Removal Of Pt Research Articles

Enhanced Piezocatalytic Water Splitting by Platinum‐Decorated Barium Titanate

AbstractPiezocatalysis has emerged as a promising field of research that uses mechanical energy to drive a chemical change. There is growing evidence that piezocatalysts can perform challenging chemical conversions from organic transformations to water splitting. A key challenge to piezocatlaysis is mitigating the inherent high relative permittivity of a ferroelectric material. This high permittivity restricts the transfer of carriers required for a chemical reaction to occur and reduces the reaction rate. Here the concept of producing a co‐catalyst system is taken to enhance carrier mobility increasing the observed reaction rate. The study highlights the importance of determining the sonochemical and piezocatalytic contributions to catalysis. The combination of a Pt metal co‐catalyst with BaTiO3 through a simple solid‐state method led to a four fold increase in the rate of H2 production compared to BaTiO3 and sonochemical reactions in the absence of a catalyst. BaTiO3/Pt is found to exhibit stable piezocatalytic performance over 12 h. Where there is a deviation from steady‐state water splitting, it is shown that this is due to mechanical removal of Pt rather than a phase change in the catalyst system. This work confirms the additive benefits of hybrid materials for improving piezocatalytic processes.

Functionalized palm biomass-derived activated carbon for the removal of Pt(IV) from a simulated leachate

Over the years, demand for Platinum Group Metals (PGMs) has grown steadily due to increased production of various advanced technologies, such as automotive and electronic products. PGMs are predominantly used in automotive catalysts in the automotive industry. Along with the increase in automotive production, deactivated automotive catalysts pose environmental and health hazards. These wastes are excellent alternative sources of PGMs, which can be exploited to bridge the gap between the demand and supply of PGMs. Adsorption is one of the most popular metal removal/recovery methods due to its various advantages, such as ease of use and cost-effectiveness. In consideration of this method, developing an inexpensive and efficient adsorbent is a crucial point. Thus, activated carbon (AC), derived from a palm kernel shell that is abundantly available in Indonesia, was functionalized using ionic liquid (ACIL) and used for Pt(IV) removal from a simulated automotive catalyst waste leachate. The functionalized AC showed a high adsorption capacity (178.6 mg g−1), in which the adsorption of Pt(IV) followed a chemisorption route, fitting with the monolayer model. The functionalized adsorbent also showed excellent performance during continuous Pt(IV) adsorption from simulated leachate. Recovery of precious metals, such as Pt(IV) and Pd(II), from the simulated leachate containing other metals was possible by maintaining the high hydrochloric acid concentration. Furthermore, targeted separation of Pt(IV) was achieved through sequential desorption using NaClO4. In addition, ACIL showed remarkable reusability after being used for three cycles without showing a noticeable decrease in performance. Thus, this study highlights the capability of a functionalized adsorbent from palm oil industry biomass to recover precious metals from simulated leachate of automotive waste.

Removal of platinum (IV) from aqueous solutions with yeast-functionalised bentonite

There is a need for cheap but, efficient methods for the removal of precious metals from wastewaters, which are normally lost during mineral processing. Moreover, the disposal of yeast waste from brewing has been a problem in many parts of the world. In this study, the removal of Pt(IV) from aqueous solutions using the readily available bentonite clay functionalised with spent yeast from brewing was investigated. The maximum adsorption capacity of Pt(IV) with 100 mg yeast-functionalised bentonite at pH 2 within 90 min was 255 μg g−1 (98.5% efficiency) but, decreased as pH increased. The adsorption capacity of Pt(IV) was insignificantly (p > 0.05) affected by the presence of competing ions (Fe(III), Ca(II), Mg(II), K(I), Co(II), Ni(II), Hf(IV), Zn(II) and other platinum group metals (PGMs)). Moreover, most of these metals were significantly adsorbed along with Pt(IV). The indicative cost-benefit analysis showed that 1 kg of the yeast-functionalised bentonite can remove ∼700 g Pt(IV) in which a profit of more than USD20000 can be made. The bentonite functionalised with spent yeast from brewing has a potential to recover lost PGMs in wastewater. Since, this is a cheap process, the mining and other industries can make much profit from such recoveries.

