Recovery Of Rhodium Research Articles

Electrochemical recovery of fission platinoids (Ru, Rh, Pd) from simulated high-level liquid waste

ABSTRACT Electrochemical behavior of ruthenium(III), rhodium(III) and palladium(II) present in the simulated high-level liquid waste (SHLLW) was studied, at 298 K, to explore the feasibility of recovering these fission platinoids from high-level liquid waste (HLLW). The cyclic voltammogram of SHLLW at platinum electrode consisted of a surge in cathodic current occurring at a potential of –0.38 V (Vs. Pd), which resulted in a large cathodic wave at –0.55 V (Vs. Pd) was attributed to the reduction of platinoid ions into their metallic forms. At stainless steel electrode, the onset of reduction occurred at –0.43 V (Vs. Pd), which resulted in a cathodic wave at –0.7 V (Vs. Pd). Electrolysis of SHLLW was carried out at various cathodic potentials and the recovery was in the order Pd >> Rh ∼ Ru. The total recovery of ruthenium, rhodium and palladium increased with increase of applied potential and about 42% was recovered at the applied potential of –1.0 V (Vs. Pd) in 4h. X-ray diffraction indicated the presence...

Efficient extraction of Rh(iii) from nitric acid medium using a hydrophobic ionic liquid

Rhodium(III) has been successfully extracted from an aqueous nitric acid solution using a hydrophobic ammonium based ionic liquid and CMPO or TODGA as extractant. This result has significant potential for the recovery of rhodium from spent nuclear fuel and thereby increasing the worldwide supply of this rare metal.

Rhodium recovery from rhodium-containing waste rinsing water via cementation using zinc powder

The present work proposes the recovery of rhodium from rhodium-containing waste rinsing water through cementation with metallic zinc powder. The effects of zinc content, reaction temperature, reaction time and shaking on rhodium recovery are investigated in detail. In addition, the cementation kinetics of rhodium is studied, and its activation energy was found to be 30 kJ/mol. After a detailed observation of the dissolution behavior of the zinc powder during the cementation process, it is demonstrated that most of the zinc is preferentially consumed by free acid, a finding corroborated by pH measurements. The proposed process is simple, straightforward and economically feasible.

Simultaneous ion exchange recovery of platinum and rhodium from chloride solutions

This work focuses on the sorption recovery of platinum (II, IV) and rhodium (III) simultaneously present in chloride solutions, freshly prepared and stored over 3 months, on commercial anion exchangers with different physical and chemical structure. The sorption was carried out from solutions with 0.001–4.0 mol/L HCl. The initial platinum and rhodium concentrations in contacting solutions were 0.25–2.5 mmol/L. Sorption and kinetic properties of the chosen anion exchangers were investigated and the basic parameters of exchange capacity, recovery, distribution coefficients, separation factors, process rate, diffusion coefficients and half-exchange times were calculated. It is shown that anion exchangers investigated possess high sorption ability to platinum and rhodium chloride complexes, which does not deteriorate in case of stored solutions. Desorption of platinum and rhodium from the resins investigated was carried out with hydrochloric acid (2 mol/L), thiourea (1 mol/L) in sulfuric acid (2 mol/L) or in potassium hydroxide (2 mol/L) as well as by ammonium thiocyanate (2 mol/L). It was shown that complete separation of platinum and rhodium can be carried out with 2 mol/L HCl on anion exchanger Purolite S 985, whereas 2 mol/L NH 4 SCN as an elution agent leads to complete separation of noble metals on anion exchangers Purolite S 985, Purolite A 500 and AM-2B.

Sorption recovery of rhodium(III) from chloride and chloride-sulfide solutions

Sorption of rhodium(III) from chloride and chloride-sulfate solutions on anion exchangers of varied physical and chemical structure was studied.

