硫掺杂ZnFe2O4/蒙脱石复合材料的铀酰吸附研究

为获得铀酰(UO2²⁺)吸附性能高的吸附剂,以蒙脱石(Montmorillonite,MMT)和铁酸盐(ZnFe₂O₄)为原材料与L-半胱氨酸通过水热反应制备了硫掺杂ZnFe₂O₄(S-ZnFe₂O₄)和ZnFe₂O₄/MMT(S-ZnFe₂O₄/MMT),采用XRD、FTIR和SEM对S-ZnFe₂O₄和S-ZnFe₂O₄/MMT进行了结构表征,研究了pH、接触时间和UO2²⁺初始质量浓度对UO2²⁺吸附效果的影响,结果表明:S-ZnFe₂O₄呈高分散的纳米颗粒状,并且均匀分布于蒙脱石片层结构表面;S-ZnFe₂O₄与蒙脱石复合后能明显提高其UO2²⁺吸附性能,最佳吸附pH为6.0;S-ZnFe₂O₄和S-ZnFe₂O₄/MMT复合材料对UO2²⁺的最大吸附量分别为51.44 mg/g和68.45 mg/g;吸附符合Langmuir等温吸附模型和伪二阶动力学模型,说明吸附过程属于表面单分子层化学吸附。     

刚柔组合桨强化软锰矿浸出过程的反应动力学特性

在软锰矿湿法浸出过程中,采用传统搅拌桨反应器,容易出现流体“打旋”现象,导致传质效果差,进而降低反应效率。因而,本研究将刚柔组合桨应用于软锰矿的还原浸出过程,强化浸出过程的传质行为,提高锰矿浸出率。结果表明,在黄铁矿与软锰矿质量比为0.20,硫酸浓度为1.5 mol/L,液固比为10,温度为363 K下,软锰矿中锰的浸出率达到90.12%,与传统桨叶相比,锰浸出率提高5.5%。同时,研究发现浸出过程遵循核收缩模型且受表面化学反应控制,黄铁矿与软锰矿质量比、初始硫酸浓度、液固比的反应级数分别为1.2679、0.4182、1.1959,反应动力学方程为1- （1-X）^1/3=0.96×10³（m_{\mathrm{F}\mathrm{e}{\mathrm{S}}_{\mathrm{2}}}/m_{\mathrm{M}\mathrm{n}{\mathrm{O}}_{\mathrm{2}}}）^1.2679 [H₂SO₄]^0.4182（L/S）^1.1959exp（-41.75 ×10³/RT）t,浸出反应的表观活化能为41.75 kJ/mol。刚柔组合桨体系下的软锰矿浸出反应表观活化能相比传统搅拌体系下的软锰矿浸出反应表观活化能的文献报道值降低4.515~20.54 kJ/mol。     

PET和关中麦秆共热解特性及其动力学研究

利用TG-FFIR技术研究陕西关中地区小麦秸秆(麦秆)、聚对苯二甲酸乙二醇酯(PET)及其两者混合物麦秆-PET(质量比1∶1)在20 K/min的升温速率下的热解行为、主要热解产物、协同效应和动力学.研究结果表明:PET热解初始温度为375℃,最大热失重速率处的温度为454.9℃,失重率为62.87％,其热解残余质量...     

一步法制备Mg改性玉米芯生物炭吸附磷酸盐研究

研究通过MgCl2溶液浸泡玉米芯后在450℃下慢速热解1 h 一步法制备获得Mg改性生物炭(Mg-BC),探究其对磷酸盐的吸附和影响因素.结果表明,Mg-BC吸附磷符合准1级、准2级动力学模型,说明吸附过程主要受物理、化学作用控制.Mg-BC对磷的等温吸附符合Langmuir方程,吸附类型为单分子层吸附,最大吸附量为5...     

