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A closed-loop process for recycling LiNi 1/3 Co 1/3 Mn 1/3 O 2 from the cathode scraps for lithium-ion batteries (LIBs) is preliminarily established in this research. Biodegradable trichloroacetic acid (TCA) with hydrogen peroxide (H 2 O 2 ) is innovatively developed to dissolve LiNi 1/3 Co 1/3 Mn 1/3 O 2 from the cathode scraps. Operational parameters are optimized to obtain a lower Al dissolution rate, but not at the expense of sacrificing other metals. Under the optimal leaching condition of 3.0 M TCA, 4 vol.% H 2 O 2 , a solid to liquid (S/L) ratio of 50 g/L at 60 °C for 30 min, the leaching rates of Ni, Co, Mn and Li are 93.0%, 91.8%, 89.8% and 99.7%, respectively. In this optimum condition, only 7.0% of Al is leached, and this could be further controlled according to the subsequent utilization of the leachate. Avrami equation is introduced to describe the leaching kinetics of LiNi 1/3 Co 1/3 Mn 1/3 O 2 from the cathode scraps. The apparent activation energies for leaching of Ni, Co, Mn and Li are determined as 44.51, 44.79, 43.81 and 28.00 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. [ABSTRACT FROM AUTHOR]

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]

Highlights • Welding electrospun hollow fiber membrane is firstly applied in ammonia removal. • The effect of membrane thickness on selectivity was intensively investigated. • Self-made membrane with high flux and selectivity favors ammonia recovery. • Self-made membrane demonstrates its potential in membrane absorption application. Abstract Excessive ammonia nitrogen in wastewater seriously endangers ecological environment, so high-flux and selectivity membrane is urgently needed for ammonia removal using membrane absorption (MA). In this paper, a high-performance electrospun hollow fiber membrane was fabricated and solvent vapor welding treatment was adopted to enhance mechanical strength. The post-treatment membrane showed 103.8% higher in the Young's modulus than the pristine membrane. High mechanical strength, porosity and hydrophobicity of the membrane make it superior in mass transfer and selectivity. The effects of membrane thickness, pH and temperature of feed solution on experimental overall mass transfer coefficient (K OE) and selectivity coefficient (S NH3/H2O (g)) were intensively investigated to examine the membrane performance in MA application. The results show K OE is 1.35 * 10−5 m s−1 and S NH3/H2O (g) is 7.58 when pH is 11, which are higher than that of commercial membrane. Moreover, the selectivity can be improved greatly from 6.91 to 9.74 by increasing the thickness of the hollow fiber membrane from 55 ± 5 μm to 115 ± 5 μm. The welded electrospun hollow fiber membrane demonstrates great potential for ammonia removal in MA application. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Asymmetric MCDI with only anion-exchange membrane (AMCDI-AEM) is proposed. • AMCDI-AEM shows better performance compared with CDI. • AEM with high IEC and low resistance and water uptake favors desalination. • AEM plays a stronger role than CEM in membrane-assisted CDI application. Abstract Membrane capacitive deionization (MCDI) usually contains both anion and cation exchange membranes (AEM, CEM) to restrict the ion desorption during charging and re-adsorption during discharging in capacitive deionization (CDI). In this study, different from conventional MCDI, an asymmetric membrane capacitive deionization (AMCDI) device packing an AEM only (AMCDI-AEM) was constructed, where the AEM was lab-synthesized from poly (2, 6-dimethyl-1, 4-phenylene oxide). The effect of the AEM properties, such as ion exchange capacity, water uptake and membrane resistance on the desalination performance of AMCDI-AEM was systematically discussed. The results indicate that an AEM with high ion exchange capacity, low membrane resistance and low water uptake is beneficial for AMCDI-AEM. Furthermore, AMCDI packed with a commercial cation exchange membrane only (AMCDI-CEM) and a conventional MCDI device were also assembled to stress the importance of AEM application. Although the charge efficiency of AMCDI-AEM is lower than a full MCDI cell (54.7 vs 95.0%) due to the unprotected cathode, AMCDI-AEM device shows comparable salt adsorption capacity to MCDI (7.4 vs 7.2 mg g−1), and is much better than that of CDI (2.3 mg g−1) and AMCDI-CEM (1.5 mg g−1), suggesting that AEM plays a stronger role than CEM for membrane-assisted CDI application. By using a single AEM and commercial activated carbon electrode, this work provides an opportunity to reduce membrane cost for the industrialization of MCDI technology. [ABSTRACT FROM AUTHOR]

The efficient and rapid selective extraction of V(V) from leaching solution with sulfated primary amine N1923 was demonstrated. In the single-stage extraction using annular centrifugal contactor (ACC), the influence of the total flow and the speed rotor on extraction percentage of V(V) was investigated using central composite design (CCD), and the results of experimental conditions were analyzed by analysis of variance. The current concentrations of V(V) and Cr(VI) in leaching solution were 23.70g/L and 1.52g/L, respectively. 99.6% of vanadium was extracted and separated from the aqueous solution by employing four-stage countercurrent extraction with annular centrifugal contactors (ACCs). The total contact/resident time of the two phases was 4.8 min, and the separation factor of V(V) and Cr(VI) was 273.9. The two metals in leaching solution can be separated primarily, and then 23.61g/L V(V) and 0.72g/L Cr(VI) in loaded organic phase can be further separated by the stripping. The NH 4 VO 3 with purity of 99.7% was obtained by two steps of separations and studied by the analyses of XRD, SEM and particle size distribution (PSD). The reactions of extraction and stripping in the separation processes were investigated in order to establish a firm conclusion. [ABSTRACT FROM AUTHOR]

