高碱性拜耳法赤泥碳酸化脱碱及其机理研究

利用二氧化碳对高碱性拜耳法赤泥进行碳酸化脱碱实验,研究了反应体系压力、时间、温度和液固比对赤泥脱碱效果的影响,并对其反应机理进行探讨.结果表明,室温下,在反应压力为0.6 MPa,反应时间为60 min,液固比为7的反应条件下,碱溶出率为6.99％.拜耳法赤泥中的碱主要以两种形式存在,一是以NaOH、NaCO3为主的游离态碱,二是以钙霞石为主的结合态碱.其脱碱机理主要是通过碳酸化作用脱除赤泥中的游离态碱,部分钙霞石与碳酸反应生成可溶性钠盐.     

二氧化碳气浮拜耳法赤泥脱碱方法的实验研究

本文以某公司提供的废弃物赤泥为研究对象,为了探究二氧化碳对赤泥的脱碱率,自主设计制作了实验室使用的二氧化碳气浮反应器,以钠离子为碱性指标,探究了不同的二氧化碳气浮工艺条件对赤泥脱碱率的影响。根据探索性试验和单因素试验结果,确定了影响赤泥脱碱率的主要因素有:反应液固质量比、反应温度、反应时间和二氧化碳压力。最终确定了优化试验条件:液固比为7∶1,反应温度为50℃,反应时间为2 h,二氧化碳压力为4 MPa。此时脱碱率达到了49.3%,并且整个实验过程中几乎没有其他废弃物的产生,吸收了大量的二氧化碳,达到了"以废治废"的目的。     

赤泥水浸脱碱实验及动力学研究

赤泥是一种碱性污染物,强碱性是制约其综合利用的关键因素。进行了拜耳法赤泥水浸脱碱实验及动力学研究,实验结果表明：赤泥在水浸次数为4次、液固体积质量比为9 mL/g、反应温度为90 ℃和反应时间为60 min的条件下,赤泥的脱碱率可达71%。采用未反应收缩核模型对水浸脱碱数据进行线性拟合,动力学分析表明：活化焙烧后赤泥的水浸脱碱过程受扩散步骤控制,线性相关系数大于0.97,表观活化能为11.72 kJ/mol。     

赤泥草酸脱碱实验研究

赤泥强碱性是影响环境和制约其综合利用的关键因素.本文提出了赤泥草酸脱碱的实验研究,考察了草酸用量,反应温度,液固比和反应时间对赤泥脱碱率的影响,同时对赤泥和脱碱渣进行了XRD物相分析.结果表明:在草酸用量为15％,反应温度为80℃,液固比为4 mL/g和反应时间为40 min条件下,赤泥脱碱率超过95％.草酸显著破坏了赤泥中钙霞石的结构,可以选择性地脱除赤泥中的钠,脱碱渣中氧化钠含量低于0.5％,而钛、钙和硅等元素含量略有提高.     

拜耳法赤泥固化CO2反应特征的研究

以拜耳法赤泥为CO2固化剂,研究了不同压力下赤泥对CO2的固化封存能力,以及固化CO2过程中矿物物相的化学转化行为.探讨了温度、液固比、粒径、时间等因素对赤泥固化CO2效率的影响以及赤泥固化CO2过程Na、K的浸出特性变化.结果表明,CO2压力为0.6 MPa、1 MPa、1.6 MPa时,赤泥固化CO2的饱和增重率分别达到2.36％、2.70％、3.07％.随反应时间的变化,赤泥浆液的pH值不断下降,最后稳定在6.40左右.液固比减小,赤泥粒径减小,在2060℃之间温度升高,有助于赤泥固化CO2效率的提高.赤泥固化CO2后Na、K的浸出量增加.XRD和红外光谱分析显示赤泥固化CO2后主要形成的矿物相是钙霞石(cancrinite)和方解石(CaCO3).不同压力下赤泥对CO2的固化反应符合准一级动力学方程.     

赤泥湿法碳化脱钠试验研究

赤泥是氧化铝冶炼过程中排出的固体废渣,目前利用率仅为15％左右,大量被堆放于露天堆场.如何有效地利用赤泥成为众多科学研究者所关注的问题.本文以朔州地区的粉煤灰通过拜耳法提铝后产生的残渣(简称:赤泥)为研究对象,探讨赤泥的碳化法脱钠的绿色环保工艺.研究了液固比、CO2通气量、反应温度等因素对脱钠工艺的影响,确定了碳化脱钠的合适条件.将脱碱后的赤泥以不同比例替代水泥配制净浆试块,分别测试其抗折、抗压强度,对其胶凝活性进行研究.结果表明赤泥经脱碱后所制成的净浆试块的胶凝活性得到了极大改善,含碱量0.86％的赤泥在掺量为20％的条件下,试样的力学性能最好.     

