Rh Ions Research Articles

Adsorption kinetics of platinum group elements onto macromolecular organic matter in seawater

Adsorption kinetics of the interaction between Pt, Pd and Rh (defined here as platinum group elements, PGEs) ions and macromolecular organic compounds (MOCs, >10 kDa), including humic acid, carrageenan and bovine serum albumin, and different cutoff fractions of natural organic matter (>1 kDa and >3 kDa) obtained from seawater using centrifugal ultrafiltration devices were investigated. For a given element, all the adsorption kinetics did not reach equilibrium except the interaction between Pt and >1 kDa cutoff, and between Pd and humic acid. For all the tested MOCs, the adsorption kinetics could be divided into two stages, a rapid adsorption process in the first 8 h and the desorption stage after the first 8 h until the equilibrium. The change trend of partition coefficient (log10Kd) values with experiment time was consistent with that of the kinetic curves. However, in the interaction between PGE ions and natural dissolved organic matter (NDOM), an obvious difference in the change trends of log10Kd and kinetic curves was observed. It indicated that the partition behavior of PGE ions interacting with NDOM in seawater was a combined effect of different organic constituents. The adsorption and log10Kd of PGEs in the >1 kDa NDOM fraction were higher and more stable than those in the >3 kDa NDOM fraction. The results also indicated that the 1–3 kDa NDOM may dominate the interaction between PGEs ions and NDOM. Moreover, no kinetic model could perfectly simulate the adsorption process. It indicated that the colloidal struction and morphology of MOCs or NDOM in seawater might be inhomogeneous. Hence, the interaction between PGE ions and organic matter in seawater was a complicated process and needs further research.

Energies, wavelengths, and transition rates for Ge-like Mo, Ru, and Rh ions

The energy levels, wavelengths, transition rates, and oscillator strengths have been calculated for the fine-structure levels of the 4s24p2, 4s4p3, 4s24p4d, and 4p4 configurations in Ge-like Mo, Ru, and Rh ions. The fully relativistic multiconfiguration Dirac–Hartree–Fock method, taking correlations within the n = 8 complex, the Breit interaction and the quantum electrodynamics effects into consideration have been used in the calculations. Valence and core–valence electron correlation effects are accounted for through single–double multireference (SD-MR) expansions to increasing sets of active orbitals. Our results are compared with available experimental and other theoretical results, and a good agreement is obtained.

Di-( m- m- m)terphenyl-Embedded Decaphyrin and Its Bis-Rh(I) Complex.

A new rectangular-shaped carbadecaphyrin was successfully synthesized by introducing a terphenylene unit ( m- m- m) in the macrocyclic core. The terphenylene moiety offers an open framework with multiple binding pockets to stabilize two Rh(I) ions in the core. The photophysical and structural studies reveal the non-aromatic character of the ligand and its bis-Rh(I) complex.

Reactions of Rh2(CH3COO)4 with thiols and thiolates: a structural study.

The structural differences between the aerobic reaction products of Rh2(AcO)4 (1; AcO- = CH3COO-) with thiols and thiolates in non-aqueous media are probed by X-ray absorption spectroscopy. For this study, ethanethiol, dihydrolipoic acid (DHLA; a dithiol) and their sodium thiolate salts were used. Coordination of simple thiols to the axial positions of Rh2(AcO)4 with Rh-SH bonds of 2.5-2.6 Å keeps the RhII-RhII bond intact (2.41 ± 0.02 Å) but leads to a colour change from emerald green to burgundy. Time-dependent density functional theory (TD-DFT) calculations were performed to explain the observed shifts in the electronic (UV-vis) absorption spectra. The corresponding sodium thiolates, however, break up the Rh2(AcO)4 framework in the presence of O2 to form an oligomeric chain of triply S-bridged Rh(III) ions, each with six Rh-S (2.36 ± 0.02 Å) bonds. The RhIII...RhIII distance, 3.18 ± 0.02 Å, in the chain is similar to that previously found for the aerobic reaction product from aqueous solutions of Rh2(AcO)4 and glutathione (H3A), {Na2[Rh2III(HA)4]·7H2O}n, in which each Rh(III) ion is surrounded by about four Rh-S (2.33 ± 0.02 Å) and about two Rh-O (2.08 ± 0.02 Å). The reaction products obtained in this study can be used to predict how dirhodium(II) tetracarboxylates would react with cysteine-rich proteins and peptides, such as metallothioneins.

