Stripping Of CO Research Articles

Efficient separation and recovery of Co and Ni from ammonium sulfate roasting‐water leaching solutions of oceanic cobalt‐rich crusts by sulfide precipitation and P507–Cyanex 272 synergistic extraction

AbstractOceanic cobalt‐rich crusts contain many valuable metals including Co, Ni, Cu, and Mn, of which Co and Ni are scarce metal resources on terrestrial land. Co, Ni, Cu, and Mn in cobalt‐rich crusts can be efficiently extracted by the ammonium sulfate roasting‐water leaching (ARWL) process, but separating and recovering Co and Ni from the leaching solution containing high concentrations of Mn is a challenging problem. In this study, a combination of sulfide precipitation and P507–Cyanex 272 synergistic extraction is proposed for the separation and recovery of Co and Ni from the ARWL solutions of oceanic cobalt‐rich crusts. Under the optimum sulfide precipitation conditions, Co and Ni were precipitated with 99.85% and 99.63% efficiency, respectively, while Mn was coprecipitated with only .79% efficiency. The Co–Ni mixed sulfides were dissolved by dilute sulfuric acid under oxidative conditions to obtain a solution containing 12.584 g/L Co, 11.012 g/L Ni, and a small amount of Mn. Subsequently, Co and Mn were extracted from this solution using P507–Cyanex 272 synergistic extraction, the single‐stage extraction efficiencies of Co and Mn were 95.76% and 99.73%, respectively, and the coextraction efficiency of Ni was 3.02%, under the conditions of a feed solution pH of 3.0, an extractant saponification degree of 70%, a total extractant concentration of 20% (P507 to Cyanex 272 ratio of 3:7), and an O/A ratio of 1.1:1. The results of the thermodynamic study showed that the reaction of Co extraction by this mixed extraction system was exothermic. Ni in the organic phase was washed with an H2SO4 concentration of .12 mol/L, followed by stripping of Co and Mn with an H2SO4 concentration of .6 mol/L. Mn in the stripping solution was removed by oxidative precipitation with (NH4)2S2O8, after which the Co3O4 product was obtained by precipitation with (NH4)2C2O4 and calcination. Similarly, NiC2O4·2H2O can be obtained from the raffinate by (NH4)2C2O4 precipitation. Finally, a flowsheet was developed for the separation and recovery of Co, Ni, Cu, and Mn from the ARWL solutions of oceanic cobalt‐rich crusts. The study provides a promising scheme for the recovery of various valuable metals from deep‐sea cobalt‐rich crusts or manganese nodules.

Separation of cobalt, nickel, and copper metal using the mixture of HCl in ethylene glycol and Aliquat 336 in kerosene

The recovery of valuable metals such as Co, Cu, and Ni from spent lithium-ion batteries has attracted much attention due to environmental issues and economic values. Separation of these metals from the synthetic metallic mixtures was investigated by employing nonaqeous solvent. In this work, the mixture of HCl in ethylene glycol (EG) and Aliquat 336 in kerosene was employed as nonaqeous solvents and the leaching conditions were optimized. Under the optimum condition, Ni was completely leached and remained in the EG phase with 99.8% purity. Meanwhile, the leaching percentage of Co(II) and Cu(II) was 62.3% and 18.3% and most of the two dissolved metal ions were extracted into Aliquat 336 phase. After complete stripping of Co(II) and Cu(II) from the loaded Aliquat 336 phase with 2.0 mol L−1 H2SO4, Cu(II) was selectively extracted over Co(II) by 0.1 mol L−1 Cynanex301 and then stripped by 50% aqua regia solution with >99.9% purity. The purity of Co(II) in the raffinate was 99.6%. Besides, Co from the leaching residue was selectively dissolved over Cu by 5.0 mol L−1 H2SO4 with 99.6% purity. A process was proposed for the separation of Co, Cu and Ni from metallic mixtures. The process showed some advantages in terms of the high purity of the metal solutions recovered and a decrease in the number of steps for the metal recovery. Thus, the application of this process to real operation can be considered.

