Biosorption of heavy metals by Saccharomyces cerevisiae: Effects of nutrient conditions

Studies took place to investigate the effects of different nutrient conditions on the biosorption ability and selectivity of heavy metals by Saccharomyces cerevisiae. After having grown in media supplemented with additional glucose, ammonium, phosphate or cysteine, the yeast was exposed to an equimolar solution of lead, cadmium, zinc and copper. Lead removal from a mixed solution was significantly higher than that of copper, followed by zinc and cadmium. Generally, yeasts from cysteine-rich media showed greatest sorption capacity whereas phosphate addition influenced zinc selectivity. In addition, glucose, fructose and sucrose as carbon sources were examined. Cultures grown in glucose had a better uptake than those cultivated with fructose at an incubation time of 30 min.     

制备低硫可膨胀石墨的研究

研究了以过二硫酸铵作氧化剂低硫可膨胀石墨的制备，找到了在较低温度下，制备低硫可膨胀石墨的最佳条件。即过二硫酸铵和石墨的重量比为１５％；反应温度为５５℃；反应时间为４０ｍｉｎ；硫酸浓度为９８％；硫酸与石墨的重量比为４∶１，草酸和硝酸（浓度为６５％）的重量比为７．５％时，所制得的可膨胀石墨含硫量为０．６５％，膨胀容积为２００ｍＬ／ｇ可膨胀石墨。并且，其终端产品柔性石墨具有优良的力学性能和抗氧化性能。     

NH4SCN从ROH-CTMAB-C12H26载金有机相中反萃金

研究了硫氰酸铵（NH4SCN）从混合醇（ROH）－十六烷基三甲基溴化铵（CTMAB）－正十二烷（C12H26）载金有机相中反萃金，考察了平衡时间，PH值，反萃剂浓度，温度等因素对反萃率的影响及有机相的循环使用，绘制了反萃等温曲线，结果表明，NH4SCN对金具有较高反萃率，可顺利实现金的反萃。     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.     

Ammonium Accumulation Caused by Reduced Tonoplast V-ATPase Activity in Arabidopsis thaliana

Plant vacuoles are unique compartments that play a critical role in plant growth and development. The vacuolar H⁺-ATPase (V-ATPase), together with the vacuolar H⁺-pyrophosphatase (V-PPase), generates the proton motive force that regulates multiple cell functions and impacts all aspects of plant life. We investigated the effect of V-ATPase activity in the vacuole on plant growth and development. We used an Arabidopsis thaliana (L.) Heynh. double mutant, vha-a2 vha-a3, which lacks two tonoplast-localized isoforms of the membrane-integral V-ATPase subunit VHA-a. The mutant is viable but exhibits impaired growth and leaf chlorosis. Nitrate assimilation led to excessive ammonium accumulation in the shoot and lower nitrogen uptake, which exacerbated growth retardation of vha-a2 vha-a3. Ion homeostasis was disturbed in plants with missing VHA-a2 and VHA-a3 genes, which might be related to limited growth. The reduced growth and excessive ammonium accumulation of the double mutant was alleviated by potassium supplementation. Our results demonstrate that plants lacking the two tonoplast-localized subunits of V-ATPase can be viable, although with defective growth caused by multiple factors, which can be alleviated by adding potassium. This study provided a new insight into the relationship between V-ATPase, growth, and ammonium accumulation, and revealed the role of potassium in mitigating ammonium toxicity.     

基于15N质量平衡法研究养殖消化废水中氨氮的去除机理

为避免养猪场消化废水对环境造成的污染,利用微藻去除消化废水中营养物质的二次处理方法受到了广泛关注。采用¹⁵N质量平衡法研究了鞘藻去除氨氮的主要机理,重点研究了鞘藻生长与氨氮去除的关系以及氨氮去除的主要途径。经高压灭菌后的消化废水在鞘藻培养期的氨氮去除率为96.2%,鞘藻特定生长率为0.04~0.15;稀释后的原消化废水氨氮的去除率为94.1%,鞘藻特定生长率为-0.14~0.13。通过曝气的汽提效应对氨的去除有显著的促进作用,尤其在高pH值试验条件下更有利于脱氨。¹⁵N同位素质量平衡分析表明,原始消化废水中存在的细菌对氨氮的去除影响小,在鞘藻培养期去除原消化废水中氨氮的主要途径是鞘藻的吸收和气体的损失,分别占总氮量的40.97%和32.59%。氨氮的去除与主要影响因素间的回归和通径分析表明,要提高氨氮去除率,需要提高鞘藻Chl-a含量和DO浓度,同时限制或保持pH值在弱碱性状态。     

湿法磷酸选择性除杂制工业级磷酸二氢铵

以湿法磷酸为原料, 通过氟化钠选择性沉淀金属离子, 使其以NaMgAl（F, OH）₆·H₂O和XMgAlF₆（X=Na ⁺、K ⁺、NH₄ ⁺）非含磷沉淀析出, 再通氨中和制得工业级磷酸二氢铵。分析了氟化钠加入量对杂质脱除（Na、K、Al、Mg、Fe和Ca等金属阳离子）及液相氟残留的影响, 结果表明氟化钠与磷酸质量比（m_NaF/m）为2.5%时, 效果较好, 此条件下制得的磷酸二氢铵纯度和五氧化二磷收率分别达到98.53%和86.2%。     

季胺萃取锌的动力学研究

以恒界面池法研究了氯化物介质中季胺萃锌的动力学。考查了搅拌转速、传质界面积和温度对萃取速率的影响，判定季爱萃锌为界面化学反应的动力学模式。进一步研究了季胺萃取剂浓度和水相Ｚｎ＾２＋浓度对萃取速率的影响，得到了与理论推断相吻合的速率方程。     

氨法处理硫酸装置尾气生产亚铵的实践

介绍用氨法处理硫酸装置尾气生产亚硫酸铵的工艺流程、控制指标、主要设备和生产运行情况。实践表明,氨法SO2吸收率高,可实现装置尾气达标排放,但也存在产品品位较低的问题。对问题进行了分析并提出改进意见。     

R12TAB/正丁醇/正癸烷/水体系相态的研究

绘制了阳离子表面活性剂R12TAB／正丁醇／正癸烷／水体系的拟三元相图，确定了微乳液区、微乳液／液晶共存区及不同液晶区域的范围。用^2HNMR和差示扫描量热法(DSC)与液晶纹理相互对照，研究了该体系的液晶结构特点。结果表明：含质量分数为25％～75％正癸烷的各相图内，除了存在着层状、六角状单相液晶区和层状／六角状／立方状共存的混合液晶区域外，还存在着液晶／微乳液共存的区域，且随着正癸烷质量分数的增加，微乳液及液晶区域逐渐缩小。