Synthesis, Characterization, Absorption Properties, and Electronic Structures of Paddlewheel-Type Dirhodium(II) Tetra-μ-(n-naphthoate) Complexes: An Experimental and Theoretical Study.

The reactions of [Rh2(O2CCH3)4(OH2)2] with n-naphthalenecarboxylic acids (n = 1: 1-HNC, n = 2: 2-HNC) afford the dirhodium tetra-μ-(n-naphthoate) complexes [Rh2(1-NC)4] (1) and [Rh2(2-NC)4] (2), respectively. Single crystal X-ray diffraction analyses of [1(OCMe2)2] and [2(OCMe2)2], which were obtained by recrystallization from acetone (OCMe2) solutions of 1 and 2, reveal that the dirhodium cores are coordinated by four equatorially bridging naphthoate ligands and two axial OCMe2 ligands. Density functional theory (DFT) calculation confirmed that (i) the single Rh–Rh bond is formed between the two Rh ions and (ii) the electronic structures between two Rh ions in [1(OCMe2)2] and [2(OCMe2)2] are best described as π4δ2σ2δ*2π*4 and δ2π4σ2δ*2π*4, respectively. Time-dependent DFT (TDDFT) calculations clarify the absorption band characters of [1(OCMe2)2] and [2(OCMe2)2]; the former shows the bands due to d–d and metal–to–metal-ligand charge transfer (MMLCT) excitations in the visible light region, whereas the latter shows the bands due to only d–d excitations in the same region. The electrochemical properties and thermal stabilities of [1(OCMe2)2] and [2(OCMe2)2] were also investigated in this study.

Ferroelectricity in the multiferroic delafossite CuFeO2 induced by ion doping or magnetic field

On the basis of a microscopic model and using the Green's function technique we have studied the induced ferroelectric polarization P[110] along the [110] direction in the triangular CuFeO2. It is shown that P[110] is induced by an external magnetic field parallel to the c axis hc or a nonmagnetic ion substitution which both can break the inversion symmetry of the system. Our Hamiltonian consists of Heisenberg antiferromagnetic interactions in and out of the ab plane and anharmonic spin-phonon interactions. P[110] decreases with increasing the temperature T. It appears at T ∼ 9 K and begins to increase below T ∼ 9 K, which is the transition temperature to a noncollinear phase. This behavior is an evidence for the multiferroic character of CuFeO2. By doping with Rh ions the polarization has a maximum in the curve P[110](x) with increasing Rh concentration x whereas by Sc doping it decreases. The observed results are in qualitative agreement with the experimental data.

Rapid preconcentration of palladium and rhodium using magnetic graphene oxide/silicon dioxide nanocomposite prior to FAAS determination

The present study was conducted to evaluate the capability of magnetic graphene oxide/silicon dioxide nanocomposites as a novel adsorbent for the separation and preconcentration of trace amounts of Pd(ii) in the presence of Rh(iii) ions prior to FAAS determination.

Methionine Binding to Dirhodium(II) Tetraacetate.

The reaction between antitumor active dirhodium(II) tetraacetate and dl-methionine (HMet) was followed in aqueous solution and showed initially mixtures of 1:1 and 1:2 adducts [Rh2(AcO)4(HMet)(H2O)] (AcO- = CH3COO-) and [Rh2(AcO)4(HMet)2] formed at room temperature (RT), as evidenced by UV-vis spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Rh K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy confirmed methionine thioether binding to the axial positions of the Rh2(AcO)4 cage structure. With excess HMet at RT, stepwise displacement of the acetate groups was observed after some time using ESI-MS. Heating the solution to 40° for 24 h accelerated the substitution reaction leading to stable dirhodium(II) species with two acetate ligands displaced by two methionine groups. The crystal structure of the purple [RhII2(AcO)2(d-Met)(l-Met)]·6H2O compound obtained from the solution revealed tridentate coordination of the methionine ligands to the Rh(II) ions, with the thioether S atoms in equatorial positions. A minor amount of a light orange monomeric [RhIII(Met)2](AcO) complex also formed in the solution was isolated by size exclusion chromatography and identified by ESI-MS. Crystals of [RhIII(d-Met)(l-Met)]Cl·3H2O were prepared by reacting RhCl3 and dl-HMet. The crystal structure showed tridentate binding of the methionine ligands to the Rh(III) ion in a trans-S, N, O arrangement.

