Efficient decontamination of heavy metals from water remains an urgent and still challenging issue. Herein, a novel adsorbent HMO@N001 was prepared by the in-situ encapsulation of hydrated manganese(IV) oxides (HMO) NPs inside the gel-type cation exchanger N001. Owing to the < 5 nm swollen pores of the N001 host, the in-situ growth of HMO NPs was restricted to sub-5 nm level (with the average size of 4.65 ± 1.17 nm). As a comparison, HMO NPs inside the commercially available macroporous analogue HMO@D001 possessed the average size of 24.52 ± 5.07 nm. The sub-5 nm nature granted HMO@N001 higher proportion (56.7%) of the reactive terminal oxygen (Mn-OH) compared with HMO@D001 (42.7%), contributing to that the maximum adsorption capacities ( Q m ) of HMO@N001 (146.6 ± 2.8 mg/g) toward Ni(II) reached to ∼1.36 times the value of HMO@D001 (107.9 ± 7.6 mg/g). Common coexisting cations including Na + , Mg 2+ , and Ca 2+ mainly suppressed the electrostatic adsorption from the N001 host, while the inner-sphere complexation between Ni(II) and HMO NPs was little affected, as verified by the SEM-EDS analysis. The used HMO@N001 was effectively regenerated using 0.05 M dimethylglyoxime solution for cyclic utilization. In fixed-bed experiments, the effective treatment capacity of the HMO@N001 column reached up to ∼4200 bed volume (BV), over 1.35 times that of the HMO@D001 column (∼3100 BV). This study may provide a promising option for advanced heavy metals decontamination.
Four new d-block metal complexes formulated as [NiII(H3thptacn)]Cl2·H2O (1), [MnIV(thptacn)]ClO4 (2), [CuII3(Hthptacn)2](ClO4)2 (3), and [CdII2(H3thptacn)2Cl2][B(C6H5)4]2 (4) were obtained from the macrocyclic ligand 1,4,7-tris(3-hydroxypropyl)-1,4,7-triazacyclononane (H3thptacn) either through solvent diffusion or by evaporation of their solutions. These complexes were characterized by single crystal X-ray structural determination, elemental analysis, and routine spectroscopic methods. Complexes 1 and 2 exhibit similar mononuclear structures with the metal centers being surrounded by both the backbone nitrogen atoms and the pendant coordinating alcohol/alkoxide groups. Complex 3 is a linear trinuclear cluster, where three Cu(II) centers are combined together by the bridging alkoxide groups in a centro-symmetric pattern. Two chloride groups join two Cd(II) atoms each chelated by one triply protonated ligand H3thptacn to afford dinuclear compound 4 with a symmetry center. When coordinating to different d-block metals, the macrocyclic ligand exhibits four types of binding modes with various dissociation status on its pendant alcohol groups and different numbers of these pendant groups participating in coordination. The magnetic measurements revealed significant zero-field splitting for mononuclear Ni(II) and Mn(IV) complexes. A moderate antiferromagnetic interaction between the neighboring Cu(II) centers governs the magnetic properties of 3 with J = −166(3) cm−1.
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