增加H2O3浓度引起反应速度降低现象的探讨

在Ｈ２Ｏ２与ＫＭｎＯ４氧化还原反应中，随着Ｈ２Ｏ２浓度的增加，化学反应速度反而下降。本文通过实验对这一现象进行了分析讨论，认为在反应过程中Ｈ２Ｏ２与Ｍｎ＾２＋形成过氧络合物是造成该现象的本质原因。     

海洋锰结核的试验研究──Ni（Ⅱ）在H_2O—NH_3—SO_2—MnO_2体系

在用亚硫酸按（ＮＨ４）２ＳＯ３浸出海洋锰结核中有价金属时发现镍从浸出液中损失。本试验就是研究这种损失的原因。在下列体系中，对Ｎｉ（Ⅱ）的行为进行研究：ａ．ＮＨ３—（ＮＨ４）２ＳＯ３—Ｈ２Ｏ；ｂ．ＮＨ３—用氧部分氧化的（ＮＨ４）２ＳＯ３—Ｈ２Ｏ；ｃ．ＮＨ３—用ＭｎＯ２部分氧化的（ＮＨ４）２ＳＯ３—Ｈ２Ｏ．在ＮＨ３—（ＮＨ４）２ＳＯ３溶液用ＭｎＯ２氧化时，加入的Ｎｉ（Ⅱ）形成晶状沉淀：Ｎｉ０．７５Ｍｎ０．２５（ＮＨ３）４Ｓ４Ｏ６·２Ｈ２Ｏ。     

海洋锰结核的试验研究：Ni（Ⅱ）在H2O—NH3—SO2—MnO2体系中的行为

在用亚硫酸铵（ＮＨ４）２ＳＯ３浸出海洋锰结核中有价金属时发现镍从浸出液中损失，本试验就是研究这种损失的原因，在下列体系中，对Ｎｉ（Ⅱ）的行为进行研究：ａ．ＮＨ３－（ＮＨ４）２ＳＯ３－Ｈ２Ｏ；ｂ．ＮＨ３－用氧部分氧化的（ＮＨ４）２ＳＯ３－Ｈ２Ｏ；ｃ．ＮＨ３－用ＭｎＯ２部分氧化的（ＮＨ４）２ＳＯ３－Ｈ２Ｏ，在ＮＨ３－（ＮＨ４）２ＳＯ３溶液用ＭｎＯ２氧化时，加入的Ｎｉ（Ⅱ）形成晶状沉淀：Ｎｉ０．７５Ｍｎ     

MnO—TiO2渣系热力学计算模型

根据炉渣结构的共存理论以及相图，确定了ＭｎＯ－ＴｉＯ２渣系的结构单元为Ｍｎ＾２＾＋，Ｏ＾２＾－简单离子和ＴｉＯ２，２ＭｎＯ．ＴｉＯ２，ＭｎＯ２分子，进而推导了本渣系的热力学计算模型，研究结果表明，在１５００℃和１５５０℃两温度下，计算的Ｎｍｎｏ与实测的αＭｎＯ完全一致，从而证明了该模的正确性。本文进一步计算了△Ｈ＾Ｍ，△Ｇ＾Ｍ随渣系组成的变化规律。     

用H2O2作还原剂稀硫酸浸出锰结核

在Ｈ＿２Ｏ＿２存在下用稀硫酸浸出太平洋锰结核，首先将高品位锰结核磨细至０．０７４ｍｍ，浸出条件：矿浆浓度ｌｇ／Ｌ、Ｈ＿２ＳＯ＿４浓度３．５×１０￣３～２５×１０￣（－２）ｍｏｌ／Ｌ、Ｈ＿２Ｏ＿２，浓度１．７×１０￣（－３）～２．６×１０￣（－２）ｍｏｌ／Ｌ、温度３０～９０℃。所得结果归纳如下含少量Ｈ＿２Ｏ＿２的稀Ｈ＿２ＳＯ＿４可于室温快速从锰结核中提取Ｎｉ、Ｃｏ、Ｃｕ和Ｍｎ，金属的提取率依赖于Ｈ＿２ＳＯ＿４和Ｈ＿２Ｏ＿２的浓度，缺少任何一种都不可能得到满意效果。该方法与以往的浸出工艺不同，金属的提取率随温度升高而下降。最佳条件下，各金属的提取不如下：Ｍｉ１００％、Ｃｏ９５％、Ｃｕ１００％、Ｍｎ１００％、Ｆｅ６０％。     

