In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90–100% using a precipitation method with alkaline solution.
Covalent organic frameworks (COFs) as a novel stationary phase have attracted much attention in the field of chromatography owing to their permanent nanoscale porosity, higher surface area, and exceptional stabilities. Here, a novel isocyanate‐β‐cyclodextrin‐modified COF (MDI‐β‐CD‐modified COF) was synthesized using isocyanate‐β‐cyclodextrin as the chiral selector and imine‐based TpPa‐1 COF as the matrix by a bottom‐up strategy. The reaction condition and the structure of MDI‐β‐CD‐modified COF were optimized and characterized by X‐ray diffraction (XRD), Fourier‐transform infrared (FT‐IR) spectra, nitrogen adsorption/desorption (Brunauer–Emmett–Teller [BET]), and thermogravimetric analysis (TGA). And then the coated open‐tubular column (OT column) was prepared using MDI‐β‐CD‐modified COF as chiral stationary phase (CSP) by in situ growth approach, which exhibited excellent stability and repeatability. For seven consecutive runs, the intraday and interday relative standard deviations (RSDs) were in range from 0.35% to 2.21% for the migration time of histidine. The column‐to‐column reproducibility ranged from 2.39% to 3.08%. Meanwhile, the separation of eight compounds including four amino acids and four β‐blockers by capillary electrochromatography sufficiently verified the favorable chiral resolution properties of the MDI‐β‐CD‐modified COF‐coated OT column. This strategy of fabricating MDI‐β‐CD‐modified COF‐coated OT column expanded the application of imine‐based COFs in chromatographic analytical fields.
A new kind of chiral zirconium-based metal–organic framework, l-Cys-PCN-222, was synthesized by the SALI method and utilized as the chiral stationary phase in a capillary electrochromatography system for enantioseparation.
In order to use the enantioseparation capability of cationic cyclodextrin and to combine the advantages of capillary electrochromatography (CEC) with opentubular (OT) column, in this study, a new OT-CEC, coated with cationic cyclodextrin (1-allylimidazolium-β-cyclodextrin [AI-β-CD]) as chiral stationary phase (CSP), was prepared and applied for enantioseparation. Synthesized AI-β-CD was characterized by infrared (IR) spectrometry and mass spectrometry (MS). The preparation conditions for the AI-β-CD-coated column were optimized with the orthogonal experiment design L 9 (3 4 ). The column prepared was characterized by scanning electron microscopy (SEM) and elemental analysis (EA). The results showed that the thickness of stationary phase in the inner surface of the AI-β-CD-coated columns was about 0.2 to 0.5 μm. The AI-β-CD content in stationary phase based on the EA was approximately 2.77 mmol·m −2 . The AI-β-CD-coated columns could separate all 14 chiral compounds (histidine, lysine, arginine, glutamate, aspartic acid, cysteine, serine, valine, isoleucine, phenylalanine, salbutamol, atenolol, ibuprofen, and napropamide) successfully in the study and exhibit excellent reproducibility and stability. We propose that the column, coated with AI-β-CD, has a great potential for enantioseparation in OT-CEC.
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