Adsorption Of Platinum Research Articles

Study of the electronic structure of Ag, Au, Pt and Pd clusters adsorption on graphene and their effect on conductivity

When metallic clusters are adsorbed by pristine graphene, the conductivity of the system is modified. In this paper the adsorption of silver, gold, platinum and palladium cluster with n atoms (n = 1, 2, 3 and 4) and their effect on conductivity are studied. Ground state properties and electronic structure calculations at DFT level are undertaken for each system. Conductivity is calculated taking three different approaches; frozen ripples, charged impurities and resonant scattering. Adsorption sites are the scattering centres of our systems. For conductivity calculations, size and scattering potential are obtained from our calculations. Systems Pt and Pd are in the chemisorption range and the network distortion is such that conductivity diminishes so that it is no longer in the ballistic regimen. Systems Ag and Au are in the physisorption range, the network preserves the natural two dimensionality of the graphene sheet and conductivity is still in the ballistic regimen.

Pt behavior in the Pt-C-S ± Fe-H2O system at 200–400°C and P tot = 1 kbar: Experimental results

The effect of sulfur on platinum adsorption on carbonaceous matter (CM) was experimentally studied at 200–400°C and Ptot = 1 kbar. The IR spectra of the experimental products indicate that sulfur accelerates HC condensation and aromatization, but the effect of sulfur on platinum concentrations in the organic fractions is within the analytical uncertainties. SEM images show the development of a multilayer porous carbonaceous film on the walls of the ampoules and platinum in physical contact with carbonaceous matter. The composition of the film varies, depending on its thickness (3–25 μm), within the following limits: 61.06–100 wt % C, 0–33.7 wt % Pt, 0–5.17 wt % O, and 0–0.74 wt % S. The film contains tiny Pt crystals, whose morphology varies with increasing duration of the experiments from nanometer- and micrometer-sized spheroids to subequant, tabular, and wire-like. Depending on their size, the composition of the crystals varies as follows: 23.30–52.45 wt % Pt, 49.57–73.52 wt % C, and 0–4.20 wt % O. According to our SEM data, the kerogen also contains tiny crystalline segregations of carbon aceous platinum whose morphology and composition are analogous to those on the film. The presence of carbon in the tiny platinum crystals deposited from solution can be explained by the background effect of the kerogen of the film and/or by their crystallization from organo-platinum complexes. In our kinetic experiments, local electrochemical reactions produced aggregates of nanometer-sized (60–250 nm) spheroids around larger micrometer-sized (up to 10 μm) spheroids, whose aggregation resulted in larger crystals and their further transformation. The polymorphism, hierarchical aggregation, and compositional variability of the platinum segregations are likely typical of car- bon-bearing systems because of their crystallization from metastable organo-platinum complexes.

Greatly enhanced adsorption of platinum on periodic graphene nanobuds: A first-principles study

The structural and electronic properties of platinum atom adsorbed on periodic graphene nanobuds (PGNBs) have been investigated and compared with graphene by means of density functional theory (DFT) calculations. Our result based on the generalized gradient approximation has been validated by the state-of-the-art B3LYP level of theory for Pt adsorption on the graphene surface. We demonstrate that the bridge site over the C–C bond center intervening between two hexagonal rings of type I PGNB and the hollow site over the nonagonal ring center of type II PGNB serve as the most thermodynamically favorable states amongst several considering starting configurations. The binding energies of about −3.34 and −3.78eV were obtained for I PGNB and II PGNB, respectively, within the BSSE corrections, which are more stronger than the Pt binding energy of −2.12eV for a pure graphene. The electronic structures for the most favorite configurations of Pt atom adsorbed on the systems of interest, in terms of the Mulliken population, the electronic density of states (DOS), and the projected density of states (PDOS) analysis have been discussed. The stability of the Pt–PGNBs and Pt–graphene complexes was confirmed within ab initio molecular dynamics simulation carrying out at ambient temperature. We also indicate that oxygen binding energies at the most energetically favorable configurations on the Pt–PGNB I and Pt–PGNB II complexes are weaker than the O2 binding energy on a Pt–graphene complex. The very desirable Pt binding energy obtained accompanied by high specific surface area (because of fastened C60 molecules) and relatively weaker O2 binding energy of PGNBs compared with the pristine graphene lead to experimentally apprehend these novel hybrid nanostructured materials as a superior media for Pt adsorption. Our study recommends possible avenues for intensification the stability and electro-catalytic activity of platinum atoms on PGNB surfaces through hybrid engineering.

