教学课程资源库 更多>>

关键词： Zeolitic imidazolate frameworks (ZIFs)   Metal-organic frameworks (MOFs)   Eriochrome black-T (EBT)   Box-Behnken design (BBD)  

摘要： Various Zeolitic Imidazolate Frameworks (ZIFs), a unique class of metal organic frameworks (MOFs), were prepared and studied for the removal efficiency against the hazardous azo dye eriochrome black-T (EBT) from water. Two type of ZIF were synthesized, Co-based (ZIF-67) and Zn-based (ZIF-8). For each type, four variations with different morphologies were chosen in order to determine the best performing candidate for the further optimization studies. ZIF-67-OAc showed a superior adsorptive EBT removal efficiency compared to the rest herein studied ZIFs. To statistically model the EBT removal, response surface methodology (RSM) using Box-Behnken design (BBD) technique was followed. According to the model, solution/suspension pH was found to play the most significant role that govern the rate of EBT adsorption. Under optimized condition, where pH, ZIF-67-OAc dose, mixing time, and EBT concentration set to be 6.82, 832.4 mg/L, 39.95 min, and 100 mg/L, respectively, a 99 % EBT removal was achieved. The equilibrium data best fitted to Freundlich isotherm model, indicating that the dye molecules accumulate in multilayer on the ZIF-67-OAc surface. Based on the Langmuir isotherm model that was also fitted well (R-2 = 0.95), the q(max) was found 263.5 mg/g. Furthermore, EBT adsorption onto ZIF-67-OAc was descripted better with the pseudo-first order kinetic model.

关键词： Fatty acids   Cooking oils   Nanoemuslions   In vitrodigestion   Bioaccessibility   Oxidative stability   Low energy method  

摘要： Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the polyunsaturated fatty acids which can determine early growth and development. Despite their supplementation benefits, the stability and bioavailability are major concerns in their fortification. In the present study, omega-3 fatty acid nanoemulsions using sunflower as the carrier oil were developed using spontaneous, low energy method and their bioaccessibility was assessed. Encapsulation of omega-3 fatty acids using sunflower oil produced stable nanoemulsions with Tween 85 and isopropanol as the surfactant mixture. Droplet size was within the range of 100-200 nm, with zeta-potential above -30 mV, and polydispersity index less than 0.3 upon storage for 28 days. omega-3 fatty acid content of the nanoemulsions decreased by similar to 15% upon storage for 4 weeks at either 4 or 25 degrees C, but suffered similar to 50% loss at 40 degrees C within 2 weeks. Bioaccessibility of omega-3 fatty acids from the prepared nanoemulsions was similar to 53% as compared to 34% of release from plain oils blended with omega-3 fatty acids. This study is the first of its kind that fabricated an efficient nanovehicle using a low energy method with cooking oil as a carrier for the delivery of long chain polyunsaturated fatty acids. The formulated nanoemulsions can be used for supportive therapies and food based approaches to improve omega-3 fatty acid nutrition.

关键词： Bloom algae   Hythane   Fermentation   Hydrothermal pre-treatment   Sustainable gaseous biofuel  

摘要： Algal bloom biomass, sourced from a freshwater lake in Chongqing, was pre-treated by hydrothermal pre-treatments with or without acid/alkali catalysts, and subsequently used as a substrate for sustainable biohythane production via fermentation. Fourier transform infrared (FTIR) spectroscopy analyses suggested hydrothermal acid/alkali pre-treatments significantly changed peak intensities of chemical compositions in algal bloom biomass. Derivative thermogravimetric (DTG) analyses showed more macromolecular substances hydrolysed after hydrothermal acid/alkali pre-treatments. When bloom algae were pretreated with 1% HCl at 140 degrees C for 10 min, an optimal specific hydrogen yield (SHY) of 39.4 mL/g volatile solid (VS) was obtained, which is 38.2% higher than raw biomass. However, a 34.4% decrease in SHY occurred under hydrothermal pre-treatment with 1% NaOH due to the enhancement of Maillard reaction. When using the effluents in methane fermentation, specific methane yields (SMYs) were 177.1-276.8 mL/g VS. Two-stage process effectively reduced the total fermentation time by 22.7% compared with single-stage fermentation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Fermented food   Flavourzyme   Free amino acids   Lactobacillus   Lactococcus   Flavor  

摘要： Flavourzyme is known to promote protein decomposition, resulting in more peptides and amino acids which can improve the quality of fermented foods. In this study, the effects of flavourzyme addition on the fermentation of Suanzhayu fish were investigated. The results showed that the addition of 50 U/g flavourzyme reduced the water activity (a(w)) of products and promoted the release of trichloroacetic acid (TCA)-soluble peptides and free amino acids (FAAs). Thus, the stability of the product was improved and its nutritional value was increased. In addition, with the addition of flavourzyme, Lactobacillus and Saccharomyces more quickly became the dominant genera in the fermentation. Furthermore, the formation of alcohols, aldehydes, and esters was promoted in flavourzyme addition group. Redundant analysis (RDA) indicated that Lactobacillus and Lactococcus play important roles in the formation of flavors, especially for the characteristic flavors of Suanzhayu. Flavourzyme addition may be a novel method to greatly improve the properties of Suanzhayu and shorten the fermentation time.

