Surface desorption and bulk diffusion models of tritium release from Li2TiO3 and Li2ZrO3 pebbles

The release of tritium from Li₂TiO₃ and Li₂ZrO₃ pebbles, in batch experiments, is studied by means of temperature programmed desorption. Data reduction focuses on the analysis of the non-oxidized and oxidized tritium components in terms of release limited by diffusion from the bulk of ceramic grains, or by first or second order surface desorption. By analytical and numerical methods the in-furnace tritium release is deconvoluted from the ionization chamber transfer functions, for which a semi-empirical form is established. The release from Li₂TiO₃ follows second order desorption kinetics, requiring a temperature for a residence time of 1 day (T_1dRes) of 620 K, and 603 K, of the non-oxidized, and the oxidized components, respectively. The release from Li₂ZrO₃ appears as limited by either diffusion from the bulk of the ceramic grains, or by first order surface desorption, the first possibility being the more probable. The respective values of T_1dRes for the non-oxidized component are 661 K, according to the first order surface desorption model, and 735 K within the bulk diffusion limited model.     

含硼石墨中甲烷的热解吸行为研究

研究了含硼石墨ＧＢ１１０（１０ｗｔ．％Ｂ）甲烷（ＣＨ４）的热解吸谱,发现甲烷的解吸谱主要由３个峰构成,估算出了ＣＨ４不同峰值的解吸激活能。为了弄清含硼石墨中甲烷的形成与解吸机理,分别对高纯石墨ＩＳＯ８８０Ｕ和Ｂ４Ｃ涂层进行了热解吸实验,同时对材料的微观结构进行了分析。经过比较,表明甲烷在含硼石墨中的形成与解吸有３个过程：氢离子注入导致甲烷沿气孔内壁形成,并通过石墨内部的微通道向表面自由扩散;被石墨中Ｂ４Ｃ析出物所俘获的氢原子与Ｂ４Ｃ化合物中的碳原子反应,从而生成甲烷并解吸出来;以及石墨晶格俘获的氢原子与碳原子化学反应产生的甲烷,通过体扩散过程解吸。其中前后两个过程起主导作用。     

Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.     

活性炭催化臭氧化处理含氰废水的试验研究

研究了活性炭催化臭氧化降解低质量浓度含氰废水,考察了臭氧投加量、活性炭用量、pH值等因素对处理效果的影响.试验结果表明:活性炭对臭氧有明显的催化作用,并可以提高臭氧的利用率;在CN-初始质量浓度150 mg/L、臭氧投加量30 mg/min、活性炭14 g/L、反应30 min条件下,CN-去除率为99.8%,相对于单...     

Intraparticle diffusivity of Cd ions in a new biosorbent material

Cadmium equilibrium sorption isotherms were determined for formaldehyde crosslinked Sargassum fluitans, establishing that an effective regeneration of the new biosorbent material is possible by an acid wash. Batch desorption kinetics were investigated at pH values of 1·0 and 2·0. By incorporating the linear and non-linear Langmuir equilibrium isotherm relationships into the rate equations, a mathematical model was proposed for modeling the metal desorption process. The model was solved numerically and a MATLAB computer program was used to curve-fit the experimental data. The model successfully predicted the Cd²⁺ elution concentration profile in a batch reactor. The average values of the intraparticle diffusivity of Cd²⁺ in the algal biosorbent calculated from the model were 3·40 × 10⁻⁶ and 1·65 × 10⁻⁶ cm² s⁻¹, 0·473 and 0·229 times the molecular diffusivity of Cd²⁺ in water, at pH values of 1·0 and 2·0, respectively. These values agreed well with theoretical predictions.     

循环载荷下HTPB推进剂温度演化及疲劳性能预测

通过红外热像法研究了端羟基聚丁二烯(HTPB)推进剂试件室温下的疲劳性能,基于极限能理论假设,建立了Miner线性累积损伤理论的能量模型以预测材料的残余寿命。采用基于热传导、热弹性和非弹性效应的理论模型解释了疲劳加载过程中的温度变化。结果表明,HTPB推进剂疲劳加载过程中的温度变化分为初始温度上升、温度稳定和温度快速上升三个阶段。红外热像法预测的HTPB推进剂疲劳极限为0.102 MPa和0.113 MPa,与试验结果 0.0985 MPa的相对误差为3.55%和14.7%。能量法得到的S-N曲线与传统试验法的S-N曲线吻合较好,Miner理论的能量模型能准确的预测循环载荷作用下HTPB推进剂的残余寿命,与实际寿命的误差不超过10%。     

Lead desorption from modified spent grain

Lead-loaded modified spent grain regenerated by desorption process was investigated. HCl, H₂SO₄, H₃PO₄, NaOH, NaCl and ultrapure water were chosen as desorption agents to treat lead-loaded modified spent grain for 30 min. The structures and components of regenerated modified spent grain before and after adsorbing Pb(II) were investigated using scanning electron microscopy(SEM), energy-dispersive analysis of X-ray(EDAX) and Fourier transform infrared spectrometry(FTIR). The results indicate that lead-loaded modified spent grain treated in 0.1 mol/L HCl exhibits higher elution efficiency (86.44%) as compared with other agents. The enrichment of carboxyl and hydroxyl groups susceptible to combine with Pb(II) are observed in the regenerated modified spent grain, which may result in high re-absorption efficiency of Pb(II). Moreover, C—Cl, N—H, C—N and O—H (polysaccharides) also play an crucial role in Pb(II) binding to regenerated modified spent grain.     

新型搅拌棒式微萃取器萃取气相色谱法分析蔬菜中毒死蜱残留量

用自制新型搅拌棒式微萃取器吸着萃取、溶剂解吸,结合配有电子捕获检测器（ECD）的气相色谱分析蔬菜中毒死蜱残留量,以此建立一种快速、简单而准确的分析方法。对影响萃取的重要参数如萃取时间、解吸时间、解吸溶剂等进行了优化。该方法在1-500ng／L有很好的线性,线性相关系数为0．9914,最低检测限为0．3ng／L。用50ng／L的毒死蜱标准品做重现性实验,其RSD低于6．7％（n=5）。并对实际蔬菜样品进行了分析,结果令人满意。     

CO2吸收富液膜法解吸的研究

为大幅降低溶剂再生过程中的解吸能耗,提出了膜解吸再生新工艺。考察了交联剂类型及其质量分数、温度、流速等工艺条件对解吸效果的影响。结果表明,当解吸温度为35℃,CO2吸收富液流速为1 709 mL/min时,以N-β(氨乙基)-γ氨丙基三甲氧基硅烷(质量分数50%)为交联剂的甲基聚硅烷-聚丙烯腈复合膜,实现了CO2从解吸富液中的有效分离,CO2富集因子达24.4,渗透通量为969.6 g.m-2.h-1。     

Reduction of NOx Stored at Low Temperatures on a NOx Adsorbing Catalyst

Isothermal storage and reduction of NO₂ with CO, C₃H₆ and H₂ as reducing agents on a lean NO _x adsorber was investigated by temperature programmed desorption (TPD) and temperature programmed reduction (TPR) studies. The reduction of NO _x was clearly favoured with H₂ as reducing agent. Carbon monoxide and C₃H₆ showed fairly low reduction of NO _x . The NO _x reduction at low temperatures with H₂ as reducing agent was found to be effective, clearly much more effective than for CO.