Removal of platinum (IV) from hydrochloric acid medium with OMImT: Theoretical and experimental evidences for a neutral complexing mechanism

As Disperser solvents are commonly toxic and volatile organic solvents in industry, disperser-free strategy enjoys the advantages of environmental benignity and cost control. In this work, 1-octyl-3-methylimidazole-2-thione (OMImT), a neutral sulfur-bearing extractant with low melting point and negligible vapor pressure, was synthesized and first utilized for the removal of Pt(IV) from hydrochloric acid medium by disperser-free precipitation owing to its excellent hydrophobicity and low viscosity. Estimation for the removal performance of Pt(IV) by disperser-free precipitation, in comparison with that by liquid-liquid extraction (LLE) with disperser cyclohexane, was conducted on the effects of the dosage of OMImT and vibration time. Subsequently, variable influence factors on the removal of Pt(IV) (e.g. phase ratio, HCl concentration, H+ concentration and Cl− concentration) were also explored. Afterwards, the removal mechanism of Pt(IV) with OMImT was first proposed and evidenced to be a special neutral complexing mechanism via a combination of quantum-chemical calculations and experimental measurements. At last, kinetic data were analyzed by kinetics fitting methods. In brief, OMImT is a highly effective, environmentally benign and cost efficient candidate for the Pt(IV) removal.

Removal of Platinum and Palladium from Wastewater by Means of Biosorption on Fungi Aspergillus sp. and Yeast Saccharomyces sp.

The emission of platinum group metals from different sources has caused elevated concentrations of platinum and palladium in samples of airborne particulate matter, soil, surface waters and sewage sludge. The ability of biomass of Aspergillus sp. and yeast Saccharomyces sp. for removal of Pt(IV) and Pd(II) from environmental samples was studied in this work. The pH of the solution, the mass of biosorbent, and contact time were optimized. The Langmuir and Freundlich adsorption isotherms and kinetic results were used for interpretation of the process equilibrium of Pt(IV) and Pd(II) on both microorganisms. The maximal efficiency of retention of Pt(IV) on yeast and fungi was obtained at acidic solutions (pH 2.0 for Pt(IV) and pH 2.5–3.5 for Pd(II)). The equilibrium of the biosorption process was attained within 45 min. The best interpretation for the experimental data was given by the Langmuir isotherm. Kinetics of the Pt and Pd adsorption process suit well the pseudo-second-order kinetics model. Fungi Aspergillus sp. shows higher adsorption capacity for both metals than yeast Saccharomyces sp. The maximum adsorption capacity of fungi was 5.49 mg g−1 for Pt(IV) and 4.28 mg g−1 for Pd(II). The fungi possess the ability for efficient removal of studied ions from different wastewater samples (sewage and road run-off water). It was also demonstrated, that quantitative recovery of Pd from industrial wastes could be obtained by biosorption using Aspergillus sp.

Kinetic studies of the removal of Pt(IV) chloride complex ions from acidic aqueous solutions using activated carbon

In this paper, results showing the possibility of activated carbon application in platinum recovery from aqueous solution are presented. The studies were performed with the commercially available activated carbon, and the results can be easily transferred directly to the industry. The influence of pH, mixing rate, and amount of activated carbon as well as platinum(IV) initial concentration on the rate of adsorption was investigated. It was shown that after adsorption platinum is present on the surface of activated carbon in two oxidation states, +2 and +4, where shares of those forms are equal to 47 and 53%. Moreover, the enthalpy and entropy of activation were determined and are equal to 16.14 ± 075 kJ mol−1 and 42.19 ± 0.28 J mol−1 K−1.