钛白废酸浸出赤泥脱碱实验研究与动力学分析

依据赤泥强碱性和钛白废酸呈酸性的特点,利用钛白废酸浸出赤泥脱碱。考察了搅拌速率、液固比、浸出温度和浸出时间对赤泥脱碱效果的影响,同时对赤泥脱碱过程进行了理论分析和动力学研究。结果表明:在浸出温度为70 ℃,搅拌速率为400 r/min,液固比为5 mL/g和反应时间为60 min的条件下,赤泥脱碱率大于99%,脱碱液pH值为6.2。利用钛白废酸浸出赤泥,赤泥脱碱率高,脱碱渣中铁品位也得到了富集,可以作为提取回收铁的二次矿产资源。钛白废酸能够显著破坏赤泥中钙霞石的晶体结构,使得结构碱几乎全部溶解,脱碱渣中出现硬石膏衍射峰,赤铁矿衍射峰也可明显分辨。该脱碱过程受未反应核收缩模型(USCM)中的内扩散关键步骤控制,线性相关系数大于0.99,脱碱反应速率常数随着温度升高而增加,表观活化能(E_a)为13.12 kJ/mol。     

常压石灰法处理烧结法赤泥脱碱及其机理研究

采用石灰（CaO）作为脱碱剂处理烧结法赤泥,研究了反应温度、反应时间、脱碱剂添加量、液固比等因素对赤泥中钾、钠溶出率等碱脱除效果的影响,分析了石灰处理赤泥的脱碱机理。结果表明：温度升高、反应时间延长、石灰掺量增加以及液固比增大均能提高赤泥的脱碱效果,其中尤以反应时间和石灰掺量的影响效果更显著。添加石灰处理烧结法赤泥的脱碱机理是部分方钠石（Na₈Al₆Si₆O₂₄CO₃）中的2个Na⁺被1个Ca²⁺置换出,生成了更难溶的钙霞石［Na₆CaAl₆Si₆（CO₃）O₂₄·2H₂O］。     

钙基水热浸出赤泥脱碱试验及机制分析

以Ca(OH)₂为脱碱剂水热浸出赤泥脱碱,考察了Ca(OH)₂掺量、反应温度、液固比对赤泥脱碱率的影响,同时对赤泥脱碱过程进行机理分析和浸出动力学分析。研究结果表明,在Ca(OH)₂掺量为60%(质量分数)、反应温度为250 ℃、液固比为8 mL/g的条件下,赤泥脱碱率可达到96.3%。Ca(OH)₂可有效脱除赤泥中的游离碱和结构碱,赤泥中的钙霞石和水钙铝榴石被分解,脱碱渣中新相铁钙榴石(水合的)是主要的衍射峰,并且赤铁矿的衍射峰明显减弱,方解石的衍射峰增强。该脱碱过程受固膜内扩散关键步骤控制,线性相关系数都大于0.97,特征常数n<1,表观活化能为5.20 kJ/mol。     

CaCl2回收液赤泥碱性调控

赤泥是氧化铝行业最大的环境污染问题,碱性调控是处置赤泥的关键。本文以赤泥资源化过程中产出的CaCl₂溶液的模拟液作为脱碱剂对赤泥进行碱性调控研究,考察了可能影响碱性调控过程的因素,并进行了柱淋洗实验以模拟实际赤泥堆存过程中的淋洗过程,进行盆栽试验来评估脱碱赤泥的土壤化潜力。结果表明：在固液比为500g/L、脱碱液Ca²⁺浓度为10g/L、反应温度为85℃、反应时间为2h的条件下,浸出液中Ca、Na浓度分别为7.74g/L和1.22g/L,pH可降低至8.39,并且一次脱碱过程即可达到脱碱平衡。柱淋洗流出液Na/Ca比高达107.8,远高于海水Na/Ca比（25.8）,可用作氯碱工业原料;脱碱后赤泥pH由11.14降至8.05。黑麦草在脱碱赤泥与锯末的混合基质中的七天发芽率达到92%,高于新鲜土壤中黑麦草发芽率（84%）,表明脱碱后赤泥适合植物生长。利用CaCl₂回收液进行赤泥碱性调控可为赤泥处置提供一种成本低廉、绿色环保的方法。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.