丁腈橡胶硫化反应动力学研究

设计了促进剂A 4种不同用量的丁腈橡胶配方;基于配方,先利用密炼机将丁腈橡胶、硬脂酸和ZnO混炼,再利用开炼机加入硫黄、促进剂和防老剂,再利用无转子硫化仪分别测试了160℃、170℃和180℃下胶料硫化曲线;基于硫化曲线计算出了每组配方胶料硫化反应速率常数K和活化能Ea。结果表明,在焦烧期时,NBR硫化反应为非一级反应,真正的一级反应开始于硫化速率达到最大时,即tdis;焦烧期后的反应可分为2个阶段且遵循一级动力学反应规律。     

The kinetics of CO2 hydrogenation on a Rh foil promoted by titania overlayers

Submonolayer deposits of titania on a Rh foil have been found to increase the rate of CO₂ hydrogenation. The primary product, methane, exhibits a maximum rate at a TiO _x coverage of 0.5 ML which is a factor of 15 higher than that over the clean Rh surface. The rate of ethane formation displays a maximum which is 70 times that over the unpromoted Rh foil; however, the selectivity for methane remains in excess of 99%. The apparent activation energy for methane formation and the dependence of the rate on H₂ and CO₂ partial pressure have been determined both for the bare Rh surface and the titania-promoted surface. These rate parameters show very small variations as titania is added to the Rh catalyst. The methanation of CO₂ is proposed to start with the dissociation of CO₂ into CO_(a) and O_(a), and then proceed through steps which are identical to those for the hydrogenation of CO. The increase in the rate of CO₂ hydrogenation in the presence of titania is attributed to an interaction between the adsorbed CO, released by CO₂ dissociation, and Ti³⁺ ions located at the edge of TiO _x islands covering the surface. Differences in the effects of titania promotion on the methanation of CO₂ and CO are discussed in terms of the mechanisms that have been proposed for these two reactions.     

Research progress on preparation of biomass-derived porous carbon and its adsorption of pharmaceuticals in wastewater

The rapid development of urban modernization and industrialization has caused increasingly serious pollution to the environment, especially water contamination. In recent years, the content of pharmaceuticals in industrial wastewater has increased year by year, and the pollution should not be ignored any more. Therefore, the development of new porous materials for the adsorption and separation of pharmaceutical molecules in wastewater has become a current research hotspot. This article summarizes the recent research on the adsorption and separation of pollutants in wastewater by biomass-derived porous carbons (biochars). First, it briefly introduces the treatment methods of pollutants in wastewater, and mainly focuses on the preparation and modification of biochars. Combined with the surface chemical properties and pore structure of the carbon materials, this paper summarizes and prospects the adsorption properties of biochar to pharmaceuticals.     

Chlorophyll adsorption on acid-activated clay

An acid-activated clay (Çanakkale montmorillonite from Turkey) was used to adsorb chlorophyll from hexane solutions. The phenomenon seems to be mainly driven by the interaction of chlorophyll with acid sites. The adsorption of chlorophyll on Brönsted acid sites was indicated by a characteristic infrared band for the -OH group at 3671 cm^?1. The variations in the structure of clay mineral and chlorophyll during adsorption have been examined by differential thermal analysis, thermogravimetry and infrared spectroscopy of the activated clay before and after adsorption of chlorophyll. Oxidation of adsorbed chlorophyll was completed at quite a high temperature.     

Densification and Sintering Kinetics in Sintered Silicon Nitride

The sintering sequence of Y₂O₃-Al₂O₃-doped Si₃N₄ was investigated with respect to the relationship between densification, α→β transformation, and microstructural development. Quenching studies were performed to reveal these interactions during a complete sintering cycle. Isothermal studies were conducted to examine the sintering kinetics and compared to Kingery's liquid-phase sintering model. The bulk density increased to ≥90% of theoretical density with only minor transformation taking place. Major transformation occurred in a late sintering stage and was accompanied by the development of elongated grains. The kinetic order of the densification process, taking into account an appropriate correction, was larger than any of the rate exponents predicted by the Kingery model, indicating that other single or mixed mechanisms were active.     

Retrograde Densification of Calcined and Glass Precursors of Approximate (Bi,Pb)2Sr2Ca2Cu3O10 Stoichiometry

Retrograde densification of pelletized calcines and glasses having an approximate (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ starting stoichiometry and sintered at ∼850°C can be described by first-order rate equations. Retrograde densification in the calcine precursors was largely due to the development of open pores, and was approximately proportional to the concentration of the (Bi,Pb)₂Sr₂CaCu₃O₁₀ phase. In the glasses, retrograde densification is mainly caused by porosity accompanying the growth of a needlelike Sr─Ca─Cu─O phase, together with (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ and (Bi,Pb)₂Sr₂CaCu₂O₈.