The extraction of Palladium(II) [Pd(II)] from hydrochloric acid solutions with nonylthiourea (NTH) dissolved in chloroform at a constant ionic strength of LOM has been studied. The extraction of Pd(II) has been investigated as a function of the concentration of the extractant, chloride ion, and proton concentrations as well as extraction temperature. The distribution data have been treated graphically and numerically. The analysis of the experimental data has shown that Pd(II) is extracted as PdCl2 . (NTH) and PdCl2 . (NTH)(2) species with the respective extraction constants of log K-11 = 5.0 +/- 0.1 and log K-12 = 9.1 +/- 0.1. The back-extraction of Pd(II) from the organic phase using different stripping reagents has been examined. The selectivity of NTH for Pd(II) against Pt(IV), Rb(III), Cu(II), Fe(III), and Zn(II) has also been investigated.

The extractant nonylthiourea (NTH) in chloroform has been investigated for the extraction of Pt(IV) from chloride solutions at ionic strength of I = 4.0 M and at 22degreesC. It has been found that chloride concentration has a negative effect on the extraction equilibrium, while proton concentration has no effect. The numerical analysis of the equilibrium data has shown that the extraction of PtCl62- with NTH can be interpreted by the formation Of PtCl4(NTH) and PtCl4(NTH)(4) species with their respective equilibrium constants of log K-11 = 5.06 +/- 0.01 and log K-14 = 14.12 +/- 0.04 in 4 M HCl. FTIR spectra of the free NTH and the NTH-Pt(IV) complex were studied to obtain some information on the interaction between Pt(IV) ions and NTH molecules.

Models of extraction equilibria of Pt(IV) and Pd(II) with Nonylthiourea (NTH) from HCl media have been studied. The conditional equilibrium constants and the stoichiometry of the extracted species of Pt(IV) with NTH at different ionic strengths obtained by numerical analysis using the LETAGROP-DISTR program are reported. The dependence of the extraction constant values on the ionic strength has been analysed using the Specific Interaction Theory (SIT), from which the respective thermodynamic equilibrium constants of the extraction of Pt(IV) and Pd(II) with NTH have been determined. The thermodynamic equilibrium constants determined for Pt(IV) are log K-11o=5+/-1 and log K-14(o)=14.6+/-0.2, while for Pd(II) log K-11(o)=4.9+/-0.1 and log K-12(o)=9.17+/-0.08. The interaction coefficients, epsilon, for the pairs (H+, PtCl62-) and (H+, PdCl42-) have also been estimated to be 0.30+/-0.08 and 0.41+/-0.02, respectively.

The facilitated transport of Pd(II) from chloride media has been investigated through a hollow-fiber supported liquid membrane using nonylthiourea (NTH) as a carrier. The influence of the chemical conditions on the permeability of Pd(II) is reported. A model is presented that describes the transport mechanism, consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion of carrier and its metal complex through the organic membrane. The diffusion resistances through organic membrane (Delta(org)) and through aqueous layer (Delta(aq)), respectively, have been calculated from the proposed model. The permeability of Pd(II) seems to be governed by the diffusion of Pd(II) species through the hollow fiber supported liquid membrane with PdCl2(NTH)(2) as a predominant carrier and PdCl2(NTH)to a lesser extent, though both have similar diffusion coefficients.

The adsorption of Co2+ ions from nitrate solutions using iron oxide nanoparticles of magnetite (Fe3O4) and maghemite (gamma-Fe2O3) has been studied. The adsorption of Co2+ ions on the surface of the particles was investigated under different conditions of oxide content, contact time, Solution pH. and initial Co2+ ion concentration. It has been found that the equilibrium can be attained in less than 5 ruin. The maximum loading capacity of Fe3O4 and gamma-Fe2O3 nanoparticles is 5.8 x 10(-5) and 3.7 x 10(-5) mol m(-2), respectively, which are much higher than the previously Studied. iron oxides and conventional ion exchange resins. Co2+ ions were also recovered by dilute nitric acid from the loaded gamma-Fe2O3 and Fe3O4 with an efficiency of 86 and 30%. respectively. That has been explained by the different mechanisms by including both the surface and Structural loadings of Co2+ ions. The Surface adsorption of Co2+ on Fe3O4 and gamma-Fe2O3 nanoparticles has been found to have the same mechanism of ion exchange reaction between Co2+ in the solution and proton bonded on the particle Surface. The conditional equilibrium constants of surface 2-adsorption of Co2+ on Fe3O4 and gamma-Fe-O-2(3) nanoparticles have been determined to be log K = -3.3 +/- 0.3 and -3.1 +/- 0.2, respectively. The Structural loading of Co2+ ions into Fe3O4 lattice has been found to be the ion exchange reaction between CO2+ and Fe2+ while that into gamma-Fe2O3 lattice to fill its vacancy. The effect of temperature on the adsorption of Co2+ was also investigated, and the value of enthalpy change was determined to be 19 kJ mol(-1)

Magnetite nanoparticles coated with nonylthiourea (NTH) were synthesizedand analyzed for the separation and recovery of platinum group metals (PGMs) fromdiluted aqueous chloride solutions. Physical characterizations of the coated nanoparticleswere performed by Transmission Electron Microscopy (TEM), ThermogravimetricAnalysis (TGA) and FT-IR Spectrometry. Separation efficiency of the coatednanoparticles and the equilibrium adsorption isotherm of PGMs were investigated.The maximum adsorption was attained in less than 30 minutes, and the maximumloading capacity of NTH-coated Fe3O4 nanoparticles for Pt(IV) and Pd(II) was determinedto be 10.7 and 8.1 mg g21, respectively. The recovery of PGMs from the loadednanoparticles was examined using different eluting solutions, including HNO3,thiourea, and NaClO4.

The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe3O4 nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H+ and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe3O4 nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g(-1), respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be log K = 1.72, 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe3O4 nanoparticles. It was found that 0.5 mol L-1 HNO3 can elute all of the metal ions simultaneously, while 1 mol L-1 NaHSO3 was an effective eluting solution for Rh(III), and 0.5 mol L-1 NaClO4 for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).