Study on the adsorption behavior of modified persimmon powder biosorbent on Pt(IV)

A glycine-modified persimmon powder was used as biosorbent for platinum adsorption in aqueous solution. The combined effects of modifying agent amount, modifying time and temperature on Pt(IV) adsorption by persimmon biosorbent were investigated, from which the optimum modification conditions with modifying agent amount of 50 %, temperature of 333 K and contact time of 4.0 h were determined. The influences of solution initial pH, solid-to-liquid ratio, contact time, temperature and initial concentration on the Pt(IV) adsorption were studied systematically by batch experiments. The optimum modification conditions were determined as follows: chemical reagent amount of 50 %, temperature of 333 K and contact time of 4.0 h. From the adsorption kinetic analysis, it was found that the adsorption kinetics of glycine-modified persimmon powder followed a pseudo-second-order kinetic model. The adsorption isotherms of the crude persimmon powder and glycine-modified persimmon powder were analyzed with the BET-type adsorption isotherm. The adsorption mechanism of Pt(IV) on the glycine-modified persimmon was considered to be adsorption-reduction mechanism. The results achieved from this study indicated that the novel persimmon adsorbent could be applied to recover trace Pt(IV) ions from a concentrated chloride solution.

Investigation of adsorption parameters for platinum and palladium onto a modified polyacrylonitrile-based sorbent

This study investigated the adsorption and desorption procedure of platinum (Pt) and palladium (Pd) onto a modified polyacrylonitrile (PAN)-based sorbent, which was designed with thiourea (TU) and glutaraldehyde (GA), from fire assay leaching solutions. Batch studies were performed and the key processing parameters were investigated in detail. The optimum pH value obtained for the adsorption of Pt and Pd by the PAN–TU–GA was 1.50. The Langmuir isotherm model described the adsorption of metal ions by the sorbent more accurately than the Freundlich model. Moreover, the activation energies (Ea) of Pt and Pd were 75.98 and 16.59kJ/mol, respectively. Elution testing with 0.50M HCl–0.50M thiourea solution for both Pd and Pt achieved an elution rate of above 93% and showed no significant decrease after five adsorption–desorption cycles, indicating that PAN–TU–GA may be regenerated and reused. As a result, a reasonable amount of non-degradable polymer material may be appropriate in industrial recovery use. Finally, PAN–TU–GA, as well as the Pt–Pd-loaded sorbent, was characterized by various techniques, including Fourier transform infrared spectroscopy (FTIR) and X-ray fluorescence (XRF).

Development of sensitive determination method for platinum in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry

A simple and cost effective preconcentration method based on modified activated carbon is proposed for the determination of traces of platinum (Pt) in geological samples by the carbon slurry sampling technique for graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Pt(IV) ions on modified activated carbon were studied and the effect of activated carbon modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Pt(IV) ions onto the modified activated carbon for diluted aqueous solution was also studied in detail in respect to the determination of platinum in solid materials following digestion steps as outlined in the analytical procedure, which usually involves the application of aqua regia. The XPS studies confirmed that not only the surface reduction of Pt(IV) ions into Pt(II) is the main platinum adsorption mechanism on the activated carbon. Determination of platinum after its preconcentration on the modified activated carbon was tested and validated by applying certified reference materials. The proposed method has been successfully applied for the determination of Pt in real samples using the standard calibration method.

