Search

[Display omitted] • An efficient CuHCF/C electrode was prepared for Cu2+ removal by CDI. • CuHCF/C achieved high Cu2+ adsorption capacity of 134.47 mg g−1 at low applied voltage of 0.8 V. • CuHCF/C manifested excellent Cu2+ selectivity in multi-ion coexisting solution. • The mechanism of removing Cu2+ by Faradaic pseudocapacitance was explained. The efficient capture of copper ions (Cu2+) in wastewater has dual significance in pollution control and resource recovery. Prussian blue analog (PBA)-based pseudocapacitive materials with open frameworks and abundant metal sites have attracted considerable attention as capacitive deionization (CDI) electrodes for copper removal. In this study, the efficiency of copper hexacyanoferrate (CuHCF) as CDI electrode for Cu2+ treating was evaluated for the first time upon the successful synthesis of copper hexacyanoferrate/carbon sheet combination (CuHCF/C) by introducing carbon sheet as conductive substrate. CuHCF/C exhibited significant pseudocapacitance and high specific capacitance (52.92 F g−1) through the intercalation, deintercalation, and coupling of Cu+/Cu2+ and Fe2+/Fe3+ redox pairs. At 0.8 an applied voltage and CuSO 4 feed liquid concentration of 100 mg L−1, the salt adsorption capacity was 134.47 mg g−1 higher than those of most reported electrodes. Moreover, CuHCF/C demonstrated excellent Cu2+ selectivity in multi-ion coexisting solutions and in actual wastewater experiments. Density functional theory (DFT) calculations were employed to elucidate the mechanism. This study not only reveals the essence of Cu2+ deionization by PBAs pseudocapacitance with promising potential applications but also provides a new strategy for selecting efficient CDI electrodes for Cu2+ removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of NC-Co(PO 3) 2 adopted facile gas-solidified phosphating strategy. • NC-Co(PO 3) 2 electrode was used for the first time in the field of CDI. • NC-Co(PO 3) 2 showed better electrosorption capacity of 95.41 mg g−1. • NC-Co(PO 3) 2 had excellent selectivity in various ion-competitive environments. • Real copper-containing wastewater confirmed the great potential of NC-Co(PO 3) 2. The increasing amount of heavy metal copper ions (Cu2+) in industrial emissions, poses a serious threat to human health, biological environment, and resource scarcity. Capacitive deionization (CDI) is considered as a green and efficient method for desalination. It is crucial to develop high-performance electrodes for efficient operation of CDI that go beyond conventional carbon and yield considerable environmental benefits. Here, metal organic frameworks (MOFs) derived carbon-loaded cobalt metaphosphate (NC-Co(PO 3) 2) was prepared by low-temperature gas–solid phosphating for Cu2+ removal as CDI electrode for the first time. NC-Co(PO 3) 2 demonstrated superior electrode structure and function due to the synergistic effects of electric double layer coupling P-O bonds, the binding tendency of metaphosphate groups with Cu2+, and interfacial redox reactions induced by the labile valence state of cobalt. The optimal electrosorption capacity of NC-Co(PO 3) 2 was 95.41 mg g−1 at 1 V in 50 mL Cu2+ solution with splendid cyclic regeneration capability. Moreover, NC-Co(PO 3) 2 exhibited excellent selectivity and outstanding electrosorption performance in the presence of multiple coexisting ions and this CDI system realized the purification of actual copper-containing wastewater. A series of characterizations further revealed the specific mechanism of Cu2+ in adsorption–desorption process. Our finding strongly supported NC-Co(PO 3) 2 electrode can extend the CDI platform's capability for effectively removing and retrieving Cu2+ from wastewater. [ABSTRACT FROM AUTHOR]