关键词： Biodegradation   Respirometric analysis   Aquatic system  

摘要： Biodegradation tests of chitosan (CH), polybutylene adipate terephthalate (PBAT) and high density polyethylene (HDPE) polymers were carried out using the standard OECD 301D guidelines. The results showed that the CH samples biodegraded faster than those of PBAT. Photographs registered exhibited the complete or partial disintegration of the samples, and a more opaque color was observed with the increase of biodegradation. FTIR analysis showed some changes in the intensity of the typical bands of the HDPE sample. The presence of P. nitroreducens bacteria was revealed on the PBAT sample surface by SEM studies. Additionally, a clear increase in elastic modulus (EM) and tensile strength (TS) values were observed in PBAT and HDPE samples on day 3, which decreased significantly at the end of the study. Furthermore, an increase in the crystallinity of the HDPE sample was observed on day 28. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 钢铁冶金   工程演化   物理化学   冶金反应工程   冶金流程工程学   工业革命  

摘要： 以工程哲学的视野,研究了钢铁冶金的起源、发展和演化进程。阐述了钢铁材料的功能与地位,论证了钢铁对人类社会进步和文明发展的重要作用。研究了古代钢铁冶金技艺的发展、传承和创新,讨论了17世纪以后,文艺复兴以及近代科学的肇始对钢铁冶金技术和科学的影响。论述了近代科学对钢铁冶金从技艺走向工程科学的重大和深远的影响,并对以冶金物理化学为代表的钢铁冶金基础科学的创建进行了详细论述。阐述了以冶金反应工程为代表的钢铁冶金技术科学对现代钢铁冶金工程的重大意义,讨论了宏观钢铁冶金工程科学、冶金流程工程学对钢铁产业发展的重要意义。提出了钢铁冶金基础科学、技术科学和工程科学协同发展、相互支撑的学科体系,以及未来钢铁工业可持续健康发展的目标和方向。

关键词： Chemical heat pump   Ammonium carbamate   Reversible chemical reaction   Enthalpy change of reaction   Thermodynamic analysis  

摘要： Heat pump is an effective technology for the utilization and upgrading of low-grade heat in building and industrial heating. A novel chemical heat pump based on the reversible reaction of ammonium carbamate (AC) is proposed. Different from the exiting AC -based thermal management system, the proposed cycle can realize the upgrading of low-grade heat. Compared with conventional heat pumps, it is more efficient and environmentally friendly. A thermodynamic model for this cycle is established based on the experimental data of AC reaction equilibrium. The influences of some key parameters, such as the intermediate pressure of the two-stage compressors, the concentration of the mixed solution and the effectiveness of the internal heat exchangers, on the cycle coefficient of performance (COP) are investigated. The results show that the internal heat recovery (intercooler and recuperator) has a huge impact on cycle performance. It can reduce 78.5% of the heat and cold offset loss and improve the cycle COP by 35.6% compared with the cycle without internal heat recovery. The performance comparison with the conventional vapor compression heat pump shows that the proposed cycle has the potential to obtain higher COP thanks to the comparatively higher reaction heat. Under the condition of temperature lift Delta t = 40 degrees C and exothermic temperature t(k) = 50 similar to 100 degrees C, the COP of the proposed cycle is 37.1% and 7.8% higher than that of the conventional cycle with R1234yf and R600 on average, respectively. However, the proposed cycle suffers from large theoretical suction volume and high exhaust temperature for compressor, which can be improved with the increase of endothermic temperature and decrease of temperature lift, respectively.

关键词： Hydrothermal treatment   Mung bean starch   Starch digestibility  

摘要： In this study, starches of three mung bean cultivars (Vigna radiata) having different amylose contents were isolated andmodified using a combination of citric acid and heat-moisture treatment (CA-HMT) or a combination of citric acid and annealing treatment (CA-ANN). Physicochemical properties and in vitro digestibility of native and treated mung bean starches were investigated. Resistant starch (RS) contents of the high-amylose, medium-amylose and low-amylose starches treated with CA-ANN were 41.1%, 35.7% and 27.1%, respectively, being higher than those treated with CA-HMT or native starches in the same variety. The CA-ANN did not affect themorphology and crystallinity of the starches. However, the starches treated by the CA-HMT were partly gelatinized and had higher degree of relative crystallinity as compared to the native starches. The DPs, swelling power, and viscosity of the treated starches were significantly lower than those of the native starches. The high-amylose mung bean starch was greatly affected by the treatments rather than medium- or low-amylose mung bean starch. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 以学生为中心   线上线下   物理化学实验  

摘要： 信息化网络时代,科技日新月异,催生了许多的网络教学平台,使得线上线下混合教学模式得以蓬勃发展。探索将线上线下混合教学推广运用至到物理化学实验的教学中,培养学生的学习自主性,实现以教为主向以学为主的变革。混合教学的模式使得学生的自主学习能力得以锻炼,还加强了他们认真、严谨的科学素养,创造了积极的课堂氛围和良好的教学效果。

关键词： 物理化学   FOX-7   喷雾重结晶   晶体粒径   热动力学分析   机械感度  

摘要： 为了改善FOX-7的性能,采用喷雾重结晶法制备了细化FOX-7,研究了溶剂与非溶剂种类、药液质量浓度及搅拌速率对重结晶细化FOX-7晶体形貌的影响,确定了最佳工艺条件;采用扫描电子显微镜(SEM)及粒度分析软件对细化FOX-7进行了粒径形貌表征;采用X射线粉末衍射系统(XRD)、傅里叶变换红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、12型落锤仪及WM-1型摩擦感度仪对微米级FOX-7晶体进行表征及性能测试。结果表明,最佳工艺条件为:溶剂-非溶剂为NMP-H2O,药液质量浓度为0.4g/mL,搅拌速率为450r/min,可获得平均粒径为1.81μm的微米级FOX-7晶体;微米级FOX-7晶型与原料FOX-7相比未发生改变;微米级FOX-7表观活化能比原料FOX-7提高了88.74kJ/mol,热爆炸临界温度提高了19℃,特性落高从82.3cm提升至136.1cm,摩擦感度从12%降至0;表明微米级FOX-7比原料FOX-7具有更好的热安定性及更低的机械感度。