FtsZ Cytoskeletal Filaments as a Template for Metallic Nanowire Fabrication

Supramolecular protein assemblies can serve as templates for the fabrication of inorganic nanowires due to their morphological reproducibility and innate proclivity to form well-ordered structures. Amongst the variety of naturally occurring nano-scale assemblies, cytoskeletal fibers from diverse biological sources represent a unique family of scaffolds for biomimetics as they efficiently self-assemble in vitro in a controllable manner to form stable filaments. Here, we harness the bacterial FtsZ filament system as a scaffold for protein-based metal nanowires, and further demonstrate the control of wire alignment with the use of an external magnetic field. Due to the ease at which the bacterial FtsZ is overexpressed and purified, as well as the extensive studies of its ultrastructural properties and physiological significance, FtsZ filaments are an ideal substrate for large-scale production and chemical manipulation. Using a biologically compatible electroless metal deposition technique initiated by adsorption of platinum as a surface catalyst, we demonstrate the coating of assembled FtsZ filaments with iron, nickel, gold, and copper to fabricate continuous nanowires with diameters ranging from 10-50 nm. Organic-inorganic hybrid wires were analyzed using high-resolution field-emission-gun transmission and scanning electron microscopy, and confirmed by energy-dispersive elemental analysis. We also achieved alignment of ferrofluid-coated FtsZ filaments using an external magnetic field. Overall, we provide evidence for the robustness of the FtsZ filament system as a molecular scaffold, and offer an efficient, biocompatible procedure for facile bottom-up assembly of metallic wires on biological templates. We believe that bottom-up fabrication methods as reported herein significantly contribute to the expanding toolkit available for the incorporation of biological materials in nano-scale devices for electronic and electromechanical applications.

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 [PtCl62− 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.

A computational study of platinum adsorption on defective and non-defective silicon carbide nanotubes

Platinum adsorption on the pristine, Stone–Wales defect, and vacancy defects sites in (8,0) zigzag silicon carbide nanotubes are studied based on the spin-polarized density functional theory. The formation of the Stone–Wales defects with the axial bond rotation is more favorable than the circumferential one. In addition, the vacancy of the carbon atom is more desirable than the silicon atom. The stable adsorption sites and their binding energies on different defect types are analyzed and compared to those on the perfect side wall. It is determined that the adsorption of Pt atom on nine-membered ring in carbon vacancy defect is the most exothermic site. Thus, the presence of intrinsic defects can enhance the reactivity of silicon carbide nanotubes toward Pt atom. Furthermore, the dangling bonds are the main driving force in preventing Pt atom from clustering. It is noticeable that the systems with Pt atom remained semiconductor with direct band gaps. Pt atom on pristine and vacancy-defective silicon carbide nanotubes were positively charged, whereas on Stone–Wales structures, Pt atom gained some charge. In addition, only silicon vacancy structure as structure without Pt atom showed ferromagnetic ordering, while all the systems in presence of Pt atom exhibited non-magnetic moment.

Recovery of precious metals from ammoniacal thiosulfate solutions by hybrid mesoporous silica: 3 – Effect of contaminants

Precious metal concentration and/or separation processes based on adsorption such as in hydrometallurgical systems are often affected by the presence of dissolved contaminant/impurity species. This research is the first report on investigation of the effect of impurity metal and oxyanion associations with gold and PGM concentration by hybrid mesoporous silica adsorbent in neutral-pH simulated thiosulfate leach solution. It was found that the increased solubility of Fe(III) or Cr(III) salts beyond a certain loading limit was accompanied by a decrease in the equilibrium pH. The latter adversely affected precious metal recovery by impeding adsorption (of platinum and gold) and causing precipitation (of palladium) in the thiosulfate solutions. Increasing loading concentration of softer Lewis acid cations such as those of nickel, zinc and lead caused gradual decrease of the precious metal adsorptions with minor effects on the pH. While platinum adsorption recovery was least affected by up to 200mg/L nickel loading, gold adsorption was almost unaffected by up to the same amount of lead addition. Arsenic oxyanions were almost fully dissolved while antimony and tellurium salts were mainly insoluble in the thiosulfate equilibrium system. Increasing total oxyanion loading concentration (up to about 1500mg/L) resulted in gradual rather slow decrease in gold and PGM adsorption recoveries. In the end, highly selective adsorption of precious metals by both thiol and amine organic functional groups on hybrid mesoporous silica was achievable provided that concentration of metal/oxyanion contaminants were controlled and pH was further stabilized at the 7–8 regime.