Soil amendment using poplar woodchips to enhance the treatment of wastewater-originated nutrients

Vegetation filters, a nature based wastewater regeneration technology, have been reported as a feasible solution for small municipalities and scattered populations with limited access to sewage networks. However even when such a treatment is properly planned, the leaching of contaminants through the unsaturated zone may occur. The amendment of soil with a readily-labile source of carbon is supposed to ameliorate the removal of contaminants by stimulating microbial activity and enhancing sorption processes. In this study, lab-scale leaching column experiments were carried out to explore if the addition of woodchips to the soil could be a feasible strategy to be integrated in a vegetation filter. Two different types of arrangement of soil and woodchips layers were tested. The soil was collected from an operating vegetation filter treating wastewater of an office building characterised by a high nutrient load. Daily pulse of synthetic wastewater were applied into the columns and effluent samples were collected and analyzed for major ions, total nitrogen (NT), total phosphorous (PT) and chemical oxygen demand (COD). By the end of the experiment, NT, NO3-N and PT soil contents were also measured. Results indicate that amendments with woodchips enhance the elimination of wastewater-originated contaminants. NT removal in the columns with woodchips reaches a value of 99.4%. The main processes responsible for this elimination are NH4-N sorption and nitrification/denitrification. This latter fostered by the reduced redox conditions due to the enhanced microbial activity. High removal of PT (99%) is achieved independently of the woodchips presence due to retention and/or precipitation phenomena. The COD removal efficiency is not affected by the presence of the woodchips. The leaching of organic carbon occurs only during the experimental start-up period.

A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) .

A Pd/C‐CeO2 Anode Catalyst for High‐Performance Platinum‐Free Anion Exchange Membrane Fuel Cells

AbstractOne of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM‐FCs). The anion exchange membrane fuel cell (AEM‐FC) has long been proposed as a solution as non‐Pt metals may be employed. Despite this, few examples of Pt‐free AEM‐FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt‐free AEM‐FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt‐free AEM‐FC that employs a mixed carbon‐CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM‐FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm−2.

Application of chelating ion-exchangers Amberlite IRC-718 and Duolite ES-346 in removal of Pt(IV) ions from chloride and chloride-nitrate media

Abstract The chelating ion exchangers of the functional iminodiacetate (Amberlite IRC-718) and amidoxime (Duolite ES-346) groups have been applied for Pt(IV) removal from the chloride (0.1 ÷ 8.0 M HCl) and chloride-nitrate (0.1 M HCl + 0.9 M HNO3, 0.5 M HCl + 0.5 M HNO3, 0.9 M HCl + 0.1 M HNO3) solutions. The monolayer sorption capacities (Q 0) for Amberlite IRC-718 determined from the Langmuir isotherm model were changed from 1.032 to 0.917 mmol g−1 and from 0.948 to 0.831 mmol g−1 in the chloride and chloride-nitrate solutions, respectively. For Duolite ES-346 Q 0 values were equal to 1.120–0.937 mmol g−1 in the chloride solutions and 0.692–0.806 mmol g−1 in the chloride-nitrate systems. The influence of acid concentrations, phase contact time and macrocomponent addition (AlCl3, CuCl2, NiCl2) on Pt(IV) sorption was also studied. The pseudo second order equation provided the best fitting of experimental values. The working and total ion exchange capacities as well as distribution coefficients of Pt(IV) w...

Parallel Fabrication of Sub-50-nm Uniformly Sized Nanoparticles by Deposition through a Patterned Silicon Nitride Nanostencil

Using low-pressure chemical vapor deposition of silicon dioxide, we have reduced the size of 56-nm features in a silicon nitride membrane, called a stencil, down to 36 nm. Sub-50-nm uniformly sized nanoparticles are fabricated by electron-beam deposition of Pt through the stencil mask. A self-assembled monolayer (SAM) of tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane was used to reduce Pt clogging of the nanosize holes during deposition as well as to protect the stencil during the postdeposition Pt removal. X-ray photoelectron spectroscopy shows that the SAM protects the stencil efficiently during this postdeposition removal of Pt.