Ion Exchange Recovery of Rhodium (III) from Chloride Solutions by Selective Anion Exchangers

The paper describes the results of a study of the recovery of rhodium (III) from chloride by sorption from strongly and weakly acidic solutions (2 M HCl and pH = 3) by macroreticular anion exchangers on the basis of methylacrylate and divinylsulfide as long-chained cross-linking agent. The initial concentration of Rh (III) in the contacting solution was 0.25–2.15 mmol/L, the process temperature was 20, 30, and 50°C. It was shown that polyfunctional anion exchanger ANS-80 has the best sorption characteristics and can be recommended for quantitative recovery of rhodium (III) at 50°C.

Process Intensification via Liquid Emulsion Membrane Technique in Extraction and Enrichment of Rhodium (III) from Chloride Media

A liquid emulsion membrane (LEM) system as a tool for process intensification has been studied for rhodium recovery using di-2-ethylhexylphosphoric acid (D2EHPA) as a metal carrier and Monemul 80 as a surfactant, dissolved in liquid paraffin. The various process parameters affecting the LEM process, such as extractant, surfactant, and strip phase concentrations, the speed of agitation, the batch contact time, and the treat ratio have been experimentally investigated to get better insight into the process. Perchloric acid was found to be a better stripping agent in the LEM process. It was observed that the extraction of Rh (III) can be significantly more in the absence of a water repelling agent. The maximum enrichment of Rh (III) in the internal phase obtained was 4.3 times with feed phase pH adjusted to 6, perchloric acid (1.5 mol/dm3), and contact time of 15 min. A mass transfer model to predict the performance of the LEM system was used and found to fit well with the experimental data.

Feasibility studies on the electrochemical recovery of fission platinoids from high-level liquid waste

The electrochemical behavior of ruthenium(III) and rhodium(III) in nitric acid medium has been studied at platinum and stainless steel electrodes by cyclic voltammetry. The cyclic voltammograms consisted of surge in cathodic current occurring at potentials of −0.13 V (Vs. Pd) and −0.15 V (Vs. Pd), which culminates into peaks at −0.47 V and −0.5 V due to the reductions of Ru(III) and Rh(III) to their metallic forms, respectively. Electrodeposition was carried out at stainless steel electrode and unlike palladium, the recovery of ruthenium and rhodium was limited to ~4% and ~14%, respectively. However, a different scenario was observed in case of electrodeposition from a ternary solution containing all these platinum metals. Ruthenium and rhodium deposited underpotentially in the presence of palladium and the recovery of ~20% and ~5% was observed for ruthenium and rhodium, respectively. Evolution of RuO4 at the anode and deposition of RuO2 in the anodic side was observed in all cases during electrolysis of ruthenium(III) containing solutions.

Rhodium and palladium joint extraction by dihexyl sulfide and alkylanilinium nitrate mixtures from nitrate solutions

We studied nonequilibrium distribution of inert rhodium(III) in extraction by dihexyl sulfide (DHS)and alkylanilinium nitrate mixtures from joint nitrate solutions of triaquatrinitrorhodium (0.1–4 g/L Rh) and palladium (0–2 g/L Pd). We discovered the effect of increasing rhodium recovery in the presence of palladium. This effect has a kinetic nature and arises from the fact that bis(alkyl sulfide) palladium(II) species catalyze the reaction between dihexyl sulfide and a rhodium intermediate based on alkylanilinium nitrate micelles. Depending on initial rhodium and palladium concentrations, the extraction system provides effective distribution factors for rhodium in the range DRh* = 8−300 and rhodium recoveries of 43–97% with ∼100% palladium recovery; single 5-min phase contact at 35°C ensures the 10-fold concentration of both metals in the extract. Our results are useful for developing processes for recovering fission rhodium from spent nuclear fuel.