The Adsorption of Gold, Palladium, and Platinum from Acidic Chloride Solutions on Mesoporous Carbons

Studies on the adsorption characteristics of gold, palladium, and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II), and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of chloride ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.

Platinum recovery from model media and a Pt–Sn/alumina spent catalyst extract using corn husk-based adsorbent

Preparation of corn husk-based adsorbent for platinum recovery is studied. The adsorbents are prepared and characterized, and the adsorption of platinum onto the adsorbents is examined. Results indicate that hydroxyl and amine groups are responsible for adsorption of platinum onto the adsorbents. Immobilized amine enhances the adsorption and aluminates interfere in adsorption of platinum ions. The adsorption capacity of the adsorbent with immobilized amine for model media and intact solution is 38.5 and 16.2mg Pt/(g adsorbent), respectively. Structural changes of the treated corn husk is explained by Mannich mechanisms. The kinetics of adsorption of Pt follows a pseudo-second-order model.

Evaluation of RuCORE@PtSHELL Structure for the Oxygen Reduction Reaction (ORR) with Methanol-Crossover during DMFC Operation

Direct Methanol Fuel Cells (DMFCs) is a promising energy conversion device operating in the low temperature operating range, and is especially appropriate for portable applications. Nevertheless, there are still many problems that need to be solved before any market penetration can be expected. Electrodes with high loadings of expensive platinum-based electrocatalysts, such as PtRu/C and Pt/C, are found as the best catalysts for methanol electrooxidation and oxygen reduction, respectively. However, while the anodic electrocatalyst suffer a serious deactivation due to the strong adsorption of methanolic residues, mainly CO, the ORR on platinum is limited by its slow kinetics. In addition, non-reacted methanol can diffuse through the solid (polymer) electrolyte (typically, a Nafion® membrane) towards the cathode due to the relative high concentration of methanol at the anode (the so-called methanol-crossover). Thus, methanol competes with oxygen for the platinum adsorption sites on the cathode and causes mixed potentials which reduce the open-circuit potential and, as a result, a serious decrease in the performance of the DMFC-device.To solve the above setbacks, one approach is to develop membranes with lower permeation for alcohols, as well as the design of cathodic electrocatalysts which operates successfully with the presence of methanol.RucorePtshell/C has shown a superior CO-tolerance than single platinum, which is assigned to an electronic effect towards the Pt shell from the covered Ru cores[1]. Additionally, it also exhibit higher stability on the anodic performance for the methanol oxidation reaction (MOR) at elevated temperatures in a single fuel cell, compared with PtRu/C[2]. Previous experiments suggest changes in the reaction mechanism for both the MOR and the ORR for the core-shell structure, related to changes induced in the energy of the d-band of the Pt shell. Results so far indicate that the Ru@Pt core-shell structures would be useful in anode fed with carbon monoxide and hydrogen (reformate), DMFC (methanol-fed) anodes, and DMFC cathodes (exposed to methanol-crossover), whereas in hydrogen-oxygen fuel cells little is gained by introducing Ru@Pt.This contribution simulates the cathodic behavior of the RucorePtshell/C catalyst, by conventional electrochemical methods and, tested in a single cell directly fed with methanol. We demonstrate results, showing a much lower increase in the overpotential for the core-shell structure over a Pt/C catalyst with similar total catalyst loading when methanol is present compared to no methanol present.The presence of ruthenium in the structure thus improves the tolerance towards methanol-crossover along the ORR, even when this ruthenium is not present in the catalyst surface, which indicates the purely electronic nature of the effect of core ruthenium on shell platinum.

