The effect of chitosan molecular weight on CO2-triggered switching between emulsification and demulsification.

The role of molecular weight as a key physical property of macromolecules in determining the CO2-triggered switching characteristics of responsive emulsions prepared using CO2-switchable macromolecules has not been studied and is the focus of the current study. In this work, CO2-switchable chitosan of four different molecular weights is used to investigate the effect of molecular weight on CO2-triggered switching of CO2-responsive emulsions. The molecular weight of chitosan is shown to have an opposite effect on emulsification and demulsification by the CO2 trigger. Before bubbling of CO2, chitosan of higher molecular weight forms a more stable three-dimensional network structure in the continuous phase of oil-in-water (O/W) emulsions, which leads to the formation of a more stable emulsion. After bubbling of CO2, the chitosan of higher molecular weight makes the continuous phase more viscous, which leads to an incomplete demulsification as compared with the chitosan of lower molecular weight. Experimental evidence from the measurement of conductivity, interfacial tension and rheological properties is provided to support the proposed mechanism. This work is of great significance in guiding the selection of desirable CO2-switchable polymers for switchable emulsions of desired switching characteristics.

Simultaneous immobilization of V and Cr availability, speciation in contaminated soil and accumulation in ryegrass by using Fe-modified pyrolysis char.

In this study, municipal waste pyrolytic char (PEWC) was prepared by pyrolysis from municipal solid waste extracted in landfills, and Fe-based modified pyrolytic char (Fe-PEWC) was prepared by modification. Focusing on the evaluation of the stabilization capacity of Fe-PEWC for vanadium (V) and chromium (Cr) in soils, the effects of PEWC addition on soil properties, bioavailability and morphological distribution of V and Cr, ryegrass growth, and V and Cr accumulation were thoroughly investigated. The results of pot experiment showed that the application of PEWC and Fe-PEWC significantly (P < 0.05) improved soil properties (such as pH, EC, total nitrogen, available phosphorus, available potassium, and organic matter). After 42 days of cultivation, Fe-PEWC has a better fixation effect on heavy metals, and the bioavailable V and Cr of 3% Fe-PEWC decreased by 14.96% and 19.48%, respectively. The exchangeable state and reducible state decreased, while the oxidizable state and residual state increased to varying degrees. The Fe-PEWC can effectively reduce the accumulation of V and Cr in ryegrass by 71.25% and 76.43%, respectively, thereby reducing their toxicity to plants. In summary, modified pyrolytic char can effectively solidify heavy metals in soil, improve soil ecology and reduce the toxicity to plants. The use of excavated waste as a raw material for the preparation of soil heavy metal curing agent has the significance of resource recycling, low price, and practical application.

1,3-Bis(4-tert-butyl-phen-yl)-4-nitro-butan-1-one.

In the crystal structure of the title compound, C(24)H(31)NO(3), mol-ecules are connected via C-H⋯O inter-molecular hydrogen bonds, forming dimers. The benzene rings are oriented at a dihedral angle of 29.8 (1)°.