Using capacitive deionization to remove heavy metal ions from water has received much attention, but the inferior salt adsorption capacity (SAC) of electrode materials has always limited its practical application. Herein, N, S co-doped two-dimensional (2D) porous glucose derived carbon nanosheets (NSPGC) was successfully fabricated, utilizing the gas exfoliation by calcination of thiourea. The NSPGC demonstrates distinct 2D lamellas, high specific surface area (2529 m2 g−1), hierarchical pore structure and high wettability. In electrochemical tests, a high specific capacitance (127 F g−1) and electrons/ions transport performance can be achieved in the NSPGC, moreover it showed a prominent SAC of 206.57 mg g−1 and recoverability in 100 mg L−1 CuSO 4 solution. Moreover, the density functional theory (DFT) calculation manifested the intrinsic affinity of Cu2+ improved by N, S co-doping, which played an essential role in enhancing the Cu2+ removal performance of CDI. Our work provided a new insight into the preparation of high-performance CDI electrode materials for Cu2+ removal and promoted the application of CDI in heavy metal wastewater. [Display omitted] • N, S co-doped two-dimensional (2D) porous glucose derived carbon nanosheets (NSPGC) were synthesized by one-step pyrolysis. • NSPGC have distinct 2D lamellas, high specific surface area (2529 m2 g-1), hierarchical pore structure and high wettability. • NSPGC exhibits excellent Cu2+ adsorption capacity (206.57 mg g-1). • N, S co-doping enhances the affinity of carbon layer for Cu2+ and improve its adsorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/Fe co-doped ZIF-8 derived porous carbon for CDI removal of Cu2+ ions. • A stable carbon cage encapsulated a porous carbon structure. • CoFe-NC has better selectivity for Cu2+ ions. • CoFe-NC shows higher electrosorption capacity in application of CDI. Due to a threat to human life from heavy metal ions pollution, unprecedented interest has been gained in the development of water purification technologies. Here, we explore another new approach to exploit a prospective carbon material for removing copper ions from aqueous solution based on rapid and easy capacitive deionization (CDI). Reasonable carbon materials modification with ideal composition and improved morphological structure is essential to additionally optimize the capabilities of CDI. We prepared a nitrogen-rich hierarchically porous carbon composites (CoFe-NC) with uniform cobalt (Co) and iron (Fe) doped metal in carbon skeleton by a simple impregnation and pyrolysis method, derived from zeolitic imidazolate framework-8, to use as highly effective CDI electrode for copper ions removal. The addition of Fe can facilitate the uniform dispersion of metals, and enable the formation of a stable carbon cage after pyrolysis. It can sufficiently expose active sites of the electrode materials and promote interfacial charge transfer, thus improving CDI electrosorption efficiency. CoFe-NC composites electrode can achieve outstanding deionization capacity (91.31 mg g−1) in 25 mg L−1 CuSO 4 solution. The carbon cage structure of CoFe-NC not only prevents aggregation of metals and avoids destruction of rich multistage pore system by pyrolysis, but also induces a faster ions transport rate. In addition, density functional theory calculations demonstrated that the co-doping of Co and Fe can remarkably increase the adsorption energies of Cu2+ ions, leading to excellent selectivity, which indicates that CoFe-NC composites can be a desired CDI electrode material. [ABSTRACT FROM AUTHOR]

• Synergistic electrosorption of HBC bilayers and MoS 2 for Cu2+ complexation. • HBC shows excellent structural stability before and after MoS 2 loading. • High selective ion removal effect is still achieved in the presence of complex ions. • Used as an electrode in capacitive deionization technology. Capacitive deionization has been considered as a promising wastewater treatment technology because of its low-cost and highly efficient. Herein, we prepared hollow bowl-type carbon materials loaded with molybdenum sulfide (HBC-MoS 2) composites and fabricated it as an innovative electrode material to remove Cu2+ in a multi-ion coexistence system. With the synergistic effect of electric double layer (EDL) and complexation between MoS 2 and Cu2+, the HBC-MoS 2 -0.02 electrode achieved effective removal of copper ions from low concentration wastewater (25 mg/L) and high electrosorption capacity of 28.97 mg g−1 at 1.0 V. Even in the presence of competing ions (Na+/Zn2+/Cu2+), the HBC-MoS 2 -0.02 electrode still can effectively remove Cu2+ with a final adsorption capacity of 28 mg g−1, showing its superiority. The mechanism of Cu2+ removal by HBC-MoS 2 is mainly due to the synergistic effect of EDL and complexation. [ABSTRACT FROM AUTHOR]