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1.
《Mendeleev Communications》2022,32(3):395-396
A new method for assembling 1,3-selenazolines by the iodine- mediated reaction of the simplest building blocks such as elemental selenium, alkenes and acetonitrile has been discovered. A proposed mechanism includes the addition of the intermediate selenium iodides to alkene with subsequent solvent interception by the formed seleniranium ion.  相似文献   
2.
Pyrolysis of rice straw (RS), a popular method for producing biochar, effectively treats heavy metal(loid)-contaminated RS. Here, we carried out this process at different temperatures and investigated the deportment of heavy metal(loid)s and the property evolution of biochars. Also, the optimal pyrolysis temperature for Pb adsorption and immobilization was studied. We observed that increasing the temperature could volatilize the heavy metal(loid)s. Cd was the most volatile metal therein, followed by As, while Ni, Cu, and Pb were relatively refractory. More than 75% of the remaining heavy metal(loid)s were non-exchangeable fractions at 700 °C, significantly reducing the environmental risk during subsequent application. Meanwhile, higher pyrolysis temperature resulted in higher pH values, higher surface areas, and stronger Pb adsorption capacity of RS biochars. The maximum adsorption capacity (Qm) of biochars was in the order of BC300 (77.2 mg·g?1) < BC500 (137.2 mg·g?1) < BC700 (222.6 mg·g?1). Besides, high-temperature biochar could significantly reduce the vertical Pb migration. And BC700 increased the fraction of residual Pb from 39.7% to 44.0% in the soil under the acid rain leaching condition. Therefore, we propose that the heavy metal(loid)-contaminated RS biochar produced at 700 °C might be more suitable for the remediation of soil heavily polluted in the Pb-smelting area.  相似文献   
3.
近期在湖北绿松石市场上出现一种带有肉眼可见的灰黑色异形杂质的绿松石,于此种绿松石的研究甚少。故选取来自湖北省十堰的一块该种绿松石原石,蓝色绿松石基底上布满形态各异、大小不一的灰黑色杂质,放大观察可见灰黑色杂质矿物呈金属光泽。对灰黑色杂质采用激光剥蚀电感耦合等离子体质谱仪进行原位微区微量元素测试、背散射电子图像物相观察、主量化学成分测试采用能谱仪进行半定量测试和电子探针定量测试以及显微激光拉曼光谱仪测试。灰黑色杂质矿物的LA-ICP-MS测试激光剥蚀束斑直径及深度的影响,测试结果表现为灰黑色杂质矿物和少量绿松石的混合物的化学成分含量,灰黑色杂质矿物处Se含量为95 927~221 394 μg·g-1明显高于蓝色基底绿松石中Se的含量(146~212 μg·g-1),灰黑色杂质处的测试结果中CuO含量为7.47%~9.28%、Al2O3含量为28.1%~35.7%,P2O5含量为30.1%~37.8%为少量绿松石混杂产生;背散射电子图像表明杂质矿物结晶颗粒细小,细小的杂质矿物与绿松石混杂在一起,他形的杂质矿物为多个晶体集合在一起形成的集合体,能谱测试结果表明杂质矿物主要含有Al,P,Fe,Cu和Se,电子探针主量化学成分定量测试结果表明杂质矿物主要含有Se,含量为79.34%~87.97%,此外,由于杂质矿物结晶颗粒细小,杂质矿物集合体中可见杂质矿物与绿松石混杂,因此化学成分定量测试结果中还呈现有绿松石中的Al,P,Fe,Cu和Al含量约为0.93%~4.13%,Cu含量约为1.30%~2.04%,P含量约为0.66%~2.40%,Fe含量约为0.31%;杂质矿物的显微激光拉曼光谱峰为位于144和235 cm-1处的尖锐拉曼谱峰,结合化学成分谱学测试结果可鉴别该杂质矿物主要为自然硒。硒矿物是绿松石中新发现的杂质矿物,绿松石中杂质矿物自然硒的发现可以为珠宝从业者鉴别绿松石提供有效的鉴定依据。  相似文献   
4.
利用酸水解稻壳中的半纤维素制备木糖, 并将糖渣经过炭化后分离出碳和硅, 碳采用稀碱溶液活化改性制备电容炭, 硅采用水热法合成了硅酸钙晶须, 从而使稻壳所有组分得到充分利用. 采用循环伏安(CV)和恒流充放电(GCD)研究了电容炭的电化学性能. 通过X射线衍射(XRD)和扫描电子显微镜(SEM)对所得硅酸钙晶须的结构和形貌进行了表征. 实验结果表明, 稻壳酸水解的最优条件为硫酸浓度7%(质量分数)、 固液比(g/mL)为1:8、 反应时间为2.0 h, 在该条件下, 一次水解、 二次水解和三次水解的木糖收率(Y1/Y2/Y3)和浓度(质量分数, C1/C2/C3)都能达到最大值, Y1=98.5%, C1=3.6%; Y2=85.4%, C2=6.3%; Y3=76.6%, C3=9.0%. 采用15 mL 8%(质量分数) NaOH稀碱溶液活化改性制得的电容炭(AC/15)比电容值为77.32 F/g, 而且具有较好的倍率性和循环稳定性; 硅酸钙晶须为扫帚状针钠钙石晶须.  相似文献   
5.
Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm−2) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm−2) with a low electrolyte/sulfur ratio (10 μL mg−1). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.  相似文献   
6.
We reported the first syntheses of 2- and 3-(2-(benzo[b]selenophen-2-yl)-indoles and their Diels–Alder reactions to furnish six unique annulated benzoselenphene carbazoles. This facile route can be used to synthesize selenium-containing biindolyl derivatives that possessed potential pharmaceutical activities.  相似文献   
7.
α-Trifluoromethylselenolated enones constitute valuable building-blocks for further synthesis of innovative fluorinated compounds. Herein, we described an easy access to such compounds in green conditions through a Morita-Baylis-Hillman like reaction. These conditions have also been extended to higher fluorinated homologs.  相似文献   
8.
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice.  相似文献   
9.
A novel tool for the investigation of stability of total mercury in water samples is presented. The study focuses on the application of enriched 196Hg stable isotopic reagent for the stability studies. Natural abundance of 196Hg in water samples is only 0.15%. Thus, the use of the 196Hg isotope spike represents a major advantage, when it can be assumed that all the measured isotope is the same as is accurately added by the analyst, and the change in its mass concentration can be followed simply and reliably. Tests were carried out with industrial waste water and two type of the natural water. Cold vapour (CV) inductively coupled plasma mass spectrometer (ICP-MS) technique was applied for the mercury measurements. Monitoring was continued for approximately 100 days. It is commonly advised that the measurement for total mercury in water samples should be carried out within 14 days. In this study the samples were observed to be stable for more than three months, if they were stored at a temperature of 4–6°C. The results of this stability study were in line with the guidance presented in EPA standard 1631. However, the samples were noticed to be stable for a much longer time than is presented in the standard method ISO 17852.  相似文献   
10.
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