Cobalt precipitation by reduction with sodium borohydride

Lü, Jianming; Dreisinger, David; Cooper, W. Charles

doi:10.1016/s0304-386x(96)00086-2

Cited by 87 publications

(51 citation statements)

References 39 publications

(109 reference statements)

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“…Normal şartlarda stokiyometrik miktarda çöktürücü çözeltide bulunan tüm Rh iyonlarının tamamını çöktürübilmesi beklenmektedir fakat çöktürme süresi tamamen kinetik faktörlere bağlıdır; ayrıca indirgeyici ajanın bir kısmı asit tarafından da teüketilmektedir. NaBH 4 miktarının arttırılması, ortamda bulunan Rh iyonları ile temas etme şansını arttırarak çok hızlı ve yüksek bir verim ile çökmeye sebep olmaktadır [12].…”

Section: Sodyum Bor Hidrür Indirgeyici Miktarının Etkisiunclassified

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Atık Rodyum Kaplama Çözeltilerinden Rodyum Geri Kazanımı

Morcali

Aktaş

2014

MUFBED

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ÖzetKuyum sektöründe ve endüstriyel uygulamalarda rodyum metal (Rh) kullanımının artması sonucu, geri dönüştürülebilir malzemelerin (konsantreler, anot çamurları, ramat atıkları ve katalitik dönüştürücüler) yanı sıra kaplama banyolarından da rodyumun geri kazanılmasında hızlı, kolay ve ucuz metotlara ihtiyaç duyulmaktadır. Bu çalışmada; çeşitli kimyasallar (sodyum bor hidrür ve etil alkol gibi) kullanarak Rh sülfat bayolarından Rh geri kazanımı araştırılmıştır. Geri kazanım deneylerinde, kimyasal miktarı, reaksiyon süresi ve sıcaklık deney parametreleri olarak incelenmiştir. Yapılan deneyler sonucunda Rh ihtiva eden kaplama banyo çözeltilerinden değerli Rh metalinin geri kazanımı mümkün olmuştur. Kimyasal çöktürme yoluyla %99+ safiyetinde rodyum siyahı elde edilmiştir. Elde edilen bu ürün rafinasyon işlemini müteakip Rh sulfat banyolarının hazırlanmasında kullanılabilir.Anahtar Kelimeler: Rodyum; Kaplama banyoları; Çöktürme; Geri kazanım. Recovery of Rhodium from Spent Rhodium Plating Solutions AbstractThe growing use of Rhodium (Rh) in jewelry and industrial applications requires fast, easy and inexpensive methods for the recovery of Rh, not only in recyclable materials, such as concentrates, anode slimes, polish waste and catalytic converters, but also from plating baths. In this paper, the recovery of Rh from spent Rh sulfate plating solutions via chemical agents (i.e. sodium borohydride and ethanol) was investigated. For the recovery experiments, the amount of reagents, reaction time and temperature were selected as variable reaction parameters. The experimental results have demonstrated that it is possible to recover the valuable Rh metal from Rh-containing plating baths. A fine Rh black powder was produced using chemical agents. The purity level of the produced metal is above 99 %. The product may be used for the preparation of fresh Rh sulfate plating solutions, after a simple refining procedure. It may then be re-used to plate items for decorative purposes.

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Section: Sodyum Bor Hidrür Indirgeyici Miktarının Etkisiunclassified

“…Ayrıca, NaBH 4 'ün çözeltiye ilave edilmesi ile reaksiyon hemen gerçekleşmekte, fakat anlık gerçekleşen bu reaksiyonun dengeye ulaşması biraz zaman almaktadır. Bu sürenin yaklaşık olarak eklenen indirgeyici miktarına da bağlı olarak 40 dakika ve üzerinde dengeye ulaştığı ilgili şekilden anlaşılmaktadır [12,13].…”

Section: şEkil-3unclassified

Atık Rodyum Kaplama Çözeltilerinden Rodyum Geri Kazanımı

Morcali

Aktaş

2014

MUFBED

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“…In contrast, for the RT catalyst, it is likely that more of the cobalt is in its unalloyed, metallic phase, which is known to exhibit lower hydrolysis activity [19,27]. A possible explanation for the increased boron content using the LT method is given in Lu et al (1997), who described the formation of the catalyst (which they referred to as Co 2 B) via the following steps:…”