Solvent extraction-based recovery of Co from leach solutions of Cu[sbnd]Co ores using a Mextral 6103H-naphthenic acid- isooctanol system

A Mextral 6103H–naphthenic acid–isooctanol synergistic extraction system was used for the selective separation of Co from pre-treated leach solutions of CuCo ores and the extraction performance, the extraction/stripping kinetics, and the phase separation properties of this system were determined. At pH 4.0, Co was selectively extracted from the feed solution containing Co, Ni, Zn, Mg, Mn, and Ca. The Co-loaded organic phase was easily stripped with a solution containing Co (100 g/L) and H2SO4 (40 g/L) at an O/A ratio of 5:1 and 25oC. Based on the McCabe-Thiele plots for Co extraction, scrubbing and stripping, tests involving simulated batch counter-current extraction (two stages), scrubbing (two stages) and stripping (two stages) were performed. A Co extraction efficiency of 99.7% (over two extraction stages) was obtained, while nearly all Mg, Mn, and Ca remained in the raffinate. The two-stage scrubbing of the co-extracted loaded organics resulted in the efficient removal of Zn (88.3%), Mn (95.2%), Mg (94.0%), and Ca (92.0%). The two-stage stripping of Co had an efficiency of 99.1%. The stripping liquor contained low levels of Zn (3.4 mg/L), Ni (0.2 mg/L), Mn (2.4 mg/L), Mg (1.2 mg/L) and Ca (0.8 mg/L), with the resulting Co purity equaling 99.98%. Thus, the developed process holds great promise for the selective recovery of Co from the leach solutions of CuCo ores containing multiple metals

Diffusion dialysis and extraction integrated system for recovery of cobalt(II) from industrial effluent

This paper presents multistage hydrometallurgical separation of Co(II) from wastewater, achieved in an integrated system containing diffusion dialysis (DD) to decrease the acidity of the industrial effluent – pregnant leach solution (PLS), followed by precipitation of Al(III), Fe(III) and Cr(III) hydroxides, selective extraction of Co(II) with bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), stripping of Co(II) from the loaded organic phase to form an electrolyte. DD results indicate that minimum metal ion content in the dialysate and high concentration of H+ (1.5−3 M) can be achieved by conducting the process at a low flow rate, but for a longer time. The feed after DD was effectively purified by precipitation of Cr(III), Al(III) hydroxides, and some admixtures of Cu(II) and Fe(III) to ensure that those metals will not disturb the liquid-liquid extraction of Co(II) at pH 5.2. High distribution ratio values for Co(II) extraction mean that ions of this metal can be selectively separated from the remaining ions present in the feed, especially Ni(II), and transported to the organic phase. The application of H2SO4 solution and the dialysate as stripping phases indicates that the dialysate more efficiently stripped most of the metal ions from the extract, thus forming Co(II) rich electrolyte for further electrodeposition of the metal. Finally, Co(II) electrowinning from a model stripping solution was investigated and the preliminary results showed that good quality metallic cobalt can be deposited.

Hydrometallurgical separation of Co(II) from Ni(II) from model and real waste solutions

This paper presents sustainable hydrometallurgical recovery of Co(II) from wastewater, achieved by application of two ionic liquids (Cyphos IL 101 or 104) and an acidic extractant (Cyanex 272). The separation of Co(II) is carried out from model aqueous chloride and sulfate solutions, as well as from a real waste sulfate solution containing also Ni(II). The extractants were investigated both as single carriers and as synergic mixtures, the latter giving no positive synergistic effect. Cyanex 272 does not allow Co(II) to be transferred from chloride solutions effectively, while extraction from sulfate mixtures reaches totally up to 100% after two stages. Cyphos IL 101 does not give satisfactory results of Co(II) recovery from sulfate solutions, while both Co(II) and Ni(II) are transferred efficiently from chloride ones. Stripping of Co(II) from the loaded organic phases with 1 M H2SO4 is very efficient (95–100%), regardless of the type of extractant (Cyanex 272 or Cyphos IL 104) and its concentration. Application of 1 M H2SO4 allows Co(II) to be recovered from the loaded organic phase (up to 100%) in one stage of stripping and to be enriched even three-to fivefold relative to that in the feed. It also allows the organic phase to be reused for further extractions. Theoretical considerations of economic feasibility of the process proposed indicated that the value of cobalt in solutions after proposed steps increases from 0.32 USD/dm3 (after two stages of extraction) to 1.42 USD/dm3 after stripping. The major novelty of this work is the design of hydrometallurgical recovery of Co(II) from real sulfate wastewater in the presence of Ni(II), which permits sustainable processing of waste, recycling and recovery of critical element and also regeneration and reuse of organic chemicals applied for extraction.