Electrochemical Sensor Based on Rh(III) Ion-Imprinted Polymer as a New Modifying Agent for Rhodium Determination.

A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.

Single crystalline thallium rhodium oxide pyrochlore for highly improved round trip efficiency of hybrid Na-air batteries.

The development of bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for electrical energy storage systems (EES). Sodium-air (Na-air) batteries are emerging as a new type of EES, due to their high specific energy density and high sodium ion conductivity. However, the undesirable sluggish kinetics of the ORR and OER limit the practical production of rechargeable Na-air batteries. Although pyrochlore oxides (A2B2O7) exhibit great potential for highly-active bifunctional electrocatalysts, the lack of studies regarding A and B-site cations has hindered the development of new pyrochlore catalysts with a comprehensive understanding of the catalytic activity. Here, we demonstrate the use of a single crystalline thallium rhodium pyrochlore oxide (Tl2Rh2O7) as a highly efficient bifunctional electrocatalyst. The high catalytic activity of Tl2Rh2O7 can be attributed to the oxidation of Tl and Rh ions in Tl2Rh2O7 during the ORR and OER. The oxidized Tl and Rh ions can donate their electrons, which easily migrate to the surface and inner layers, following the low-resistance electron pathway during the electrocatalytic reaction. The hybrid Na-air batteries using the prepared Tl2Rh2O7 achieve greatly improved round-trip efficiency with a high power density for 50 cycles.

Aerobic reactions of antitumor active dirhodium(II) tetraacetate Rh2(CH3COO)4 with glutathione.

The aerobic reaction between glutathione (H3A) and dirhodium(II) tetraacetate, Rh2(AcO)4 (AcO-=CH3COO-), in aqueous solution (pH 7.4) breaks up the direct RhII-RhII bond and its carboxylate framework, as evidenced by UV-Vis spectroscopy. After purifying the reaction product using size exclusion chromatography, electrospray ionization mass spectrometry (ESI-MS) of the solution showed binuclear [Formula: see text] and [Formula: see text] ions. Evaporation yielded a solid compound, [Formula: see text], for which Rh K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed~2 Rh-O (2.08±0.02 Å) and~4 Rh-S (2.33±0.02 Å) bond distances around each RhIII center, and the RhIII··RhIII distance 3.11±0.02 Å, close to that in dirhodium(III) complexes with three bridging thiolates connecting [Formula: see text] units. The 13C CPMAS NMR spectrum of the RhIII-glutathione complex showed a change ∆δ C>6ppm in the chemical shift of the COO- signal, indicating some carboxylate coordination to the Rh(III) ions. This study shows that under aerobic conditions glutathione enables oxidation of Rh2(AcO)4 and thus reduces its antitumor efficiency. The reaction of Rh2(AcO)4 with glutathione was investigated by ESI-MS, UV-Vis, 13C NMR and X-ray absorption spectroscopy, revealing that glutathione breaks down the carboxylate framework enabling oxidization of the [Formula: see text] core to Rh(III) dimeric units, bridged by three thiolates.

Bioselective synthesis of gold nanoparticles from diluted mixed Au, Ir, and Rh ion solution by Anabaena cylindrica