Section: Comparison Of Catalyst Synthesis Methodsmentioning

confidence: 99%

Sodium borohydride production and utilisation for improved hydrogen storage

Muir¹

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Sodium borohydride (NaBH 4 ) has been the subject of extensive investigation as a potential hydrogen storage material. Its advantages include its ability to be stored as a stabilised aqueous solution and hydrolysed catalytically on demand, providing hydrogen safely, controllably, and at mild conditions. However, several drawbacks were identified by the US Department of Energy (DOE) in their "No-Go" recommendation in 2007; namely, the limitations on its gravimetric hydrogen storage capacity (GHSC) and its prohibitive manufacturing cost.This thesis aims to address some of the major issues associated with the use of NaBH 4 for hydrogen storage. Efforts have been spread across three key research areas, which were identified in a review of the recent literature: Synthesising an efficient, durable, and inexpensive catalyst for the hydrolysis of aqueous NaBH 4 solution  The design of a hydrogen storage system based on NaBH 4 which can overcome the GHSC constraints imposed by the solubility of its hydrolysis by-product, NaBO 2  The development of a novel recycling process for regenerating NaBH 4 from NaBO 2 , with the goal of reducing its production cost to within the DOE's target range of $2-4 per gallon of gasoline equivalent (gge) To achieve the first goal, a new electroless plating method was developed for preparing cobalt-boron (Co-B) catalysts supported on shaped substrates. This method involves mixing the plating solutions at low temperature (<5 o C), in contrast to previously employed methods, which are generally carried out at room temperature or higher. The new method requires only one plating step to achieve the desired catalyst loading, and has higher loading efficiency than processes requiring multiple plating steps, due to reduced catalyst wastage. The catalysts produced by this method show significantly higher NaBH 4 hydrolysis activity than those prepared by conventional methods, with a hydrogen generation rate over 24000 mL/min/g recorded at a temperature of 30 o C and a NaBH 4 concentration of 15 wt%. The improved activity of these catalysts was thought to be due to their increased boron content and nanosheet-like morphology, both of which are products of the low temperature preparation method.ii The stability of these catalysts was examined over several usage and deactivation cycles, which involved long-term exposure to alkaline solution. It was found that the deactivated catalysts were able to recover 80-90% of their initial activity even after 10 cycles, if operated at 40 o C or higher. Characterisation of the deactivated catalysts revealed that a layer of NaBO 2 had formed on the surface, blocking the catalytically active Co sites. The improved cyclic stability is most likely due to the dissolution of this layer at higher temperatures.A new reactor design for a NaBH 4 -based hydrogen storage system was developed, with the goal of overcoming the GHSC limitations encountered by conventional system designs. The new design is based on a fed-batch configuration in which solid NaBH 4 is added ...

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“…25 Hence, the disappearance rate of primary particles depends on P(X,t), which can be determined assuming pseudo-steady state and spherically-symmetric direct pair interactions, (r), reducing Eq. 17 to,…”

Section: 28mentioning

confidence: 99%

“…[24][25][26][27][28][29][30] from the parameters and constants in Table 1to elucidate the reaction conditions that control the early-stage growth of the dodecanethiol-functionalized Ag nanoparticles.…”

Section: Analysis Of the Net Interaction Potential And Its Implicatiomentioning

confidence: 99%

A Straightforward, One-Step Synthesis of Alkyl Thiol Capped Silver Nanoparticles

Farrell¹

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Classical nucleation theory and Derjaguin, Landau, Verwey, Overbeek (DLVO) theory for colloidal stability were applied to gain insight into the synthesis of dodecanethiol (DDT)-functionalized silver nanoparticles (NPs) by reduction of silver nitrate with sodium borohydride in ethanol. This analysis indicated the importance of quickly establishing a dense DDT ligand brush on inherently unstable primary particles to achieve colloidal stability. The DLVO calculations also indicated that the electrostatic potential was a minor contributor to repulsive interactions, signifying that it would be possible to control NP size and uniformity in solutions with high ionic strength, as long as sufficient DDT was available to form a densely packed ligand layer on the NPs. These insights were applied to design a new straightforward, one-step, one-phase synthesis for the production of alkyl thiol-functionalized silver NPs. To test the insights from DLVO theory, a battery of 16 samples were synthesized in the parameter space R=3-12, S=1-12 where R= [NaBH 4 samples with R=3 or S=1 were polydisperse, however, samples in the R=6-12 and S=3-12 range had uniform particle sizes with average diameters between 3.5-4.7 nm.Additionally, samples with R=72-108 and S=12 were synthesized to test particle stability at high ionic strength; again uniform NPs with average diameters from 3.5-3.8 nm were produced. Ultimately, the insights gained from DLVO theory successfully guided the development of a one-step, one-phase technique for the synthesis of uniform, spherical alkyl thiol-functionalized silver NPs. In future work, this technique will be extended to facilitate the grafting of polymers from phase-separated ligand domains on NP surfaces.ii AcknowledgementsThere are a number of individuals who deserve recognition and thanks for enabling the work contained in this thesis. First, I would like to thank my advisor, Dr.David Green for humoring my constant skepticism and questions throughout this project; I know so much more now than when we started. I would also like to specifically thank Cameron Shelton, whose assistance in managing the seemingly endless number of nanoparticle syntheses was invaluable. Finally, I would like to thank the members of Dr.Green's research group (current and past) for their help and input: Dan Sunday, Allison Galey, and Caroline Dunn.iii Figure 12: UV-VIS spectra of DDT functionalized silver nanoparticles in toluene. Curve color is consistent within a given R value. The primary feature of interest is the presence of a strong plasmon band at ~450 nm which serves to confirm the presence of silver nanoparticles. With larger particles, it is possible to make size determinations from UV-VIS spectra, however, we know from TEM that the nanoparticles are smaller than 15 nm in diameter, placing them in a size-independent regime with respect to UV-VIS. .......... 50 Figure 13: UV-VIS spectrum of R=72 S=12 silver nanoparticles with TEM inset. The peak at 450 nm demonstrates the presence of small silver nanoparticl...

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Cobalt precipitation by reduction with sodium borohydride

Cited by 87 publications

References 39 publications

Atık Rodyum Kaplama Çözeltilerinden Rodyum Geri Kazanımı

Atık Rodyum Kaplama Çözeltilerinden Rodyum Geri Kazanımı

Sodium borohydride production and utilisation for improved hydrogen storage

A Straightforward, One-Step Synthesis of Alkyl Thiol Capped Silver Nanoparticles

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