higher adsorption capacity was obtained for both activated carbons than that for resin, being the maximum adsorption capacity three times higher. Nevertheless, the aniline adsorption capacity onto resin is much more influenced by the temperature.

The dynamic behavior of aniline onto Sepabeads SP206 resin and activated carbon Jacobi was also studied. Breakthroughs and reverse breakthroughs were carried out in a laboratory-scale column to study the adsorbent regeneration. A Linear Driving Force (LDF) model was used to predict the experiments for the two adsorbents. The results demonstrated that Sepabeads SP206 resin can be easily regenerated by using water, while around 50% of aniline remains adsorbed in the activated carbon. Furthermore, after 4 cycles of adsorption-desorption, only around 60% of aniline can be recovered from the activated carbon Jacobi; this behavior can be explained by the aniline that is chemically adsorbed into the activated carbon.     

Real-time Monitoring of Catalytic Surfaces Using a Mass/Heat Flow Sensor: Hydrogenation of Ethylene on Platinum and Palladium

A quartz crystal microbalance/heat conduction calorimeter has been used to monitor simultaneously the heat of reaction and the change in surface mass when H₂ and C₂H₄ in a N₂ carrier react on palladium and on platinum surfaces at temperatures of 25–50 °C. The measured turnover rate of the H₂ + C₂H₄ reaction on platinum at 50 °C is consistent with literature values.     

Catalytic Oxidative Cyclisation Reactions of 1,6-Enynes: A Critical Comparison Between Gold and Palladium

In transition-metal catalysis, similar reactivities are often described for related metals, thereby resulting in the formation of similar/identical products. However, only in rare cases can similar/identical product be obtained by using non-related metals. Amongst these reactions is the oxidative cyclisation of 1,6-enynes by using palladium or gold. Similarities and differences will be discussed with a special focus on the diastereo- and enantioselective course of the reaction.     

The Development of Palladium(II)-Specific Amine-Functionalized Silica-Based Microparticles: Adsorption and Column Separation Studies

The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl₆]^2? and [PdCl₄]^2?) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl₆^2? and PdCl₄]^2?. The adsorption model for both [PtCl₆]^2? and [PdCl₄]^2? on the different sorbent materials fitted the Freundlich isotherm with R² values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl₆]^2? with 0.5 M of NaClO₄ in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.     

Carbenes Made Easy: Formation of Unsymmetrically Substituted N‐Heterocyclic Carbene Complexes of Palladium(II), Platinum(II) and Gold(I) from Coordinated Isonitriles and their Catalytic Activity

From palladium(II) or platinum(II) bis(isonitrile) complexes and from gold(I) isonitrile complexes, both easily available from simple precursors, the corresponding mono‐N‐heterocyclic carbene (NHC) complexes could be obtained selectively in good yields under very mild conditions. The reagents are simple β‐chloroammonium salts in the presence of a weak base. Unsymmetric NHC complexes are accessible. Thus over only two steps from simple metal precursors a broad variety of NHC complexes is available, the method is ideal to quickly assemble catalyst libraries. The palladium complexes are active pre‐catalysts in Suzuki cross‐coupling even with the additional isonitrile ligand on palladium.     

磁性介孔炭合成及其氨化改性

以糠醇为炭源,Fe(NO3)2·9H2O为磁性前躯体,SiO2微球为模板采用一步浸渍法合成了磁性介孔炭,并用化学方法将含胺基官能团嫁接于磁性介孔炭的表面。利用扫描电子显微镜(SEM),红外光谱(FT-IR)和氮气吸-脱附(BET)对经乙二胺表面改性后氨化磁性介孔炭进行表征。结果表明:所合成的氨化磁性介孔炭比表面积为384 m2/g,平均孔容积为0.7 cm3/g,并具有双介孔微球结构。     

强碱性阴离子交换树脂吸附分离铂族元素条件的探讨

采用强碱性阴离子交换树脂吸附分离贵金属铂族元素,并对吸附分离条件酸性、吸附容量、流速、树脂粒度、溶液放置时间及Rh在不同配合物存在下的吸附情况进行了研究和探讨。     

炭气凝胶微球的合成工艺调控及其吸附性能研究

采用反相乳液聚合法成功制备炭气凝胶微球,研究了合成条件对凝胶时间的影响。利用所得产品吸附氯化钯溶液,探讨炭气凝胶微球对Pd2+的吸附性能。结果表明,通过调控合成条件可以实现对合成过程的有效控制,炭气凝胶微球对Pd2+有优异的吸附性能,吸附率最高可达99.2%。