MnO－TiO_2渣系热力学计算模型

根据炉渣结构的共存理论以及相图，确定了ＭｎＯ－ＴｉＯ＿２渣系的结构单元为Ｍｎ￣（２＋），Ｏ￣（２－）简单离子和ＴｉＯ＿２，２ＭｎＯ·ＴｉＯ＿２，ＭｎＯ·ＴｉＯ＿２分子，进而推导了本渣系的热力学计算模型。研究结果表明，在１５００℃和１５５０℃两温度下，计算的Ｎ＿（ＭｎＯ）与实测的α＿（ＭｎＯ）完全一致，从而证明了该模型的正确性。本文进一步计算了△Ｈ￣Ｍ，△Ｇ￣Ｍ随渣系组成的变化规律。     

NH3-CO2系统中Y(OH)3完全沉淀条件的研究

Ｙ３＋在氨的水溶液中可形成Ｙ（ＯＨ）３沉淀。在该体系中通入二氧化碳气体，随终点ｐＨ的不同，体系中存在的ＨＣＯ３－、ＣＯ３２－使Ｙ（ＯＨ）３溶解为［Ｙ（ＣＯ３）ｎ］３－２ｎ或［Ｙ（ＨＣＯ３）］３－络合离子。本试验研究了体系终点ｐＨ及起始氨浓度对ＣＯ３２－、ＨＣＯ３－浓度的影响以及进而对Ｙ（ＯＨ）３沉淀率的影响，得到了使Ｙ（ＯＨ）３完全沉淀的反应条件。     

（100）n－GaAs在H_2SO_4－H_2O_2－H_2O溶液中的腐蚀速度

以Ｃ－Ｖ测量、击穿电压测量并结合逐层腐蚀技术，对ＧａＡｓ外延多层结构的剖面分布进行了测量，获得了ＧａＡｓ（１００）晶片在不同温度下的Ｈ＿２ＳＯ＿４－Ｈ＿２Ｏ溶液中的腐蚀速度数据。结果表明，当Ｈ＿２ＳＯ＿４：Ｈ＿２Ｏ＿２：Ｈ＿２Ｏ＝９：１：１时，对ｎ＝１．１０￣（１４）～１．１０￣（１８）ｃｍ￣－３的ＧａＡｓ（１００）晶片，２０℃时的腐蚀速度为ｖ＝０．３～０．９μｍ／ｍｉｎ．作者认为，这一配方对ＧａＡｓ（１００）多层结构是一个最为理想的减薄腐蚀剂。     

提高Mn_3O_4粉末比表面积的方法初探

在不同温度下对用金属锰法制得Ｍｎ３Ｏ４粉末和含有部分Ｍｎ（ＯＨ）２的Ｍｎ３Ｏ４粉末分别进行除气处理，然后用静态氮吸附法对其进行对比实验，测试其在各自温度处理后的比表面积。结果表明，在金属锰法制取高纯Ｍｎ３Ｏ４粉末时，应使部分Ｍｎ（ＯＨ）２保留下来，然后对其进行高温（如２００℃）处理，这样可以大大提高高Ｍｎ３Ｏ４粉末的比表面积。     

Synthesis and Crystal Structure of a Heteronuclear Complex［MnSc（DTPA）（H_2O）_2］·2H_2O

ＳｙｎｔｈｅｓｉｓａｎｄＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆａＨｅｔｅｒｏｎｕｃｌｅａｒＣｏｍｐｌｅｘ［ＭｎＳｃ（ＤＴＰＡ）（Ｈ_２Ｏ）_２］·２Ｈ_２ＯＺｈａｎｇＹｉ；ＬｉＢｉａｏｇｕｏ；ＧａｏＳｏｎｇ；ＪｉｎＴｉａｎｚｈｕ；ＸｕＧｕａｎｇｘｉａｎ（?..     

Mechanism of horseradish peroxidase catalyzed epinephrine oxidation: obligatory role of endogenous O2- and H2O2

