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• Cu-MOF is used to recycle Au(S 2 O 3) 2 3− from alkaline leachate for the first time. • The adsorption capacity of 206.19 mg/g is the highest in the adsorption method. • Diphenylamine and copper cluster defects are used as active sites. • Local exotherms of DMF facilitate the recovery of Au(S 2 O 3) 2 3−. • The interaction between Cu-ADA and Au(S 2 O 3) 2 3− was investigated with DFT calculation. Recycling gold from electronic waste is essential for environmental protection and resource sustainability. However, the design of adsorbents for effective recycling of Au(S 2 O 3) 2 3− from alkaline leach solutions is of great challenge and has not been investigated by using MOFs. Herein, we report the design and preparation of a Cu-MOF based on the structural characteristics of Au(S 2 O 3) 2 3−, which is constructed by 4,4′-di carboxy diphenylamine and Cu 2 -paddlewheel. Cu-ADA-53 demonstrates ultra-high adsorption capacity of 206.19 mg g -1, and the gold recovery in actual alkaline leach solutions is more than 99 %. X-ray photoelectron spectroscopy, thermodynamic study, and density functional theory calculations reveal the excellent performance of Cu-ADA-53 for Au(S 2 O 3) 2 3− results from the abundant Lewis base diphenylamine groups and open copper sites. More importantly, different from pore diffusion-promoting adsorption, the axial coordination DMF of Cu 2 -paddlewheel fell off into the water phase and then released heat locally at the adsorption sites. The local exotherms increase the temperature of the adsorption sites, further promoting the adsorption of Au(S 2 O 3) 2 3− by Cu-ADA-53. The local exotherms at adsorption sites provide a novel insight to efficiently recover Au(S 2 O 3) 2 3−. [Display omitted] [ABSTRACT FROM AUTHOR]

• A noticeable dissolution of Mn was observed in adsorption of antimony on MnO 2. • Dissolved amount of Mn depended on antimony adsorption capacity of MnO 2. • Variation of crystalline phases possessed an insignificant effect on Mn release. • Mechanisms of Sb capture and Mn release were unveiled at the atomic scale. Manganese dioxide (MnO 2) exhibits great potential for the uptake of antimony (Sb) from wastewater. Much research has been dedicated to enhancing the capacity of MnO 2 for Sb sequestration. However, the dissolution behavior of Mn has been overlooked, and the underlying relationship between Sb(III) adsorption and Mn dissolution is not clear. In this study, batch experiments evidenced that there was a noticeable dissolution of Mn during the adsorption of Sb(III) on MnO 2. A correlation analysis demonstrated that the amount of Mn dissolved was dependent on the Sb(III) adsorption capacity of MnO 2 , regardless of the crystalline phase of MnO 2. Further experimental and theoretical results (taking α-MnO 2 as an example) unveiled that Mn dissolution involved the following stages. First, Sb(III) adsorbed onto the (3 1 0) crystal plane of α-MnO 2 to form a complex via two Mn-O-Sb bonds, which can be proven by the delicate adsorption configuration and corresponding adsorption energy (E ad) of −4.04 eV. Then, three O atoms from the α-MnO 2 progressively deprived two H atoms from Sb(OH) 3 and one H atom from a water molecule bound to Sb(OH) 3 , respectively. This process was verified by the configuration of the transition state (transition state #3) and the occurrence of electron transfer (i.e., the net charge changed by + 2 e). Finally, the Mn-O bonds of α-MnO 2 were weakened and disrupted, leading to the release of Mn into the aqueous solution. This work advances the fundamental understanding of Sb adsorption onto MnO 2 , which not only promotes a re-evaluation of the utility of MnO 2 for Sb(III) elimination but also provides a theoretical guide for the design of robust MnO 2 -based adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • POP-BPy exhibits excellent stability in extreme water environments. • Selective capture of palladium from aqua regia was achieved by POP-BPy. • Protonation-armed pyridine nitrogen served as active site for Pd capture. • Almost all of Pd in leachate of spent catalysts was recovered by POP-BPy. Due to the hostile environment in which it is recovered, selective separation of palladium from the leachate of spent catalysts containing palladium is of considerable utility but faces substantial obstacles. This work designed and synthesized a bipyridine-based porous organic polymer (POP-BPy) via free radical polymerization. Meanwhile, its adsorption characteristics and the mechanism of adsorption in extreme environments were examined. In hostile conditions, the resultant POP-BPy display exceptional mechanical stability and environmental resistance. Impressively, POP-BPy has an excellent adsorption capacity of Pd(II) (248 mg/g) in harsh environments (aqua regia: AR; half-diluted aqua regia: AR"1 + 1"), and also had superior selectivity and rapid kinetics. The selectivity of POP-BPy for Pd(II) was verified in combination with relevant experiments (β Pd(II)/Pt(II) = 36.19, β Pd(II)/Pt(II) = 23.90). Furthermore, combining density functional theory (DFT) and molecular dynamics (MD) simulations, the mechanism of selectivity of POP-BPy for Pd(II) was revealed from static adsorption sites to dynamic adsorption processes in a holistic manner, which attributed to the strong attraction of protonated pyridine nitrogen to PdCl 4 2- and site suitability. Furthermore, the application of POP-BPy to spent catalyst recovery resulted in up to 100% removal of Pd(II) from the actual leaching solution, and fixed bed column experiments can effectively treat 2688 bed volumes (L) of feed streams (10 mg/L) before reaching the breakthrough point (<1 mg/L). Overall, this work has opened up new avenues for the selective recycling of valuable metals in harsh environments. [ABSTRACT FROM AUTHOR]

Given the large amount of toxic Cr(VI) wastewater from various industries, it is urgent to take effective treatment measures. Adsorption has been regarded as highly desirable for Cr(VI) removal, but the effectiveness of most adsorbents is significantly dependent on pH value, in which precipitous performance drop and even structural collapse generally occur in strong acidic/alkaline aqueous. Thus, maintaining high adsorption performance and structural integrity over a wide pH range is challenging. To efficiently remove Cr(VI), we designed and prepared of an acid-base resistant metal-organic framework (MOF) Zr-BDPO, by introducing weak acid-base groups (-NH-, -N= and -OH) onto the ligand. Zr-BDPO achieved a maximum adsorption capacity of 555.6 mg · g−1 and retained skeletal structure at pH= 1–11. Interestingly, all these groups can generate conjugate acid-base pairs by means of H+ and OH- in the external solution and then form buffer layer. The removal of Cr(VI) at a broad range of pH values primarily via hydrogen bonds between -NH- and -OH, and the oxoanion species of Cr(VI) is unusual. This strategy that insulating high concentrations of acids and bases and relying on hydrogen bonds to capture Cr(VI) oxoanions provides a new perspective for actual Cr(VI) wastewater treatment. [Display omitted] • A Zr-based metal organic framework with a buffer layer was designed and prepared. • Weak acid-base groups at high or low pH can form conjugate acid-base pairs with itself. • Cr(VI) can be removed over a wide pH range by Zr-BDPO. • The interaction between Zr-BDPO and Cr(VI) was investigated with characterization analysis and DFT calculations. [ABSTRACT FROM AUTHOR]