Adsorption and separation of palladium and platinum with microcapsules containing tri-n-octylamine hydrochloride

The adsorption and separation of palladium and platinum from an acidic aqueous solution were conducted using microcapsules containing a metal extractant, tri-n-octylamine hydrochloride. The spherical microcapsules with an average diameter of 208μm were prepared through encapsulation of the extractant by in situ radical polymerization of divinylbenzene. Results for the adsorption equilibrium of each metal were applied to the Langmuir adsorption isotherm model to explain the experimental results. The adsorption rate of the metals was also measured using a shallow bed reactor, and indicated that diffusion of the metal-chloro complexes through the pores in the microcapsules contributed to the overall adsorption process of the metals. Separation of the metals was conducted using a glass column packed with the microcapsules. The separation efficiency increased when the flow rate of a feed solution containing both metals was 3mL/min. Separation of the metals was almost achieved under appropriate experimental conditions during the adsorption step.

Evaluation of chitosan flakes as adsorbent for palladium and platinum recovery from binary dilute solutions

In the recent years, special attention has been paid to the competitive recovery or separation of metals from industrial wastewaters or solid wastes that contain more than one chemical component. Platinum group metals (PGMs), particularly palladium and platinum, are used together in many fields such as industrial catalyst production. The recovery of these metals from industrial waste streams has required development of present processes and new technologies. In this work, the potential of chitosan for palladium and platinum recovery from aqueous solutions was investigated. The observed results showed that the optimum operating conditions for palladium and platinum recovery by chitosan were initially pH = 2, particle size of adsorbent = 0.21 mm and adsorbent dose = 10 g/L. Experimental results indicated that Freundlich isotherm and Langmuir models best fitted with the equilibrium data of platinum and palladium adsorption on chitosan in single solutions, respectively. In binary solutions, the competitive adsorption of palladium and platinum were successfully described by the Langmuir competitive model (LCM). As it was expected, experimental results indicated that, equilibrium capacity for each metal decreased in presence of another ion due to competition of palladium and platinum anions for active sites on the chitosan surface.

Adsorption and separation of platinum and palladium by polyamine functionalized polystyrene-based beads and nanofibers

Adsorption and separation of platinum and palladium chlorido species (PtCl62- and PdCl42-) on polystyrene beads as well as nanofibers functionalized with ammonium centres based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tris-(2-aminoethyl)amine (TAEA) are described. The functionalized sorbent materials were characterized by microanalysis, SEM, XPS, BET and FTIR. The surface area of the functionalized fibers was in the range 69–241m2/g while it was 73–107m2/g for the beads. The adsorption and loading capacities of the sorption materials were investigated using both the batch and column studies at 1M HCl concentration. The adsorption studies for both PtCl62- and PdCl42- on the different sorbent materials fit the Langmuir isotherm with R2 values >0.99. The highest loading capacity of Pt and Pd were 7.4mg/g and 4.3mg/g respectively for the nanofiber sorbent material based on ethylenediamine (EDA) while the beads with ethylenediamine (EDA) gave 1.0mg/g and 0.2mg/g for Pt and Pd respectively. Metals loaded on the sorbent materials were recovered by using 3% m/v thiourea solution as the eluting agent with quantitative desorption efficiency under the selected experimental conditions. Separation of platinum from palladium was partially achieved by selective stripping of PtCl62- with 0.5M of NaClO4 in 1.0M HCl while PdCl42- was eluted with 0.5M thiourea in 1.0M HCl. Separation of platinum from iridium and rhodium under 1M HCl concentration was successful on triethylenetriamine (TETA)-functionalized Merrifield beads. This material (M-TETA) showed selectivity for platinum albeit the low loading capacity.

