Liao Chen,Tao Ye,Xinyi Jin,Jie Ren,Boning Huang,Zhi-Kang Xu,Hongzheng Chen,Hanying Li
Crystallization in gel media has been occasionally found to result in single crystals with gel networks incorporated inside, extending the gel method with a long history for crystallization into a platform to design the internal composite structures of a crystal. The limited number of gel-incorporated crystals has inspired the investigation on how general gel incorporation is. Crystallization in gels through decomplexation has been widely used to grow crystals with extremely low water solubility, while whether the gel networks are incorporated inside these crystals has not been studied. In this work, crystals of AgCl, AgI and CuCl have been grown in both agarose gels and silica gels by decomplexation. The crystallographic structures of the crystals were identified by powder and/or single X-ray diffraction. The internal hybrid structures were studied by examining the residue materials after gentle etching and complete dissolution of the crystals. When grown from agarose gels containing self-assembled fibrous structures, gel networks were incorporated into single crystals of all the three compounds. In sharp contrast, the gel networks were pushed away when the crystals were grown in silica gels. The discrepancy between the crystals grown from agarose gels and those from silica gels is consistent with the effect of gel strength on gel incorporation. This work may help to harvest gel-incorporated crystals.
Polyelectrolyte-enhanced ultrafiltration was investigated for rhenium(VII) recovery from aqueous solutions by using polyquaternium-6 (PQ6) as a complexing agent. The effects of the operating parameters on the permeate flux ( J ) and the rhenium rejection coefficient ( R ) were studied. In the process of concentration, J declines slowly and R is about 1. The concentrated solution was used for the decomplexation. It takes 10 min to achieve the decomplexation equilibrium at a chloride ion concentration of 100 mg L –1 . The decomplexation percentage reaches 45.6 %. In the diafiltration process, rhenium is extracted effectively, and the purification of the regenerated PQ6 is satisfactory. The regenerated PQ6 was used to bind rhenium(VII). The binding capacity of the regenerated PQ6 is close to that of fresh PQ6.
Low-level radioactive wastewater containing Co(II)–EDTA generated in the nuclear industry is harmful to the environment, but it is difficult to remove owing to the high stability of metal–organic complexes. Here, we report efficient contact-electro-catalysis (CEC) to achieve the decomplexation of Co(II)–EDTA by using commercial fluorinated ethylene propylene (FEP) powder as a dielectric catalyst. The reaction generated reactive oxygen species through solid–liquid interfacial charge transfer, disrupting the chemical bonds and then oxidizing the central atoms in Co(II)–EDTA to form Co(III)–EDTA with vacancies. The Co(III)–EDTA could be easily removed from the solution under alkaline conditions. The decomplexation efficiency reached a high value of 41.6%, with a constant reaction rate of 0.024 min−1 in 240 minutes. The FEP also exhibited excellent recyclability over 40 h without obvious changes. Unlike conventional advanced oxidation processes, this approach does not require the use of electrodes or chemical oxidants, leading to low energy consumption. This approach also holds great potential for green wastewater management via integration with ambient mechanical energy sources (e.g., wind and hydrostatic pressure).
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