Organo-chromium(III) complex is one of the chromium contaminant species, which would transform to high-toxic Cr(VI) during migrating in the environment. Such natural organo-chromium(III) (NOCr) is difficult to remove by traditional degradation or precipitation methods, due to its high stability and solubility. Herein, we demonstrated a novel NOCr removing method by transforming it to certain structures similar to Cr-Fe minerals in nature, through a self-circulating decomplex and immobilization mechanism with nano zero-valent iron (nZVI). Taking chromium glycinate (Cr-Gly) as a probe, nZVI showed a high Cr removal efficiency of 99.4% under ambient conditions. The removal process included three stages of adsorption, decomplexation, and re-immobilization. Cr-Gly was first adsorbed on the surface of nZVI by chemisorption of the oxide shell. Then, the adsorbed Cr-Gly was decomplexed and oxidized to Cr(VI) by ·OH and 1 O 2 , which were generated from molecular oxygen activated by nZVI. Meanwhile, the released Cr(VI) could be in-situ adsorbed and re-reduced to Cr(III), which was further immobilized in form of Cr-O-Fe complex. As the Cr-O-Fe complexing structure was similar to that of Cr-Fe minerals (such as chromohercynite) in nature, this work explored a novel and efficient NOCr removing method that was potential to weaken chromium pollution in the environment.
The ring-opening reaction of ethylene oxide with acrylic acid catalyzed by organochromium(III) complexes is the most promising route for the industrial synthesis of 2-hydroxyethyl acrylate. However, the heterogeneous batch process with highly explosive gaseous ethylene oxide possesses difficulties on the process optimization and safety. To resolve these problems, homogeneous synthesis process is developed by pressurization and in-line mixing of ethylene oxide and acrylic acid. Stop-flow microreactor is applied to investigate the homogeneous reaction characteristics with high efficiency. A reduced kinetic model on the basis of the simplified reaction network is proposed with good calibration results. The catalytic process of ring-opening reaction is distinguished from the non-catalytic one according to the kinetic model parameters. After recognizing the activation process of catalyst during reaction and fulfilling it before reaction, the ligand effect is quantitatively studied by carefully comparing the catalytic features of four types of organochromium catalysts, chromium(III) acetate, chromium(III) 2-ethylhexanoate, chromium(III) picolinate and chromium(III) acetylacetonate, indicating a high efficiency catalyst might contain such ligand (or support) that possesses weak interaction with Cr metal center as well as considerable steric hindrance.
危险品化学品经营许可证（带存储）