Conversion of Au(Ⅲ)-polluted waste eggshell into functional CaO/Au nanocatalyst for biodiesel production

Developing an environmental-friendly and highly active catalyst in transesterification for biodiesel production is of great importance for a more economic biodisel process.Herein,we reported that waste eggshells were used to adsorb Au(Ⅲ) in water and convert the Au(Ⅲ)-polluted eggshells into the functional nanocatalyst-Ca O/Au for the transesterification reaction between soybean oil and methanol to the preparation of biodiesel.By coupling of Ca O and Au nanoparticles,Ca O/Au nanoparticles showed superior catalytic activity for the transesterification reaction between soybean oil and methanol.An optimum performance was observed over Ca O/Au nanocomposites in a methanol-oil molar ratio at 12:1with catalyst content of 1.0 wt% at 70°C for 3 h.Besides,the catalytic activity of Ca O/Au nanocatalyst was almost unchanged after recycling for 5 times and the yield of biodiesel still kept at 88.9%.The proof-of concept study provided us a sustainable method for utilization of waste eggshells to remedy the metal ions-polluted wastewater and the synthesis of functional nanocomposite for biodiesel production,show great potential application of waste eggshell in adsorption and catalytic reactions.

Novel isostructural iron‐series‐MOF calcined derivatives as positive and negative electrodes: A new strategy to obtain matched electrodes in a supercapacitor device

The performance of asymmetric supercapacitors(ASCs)is strongly restricted by the capacity gap between the positive and negative electrodes.To address this issue,two new electrode materials deriving from Co‐and Fe‐based metal–organic frameworks(MOFs,Co‐TAMBA‐d,and Fe‐TAMBA‐d)through a single‐step sintering method have been developed by considering the superiorities of the derivatives of MOFs including large surface areas,sufficient metal‐atom‐doping content,and extreme surface wettability to the bath solution.The as‐prepared Co‐TAMBA‐d as a positive electrode delivers typical pseudocapacitive behavior with the improvement of capacity,which is better than those of pristine MOF materials,while Fe‐TAMBA‐d as negative electrodes displays better electrochemical behavior than those of activated carbon.ASCs based on these two electrodes exhibits excellent energy density and power density of 47Wh/kg and 1658 W/kg,respectively,where this device can maintain prominent cycling stability with capacity retention after 5000 cycles being about 75%.Furthermore,the capacity can feed a series of red light‐emitting diodes,which gives solid evidence of the potential utilization.These results can afford the feasibility of isostructural MOF derivatives as promising electrodes in novel ASCs.

钢木组合结构自攻螺钉单剪节点试验研究

钢木组合体系兼具了两种材料的优势,在村镇住宅、大跨度结构等建筑体系中均有一定的应用前景。销轴类节点是钢木组合体系中常见的连接形式,其力学特性显著影响结构体系的性能,其中螺栓和钉为销轴的常见形式。为准确评估薄壁钢———木的自攻螺钉连接节点的抗剪性能,从节点抗剪试验、理论推导两个方面进行了研究。同时对潜在的结构材———速生木的力学性能进行了校核。为研究木材与薄壁型钢(2 mm)小直径自攻螺钉(直径<6 mm)连接节点的抗剪性能,设计了11种单调荷载下的单剪连接节点并进行了相关试验。对木材种类、钉的尺寸、连接方向等参数进行分析,得到了自攻螺钉连接节点的破坏模式、承载力及刚度、延性系数、割线刚度等力学特性。在GB 50005—2017《木结构设计标准》的基础上,对薄壁钢-木自攻螺钉连接节点典型破坏模式的承载力进行了分析。结果表明:速生木材的强度可满足连接需求,木材种类的变化对自攻螺钉连接节点的抗剪性能有一定的影响,但钉尺寸、类型、嵌入长度的改变显著影响节点的破坏模式、峰值承载力,国产杉木、杨木以及辐射虽低于常见建材———花旗松、樟子松,但仍有足够的连接强度;自攻螺钉-钢木组合连接节点主要有自攻螺钉钉杆剪断、钉拔出、木材破坏三种破坏模式,其中自攻螺钉剪断是最为常见的破坏情况,在螺钉的嵌入长度较小时,易发生自攻螺钉拔出的破坏情况,木材横纹钉节点时,易因横纹受拉发生脆性断裂,实际情况应避免;燕尾自攻螺钉连接节点在钢板-木结构构件中有着较好的峰值承载力(3 kN左右),但其因螺钉的脆性断裂延性较差,平均延性系数为2,减小嵌入长度可增加连接节点的延性;对自攻螺钉连接节点的抗剪承载力进行了理论推导和机理分析,基于GB 50005—2017等国内规范基础上的分析和校核结果表明,现有标准因未充分考虑绳效应,承载力均小于试验实测值,且不同于纯钢或纯木的销轴类连接节点,薄壁钢-木自攻螺钉连接节点以弯剪破坏为主,由GB 50005—2017得出的设计值约占承载力实际值的30%~45%。