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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]

One of the most widely used CDI processes is flow electrode capacitive deionization (FCDI), which is preferred over conventional CDI with static electrode due to its continuous treatment of high-salt wastewater and ability to scale production. However, the discontinuous charge transport network in flow electrodes restricts the improvement of desalination performance. In this study, we prepared nickel hexacyanoferrate and carbon nanotubes composites (NiHCF@CNTs) by a simple ball-milling method and constructed an asymmetric FCDI (AFCDI) system using NiHCF@CNTs and AC as flow cathode and anode, respectively. Then the desalination performance of AFCDI was examined and compared with that of symmetric FCDI system using AC as both flow electrodes under different conditions. The stability was also investigated by a 20-cycle operation test. It was found that AFCDI system showed higher average salt removal rate and lower energy consumption compared with FCDI, owing to the enhancement of charge transport resulting from the couple of high specific capacitance of NiHCF and excellent electrical conductivity of CNTs. Moreover, AFCDI system has stable desalination performance in continuous operation. These results indicate that compositing Faradic materials and CNTs is an effective strategy for improving desalination performance of FCDI. [Display omitted] • NiHCF@CNTs composite was prepared by a simple ball-milling method. • AFCDI was constructed with NiHCF@CNTs as cathode and AC as anode. • Composite of NiHCF and CNTs can strengthen charge transport of flow electrode. • AFCDI showed better desalination performance than FCDI-AC. • AFCDI has stable and efficient desalination performance in continuous operation. [ABSTRACT FROM AUTHOR]

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]

[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]

Flow electrode capacitive deionization (FCDI) has attracted growing attention for the treatment of high-concentration saline water and continuous operation, but the mechanism responsible for the separation of ions has so far received minimal attention. In this study, an asymmetric FCDI (AFCDI) was assembled with nickel hexacyanoferrate (NiHCF) as cathode and activated carbon (AC) as anode. Its desalination performance and distribution of the removed ions were investigated and compared with FCDI using AC as both cathode and anode. Results showed better desalination performance for AFCDI than FCDI at high applied voltages of 2.4 and 2.8 V. The removed ions were adsorbed by active materials (capacitance contribution) and existed in the electrode electrolyte (charge neutralization contribution). However, the contribution of capacitance and charge neutralization was significantly different between NiHCF electrode and AC electrode. When NiHCF was used as electrode, capacitance contribution dominated the removal of sodium and more than 80% sodium was adsorbed by NiHCF at applied voltages of 1.2–2.8 V. On the contrary, the removed ions mainly existed in electrode solution when AC was used as electrode and charge neutralization contributed to about 80% of removed ions at 2.8 V. These results clarify the mechanism of ions removal in FCDI. [Display omitted] • AFCDI was assembled with NiHCF as cathode and AC as anode. • AFCDI showed better desalination performance than FCDI under higher voltage. • Both charge neutralization and capacitance contributed to the removal of ions. • Capacitance contribution dominated the removal of sodium in AFCDI. • Removed ions mainly existed in electrode solution in FCDI. [ABSTRACT FROM AUTHOR]