Effects of the modulating agent WR2721 and its main metabolites on the formation and stability of cisplatin-DNA adducts in vitro in comparison to the effects of thiosulphate and diethyldithiocarbamate

The influence of the modulating agent WR2721, its active thiol-metabolite WR1065 and the symmetrical disulphide WR33278 on the in vitro formation and stability of cis-diamminedichloroplatinum(II) (cisplatin, CDDP)-DNA adducts was investigated and compared with the effects of the highly nucleophilic modulating agents diethyldithiocarbamate (DDTC) and thiosulphate (TS). Salmon sperm DNA (0.5 mg/mL) was incubated with 25 μg/mL (83 μM) cisplatin for 1 hr in 50 mM phosphate buffer, pH7.2 at 37° in the absence or presence of modulating agent. DDTC and TS were potent inhibitors of the platination of the DNA (95 and 89%, respectively, with 4.2 mM of modulating agent). The WR-compounds were also remarkably active in the inhibition of DNA platination. Prevention of adduct formation in the presence of 4.2 mM WR-compound decreased in the order WR1065 (74%) > WR33278 (63%) > WR2721 (51%). The prevention of CDDP-DNA adduct formation by WR1065 was strongly concentration-dependent up to 4.2 mM but at higher concentrations this protection hardly increased at all. In the presence of the modulating agents, increased levels of CDDP monofunctionally bound to a guanine residue were observed with a simultaneous decrease in the relative abundance of bifunctional adducts. All modulators were also able to reverse part of the CDDP-DNA adducts formed. After a 2-hr incubation of already platinated salmon sperm DNA with 4.2 mM of modulating agent, the removal of Pt from DNA amounted to about 43% with DDTC, 28% with WR1065 and 13–14% with TS, WR2721 and WR33278. Even CDDP bifunctionally bound to two adjacent guanines in the same DNA strand, which is considered to be a very stable adduct, was partly reversed. Our observations suggest that WR2721, especially when administered prior to or concomitantly with CDDP, can be expected to protect those tissues from CDDP-induced damage to DNA that are able to efficiently dephosphorylate WR2721 followed by uptake of the thiol metabolite WR1065. This stresses the importance of a selective formation and uptake of WR1065 by non-tumour tissues for the successful use of WR2721 as a protective agent in combination with platinum-based cancer chemotherapy.

The Pt—O + H 2 reaction from initial steady-state potentiostatic conditions

H 2 reactivity with steady-state formed Pt—O is far slower and more complex than H 2 reactivity with transient formed Pt—O ad. Under steady state, dermasorbed oxygen, adsorbed sulphate ions, and the uncertainty in the types and total quantities of associated oxygen make the relationship between the concentration of oxygen and time, or potential, too complex for direct kinetic evaluation. The early, diffusion-independent, open-circuit potential decay from steady state, however, can be described using a model of two capacitive discharges. One process is a double-layer capacitance discharge plus complex adsorption/desorption effects, while the second is the chemical removal of Pt—O by reaction with H 2.

Isotopic exchange of bromide ligands in platinum(II)

The kinetics of the replacement of the bromide ligands for cis-Pt(NH 3) 2Br 2 by H 2O and by 82Br − in water at 25° and 35° have been studied. An ion exchange procedure to remove Br − was utilized although the conditions had to be rigorously controlled to prevent excessive removal of Pt(NH 3) 2Br 2. The first aquation occurs with a first order rate constant of 3.0 × 10 −5 sec −1 at 25°, ΔH * = 18 kcal/mole. In addition, a direct second order bromide exchange for cis-Pt(NH 3) 2Br 2 is measurable, K Br = 3.3 × 10 −4 M −1 sec −1 at 25°; ΔH * = 18 kcal/mole. The equilibrium quotients for the replacement of the first and second Br-ligands are K 1 = 9.6±.8 × 10 −4 M and K 2 = 9±2 × 10 −5 M, respectively.