Sorption of platinum and rhodium on carbon adsorbents from chloride solutions

Sorption recovery of platinum (II, IV) and rhodium (III) on different carbon adsorbents has been studied using fresh chloride model solutions with platinum and rhodium concentrations of 0.25–1.0 and 0.049 mmol/L, respectively. The concentration of hydrochloric acid in these solutions varied from 0.001 to 1.0 mol/L. The maximum recovery of platinum and rhodium was achieved with the carbon adsorbent based on charcoal (wood). This sorbent possesses the highest sorption ability to noble metals in medium acidic solutions (0.01–0.1 M HCl). However, the sorption from higher acid solutions (0.5–1.0 M HCl) proceeds on sufficiently high level as well (>80%). The use of thiocarbamide (10%) solutions in sulfuric acid (0.3 mol/L) as a desorption agent results in almost complete elution of rhodium (more than 95%), whereas platinum is retained in carbon adsorbent. This brings out some prospects for separation of these noble metals during their recovery from solutions of spent platinum–rhodium catalysts.

Purification and Recovery of Rhodium Metal by the Formation of Intermetallic Compounds

The catalysts manufacturing industry is the second largest consumer of PGMs after the jewelry industry. Automotive catalysts comprise refractory oxides support on which two or more precious metals (platinum, palladium, rhodium etc.) are dispersed in very low concentration (0.1-0.3 wt.% of the monolith). The honeycomb type monolith is typically made of a cordierite (2Al2O3·2MgO·5SiO2). 2 Several researchers have dealt with the recovery of these metals as the recovery of precious metals from spent automotive catalysts is of economical importance. 3-7 Spent autocatalysts are usually smelted in the presence of larger amounts of collector metals (Cu, Fe, Pb, Ni etc.) After leaching the precious metals enriched in the collector metals with acid, the precious metals can be selectively recovered. Among PGMs, rhodium (Rh) is an exceedingly rare element, comprising only 0.0001 PPM of the earth’s crust. 8 Moreover, rhodium is especially notable for its extreme inertness to acids, even aqua regia. Because of scarcity and high price, the recovery of rhodium from scrap is an important issue. Rhodium has a special catalytic activity to reduce nitrogen oxides (NOx) to N2, and is a main element as an autocatalyst. 9 Rhodium plated electrodes are used in the soda industry for electrolysis of salt water, and for electrodes for domestic water treatment. Rhodium plating is used widely in the jewelry industry. In the electronics industry, rhodium plating is used for electric contacts, e.g., ferreed switches. 10 The purification and recovery of rhodium from the other precious metals has always been difficult because of its complex aqueous chemistry in chloride solution as well as extreme inertness to acids, even aqua regia. It should be pointed out that the key factor for success in the separation of rhodium from the other precious metals is the developing an effective dissolution process for rhodium. It is well known that the disulfate melt technique on rhodium metal is utilized for quantitative dissolution of rhodium and its separation from iridium and platinum. 11 Another method has been developed for recovering PGMs from scrap with the propose of improving Rh dissolution in acid. Reactive metal vapours such as magnesium (Mg) and calcium (Ca) were reacted with powdered Rh in a closed stainless steel reaction vessel at a constant temperature ranging from 873 to 1173 K. 9 Iron(II) oxide with NaCl structure was successfully synthesized in a quartz tube sealed under vacuum. Hematite in an evacuated silica tube progressively loses oxide ions at 1373 K depending on the heating time. Finally, α-Fe2O3 is completely transformed into the well crystallized Fe0.935O after heat treatment at 1373 K for 84 h. 12 Silica tube is very suitable one for the chemical vapour transport reactions in an inert atmosphere because of hightemperature resistance, no-contaminants including foreign metals, and the ease of sealing under vacuum. In this work, the chemical vapour transport reactions between magnesium and rhodium are attempted using silica ampules sealed under vacuum. And also, the verifications, such as the formation and dissolution of intermetallic compounds (MgxRhy), purification and recovery of rhodium, are performed.

Biological nitrogenous compound removal and subsequent rhodium recovery from simulated metal refinery wastewater

Developing bioprocesses to remove nitrogenous compounds from wastewater and metal recovery is important in the competitive metal refinery industry in terms of process economic factors such as efficient use of natural resources, low energy intensive processes and minimum discharge of contaminated process wastewater to the environment. Experiments were carried out to remove nitrogenous compounds from simulated metal refinery wastewater and to subsequently recover the rhodium it contained. A bench-scale serially connected continuously stirred tank and packed-bed reactor system removed >80% of NH 4 + -N and >95% of NO 3 - -N over a period of 80 days. Subsequently rhodium recovery efficiencies of >50% and >66% were achieved using two biosorbents and an adsorbent without pH and sorbent optimisation. This study demonstrated the potential of biological removal of nitrogenous compounds and the effect of nitrogenous compounds on metal recovery from metal refinery wastewaters.