High-efficient synergistic extraction of Co(II) and Mn(II) from wastewater via novel microemulsion and annular centrifugal extractor

Environmental pollution by industrial effluents polluted with hazardous heavy metals has great concern. A novel microemulsion system (sodium dodecanoate/pentan-1-ol/heptane/NaCl) was prepared for the treatment of cobalt (Co) and manganese (Mn) wastewater. The effects of the batch extraction conditions were systematically studied and the extraction efficiency of Co(II) and Mn(II) were 98.2% and 97.5% respectively at the optimal conditions. Utilizing the centrifugal reinforcement of the annular centrifugal extractor (ACE), the continuous extraction of cobalt and manganese wastewater by microemulsion could be achieved. Under the optimized operation conditions: the motor speed of 1988 rpm, a flow ratio of 1/5, and a total flow rate of 48 L/h, the maximum extraction efficiency reached up to 99.9% for Co(II) and 99.1% for Mn(II), respectively. The stripping of Co(II) and Mn(II) from the microemulsion phase was also conducted using hydrogen chloride solution, indicating a high stripping efficiency. The investigation of synergistic extraction with microemulsion and ACE proposed an efficient treatment for Co and Mn wastewater.

Cooperative influence of D2EHPA and TBP on the reactive extraction of cobalt from sulfuric acid leach solution in a horizontal semi-industrial column

This article concerns the recovery of cobalt from a sulfuric acid leach solution in a horizontal pulsed perforated-plate column. Firstly, the influence of initial aqueous pH and the concentration of di(2-ethylhexly) phosphoric acid+tri-butyl phosphate has been investigated. It is observed that the mixture of these extractants is able to satisfactorily extract Co(II) from sulfate solution. Moreover, the influences of operational parameters including the phase flow rates along with pulsation intensity on the holdup, drop sizes and their distribution as well as extraction and stripping efficiencies and dispersion coefficients have been evaluated. Results show the highest efficiency of 95.3% and 93.2% for extraction and stripping of Co(II) at pulsation intensity of 1.30cm/s. Finally, new correlations for predicting mean drop size and holdup in the column are presented, which provide the average absolute relative error of 8.27% and 5.46% respectively.

Synergistic extraction of Co(II) over Ni(II) from chloride solutions by a mixture of Cyanex 301 and LIX 63

It is difficult to separate Co(II) and Ni(II) by extraction with single Cyanex 301 from acidic solution. The synergistic extraction of Co(II) over Ni(II) from aqueous chloride solutions was studied using a mixture of Cyanex 301 and LIX 63. A significant synergistic extraction of Co(II) with the synergistic enhancement factor of 191 was obtained by adding LIX 63 to Cyanex 301, while Ni(II) extraction was little affected. The highest separation factor of 10 was obtained at an optimum composition of the mixture. The extraction reactions with this mixture were proposed on the basis of slope analysis. The extracted species of Co(II) and Ni(II) was found to be Co(HA2)2·HB and Ni(HA2)2, respectively. Effective stripping of Co(II) and Ni(II) was attained by using different concentrations of HCl solution. It is feasible to apply this mixture for the separation of Co(II) and Ni(II) from the leach liquor of laterite ore.

Glycerol Electrooxidation on Platinum-Tin Electrodeposited Films: Inducing Changes in Surface Composition by Cyclic Voltammetry

In this work, PtSn binary electrodeposits were prepared in three compositions and submitted to successive voltammetric cycles in presence of glycerol (1.0 mol L−1) in acidic media. Catalysts were characterized by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy before and after the cycles being performed, in order to check eventual changes in their compositions during the process. Spectroscopic results show that surface compositions are sensibly richer in Sn than their bulk counterparts. Overall, PtSn catalysts show a poor initial catalytic activity toward glycerol electrooxidation. However, as the cycles succeed, the voltammetric responses increasingly resemble that of Pt, while the oxidation currents increase. Results are rationalized in terms of a continuous enrichment of the surface by Pt at the expenses of a loss of Sn. Moreover, when the electrochemical surface area (ECSA) is estimated by stripping of CO, it becomes evident that electrooxidation currents remain growing, even when the ECSA is decreased, which makes the gain in catalytic activity particularly relevant. Ultimately, from a broader perspective, our results suggest that catalytic surfaces with tunable features (such as surface composition and catalytic response) can be obtained by the application of easily executable electrochemical protocols.