In this report the extraction of V(V) and Cr(VI) from a synthetic feed solution and real leaching solution of the chromium-bearing vanadium slag (V–Cr slag) using primary amine LK-N21 was studied. Detailed fundamental research work was conducted to investigate the primary amine extracting V(V) and Cr(VI). The mechanism and the difference between the two metals of extraction were studied and the experimental results were compared with previously published data. The optimum technological parameters for the separation of two metals were determined including: pH value in feed solution, phase ratio, mixing time, as well as others. The results showed that primary amine LK-N21 can extract V(V) selectively by hydrogen bonding association. Cr(VI) competed V(V) to combine with the primary amine, and the concentration of Cr(VI) decided the percentage extraction of V(V) and Cr(VI). Primary amine LK-N21 extracted more than 90% of V(V) which resulted in over 90% of Cr(VI) left in the leaching solution of the V–Cr slag in the optimal conditions. Based on the results of experiments, V(V) and Cr(VI) can be separated with a high degree of selectivity. [ABSTRACT FROM AUTHOR]

Abstract: After leaching of the waste printed circuit boards with HNO3, the leach liquor bearing 5.13kg/m3 Cu, 0.63kg/m3 Fe (III), 0.36kg/m3 Zn, 1.31kg/m3 Ni and 34.59kg/m3 nitrate was obtained. Development of a solvent extraction flow chart for the separation and recovery of Cu, Ni and Fe (III) using LK-C2 as the extractant from nitrate solution was investigated. Extraction of the metals depends on the equilibrium pH in the aqueous phase and the increases with rise in equilibrium pH. Based on the difference in their extraction behavior as a function of equilibrium pH in the aqueous phase, it was possible to separate and recover copper, nickel and iron. Copper is extracted using 15% LK-C2 in kerosene at two stages at initial pH of 2.60 and the extraction percentage is 99.98%. Copper is stripped by 2.00mol/L H2SO4 at three stages and the stripping percentage is 97.51%. Fe and Ni are extracted using 20% LK-C2 in kerosene at two stages at initial pH of 3.00 and 10.00, and the extraction percentages are 96.14 and 99.35%, respectively. Fe is stripped by 2.00mol/L HCl at two stages and the stripping rate is 99.18%. Ni is stripped by 3.00mol/L H2SO4 at three stages and the stripping percentage is 98.32%. [Copyright &y& Elsevier]

The saponification and extraction mechanism drives Mg(HCO 3) 2 as a substitution of NaOH to achieve higher separation factor and greener technique. [Display omitted] • Mechanism-driven saponifying agent tuning achieves β increase from 148.98 to 3189.95. • The extraction mechanism of nickel and cobalt has been supplied and visual. • The released alkalinity in saponification-extraction is the key factor in separation. The carbon neutralization urgently requires massive applications of energy storage materials such as lithium-ion batteries. As the critical metal for lithium-ion batteries, the sustainable utilization of nickel and cobalt still takes a long process due to the low separation factor resulting in high costs and environmental concerns, especially in spent lithium-ion batteries (LIBs). In this work, based on the further revealing whole-process mechanism of the typical saponification-extraction process, a new saponifying reagent is proposed to achieve the separation ability of a multistage countercurrent through single-stage extraction solely along with shorter processes and less pollution. The separation factor of cobalt/nickel enhances from 148.98 to 3189.95. and the new saponification-extraction process applies in the recycling of LIBs successfully. The mechanism shows that the alkalinity introduced by saponification is the key factor affecting the separation and purity. Saponification by traditional NaOH releases all putting-in-organic-phase strong alkalinity to aqueous, providing excessive extraction capacity but hindering separation. Therefore, the mild released alkalinity tuning instructs seeking Mg(HCO 3) 2 as an alternative saponifying agent to achieve the balance between released alkalinity and capacity. A cleaner avenue for the high-purity recovery of cobalt and nickel is proposed by mechanism driving, which has the ideological guiding significance to other process improvements. [ABSTRACT FROM AUTHOR]