Horseradish peroxidase (HRP) catalyzes cyanide sensitive oxidation of epinephrine to adrenochrome at physiological pH in the absence of added H2O2 with concurrent consumption of O2. Both adrenochrome formation and O2 consumption are significantly inhibited by catalase, indicating a peroxidative mechanism as a major part of oxidation due to intermediate formation of H2O2. Sensitivity to superoxide dismutase (SOD) also indicates involvement of O2- in the oxidation. Although SOD-mediated H2O2 formation should continue epinephrine oxidation through a peroxidative mechanism, low catalytic turnover, on the contrary, indicates that O2- takes part in a vital reaction to form an intermediate for adrenochrome formation and O2 consumption. Generation of O2- is evidenced by ferricytochrome c reduction sensitive to SOD. On addition of H2O2, both adrenochrome formation and O2 consumption are further increased due to reaction of molecular oxygen with some intermediate oxidation product. Peroxidative oxidation proceeds by one-electron transfer generating o-semiquinone and similar free radicals which when stabilized with Zn2+ or spin-trap, alpha-phenyl-tert-butylnitrone (PBN), inhibit adrenochrome formation and O2 consumption. The free radicals thus favor reduction of O2 rather than the disproportionation reaction. Spectral studies indicate that, during epinephrine oxidation in the presence of catalase, HRP remains in the ferric state absorbing at 403 nm. This suggests that HRP catalyzes epinephrine oxidation by its oxidase activity through Fe3+/Fe2+ shuttle consuming O2, where the rate of reduction of ferric HRP with epinephrine is slower than subsequent oxidation of ferrous HRP by O2 to form compound III. Compound III was not detected spectrally because of its quick reduction to the ferric state by epinephrine or its subsequent oxidation product. In the absence of catalase, peroxidative cycles predominate when HRP still remains in the ferric state through the transient formation of compounds I and II not detectable spectrally. Among various mono- and dihydroxyl aromatic donors tested, only epinephrine shows the oxidase reaction. Binding studies indicate that epinephrine interferes with the binding of CN-, SCN-, and guaiacol indicating that HRP preferentially binds epinephrine near the heme iron close to the anion or aromatic donor binding site to catalyze electron transfer for oxidation. HRP thus initiates epinephrine oxidation by its oxidase activity generating O2- and H2O2. Once H2O2 is generated, the peroxidative cycle continues with the consumption of O2, through the intermediate formation of O2- and H2O2 which play an obligatory role in subsequent cycles of peroxidation.     

Modeling the Transformation of Chromophoric Natural Organic Matter during UV/H2O2 Advanced Oxidation

This research developed a differential kinetic model to predict the partial degradation of natural organic matter (NOM) during ultraviolet plus hydrogen peroxide (UV/H2O2) advanced oxidation treatment. The absorbance of 254?nm UV, representing chromophoric NOM (CNOM) was used as a surrogate to track the degradation of NOM. To obtain reaction rate constants not available in the literature, i.e., reactions between the hydroxyl radical (?OH) and NOM, experiments were conducted with “synthetic” water, using isolated Suwannee River NOM, and parameter estimation was applied to obtain the unknown model parameters. The reaction rate constant for the reaction between ?OH and total organic carbon (TOC), k?OH,TOC, was estimated at 1.14(±0.10)×104??L?mg-1?s-1, and the reaction rate constant between ?OH and CNOM, k?OH,CNOM, was estimated at 3.04(±0.33)×104??L?mol-1?s-1. The model was evaluated on two natural waters to predict the degradation of CNOM and H2O2 during UV/H2O2 treatment. Model predictions of CNOM degradation agreed well with the experimental results for UV/H2O2 treatment of the natural waters, with errors up to 6%. For the natural water with additional alkalinity, the model also predicted well the slower degradation of CNOM during UV/H2O2 treatment, owing to scavenging of ?OH by carbonate species. The model, however, underpredicted the degradation of H2O2, suggesting that, when NOM is present, mechanisms besides the photolysis of H2O2 contribute appreciably to H2O2 degradation.     

MoO2氢还原机理探索

在MoO2还原为钼粉的过程中,大颗粒钼粉(指筛上物)的杂质含量会远远高于小颗粒钼粉。本文采用"核收缩"的理论模型来解释了这一现象。在MoO2氢还原为Mo的过程中,产生一种比起钼的其他化合物挥发性更强的氧化钼的水合物MoO3.H2O或MoO2(OH)2,这种水合物结合从MoO2收缩核中扩散出来的杂质,挥发沉积到长大的Mo颗粒的表面。大颗粒Mo粉的表面积大、表面能低,挥发性水合物更容易沉积在由众多细小颗粒团聚而成的大颗粒表面,从而造成大颗粒钼粉的杂质含量较高。     

H2O2-driven reduction of the Fe3+-quin2 chelate and the subsequent formation of oxidizing species

The objective of this study was to compare effects of quin2 and EDTA in iron-driven Fenton-type reactions. Seven different assays for detection of strong oxidants were used: the DMSO, deoxyribose, benzoate hydroxylation, and plasmid DNA strand breakage assays, detection of 8-oxo-deoxyguanosine in deoxyguanosine mononucleosides and calf thymus DNA, and electron spin resonance with the spin-trap (4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) in the presence of ethanol or DMSO. With H2O2 and Fe3+, quin2 generally strongly increased the formation of reactive species in all assays, whereas with EDTA the results varied between the assays from barely detectable to highly significant increases compared to H2O2 and unchelated Fe3+. We found that the species produced in the reaction between Fe3+-quin2 and H2O2 behaved like the hydroxyl radical in all assays, whereas with Fe3+-EDTA no clear conclusion could be drawn about the nature of the oxidant. The effect of quin2 on the formation of oxidants on Fe2+ autoxidation, varied from generally inhibiting to slightly promoting, depending on the assay used. EDTA had a promoting effect on the amount of oxidant detected by all but one assay. None of the autoxidation systems produced DMSO or ethanol radical adducts with 4-POBN. In the presence of either chelator, H2O2, and Fe2+ DMSO and ethanol radical adducts of 4-POBN were produced. Using the Fe2+ indicator ferrozine, evidence for direct reduction of Fe3+-quin2 by H2O2 was found. Superoxide anion radical appeared to be less efficient than H2O2 as reductant of Fe3+-quin2 as addition of superoxide dismutase in the ferrozine experiments only decreased the amount of Fe2+ available for Fenton reaction by 10-20%. The main conclusions from our study are that the reduction of Fe3+-quin2 can be driven by H2O2 and that Fe2+ in the following oxidation step produces a species indistinguishable from free hydroxyl radical.     