Surface Limited Redox Replacement Deposition of Platinum Ultrathin Films on Gold: Thickness and Structure Dependent Activity towards the Carbon Monoxide and Formic Acid Oxidation reactions

The Surface Limited Redox Replacement (SLRR) method in one-cell configuration has been used to grow Pt ultra-thin films on Au using two different sacrificial underpotentially deposited (UPD) layers: Cu and Pb. The Pt films grown by multiple Pb UPD-SLRR cycles (1–10) exhibit comparable roughness as determined by integration of the H UPD charge. In contrast to that, due to the 2:1 stoichiometry of the replacement between Cu UPD layer and PtCl42+ ions, the Pt films grown by Cu UPD-SLRR show a steady increase of the roughness with the number of deposition cycles (1–10). The differences in the structure of the films have been used as a platform to study the stripping of pre-adsorbed CO and the formic acid oxidation (FAO) reaction as a function of their thickness. On Pt films of comparable roughness grown by SLRR of Pb UPD, the CO stripping peak shows no significant changes in the onset potential and a small peak maximum shift of ∼7mV between the film of lowest (1ML) and all higher thicknesses (2–10ML). However, Pt films grown by SLRR of Cu UPD show a larger potential window of differences of ∼26mV over which the peak maximum potentials shift more negative with the number of deposition cycles. The most positive CO stripping potential obtained for a sub-ML Pt (∼0.56ML) grown by a single SLRR cycle suggests CO is more strongly bonded than on films grown by multiple replacements that completely cover the Au substrate. The measured activity toward FAO is in agreement with the CO electro-oxidation results. No significant differences in the activity for FAO have been observed on Pt films of comparable roughness grown by SLRR of Pb UPD which show activity close to that of pure Pt. However, a more significant change of FAO reactivity has been measured for Pt films grown via SLRR of Cu UPD with the highest activity measured for a sub-ML Pt deposit. Following subsequent replacements, the FAO activity tends towards that of pure Pt. The observed differences in the catalytic behaviour of Pt films grown by SLRR are the result of the differences in their morphology and the nanocluster structure of the films. On sub-monolayer Pt films, the behaviour is dominated by nanocluster size and coverage of the deposit. For a completely covered surface of Au, the effect of roughness of Pt films and nanocluster nature of the deposit has a dominant role in the behaviour and activity.

Development of a hydrometallurgical process for the recovery of calcium molybdate and cobalt oxalate powders from spent hydrodesulphurization (HDS) catalyst

Abstract In order to recover molybdenum and cobalt from spent hydrodesulphurization (HDS) catalysts, a hydrometallurgical process consisting of leaching, solvent extraction and precipitation was developed. The Mo and Co in the spent HDS catalysts were leached in HCl solution. Mo was first separated by solvent extraction with TBP and the Mo free raffinate was then contacted with TEHA to separate Co. Stripping of Mo and Co from the loaded organic phases was carried out using dilute HCl solution and distilled water. The extraction and stripping isotherms were constructed to get the required number of multi-stages. 99.8% of Mo and 99.4% of Co were recovered by solvent extraction and the purity of Mo and Co stripping solutions was found to be 99.99%. CaMoO 4 powders with uniform morphology were obtained by adding calcium chloride to the Mo stripping solution at pH 5.0 and 90 °C. The optimum conditions for the formation of uniform rod-like CoC 2 O 4 particles by adding oxalic acid were at pH 5.0 and 60 °C. The overall recovery of Mo and Co from spent HDS catalyst was 96% and 93%.

