Investigation of the solubility and dispersion degree of calf skin collagen in ionic liquids

The dissolution of collagen in ionic liquids(ILs)was highly dependent on the polarity of ILs,which was influenced by their sorts and concentrations.Herein,the solubility and dispersion degree of collagen in two sorts of ILs,namely 1-ethyl-methylimidazolium tetrafluoroborate([EMIM][BF4])with low polarity and 1-ethyl-3-methylimidazolium acetate([EMIM][Ac])with high polarity in a concentration range from 10% to 70% at 10℃ were investigated.When 150 mg of collagen was added to 30 mg of ILs,the minimum soluble collagen concentration was 0.02 mg/mL in 70%[EMIM][BF4]with lowest polarity and the maximum was 3.57 mg/mL in 70%[EMIM][Ac]with highest polarity,which indicates that soluble collagen and insoluble collagen fibers were both present.For insoluble collagens,differential scanning calorimetry showed that the thermal-stability was weakened when increasing the ILs concentration and polarity,and the fiber arrangement was looser with a more uniform lyophilized structure,observed by atomic force microscopy and scanning electron microscopy.For soluble collagens,electrophoresis patterns and Fourier transform infrared spectroscopy showed that no polypeptide chain degradation occurred during dissolution,but the thermal denaturation temperature decreased by 0.26℃~7.63℃ with the increase of ILs concentrations,measured by ultra-sensitive differential scanning calorimetry.Moreover,the aggregation of collagen molecules was reduced when ILs polarity was increased as determined by fluorescence measurements and dynamic light scattering,which resulted in an increased loose fiber arrangement observed by atomic force microscopy.If the structural integrity of collagen needs to be retained,then the ILs sorts and concentrations should be considered.

Chlorination pattern effect on thermodynamic parameters and environmental degradability for C_(10)-SCCPs: Quantum chemical calculation based on virtual combinational library

Short-chain chlorinated paraffins（SCCPs） are still controversial candidates for inclusion in the Stockholm Convention.The inherent mixture nature of SCCPs makes it rather difficult to explore their environmental behaviors.A virtual molecule library of 42,720 C10-SCCP congeners covering the full structure spectrum was constructed.We explored the structural effects on the thermodynamic parameters and environmental degradability of C10-SCCPs through semi-empirical quantum chemical calculations.The thermodynamic properties were acquired using the AM1 method,and frontier molecular orbital analysis was carried out to obtain the EHOMO,ELUMO and ELUMO-EHOMO for degradability exploration at the same level.The influence of the chlorination degree（NCl on the relative stability and environmental degradation was elucidated.A novel structural descriptor,μ,was proposed to measure the dispersion of the chlorine atoms within a molecule.There were significant correlations between thermodynamic values and NCl,while the reported NCl-dependent pollution profile of C10-SCCPs in environmental samples was basically consistent with the predicted order of formation stability of C10-SCCP congeners.In addition,isomers with largeμ showed higher relative stability than those with small μ.This could be further verified by the relationship between μ and the reactivity of nucleophilic substitution and · OH attack respectively.The C10-SCCP congeners with less Cl substitution and lower dispersion degree are susceptible to environmental degradation via nucleophilic substitution and hydroxyl radical attack,while direct photolysis of C10-SCCP congeners cannot readily occur due to the large ELUMO-EHOMO values.The chlorination effect and the conclusions were further checked with appropriate density functional theory（DFT） calculations.

Effects of the support material addition on the hydrodynamic behavior of an anaerobic expanded granular sludge bed reactor

As a support material, zeolite can be used to promote the granulation process due to its high settable property and the ability to retain biomass on its surface. The present paper reports on the influence of zeolite addition on the hydrodynamic behavior of an expanded granular sludge bed reactor（EGSB）. Different models were applied to fit the flow pattern and to compare EGSB hydrodynamic performance with and without the addition of zeolite. The experimental data fit the tanks in a series model for zeolite bed height of 5 cm and upflow velocity of 6 m/hr.Higher axial dispersion degree（D/uL） was obtained at lower heights of zeolite. The real hydraulic retention time（HRTr） was increased with both increased zeolite bed height and increased upflow velocity. The short-circuit results for 5 cm of zeolite bed and 6, 8 and 10 m/hr upflow velocity were 0.3, 0.24 and 0.19 respectively, demonstrating the feasibility of using zeolite for a proper hydrodynamic environment to operate the EGSB reactor. The presence of zeolite resulted in the higher percentage values of dead zones, ranging from 12% to 24%.Zeolite addition exerted a positive effect on the hydrodynamics pattern for this technology being advantageous for the anaerobic process because of its possible contribution to better biofilm agglomeration, granule formation and substrate-microorganism contact.