Over the last years, an environmentally friendly and economically efficient way of nanoparticle production has been found in the biosynthesis of metal nanoparticles by bacteria and cyanobacteria. In this study, Anabaena cylindrica, a non-toxic cyanobacterium, is deployed in a diluted ionic aqueous mixture of equal concentrations of gold, iridium, and rhodium, of 0.1 mM each, for the selective biosynthesis of metal nanoparticles (NPs). To analyze the cyanobacterial metal uptake, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometry (ICP-MS) were applied. Only gold can be found in crystalline and nanoparticle form inside the cells of A. cylindrica, and it is the only metal for which ICP-MS analyses show a rapid decrease of the concentration in the culture medium. A slight decrease of rhodium and none of iridium was observed in the evaluated timeline of 51 h. The average diameter size of the emerging gold nanoparticles increased over the first few days, but is found to be below 10 nm even after more than 2 days. A new evaluation method was used to determine the spatially resolved distribution of the nanoparticles inside the cyanobacterial cells. This new method was also used to analyze TEM images from earlier studies of A. cylindrica and Anabaena sp., both incubated with an overall concentration of 0.8 mM Au3+ to compare the metal uptake. A. cylindrica was found to be highly selective towards the formation of gold nanoparticles in the presence of rhodium and iridium.

Superior acetone gas sensor based on electrospun SnO2 nanofibers by Rh doping

Undoped and 0.2-1.0 mol% Rh-doped SnO2 nanofibers were fabricated using electrospinning combined with calcination treatment. The fibrous morphology of these nanofibers were maintained and the grain size of the SnO2 nanocrystals were greatly decreased after Rh doping. Sensors based on these nanofibers were fabricated through a hot pressing mathod. The gas sensing properties of these nanofibers were investigated systematically. The results indicated that the response to 50ppm acetone of 0.5 mol% Rh-doped SnO2 nanofibers was 60.6, which was 9.6 times higher than that of undoped SnO2 nanofibers. In addition, the Rh-doped SnO2 nanofibers showed a decreased cross-response to ethanol, whereas pure SnO2 naofibers did not show selective detection of ethanol and acetone gases. The doping of Rh ions into SnO2 nanocrystals modulates the electron concentration, and induces the changes of the oxygen vacancies and chemisorbed oxygen of SnO2 naofibers. Thus, the doping of Rh3+ into SnO2 nanofibers should be a promising method for designing and fabricating acetone gas sensor with high gas sensing performance.

Photochemical hydrogen evolution on metal ion surface-grafted TiO2-particles prepared by sol/gel method without calcination

We report here a new class of co-catalysts for hydrogen evolution on TiO2 particles upon photo-irradiation. TiO2 particles prepared by sol/gel method was allowed to graft metal ion by a simple treatment with metal salts (Pt (IV), Rh (III), Cu (II), Fe(III), Al (III) ions) in water. The metal ion surface-grafted particles of TiO2(sol/gel) exhibit excellent photochemical hydrogen evolution compared to Pt (0) cluster loaded particles of TiO2(sol/gel) under the UV light irradiation of λ>290nm. XPS analysis shows that the valence states of the metal ions grafted on the TiO2 particles are the same with the parent metal ion salts and no metal (0) clusters were detected. DFT calculation of the simple model of metal ion/TiO2 indicated that an injected electron mostly localized on the metal ion sites, but not on Ti sites, which rationalizes the metal ion serve as the hydrogen evolution sites. Earth abundant metal ions, Cu (II), Fe (III), and Al (III) thus can provide new class of hydrogen evolution sites for artificial photosynthetic systems. To explore the possibility of utilizing semiconductor as an electron relay in the future system of molecular-catalyst-sensitized water splitting into hydrogen and hydrogen peroxide, the stability of hydrogen peroxide on various TiO2 surfaces was examined. Hydrogen peroxide was found to be pretty stable on Rh (III), Fe (III), and Al (III) ions surface-grafted TiO2, while Pt (IV) and Cu (II) ion grafted one similarly caused decomposition of hydrogen peroxide as Pt (0) cluster loaded TiO2 (Pt(0)/TiO2).

Reactions of Antitumor Active Dirhodium(II) Tetraacetate Rh2(CH3COO)4 with Cysteine and Its Derivatives.

