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Abstract: The roles of the emulsifiers in the crud formation during the long-term operation during the vanadium and chromium extraction were studied. The crud produced in the long-term operation of extraction was determined by GC–MS for organic phase and XPS for solid particles. The results indicate that the redox reaction occurs between Cr(VI) and organic compounds, and the reduction products of Cr(VI) induce more stable emulsion. Additionally, the roles of other types of solid particles and organic compounds confirmed before were carried out by thermodynamic calculation and experiments combined with discussion. Three-dimensional network structure of silica and precipitation of various cations act as the major incentives to stimulate the emulsion. Whereafter, crystallization of sodium sulfate and the reduction of Cr(VI) take place at the surface of emulsion droplet, and the organic compounds are prone to be adsorbed by these fine solids which subsequently consolidate the newly formed surface of droplet. The interactions between emulsion droplets were calculated according to the extended DLVO theory. The comprehensive stabilization mechanisms were also proposed, including the composite interfacial film mechanism, the steric hindrance mechanism and the double electric layer mechanism. [Copyright &y& Elsevier]

Abstract: Selectively extracting tungsten to purify sodium molybdate solution was studied using primary amine N1923, including various conditions, such as equilibrium pH values, concentrations of extractant in organic phase and metals in feed solution, contact time of extraction and stripping, types of acidic solutions added, temperature of extraction and the dosage of stripping agent. Graphical method using McCabe-Thiele diagram and counter-current extraction simulation (CCES) were used to determine the required stages of deep removal of tungsten. The results show that appropriate concentrations of tungsten and molybdenum in feed solution have great influence on the difficult degree of the separation between the two metals. Organic phase including 0.051M of N1923 modified by LK-N21X diluted in kerosene can extract 92.7% of tungsten in sulfuric acid solution at equilibrium pH value of 7.07 for 10min in one-stage extraction at 15.5°C, and the separation factor reaches 329 under those optimum conditions. A two-stage CCES removes 99.83% of tungsten and obtains the purified sodium molybdate solution where W/Mo (mass ratio) reaches 2.9×10−5. Stripping can be accomplished by NaOH solution completely and quickly. Furthermore, the extraction and stripping reactions of tungsten and molybdenum in equilibrium were proposed. [Copyright &y& Elsevier]

A thermodynamic model for the extraction of tungstic acid from sodium tungstate in sulfuric acid using the primary amine N1923 diluted in toluene has been developed. The liquid–liquid extraction equilibrium data were determined by performing a series of experiments at 293.15 K. The activity coefficients of the ions and molecules in the aqueous and organic phases were calculated using the Pitzer equations. Nonlinear regression, based on the balance equations of chemical, mass and charge equilibria and the experimental data, was used as the optimization method. Next, the thermodynamic equilibrium constant and the new Pitzer parameters for sodium tungstate electrolytes in the aqueous phase and the binary interactions between the species in the organic phase were obtained. The new model was used to predict the extraction efficiency from different initial conditions. Experiments were performed to verify the new model. The results indicated that the model could moderately predict this extraction system. Furthermore, the extraction reaction mechanism was investigated using the new model, and the scope of the new model is discussed. [ABSTRACT FROM AUTHOR]

Coking wastewater is generated during high-temperature coal carbonization, coal gas purification and chemical products refining. There is a large amount of coke powder in coking wastewater. Various problems have been brought by coke powder. In this study, a novel method was proposed to remove coke powder from coking wastewater. The removal of coke powder was linked with extraction technology. A series of physical and chemical properties of coke powder were characterized by investigating XRF, XPS, elemental analysis and contact angle. Based on “Like Dissolve Like” principle, different extractants were selected to test contact angle of coke powder. Coke powder extraction experiments with the analysis results were carried out. This study provides a new insight to remove coke powder from coking wastewater. [ABSTRACT FROM AUTHOR]

The high-efficient extraction of vanadium using primary amine and its application in the utilization of the chromium-bearing vanadium slag (V–Cr slag) were studied in this work. The extraction mechanism and the possible difficulties in the application were both considered. From the results, the extraction percentage of vanadium using free primary amine with the hydrogen bond association mechanism is higher than that in the acidic environment by primary amine salts. The inorganic ions and other impurities existing in the system were all considered to research for the continuous operation of the extraction. Furthermore, the viscosities of the fresh organic phase and the recycled organic phase were determined using the extractant not only N1923 but also LK-N21, where the viscosity of the latter system increased slightly during the recycled process of the extractant. Based on the above results, the pilot and the commercial experiment were carried out. In the large-scale experiment, the vanadium was extracted and the product of 99.5 wt.% vanadium pentoxide was obtained, and the mass loss of the extractant was only 0.1%. [ABSTRACT FROM AUTHOR]

Critical metal sustainability is a worldwide issue whose extraction relies on hydrometallurgy mostly. The significance of metal ion species evolution in critical metal hydrometallurgy-extraction has got more and more attention. Here, the importance of the metal ion species during the whole vanadium recycling process has been evaluated quantitatively for the first time. Metal ion species as the key parameter was investigated through efficiency, material and energy accounting, and emission accounting to illustrate the effect of the metal ion species, which donated as ion species contribution (ISC). Specifically, 7 types of vanadium ion species were assessed in the process of V 2 O 5 production from leachate, including H 2 VO 4 −, HV 2 O 6 −, V 4 O 12 4−, H 2 V 5 O 14 −, V 10 O 28 6−, HVO 4 2− and VO2+. The results demonstrated that different vanadium ion species were closely related to recovery efficiency and purity, and they impact separation section, materials and energy consumption mostly in whole process. Consequently, V 4 O 12 4− occupied the highest ISC which was 1.11 times than V 10 O 28 6−, 1.37 times than VO2+ and 4.85 times than H 2 VO 4 −. Correspondingly, control of V 4 O 12 4− as dominant species appeared to be the most potential in the vanadium extraction process, which showed the feasibility of whole process optimization. With this research, ISC can help to point out dominant ion species in holistic critical metals supply chain, thus promote sustainability of critical metals in a new perspective. • Evaluating in detail the contribution of ion species to the whole V 2 O 5 production. • Covering comprehensive indicators related to ion species evolution. • An effective method for ion species regulation in critical metal resources recovery. [ABSTRACT FROM AUTHOR]

The complete separation of vanadium (V) and chromium (Cr) from chrome vanadium slag is still challenging. Many studies focus on the activity of vanadium, while the effect of the other element chromium and their mutual interaction are ignored. Here, we found that proper concentration of chromium can promote the extraction efficiency of vanadium. The extraction of V and Cr with various mass ratios ranging from 8:1–4:3 at different initial pH values using primary amine N1923 were studied. The extraction efficiency of V reached nearly 100%, while none of Cr was extracted when the mass ratio of Cr and V is 0.5 under proper pH. Through the dynamic monitoring of species evolutions during extraction, the transformation of the two metals and advantage extracted species were analyzed. Cr would transfer H+ for the combination of V 3 O 9 3-/V 4 O 12 4-, providing a great contribution to the continuous extraction of V. The real leachate was applied and 99.9% vanadium pentoxide was produced at a scale of 50 L/h. This paper offers deep insights of the separation of similar metal elements, and guide sustainable vanadium recovery from hazardous waste. [Display omitted] • Promotive action of competitive chromium species was explored. • The extraction efficiency of vanadium increased under proper addition of chromium. • The transformation and advantage extracted species of V and Cr were discussed. • Chromium species contributed continuous extraction by offering acid. • This paper encourage people to focus on the metal species transformation. [ABSTRACT FROM AUTHOR]