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Highlights Analyze the primary causes of cathode failure in three representative batteries, illustrating their underlying regeneration mechanism. The latest research status of direct regeneration of spent lithium–ion batteries was reviewed and summarized in focus. The application examples of direct regeneration technology in production practice are introduced for the first time, and the problems exposed in the initial stage of industrialization were revealed.

Silver ions in wastewater are a major health hazard, and there is an urgent need to develop methods to reliably extract them. Here, the authors show that mixed-valence molybdenum oxide can selectively adsorb and reduce Ag+ from wastewater and be easily recycled while maintaining high selectivity towards Ag+.

Because of its unique molecular structure and renewable properties, vegetable oil has gradually become the focus of researchers. In this work, castor oil was first transformed into a castor oil-based triacrylate structure (MACOG) using two steps of chemical modification, then it was prepared into castor oil-based waterborne polyurethane acrylate emulsion, and finally, a series of coating materials were prepared under UV curing. The results showed that with the increase in MACOG content, the glass transition temperature of the sample was increased from 20.3 °C to 46.6 °C, and the water contact angle of its surface was increased from 73.85 °C to 90.57 °C. In addition, the thermal decomposition temperature, mechanical strength, and water resistance of the samples were also greatly improved. This study not only provides a new idea for the preparation of waterborne polyurethane coatings with excellent comprehensive properties but also expands the application of biomass material castor oil in the field of coating.

The efficient and selective recovery of gold from secondary sources is key to sustainable development. However, the complexity of the recovery environment can significantly complicate the compositions of utilized sorbents. Here, we report a straw-derived mesoporous carbon as an inexpensive support material. This mesoporous carbon is modified by anions (sulfur modulation, C-S-180) to improve its electron-transfer efficiency and tune the electronic structure of its skeleton toward enhanced gold reduction. The high surface area of C-S-180 (989.4 m2/g), as well as the presence of abundant C–S in the porous structure of the adsorbent, resulted in an outstanding Au3+-uptake capacity (3422.75 mg/g), excellent resistance to interference, and favorable Au3+ selectivity. Dissimilar to most existing carbon-based adsorbents, electrochemistry-based studies on the electron-transfer efficiencies of adsorbents reveal that sulfur modulation is crucial to optimizing their adsorption performances. Furthermore, the density functional theory reveals that the optimization mechanism is attributable to the adjustment of the electronic structure of the carbon skeleton by C–S, which optimizes the band-gap energy for enhanced Au3+ reduction. These findings offer a strategy for constructing green and efficient adsorbents, as well as a basis for extending the applications of inexpensive carbon materials in gold recovery from complex environments.

Thermal-responsive block copolymers are a special type of macromolecule that exhibit a wide range of applications in various fields. In this contribution, we report a new type of polyacrylamide-based block copolymer bearing pyridine groups of polyethylene glycol-block-poly(N-(2-methylpyridine)-acrylamide; Px) that display distinct salt-induced lower critical solution temperature (LCST) behavior. Unexpectedly, the phase-transition mechanism of the salt-induced LCST behavior of Px block copolymers is different from that of the reported LCST-featured analogues. Moreover, their thermo-responsive behavior can be significantly regulated by several parameters such as salt species and concentration, urea, polymerization degree, polymer concentration and pH values. This unique thermal behavior of pyridine-containing block copolymers provides a new avenue for the fabrication of smart polymer materials with potential applications in biomedicine.

In this study, a novel Co(II)-based adsorbent Co-H2L is developed for the removal of phosphate. The batch experiments demonstrate that the Co-H2L possesses preferable ability of phosphate capture from water in mildly acidic to neutral pHs, with a maximum adsorption capacity of 194.44 mg P g−1. Adsorption isotherms for phosphate agree with the Langmuir model, suggesting a monolayer process. The mechanism for phosphate adsorption onto Co-H2L mainly followed the coordination mechanism, and the Co valence electron orbitals play the key role in the phosphate adsorption. In addition, the Co-H2L adsorbent can selectively remove phosphate ions in the presence of the competing ions (Cl−, NO3−, and SO42−) at higher concentrations. Our results therefore indicate that the Co(II)-based adsorbent is expected to find extensive applications in phosphate removal for water management.

Wastewater treatment for heavy metals is currently transitioning from pollution remediation towards resource recovery. As a controllable and environment-friendly method, electrochemical technologies have recently gained significant attention. However, there is a lack of systematic and goal oriented summarize of electrochemical metal recovery techniques, which has inhibited the optimized application of these methods. This review aims at recent advances in electrochemical metal recovery techniques, by comparing different electrochemical recovery methods, attempts to target recycling heavy metal resources with minimize energy consumption, boost recovery efficiency and realize the commercial application. In this review, different electrochemical recovery methods (including E-adsorption recovery, E-oxidation recovery, E-reduction recovery, and E-precipitation recovery) for recovering heavy metals are introduced, followed an analysis of their corresponding mechanisms, influencing factors, and recovery efficiencies. In addition, the mass transfer efficiency can be promoted further through optimizing electrodes and reactors, and multiple technologies (photo-electrochemical and sono-electrochemical) could to be used synergistically improve recovery efficiencies. Finally, the most promising directions for electrochemical recovery of heavy metals are discussed along with the challenges and future opportunities of electrochemical technology in recycling heavy metals from wastewater.

Graphitic carbon nitride (g-C3N4) is a promising semiconductor material which has been widely studied in nanoscience. However, the effect of modifying the performance of g-C3N4 is still under debate. In this communication, we show the size and functional group effects on the g-C3N4 using density functional theory (DFT) calculations. It was found that a molecule with six repeated g-C3N4 units (g-C3N4-6) could be the smallest unit that converges to the limit of its HOMO–LUMO gap. Calculations of g-C3N4-6 with varying numbers of substituted C≡N, C=O, and O−H functional groups show that C≡N and C=O could narrow down the HOMO–LUMO gap, while O−H could slightly raise the gap. This study shows that the change of substituents could tune the band gap of g-C3N4, suggesting that rationally modifying the substituent at the edge of g-C3N4-based materials could help to significantly increase the photocatalytic properties of a metal-free g-C3N4.

Reusing spent anodes is a pivotal step for recycling lithium-ion batteries (LIBs). However, it proves challenging to completely eliminate Cu impurities from spent graphite (SG), which hinders the effective recycling of spent anodes. In this paper, a straightforward air oxidation method is proposed to directly upgrade spent anodes into stable CuO/C anodes by harnessing the inherent Cu impurities in spent anodes. The air oxidation process not only repairs the SG to some extent but also generates uniformly dispersed CuO nanoparticles, which chemically bind with the repaired graphite (RG) through Cu–O–C bonds. The specific discharge capacity of the CuO/RG anode can reach as high as 647 mA h g−1 even after 500 cycles (at 372 mA g−1 ). In addition, this program is found to reduce energy consumption and greenhouse gas emissions by ∼80% compared to previously reported CuO/C production programs. Clearly, this approach provides a new direction for large-scale recycling of spent LIBs and low-cost production of high-performance CuO/C anodes. [ABSTRACT FROM AUTHOR]