Recovery of Rhodium(III) from Solutions and Industrial Wastewaters by a Sulfate-Reducing Bacteria Consortium

A quantitative analysis of the rate of removal of rhodium(III) by a resting sulfate-reducing bacteria (SRB) consortium under different initial rhodium and biomass concentrations, pH, temperature, and electron donor was studied. Rhodium speciation was found to be the main factor controlling the rate of its removal from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached. Consequently, a pH-dependent rate of rhodium removal from solution was observed. The maximum SRB uptake capacity for rhodium was found to be 66 mg of rhodium per gram of resting SRB biomass. Electron microscopy studies revealed a time-dependent localization and distribution of rhodium precipitates, initially intracellularly and then extracellularly, suggesting the involvement of an enzymatic reductive precipitation process. When a purified hydrogenase enzyme was incubated with rhodium chloride solution under hydrogen, 88% of the rhodium was removed within 1 h, whereas with a soluble extract from SRB 77% was removed within 10 min. Due to the low pH of the industrial effluent (1.31), the enzymatic reduction of rhodium by the purified hydrogenase was greatly limited, and it was apparent that an industrial effluent pretreatment was necessary before the application of an enzymatic treatment. In the present study, however, it was established that SRB are good candidates for the enzymatic recovery of rhodium from both aqueous solution and industrial effluent.

Recovery of Rhodium(III) from Solutions and Industrial Wastewaters by a Sulfate-Reducing Bacteria Consortium

Recovery of Rhodium(III) from Solutions and Industrial Wastewaters by a Sulfate-Reducing Bacteria Consortium

Leaching of Pt, Pd and Rh from Automotive Catalyst Residue in Various Chloride Based Solutions

Platinum-group metals (PGM) are important precious metals in many industrial fields. However, their natural resource deposits are strictly limited. Accordingly, their recycling process from wastes and/or secondary resources must be considered. In this study, the leaching of PGM from automotive catalyst residue was performed based on the formation of their chloro-complexes in various concentration of acidic solution. The recovery of platinum, palladium and rhodium from the samples after hydrogen reduction pretreatments was examined in the leaching process by using a mild solution mixture of NaClO–HCl and H2O2 at 65 � C for 3 h. Effect of other solution mixtures on the extraction of the precious metals was also compared with NaClO–HCl–H2O2, such as HCl–H2O2 and NaClO–HCl. The optimum condition to dissolve platinum,

Leaching platinum-group metals in a sulfuric acid/chloride solution

A leaching process was established based on the ability of platinum-group metals to form stable chloro-complexes in acidic chloride solutions. Industrial catalyst losses were examined for the recovery of platinum, palladium, and rhodium by leaching with a mixture of sulfuric acid and sodium chloride to avoid using aqua regia or autoclave conditions. Extraction of platinum and rhodium in 60% H2SO4 at 135°C steadily increased with increasing NaCl concentrations reaching 95% and 85%, respectively, at 0.1 M NaCl after two hours. By comparison, palladium was dissolved more quickly but also reached 85% under the same conditions. Extraction of each metal increased with temperatures up to 125°C but plateaued at higher temperatures. Similar behavior was observed with increasing H2SO4 concentrations up to 60%. More than 99% extraction of each metal was obtained after ten hours using 0.1 M NaCl and 60% H2SO4 at 125°C.