We have combined results from several spectroscopic techniques to investigate the aerobic reactions of Rh2(AcO)4 (AcO– = CH3COO–) with l-cysteine (H2Cys) and its derivatives d-penicillamine (3,3′-dimethylcysteine, H2Pen), with steric hindrance at the thiol group, and N-acetyl-l-cysteine (H2NAC), with its amino group blocked. Previous investigations have shown that antitumor active dirhodium(II) carboxylates may irreversibly inhibit enzymes containing a thiol group at or near their active sites. Also, cysteine, the only thiol-containing proteinogenic amino acid, interacts in vivo with this class of antitumor compounds, but structural information on the products of such reactions is lacking. In the present study, the reactions of Rh2(AcO)4 and H2L were carried out in aqueous solutions at the pH of mixing (acidic) and at physiological pH, using the different mole ratios 1:2, 1:4, and 1:6, which resulted in the same products in increasing yields. Electrospray ionization mass spectrometry (ESI-MS) indicates formation of dimeric [RhIII2Pen4]2– or oligomeric {RhIII2L4}n (L = Cys, NAC) complexes with bridging thiolate groups. Analyses of Rh K edge extended X-ray absorption fine structure (EXAFS) data reveal 3–4 Rh–S and 2–3 Rh–(N/O) bonds around six-coordinated Rh(III) ions at mean distances of 2.33 ± 0.02 and 2.09 ± 0.02 Å, respectively. In the N-acetyl-l-cysteine compound, the RhIII···RhIII distance 3.10 ± 0.02 Å obtained from the EXAFS spectrum supports trithiolate bridges between the Rh(III) ions, as was also found when using glutathione as ligand. In the cysteine and penicillamine complexes, double thiolate bridges join the Rh(III) ions, with the nonbridging Cys2– and Pen2– ligands in tridentate chelating (S,N,O) mode, which is consistent with the ΔδC = 7.3–8.4 ppm shift of the COO– signal in their carbon-13 cross polarization magic angle spinning (CPMAS) NMR spectra. For the penicillamine complex, the 2475.6 eV peak in its S K edge X-ray absorption near edge structure (XANES) spectrum shows partial oxidation, probably caused by peroxide generated from reduction of dissolved O2, of thiolato to sulfenato (S=O) groups, which were also identified by ESI-MS for all three {RhIII2L4}n compounds.

Synthesis of pincer-type extractants for selective extraction of palladium from PGMs: An improved liquid-liquid extraction approach to current refining processes

SCS pincer ligands 1–4 were synthesised, and their ability to extract Pd(II) from HCl and HNO3 media was studied. The Pd(II) extraction properties of 1–4 were compared with those of commercial extractants (DOS and LIX®84-I) in kerosene. 1 and 2 showed superior Pd(II) extractability (E% = 99.9) relative to DOS and LIX®84-I from 0.1–8.0 M HCl and to DOS from 0.1–8.0 M HNO3 and mixed HCl + HNO3 media. The Pd(II) extraction rate, acid durability, the most suitable organic/aqueous (O/A) phase ratio, and Pd(II) loading capacity of extractants 1, 2, and DOS were evaluated. 1 and 2 exhibited a greater Pd(II) extraction rate and Pd(II) loading capacity than DOS. 1 was very stable in acid media (HCl and HCl + HNO3), whereas 2 and DOS deteriorated in HCl + HNO3. Selective extraction of Pd(II) by 1 and 2 was achieved from a mixed solution containing Pd, Pt, Rh, rare metals, and base metal ions that simulated the leach liquors of automotive catalysts. The back extraction of Pd(II) and reusability of extractants 1 and 2 were studied. The Pd(II) extraction mechanism of 1–4 was investigated using FT-IR, UV-visible, and NMR spectroscopy.

Palladium(II) sorption of a diethylphosphate-modified thiacalix[6]arene immobilized on amberlite resin

p-Diethylphosphonomethylthiacalix[6]arene (1) was impregnated on Amberlite XAD-7 resin (1-XAD), and the sorption kinetics of 1-XAD towards Pd(II) ions in HCl media were investigated. The maximum Pd(II) sorption capacity (SC) of 1-XAD was 18.7mgg−1 after a contact time of 24h in a 200mgL−1 Pd(II) solution. Batch sorption studies were then conducted to optimize a range of equilibration conditions, such as contact time, Pd(II) concentration, and temperature. The sorption process was then explained in the context of Freundlich and Langmuir isotherm models, thermodynamic parameters ∆G°, ∆H°, and ∆S°, and sorption kinetics were calculated to understand the nature of the sorption. Pd(II) sorption with 1-XAD was found to be spontaneous and endothermic nature. Pd(II) sorption kinetics follows a pseudo-second-order model. In addition, the SC of 1-XAD was investigated using the leach liquors of automotive catalysts containing Al, Ba, Ce, La, Pd, Pt, and Rh ions. The resin developed herein exhibited high selectivity towards Pd(II) ions, with a SC value of 4.12mgg−1 being obtained from leach liquors of automotive catalysts. Finally, Pd(II) desorption from Pd(II)-sorbed 1-XAD was achieved using a thiourea solution as the desorption reagent, and the resin was reused effectively over 5cycles. Pd(II) separation using the 1-XAD as a adsorbent is eco-friendly method as compared with conventional solvent extraction. The 1-XAD is highly useful for selective recovery of Pd(II) from leach liquors of automotive catalysts and secondary resources.

