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[Display omitted] Adsorption is a green technology of treating heavy metal-contaminated strong acid wastewaters for the recycling of heavy metal and reuse of strong acid. Herein, three amine polymers (APs) with different alkalinities and electron donating abilities were prepared to investigate the adsorption-reduction processes of Cr(VI). It was found that the removal of Cr(VI) was controlled by the concentration of –NRH+ on the surface of APs at pH > 2, which relies on the alkalinity of APs. However, the high concentration of NRH+ significantly facilitated the adsorption of Cr(VI) on the surface of APs and accelerated the mass transfer between Cr(VI) and APs at strong acid environment (pH ≤ 2). More importantly, the reduction of Cr(VI) was enhanced at pH ≤ 2, due to the high reduction potential of Cr(VI) (E ≥ 0.437). The ratio of reduction to adsorption (α) of Cr(VI) was above 0.70, and the proportion of Cr(III) bonding on Ph-AP excessed 67.6 %. Finally, a proton-enhanced mechanism of Cr(VI) removal was verified by analyzing FTIR and XPS spectra as well as constructing DFT model. This study provides a theoretical basis for the removal of Cr(VI) in the strong acid wastewater. [ABSTRACT FROM AUTHOR]

A novel cyclic functional monomer (CFM) was used to develop an As(III)-ion imprinted polymer (As-IIP). CFM possesses a positively charged imidazolium moiety and its specific cyclic size matches that of As(III). Batch adsorption experiments showed that the As-IIP has a maximum As(III) adsorption capacity of 55 mg/g, while that of the control polymer (CP) is only 25 mg As(III)/g. Adsorption isotherms for As(III) agree with the Langmuir model, suggesting monolayer adsorption. Kinetic studies showed that the adsorption process followed pseudo-second-order kinetics. The relative selectivity coefficients of As-IIP compared to CP for Cl − /H 2 AsO 3 − , SO 4 2− /H 2 AsO 3 − , HPO 4 2− /H 2 AsO 3 − , NO 3 − /H 2 AsO 3 − , and Mo 7 O 24 6− /H 2 AsO 3 − are 1.03, 1.95, 2.55, 1.52 and 2.51, respectively. The removal efficiency of As-IIP for As(III) in actual industrial wastewater was nearly 100%, which confirms that As-IIP has a high adsorption capacity as well as selectivity for the removal of As(III) from 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]

[Display omitted] • A new ion-imprinted polymer that utilizes VTA was prepared for Cr(VI) removal. • The coordination effect and template effect were deep analyzed. • The role of cross-linking agents was investigated and clarified. • The results were successful used to design adsorbents for real wastewater. The template effect is known as the most important feature of ion imprinted polymer (IIP) technology. However, there has been a gap in the theorization of the template effect and apply the template effect to practice. In this work, we propose a method to control the template effect of IIPs by adjusting the ratio of cross-linking. A series of Cr(VI)-IIPs with various contents of the cross-linking agent were synthesized. Based on the qualitative analysis of the coordination selectivity and template effect, the theoretical equation of the template effect generated by the cross-linking agent was established rely on the Scatchard equation. In the Cr(VI) removal process, the contribution of template effect began to surpass the coordination effect when the molar ratio of functional monomer to cross-linking agent was 1/5.46, and the template effect further enhanced with the increase of cross-linking agent content. In the application of actual wastewater treatment, the IIP-1/12 and IIP-1/6 which are designed according to the resulting equation are effective to treat two different types of wastewater. The normalization equations and design concepts proposed in this study theoretically illustrate the role of cross-linking agent in the selectivity of materials. This allows for more flexibility in modulating the template effect of Ion Imprinted Technology for design and application. [ABSTRACT FROM AUTHOR]

• UiO-66-NH 2 -Rd adsorbent with dual coordination sites was designed and synthesized. • UiO-66-NH 2 -Rd exhibited high capacity and outstanding selectivity for Ag(I) capture. • Amide bonds endowed UiO-66-NH 2 -Rd with excellent recyclability and durability. • Specific adsorption site was identified by theoretical and experimental studies. Selective capture and maximum recovery of Ag(I) from wastewater is of great significance for a sustainable future. In this work, novel rhodanine (Rd)-functionalized UiO-66 adsorbents (i.e., UiO-66-Rd and UiO-66-NH 2 -Rd) were designed and synthesized. Different from previously reported UiO-66 derivatives with single metal coordination sites, the as-synthesized UiO-66-Rd and UiO-66-NH 2 -Rd have dual coordination sites, resulting in higher capacity and outstanding selectivity. The maximum capacities of UiO-66-Rd and UiO-66-NH 2 -Rd are 112 and 163 mg·g−1, nearly 5.6 and 8.2 times higher than that of UiO-66, respectively. Impressively, the maximum selectivity coefficient of UiO-66-NH 2 -Rd is approximately 1795 and 1173 folds higher than that of UiO-66 and UiO-66-NH 2. The experimental characterizations and theoretical calculations indicate that the Rd-induced enhancement in the adsorptivity and selectivity are mainly attributed to the dual coordination sites (i.e., C S and C S bonds), which collectively coordinate with Ag(I) in the form of Ag mono-coordinated with S. Compared with the UiO-66-Rd, UiO-66-NH 2 -Rd possesses excellent recyclability and durability due to the vital role of amide bonds generated from NH 2 group in the functionalization of UiO-66 with Rd. Furthermore, UiO-66-NH 2 -Rd can almost completely remove Ag(I) from the actual wastewater with complex matrix, satisfying the national integrated wastewater discharge standard and industrial wastewater emission standard, highlighting a great potential of practical application. [ABSTRACT FROM AUTHOR]