Platinum adsorption from chloride media using carbonized biomass and commercial sorbent

Pistachio nut shells, an agricultural waste biomass, and Lewatit TP 214, a commercial sorbent, were investigated as adsorbents for the adsorption of platinum from dilute hexachloroplatinic acid solutions. Before the pistachio nut shells were carbonized, adsorption percentage was 65%, whereas Lewatit TP 214 ensured almost 100% adsorption. However, after the pistachio nut shell was carbonized at 1,000° C under an argon atmosphere, the platinum adsorption (%) increased two-fold. The effects of such parameters as sorbent dosage, contact time, temperature and solution pH on adsorption were studied in detail in batch mode. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Qmax, at 25° C were found to be 38.31 and 33.22 mg/g for the carbonized pistachio nut shell and Lewatit TP 214, respectively. The adsorption of platinum on both sorbents was found to be described by the pseudo-second-order kinetic model. The results indicated that the activated carbon prepared from pistachio nut shells can be effectively used for the removal of platinum from acidic solutions.

Adsorption and reduction of platinum(IV) chloride complex ions on activated carbon

The adsorption kinetics of platinum(IV) chloride complex ions on the activated carbon Norit GF40 was investigated. Experiments were carried out at different initial concentrations of Pt(IV) chloride complex ions, temperature, rate of mixing and pH. It was found that the value of activation energy of the studied process is equal to 19.7 kJ/mol. From the ICP MS analysis it was confirmed that platinum ions (Pt(IV) and Pt(II)) are removed from the solution due to the adsorption and are further reduced to the metallic state. Such mechanism was confirmed by XPS analysis which showed that on the carbon surface three forms of platinum species, i.e. Pt(0), Pt(II) and Pt(IV), exist. The presence of platinum in the solution at different oxidation states was also confirmed spectrophotometrically by identification of their characteristic absorption bands. The metallic form of Pt present on the surface of activated carbon was observed in the form of small spherical islands with the diameter not exceeding 500 nm. Those islands consist of smaller, flake-shape particles with a thickness of about 35 nm.

Comparison of adsorptions by rice hull and Lewatit TP 214 of platinum in chloride solution

Rice hull, a biomass waste product, and Lewatit TP 214, a thiosemicarbazide sorbent, were investigated as adsorbents for the adsorption of platinum (IV) ions from synthetically prepared dilute chloroplatinic acid solutions. The rice hull was characterized by Attenuated Total Reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The effects of the different adsorption parameters, sorbent dosage, contact time, temperature and pH of solution on adsorption percentage were studied in detail on a batch sorption. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum monolayer adsorption capacities, Qmax, at 25?C were found to be 42.02 and 33.22 mg g-1 for the rice hull and Lewatit TP 214, respectively. Thermodynamic calculations using the measured ?H?, ?S? and ?G? values indicate that the adsorption process was spontaneous and exothermic. The pseudo-first-order and pseudo-second-order rate equations were investigated; the adsorption of platinum ions for both sorbents was found to be described by the pseudo-second-order kinetic model. The kinetic rate, k2, using 30 mg sorbent at 25?C was found to be 0.0289 and 0.0039 g min-1 mg-1 for the rice hull and Lewatit TP 214, respectively. The results indicated that the rice hull can be effectively used for the removal of platinum from aqueous solution.

Adsorption of palladium and platinum from aqueous solutions by chitosan and activated carbon coated with chitosan

ABSTRACTIn this work, the potential of chitosan and activated carbon coated with chitosan for palladium and platinum adsorption from aqueous solutions was investigated. The observed results showed that the optimum operating conditions for palladium and platinum adsorption on chitosan were initial pH 2, particle size of adsorbent = 0.21 mm and adsorbent dose = 10 g/L. Equilibrium studies showed that palladium and platinum adsorption on chitosan was of spontaneous and exothermic nature. Equilibrium results fitted with Langmuir, Freundlich, Temkin and Dubinin‐Radushkevich models for two adsorbents. The maximum adsorption capacities for palladium and platinum adsorption were 62.50 and 66.66 mg/g of chitosan and 43.48 and 52.63 mg/g of activated carbon coated with chitosan, respectively. Kinetic data were found to confirm pseudo‐second‐order kinetic model. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.