The practical applications of membrane distillation (MD) are hindered by the absence of effective membranes with high porosity, sufficient strength, and durable wetting repellency for long term operation. In this study, we developed a facile method to construct composite membranes with high MD performance via one-step electrospinning of PVDF solutions blended with hydrophobic silica nanoparticles (NPs). The characterizations reveal that the incorporation of silica NPs have altered the membrane surface morphology and endowed the composite membrane with hierarchical structure on both surface and bulk layers (three-dimensional (3D) superhydrophobic membrane). The hydrophobicity of the membranes can be easily tailored by the dosage of silica NPs, and the water contact angle (WCA) of the membranes can be optimized to be 157 ± 1°, which was close to that of the lotus leaf (160°). Furthermore, the incorporation of silica NPs have promoted the mechanical strength, salt rejection, and water permeation flux of the membranes. The composite membrane containing 7.47 wt% silica NPs (designated as SIL40) can achieve a high MD performance with a water flux of 25.73 kg m −2 h −1 and a permeate conductivity below 5.0 μS cm −1 during a 100 h test-period. The SIL40 also shows a tensile strength and a Young’s modulus of 3.18 and 12.8 MPa, respectively; the values surpassed those of the pristine PVDF membrane (1.5 and 5.4 MPa, respectively). In addition, the MD test indicates that the 3D superhydrophobic membrane exhibits a more durable wetting resistance and a more stable MD performance than the surface-modified superhydrophobic membranes. [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]

[Display omitted] • Lactic acid addition increased the selectivity of Co/Ni separation. • The complexing of lactic acid is the main driving force for effective separation. • QSAR modeling of the complexing group guides the design of better complexing agents. • The non-saponified extraction process was designed based on the stripping strategy. Ternary cathodes account for more than half of the Lithium-Ion Batteries (LIBs) cathode market share and their recycling draws the most attention. Solvent extraction is the most efficient and common method to separate and recover Co and Ni from spent ternary cathode leachates. However, the traditional extraction process produces a large amount of saline wastewater, thus will seriously pollute the environment. In this work, an environmental approach is proposed by adding a water-soluble complexing agent into the aqueous phase, the separation factor is 2 times higher and the consumption of NaOH is 90% reduced compared to the Na-saponified counterpart, which was attributed to the differences of the complexation between metal ions and complexing agent in aqueous phase. The differences in the complexing ability are enhanced with an increased local nucleophilicity index of the active sites along with a reduced molecular volume in complexing agent, thus leading to superior cobalt extraction efficiency (∼98.9%) and separation factor (∼345). In addition, because of the fact that the whole-process pollution control is needed for cleaner chemical production, a green process is developed by recovering additives through Tri-n-butyphosphate. This excellent separation performance suggests that adding complexing agent in solvometallurgical recovery process may aid in the future development of high-purity raw metals for advanced fields. [ABSTRACT FROM AUTHOR]

Abstract: Three-liquid-phase systems containing polyethylene glycol with different molecular weight were explored to investigate the partitioning behavior of simulated wastewater-containing isomers of p-Nitrophenol (p-NP) and o-Nitrophenol (o-NP). The distribution behaviors of p-NP and o-NP with different parameters in three-liquid-phase system were investigated. The results showed a great effect of the solution pH, extractant type on the partition coefficient of the two isomers. In the three-liquid-phase systems, the satisfying separation results were obtained with hexane as extractant. At pH=4.00, about 85% o-NP and 90% p-NP partitioned into the top organic phase and middle polymer-rich phase, respectively. The separation factor decreased sharply with the increase of the solution pH from 6.5 to 8.5. After once back extraction with 10wt.% sodium hydroxide, high recovery percentage of o-NP was obtained from the top phase. The removal efficiency of phenolic compounds in the polymer-rich phase could reach 95% when the middle phase was extracted with butyl acetate (BA) twice. p-NP could be recovered when the BA phase was back extracted with 10wt.% sodium hydroxide aqueous solution. [Copyright &y& Elsevier]

• Bismuth (Bi) material is electrochemically active to Cl− and inert to SO 4 2− ions. • SO 4 2− ions decreases chloride storage capacity in Bi electrode. • Bi can selectively remove Cl− from mixed solution with lower SO 4 2− concentration. Common methods in capacitive deionization (CDI) for selective removal are derived from membrane separation mechanism or size-based intercalation mechanism. In this study, based on the electrochemical activity of bismuth (Bi) material to chloride ions (Cl−) and inertness to sulfate ions (SO 4 2−), Bi electrode is used as anode in CDI to selectively remove Cl− ions from mixed NaCl and Na 2 SO 4 solution. Through the reaction with Bi, Cl− ions are stored in bismuth oxychloride (BiOCl). Results show that Bi electrode exhibits selectivity for Cl− over SO 4 2− with a selectivity coefficient of more than 1.5 in solutions with mole ratio of Cl− to SO 4 2− larger than 1. The selectivity coefficient is greatly dependent on the mole ratio of Cl− to SO 4 2− and increases when the ratio rises. In solution with a fixed Cl−/SO 4 2− mole ratio, higher applied voltage and prolonged time result in higher Cl− ion removal capacity, but not necessarily better selectivity. The highest selectivity coefficient of 4.5 is achieved in 8.5 mM NaCl and 1.1 mM Na 2 SO 4 mixed solution at voltage of 1.6 and 2.0 V after charging for 1 h. These results demonstrate that Bi electrode can selectively remove Cl− ions from mixed solution with a relatively lower concentration of SO 4 2− ions, which provides new insights into ion separation and selective removal by CDI. [ABSTRACT FROM AUTHOR]