Acridine‐containing RuII, OsII, RhIII and IrIII Half‐Sandwich Complexes: Synthesis, Structure and Antiproliferative Activity

Research aimed at enhancing the efficacy of organometallic complexes against cancer, has shown that attaching bio‐active molecules to (metallo)drugs often enhances their biological properties. New salicylaldimine and 2‐pyridylimine ligands (L2 and L3), containing a bio‐active acridine scaffold, were synthesized and complexed to Rh(III), Ir(III), Ru(II) and Os(II) metal ion centers. The resulting acridine‐containing half‐sandwich complexes have been characterized fully by elemental analysis, FT‐IR and NMR spectroscopy, HR‐ESI mass spectrometry as well as single crystal X‐ray diffraction, for the Rh(III) N^N bidentate complex [RhCp*Cl(L3)][BPh4]. The antiproliferative activity of the ligands (L2 and L3) and complexes (C1 to C9) were evaluated in vitro against human promyelocytic leukemia cells (HL60) and normal skin fibroblast cells (FG0). The compounds exhibit good activities against HL60 cells and are consistently selective towards cancerous cells over non‐tumorous cells. This study demonstrates the potential of such hybrid compounds to target cancer cells specifically. The most active complex, [RhCp*Cl(L2)], exhibited binding to DNA model guanosine‐5’‐monophosphate (5’‐GMP) which suggests a mode of action involving interaction of the complex with 5’‐GMP found on DNA backbone.

Adsorption of rhodium by modified mesoporous cellulose/silica sorbents: equilibrium, kinetic, and thermodynamic studies

A cellulose/silica hybrid was fabricated through the simultaneous deposition of silica and cellulose from their blends. The product was treated with ethylenediamine then carbon disulfide to functionalize amine and thio moieties to the hybrid surface to obtain R-N and R-NS, respectively. The new sorbents obtained were characterized by FT-IR, SEM, and BET. The data obtained indicated the functionalization of amine and thio moieties to the hybrid surface and the formation of thermally stable mesoporous particles with surface area of 319 and 63.5 m2 for R-N and R-NS, respectively. Batch and column studies were carried out to verify the behavior of the two sorbents towards Rh(III) ions from their chloride solutions. The batch studies showed maximum uptake capacity values of 51 and 60 mg g−1, where column studies showed 76.5 and 90 mg g−1 for R-N, R-NS, respectively. The data obtained were interpreted to get the equilibrium, isotherm, kinetics, and thermodynamics adsorption parameters. The adsorption process is favorable and dominated by entropic changes, follow the pseudo-second order kinetics, and fitted well with Langmuir and Dubinin–Radushkevitch adsorption isotherms. The data obtained from batch and column studies indicates the applicability of the obtained cellulose/silica composites in retrieval of Rh(III) ions at higher efficiency.

Optical evidence for the spin-state disorder in LaCo1−xRhxO3

We have measured the infrared reflectivity of single-crystalline samples of LaCo1−xRhxO3 (x = 0, 0.05 and 0.10) from 10 to 300 K from 0.05 to 0.15 eV. We find that the optical phonons of the Co-O stretching mode depend on temperature and the Rh content. Analysis with three Lorentz oscillators reveals that the spin state of Co3+ in LaCo1−xRhxO3 can be understood in terms of a solid solution of low-spin- and high-spin-state Co3+ ions, and the substituted Rh ion retains some fraction of the high-spin Co3+ ions down to low temperature.