Electrochemical surface area measurements of platinum- and palladium-based nanoparticles

The electrochemical surface area (ECA) calculation was studied using the charges associated with stripping of CO and underpotentially deposited H and Cu on highly dispersed Pt- and Pd-based nanoparticles. The surface areas followed a general trend of HUPD<CO striping<CuUPD. Transition metals in the alloys were found to have a significant effect on the determination of surface area. The surface area could be underestimated by nearly 50% using HUPD on conventional (non-shape-controlled) PtNi/C. In addition to the effect from Ni, the shape/structure of the nanoparticles also made the calculation more complicated. The surface area could be underestimated by more than two times using HUPD on octahedral PtNi/C compared to using CuUPD. CuUPD was demonstrated to be a more accurate method to estimate the electrochemical active areas than HUPD and CO striping.

Comparison of several packings for CO 2 chemical absorption in a packed column

CO 2 capture and storage has gained widespread attention as an option for reducing greenhouse gas emissions. Chemical absorption and stripping of CO 2 with hot potassium carbonate (K 2CO 3) solutions has been used in the past, however potassium carbonate solutions have a low CO 2 absorption efficiency. Various techniques can be used to improve the absorption efficiency of this system with one option being the addition of promoters to the solvent and another option being an improvement in the mass transfer efficiency of the equipment. This study has focused on improving the efficiency of the packed column by replacing traditional packings with newer types of packing which have been shown to have enhanced mass transfer performance. Three different packings (Super Mini Rings (SMRs), Pall Rings and Mellapak) have been studied under atmospheric conditions in a laboratory scale column for CO 2 absorption using a 30 wt% K 2CO 3 solution. It was found that SMR packing resulted in a mass transfer coefficient approximately 20% and 30% higher than that of Mellapak and Pall Rings, respectively. Therefore, the height of packed column with SMR packing would be substantially lower than with Pall Rings or Mellapak. Meanwhile, the pressure drop using SMR was comparable to other packings while the gas flooding velocity was higher when the liquid load was above 25 kg m −2 s −1. Correlations for predicting flooding gas velocities and pressure drop were fitted to the experimental data, allowing the relevant parameters to be estimated for use in later design.

Analysis of carbon dioxide absorption in and stripping from aqueous monoethanolamine

A linearization scheme is presented that enables near-exact solution of the nonlinear ordinary differential equations associated with Film Theory-based modeling of absorption with multiple reversible chemical reactions. The technique, a variant of singular perturbation methods, is applied here to the analysis of absorption of carbon dioxide in aqueous monoethanolamine and stripping of CO 2 from the same solutions. Enhancement factors by which reactions multiply mass transfer rates are in excellent agreement with values obtained via numerical methods. Unlike previously published approximate techniques, the computationally efficient method outlined here is applicable whether the reversible reactions are fast or slow, and whether the solvent is lean or loaded.

Codeposited PtSb/C catalysts for direct formic acid fuel cells

Carbon supported PtSb catalysts were synthesized by codeposition of platinum and antimony on Vulcan® carbon black. X-ray diffraction (XRD) analysis revealed that the Sb was alloyed with the Pt while XPS indicated that a large fraction of the Sb was in an oxidized state, with only partial alloying. The performances of catalysts with a range of compositions were compared in a multi-anode direct formic acid fuel cell (DFAFC). A 0.29mol fraction of Sb was found to provide the best performance with a maximum specific power output of 280Wg−1 Pt. CO stripping results indicated that the addition of Sb at this optimum level greatly suppressed both CO adsorption and H adsorption/desorption, as well as promoting oxidative stripping of CO. The results are compared with those for previously studied catalysts prepared by the reductive deposition of Sb on a carbon supported Pt catalyst.

Electrocatalytic Oxidation of CO at Pt Modified with Manganese Oxide Nanorods

CO oxidation at Pt anodes modified with manganese oxide nanorods (nano-MnOx/Pt) has been studied by cyclic and linear sweep voltammetry. Both CO adlayer stripping and oxidation of bulk CO are enhanced by nano-MnOx as compared to unmodified Pt electrodes. This is manifested by a negative shift of approximately 200 mV in the peak potential of CO adlayer stripping at the modified compared to the unmodified Pt surface. This enhancement is attributed to the catalytic mediation of manganese oxide nanorods (electrodeposited in a γ-MnOOH single crystalline phase), which supplies oxygen species at relatively low anodic potentials and thus facilitates the oxidation of CO to CO2. This finding sheds new light on the formic acid oxidation in the presence of MnOx, as the latter can remove CO efficiently from the Pt surface, and hence, prevents its de-activation.

