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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]

Enhancing the performance of adsorbents to the utmost extent is an objective but challenging in applying adsorption technology to wastewater treatment. In this work, novel quaternary ammonium polymers (QAPs) with high density adsorption site (i.e., quaternized N, confirmed by FT-IR results) were designed and prepared for rapid selective removal of Cr(VI) from water. The results of EDS analysis indicated the maximum exposure rate of N on the surface of QAPs was as high as 86.1%, which almost doubled comparing to that of Cr(VI) ions imprinted polymers (Cr(VI)-IIP) (46.2%). Interestingly, the maximum adsorption capacity (211.8 mg/g) and initial adsorption rate (h0 , 66.6 mg/ (g·min)) of QAPs (i.e., 5:1(TRIM)) for Cr(VI) are about 3.6 times and 4.9 times those of Cr(VI)-IIP (63.0 mg/g and 13.5 mg/(g·min)), respectively. Impressively, flow-through adsorption experiments demonstrated 5:1(TRIM) can completely remove 5 mg/L of Cr(VI) within five seconds. Additionally, 5:1(TRIM) exhibited a remarkable selectivity for Cr(VI) adsorption, and high purity (100%) of chromium can be readily obtained. The proposed idea of high exposure effect of the adsorption site can provide a valuable guidance for designing rapid selective adsorbents to remove and reclaim Cr(VI) from wastewater. Schematic Diagram for mechanism of Cr(VI) adsorption on QAPs and correlation between exposure rate of N and Q m. [Display omitted] • QAPs is a kind of adsorbent with high density adsorption sites on its surface. • Adsorption capacity (Q m) of QAPs was positively correlated with exposure rate of N. • QAPs exhibit high capacity, rapid adsorption rate for the Cr(VI) adsorption. • QAPs can achieve high purity chromate recovery due to the high selectivity. • QAPs has a good economic benefit in the recovery of chromate from wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Palladium ion-imprinted polymers grafted with PHEMA brushes were synthesized. • Polymerization degree of PHEMA brushes can be regulated. • Grafted IIPs exhibited outstanding adsorption capacity and selectivity. • Anti-interference ability of IIP-3 outperformed the ungrafted IIPs. • Anti-interference mechanism of IIP-3 was proposed. Abstract Ion-imprinted polymers (IIPs) exhibit great potential as the adsorbent for adsorption of palladium from the industrial wastewater. However, co-existence of complicated water matrixes can readily block the imprinting cavities and disturb the adsorption of target ions. Therefore, it is meaningful to endow the IIPs with an excellent anti-interference ability toward practical applications. In this work, the polymer 2-hydroxyethyl methacylate (PHEMA) polymer brushes with different polymerization degree were successfully grafted on the IIPs. The polymerization degrees of PHEMA brushes are 43, 49, 73, 122, and 294 for the IIP-1, IIP-2, IIP-3, IIP-4, and IIP-5, respectively. Batch experiments reveal that polymerization degree has an inconspicuous effect on the adsorption capacity of IIPs. And their adsorption capacities are in the range from 42 to 46 mg/g, which is much higher than most adsorbents documented in literature. The kinetic constant has increased from 0.021 to 0.042 g/(mg·min) with the increase of polymerization degree from 43 to 294, respectively. This result implies that the high-polymerization PHEMA brush can accelerate the adsorption of Pd. More importantly, the anti-interference ability of IIP-3 significantly outperforms the ungrafted IIPs; and corresponding anti-interference mechanism has been proposed. This work provides a fundamental insight into the inter-relation between polymerization degree of polymer brushes and its anti-interference ability, which may facilitate the IIPs-based technology for the adsorption and recovery of valuable metals from complex wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • UiO-66-Rd i-s and UiO-66-Rd p-m adsorbents were designed for capturing Ag(I) from wastewater. • Rhodanine groups were confirmed to be modified outside of UiO-66-Rd p-m and inside of UiO-66-Rd i-s. • UiO-66-Rd p-m exhibited faster kinetic and higher selectivity for Ag(I) capture than UiO-66-Rd i-s. • Enhanced selectivity was dominated by high-exposure rhodanine sites outside of UiO-66-Rd p-m. Highly efficient capturing of silver from wastewater is critical for environmental and economic sustainability but remains significantly challenging to achieve fast kinetics and precise selectivity. Herein, we present two approaches based on rhodanine (Rd)-modified UiO-66 including post-modified ligand exchange for UiO-66-Rd p-m and in-situ solvothermal for UiO-66-Rd i-s. The resultant UiO-66-Rd p-m and UiO-66-Rd i-s perform maximum adsorption capacity of 120 and 109 mg·g−1, respectively, which are both about 6 times higher than pristine UiO-66. Benefitting from high-exposure Rd groups over the surface, UiO-66-Rd p-m exhibits about 3 times faster kinetic adsorption and nearly 15 times higher maximum selectivity coefficient than UiO-66-Rd i-s. Experiment and calculation demonstrate that the excellent performance of Rd-modified UiO-66 is dominantly owing to S chelation in the Rd group. In addition, site energy distributions of the Dubinin-Ashtakhov isotherm model confirm that UiO-66-Rd p-m has more effective sites for Ag(I) adsorption relative to UiO-66-Rd i-s. While a higher density of Rd outside the UiO-66-Rd p-m provides a larger coordination number of S/Ag (1.41) than UiO-66-Rd i-s (0.59), which is attributed to its sufficient exposed active S sites for multidentate coordination of Ag(I), thus significantly enhancing adsorption rate and selectivity. These findings are exploited to shed new insight into the design of adsorbents for the efficient recycling of noble metals from water. [ABSTRACT FROM AUTHOR]