Recovery of Value Fission Platinoids from Spent Nuclear Fuel

Radioactive high-level liquid wastes originating from reprocessing spent nuclear fuel can be a valuable source of platinum metals. The recovery of fission palladium and rhodium is of particular interest and is being investigated worldwide. The radioactivity of fission platinoids is reduced to a non-hazardous level after decontamination from other fission products by a factor of 1010. The intrinsic radioactivity of fission palladium is weak and can be tolerated in many applications, while that of fission rhodium decays to an acceptable level only after storing for about 30 years. With emphasis on recent achievements, this paper, which covers periodical, report and patent literature, reviews the behaviour of fission platinoids in basic separation operations. Aqueous methods, such as solvent extraction, ion exchange, electrolysis, precipitation and redox reactions, are dealt with as well as pyrochemical methods, such as molten salts/metal extraction and solid phase reactions. A second part, to be published in a later issue, considers separation processes.

Separation and recovery of platinum and rhodium by supported liquid membranes using bis(2-ethylhexyl)phosphoric acid (HDEHP) as a mobile carrier

Transport of Pt and Rh ions from an aqueous 1 mol dm −3 HCl feed solution containing 20% stannous chloride into a stripping solution 8 mol dm −3 HCl through a supported liquid membrane (SLM) consisting of bis(2-ethylhexyl)phosphoric acid (HDEHP) in kerosene, supported on PVDF film, have been studied. Various parameters, such as concentration of HCl in feed and stripping solutions, concentration of HDEHP in the membrane, stirring time and concentration of SnCl 2 in 1 mol dm −3 HCl, have been investigated. Transport of Pt is independent whereas that of Rh increases with HDEHP concentration (0.003–2 mol dm −3) in the membrane phase. Mutual separation of Pt and Rh is achieved by preferential transport of Pt at low concentration of HDEHP (0.003 mol dm −3) and Rh left behind is recovered by transport at high concentration of HDEHP (2 mol dm −3) in membrane. Selective recovery of Pt and Rh have been achieved from other platinum group metal ions, gold and other metal ions. The methods have been demonstrated to recover Pt and demonstrated to recover Pt and Rh selectively from industrial waste samples such as catalyst, anode slime and artificial mixtures.

FIA-FAAS system including on-line solid phase extraction for the determination of palladium, platinum and rhodium in alloys and ores

A number of aliphatic mono- and triamines have been investigated as potential reagents for solid phase extraction of Rh, Pd and Pt. Platinum group metals are recovered from hydrochloric acid solutions as ionic associates of their chloride complexes with protonated amines. The recovery of metals depends both on hydrophobic properties of amine and sorbent and on sorption behaviour of amine itself. For on-line solid phase extraction of platinum group metals 4-(n-octyl)diethylenetriamine and hyper cross-linked polystyrene sorbent SSPS have been applied. Quantitative recovery of rhodium and platinum in the form of their hexachloride complexes was achieved under non-equilibrium conditions of on-line dilution. Metals recovered are quantitatively eluted with 1 M hydrochloric acid solution in ethanol. A new FIA-FAAS method for the determination of Rh, Pd and Pt in solutions based on the decomposition of ores and alloys has been proposed. The RSD values are 0.03–0.08 at 50-ppb concentration level. The detection limits are 3–8 ppb for 1 min of preconcentration. The accuracy of the procedure was verified by the analysis of standard reference materials of sulfide ores and alloys.

Recovery of Platinum-Group Metals from Recycled Automotive Catalytic Converters by Carbochlorination

The carbochlorination behavior of scrapped honeycomb-type automobile catalysts was investigated using a chlorine and carbon monoxide gas mixture to fully extract platinum and rhodium in the catalysts. The recoveries of platinum, rhodium, and base metals are monitored by ICP-AES analyses. Upflow type of fixed-bed carbochlorination experiments were performed between 250 and 700 °C. The effects of flow rate, time, and partial pressures of chlorine and carbon monoxide were also determined. After optimization of these parameters, the recoveries of about 95.9% of platinum and 92.9% of rhodium were obtained at 550 °C. The recovered condensate was contaminated by various base metal chlorides. The chlorides generated from the base metals could be minimized by decreasing the flow rate of the gas mixture without any deterioration of PGM recoveries, but at the expense of the volatility. The carbochlorination of scrapped automobile catalysts could be an efficient way for the profitable recovery of platinum and rhodium...