Stable Crystalline Nanohoop Radical and Its Self-Association Promoted by van der Waals Interactions.

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X-ray crystallographic analysis reveals that OR3 forms a unique head-to-tail dimer that further aggregates into a one-dimensional chain in the solid state. Variable-temperature NMR and concentration-dependent absorption measurements indicate that the π-dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self-association process, in contrast with other olympicenyl derivatives that favor π-dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one-electron chemical oxidation. This study offers a new molecular design to modulate the self-association of organic radicals for overcoming the spin-Peierls transition, and to prepare novel nanohoop compounds with spin-related properties.

Construction of a Lignosulfonate-Lysine Hydrogel for the Adsorption of Heavy Metal Ions.

Industrial wastewater has brought great disaster to water bodies and soils and seriously affected the growth of crops. It is necessary to prepare a stable, effective, and sustainable treatment agent to control water pollution to obtain clean water. The adsorption effect of a lignosulfonate-lysine hydrogel (CLS-Lys adsorbent) on heavy metal ions (Cu2+ and Co2+) in water is studied. In the synthesis experiment, a response surface method is used to optimize the content of sodium lignosulfonate, lysine, initiator, and cross-linker. The CLS-Lys adsorbent is characterized by Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, thermal analysis, and zeta potential analysis. The performance of the CLS-Lys adsorbent under different influencing factors is studied. The kinetic and isothermal models of the CLS-Lys adsorbent are established. The results show that the main adsorption model of the CLS-Lys adsorbent is chemical adsorption, accompanied by electrostatic adsorption. These two ions have a competitive adsorption relationship, and when the two ions are present at the same time, they inhibit each other. In addition, the CLS-Lys adsorbent has good adsorption and analytical regeneration performance. It is an economic and effective adsorbent and has a broad application prospect.

Construction of magnetic lignin-based adsorbent and its adsorption properties for dyes.

The magnetic lignin-based adsorbent (Fe3O4/C-ACLS) has been successfully prepared and applied to adsorbing azo dyes Congo red, Titan yellow and Eriochrome blue black R. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray powder diffraction (XRD), vibration sample magnetometer (VSM), Raman spectroscopy and elemental analysis. In the process of adsorption, five kinds of influencing factors and recycling regeneration were discussed, and the adsorption mechanisms such as kinetics, isotherm, thermodynamics were explored. The results show that Fe3O4/C-ACLS can remove 98%, 92% and 99% of Congo red, Titan yellow and Eriochrome blue black R, respectively. Under the same conditions, the removal rate was 87%, 84% and 88% after 5 times adsorption cycle, respectively. Pseudo-first-order, pseudo-second-order kinetics, Elovich model and intraparticle diffusion model were studied, and the results show that the adsorption process conforms to pseudo-second-order kinetics model, and the diffusion rate is controlled by many steps. The results of isotherm model and thermodynamics show that the adsorption process is consistent with Langmuir model and is mainly a spontaneous chemical endothermic process of monolayer.

Carbon composite lignin-based adsorbents for the adsorption of dyes.

Carbon composite lignin-based adsorbent were prepared through hydrothermal method with glucose as carbon source, calcium lignosulfonate and triethylene tetramine as raw materials, respectively. The optimum synthesis conditions were determined by investigating the addition of carbon and triethylene tetramine. The adsorbent was used for the adsorption of azo dyes Congo red and Eriochrome blue black R, and the five factors affecting the adsorption were discussed, including pH of dyes, initial concentration, adsorption time, adsorption temperature and adsorbent dosage. The corresponding adsorption mechanism such as pseudo first order kinetics, pseudo second order kinetics, intraparticle diffusion, Langmuir adsorption isotherm, Freundlich isotherm, Temkin isotherm, Dubinin-Radushkevich adsorption isotherm, thermodynamics were also studied. When the dye concentration is 40 mg L-1, Congo red and Eriochrome blue black R dye removal rates reach 99%. Moreover, the adsorption process of two kinds of dyes follow the pseudo second order kinetics and the Langmuir adsorption isotherm.