High recovery brackish water desalination process devoid of precipitation chemicals

The present paper describes pilot plant development of a novel process enabling increase of water recovery in brackish water desalination without using any chemicals. This is achieved by precipitating the scaling salts of a carbonate-rich concentrate by increasing the pH through air stripping of CO 2 from the solution. Additional permeate is extracted from the treated concentrate by a secondary RO unit. The pilot plant data confirmed that a precipitation conversion of CaCO 3 of at least 70% can be achieved by the aeration process at a retention time of about 2 h in the precipitation vessel. Integration of the concentrate treatment with the primary desalination process enabled increase of the overall water recovery from 78% to 90%. Higher recoveries exceeding 95% can be anticipated in processing concentrate solutions of sufficiently high carbonate content.

Synergistic extraction and separation of valuable metals from waste cathodic material of lithium ion batteries using Cyanex272 and PC-88A

Synergistic extraction and separation of cobalt (II), manganese (II) and lithium (I) from simulated sulfuric acid leaching of waste cathodic materials, using mixture of bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272, HA) and 2-ethylhexyl phosphinic acid mono-2-ethylhexyl ester (PC-88A, HL) in n-heptane have been investigated. Extraction of Co 2+, Mn 2+ and Li + follows the order as: Mn > Co ≫ Li independent on taking the single Cyanex272 or PC-88A or their mixtures as extractants. The possible extracted species are MA 2·3HA or M(OH)A·3HA for single extractant (PC-88A and Cyanex272 are same) and MH 3A 2L 3 for the mixed-extractant (M 2+ is Co 2+ or Mn 2+). Cyanex272 + PC-88A shows an evident synergistic effect. The maximum synergistic enhancement coefficients, R max, are obtained for Co 2+ (3.48) and Mn 2+ (4.12) at the mole fraction X Cyanex272 around 0.6 at pH e 4.95. Furthermore, the separation factors (Mn/Co) have been improved around two orders of magnitude upon adding EDTA into the synergistic extraction system. The entire stripping of Co and Mn can be achieved in one single stage when the concentration of hydrochloric acid or sulfuric acid is larger than 0.04 M or 0.01 M, respectively. Finally, a feasible process for recycling of spent cathodic materials of LIBs was proposed with industrial applications prospects.

Insulating diamond particles as substrate for Pd electrocatalysts

The suitability of insulating highly crystalline diamond particles as support for Pd based electrocatalysts is explored for the first time by evaluating the electrochemical stripping of CO and oxidation of formic acid in acid solutions.

PtSnCo/C Anode Catalyst for Methanol Oxidation

A binary metallic catalyst(PtSn/C) and a ternary metallic catalyst(PtSnCo/C) with a metal mass fraction of 20% were prepared by borohydride reduction and subsequent hydrothermal treatment in a glycol liquid phase.The structure and composition of the as-prepared electrocatalysts were characterized by X-ray diffraction(XRD) and energy-dispersive spectrometry(EDS).Their activity and stability for the catalysis of methanol oxidation were evaluated by anodic linear sweep voltammetry(LSV),cyclic voltammetry(CV),and the anodic stripping of a pre-adsorbed CO monolayer.We found that the PtSnCo/C catalyst gave the best catalytic activity for the methanol oxidation of all the catalysts including the commercial JM-PtRu/C catalyst.After 100 cycles,the peak current of methanol oxidation for the PtSn/C catalyst rapidly decreased to 11% of its initial peak current but PtSnCo/C decreased to only 50%.This result suggests that the PtSnCo/C catalyst has better chemical stability for the catalysis of methanol oxidation compared to the PtSn/C catalyst.The more negative onset potential of methanol oxidation for the PtSnCo/C catalyst relative to pre-adsorbed CO oxidation implies that the intermediates of methanol oxidation on the PtSnCo/C catalyst may be ones,which can be more easily oxidized than CO,instead of CO.