基于过氧化氢-紫外体系对NO脱除的试验研究

建立了烟气发生模拟试验装置,采用紫外光在较低温度下激发H2O2产生的活性基团对烟气中的NO进行氧化脱除。研究了H2O2浓度、H2O2温度、NO初始浓度、O2浓度、金属离子催化剂和烟气流量等因素对系统NO脱除效果的不同影响,并通过正交试验得出了该体系的最佳工艺条件。对该条件下的反应产物分析发现,反应后溶液中主要为NO-3,NO-2,Fe3+和过量的H2O2。正交试验证明,该体系NO最大脱除率可达到88.6%,高于其他工艺的脱除效率,具有工程应用价值。     

Cobalt and desferrioxamine reveal crucial members of the oxygen sensing pathway in HepG2 cells

Cobalt and desferrioxamine, like hypoxia, stimulate the production of erythropoietin in HepG2 cells. It is believed that cobalt as well as desferrioxamine interact with the central iron atom of heme proteins by changing their redox state similar to hypoxia. A subsequent decrease of the intracellular H2O2 levels under hypoxia was presumed to be the key event for stimulating erythropoietin production. We therefore investigated whether cobalt and desferrioxamine control the intracellular H2O2 levels that regulate gene expression by interacting with hemeproteins. Deconvolution of light absorption spectra revealed respiratory heme proteins such as cytochrome c, b558 and cytochrome aa3, as well as cytochrome b558, which is a nonrespiratory heme protein found in HepG2 cells. Whereas respiratory heme proteins are located in mitochondria, cytochrome b558 similar to the one described for the neutrophil NADPH oxidase can be visualized in the cell membrane of HepG2 cells by immunohistochemistry. Incubation with cobalt (100 microM/24 hr) interacts predominantly with cytochrome b558 and cytochrome b558. The interaction of cobalt with the respiratory chain results in an increased oxygen consumption of HepG2 cells as revealed by PO2 microelectrode measurements. Desferrioxamine (130 microM/24 hr), however has no influence on the cytochromes. In response to an external application of NADH (1 mM), the membrane bound cytochrome b558 produces two times more O2- than to the external NADPH (1 mM) application. Neither desferrioxamine not cobalt has any influence on the NADH stimulated O2- generation. Incubation with cobalt or with desferrioxamine, however, leads to a decrease of the intracellular H2O2 level as revealed by the dihydrorhodamine 123 technique, perhaps causing the well-known enhanced erythropoietin production. The cobalt-induced H2O2 decrease seems to be caused by an increased activity of the glutathion peroxidase that is also induced under hypoxia. Desferrioxamine, however, leads to an apparent H2O2 decrease only because it seems to inhibit the iron catalyzed reaction of H2O2 with dihydrorhodamine 123, hinting at the occurrence of the Fenton reaction in HepG2 cells. Therefore, it must be determined whether or not degradation products of H2O2 by the Fenton reaction suppress erythropoietin production under normoxia.     

Thermal Decomposition Mechanism and Non Isothermal Kinetics of Complex of [La_2(P-MBA)_6(PHEN)_2]2H_2O

Ｏｗｉｎｇｔｏｔｈｅｖａｒｉａｔｉｏｎｏｆｃｏｏｒｄｉｎａｔｅｄｍｏｄｅｓｆｏｒｃａｒｂｏｘｙｌａｔｅａｎｉｏｎｓ ,ｍａｎｙｄｉｆｆｅｒｅｎｔｔｙｐｅｓｏｆｃｒｙｓｔａｌｓｔｒｕｃｔｕｒｅｓｆｏｒｔｈｅｒａｒｅｅａｒｔｈｃｏｍｐｌｅｘｅｓｗｉｔｈａｒｏｍａｔｉｃａｃｉｄａｎｄｎｉｔｒｏｇｅｎ ｃｏｎｔａｉｎｉｎｇｌｉｇａｎｄｓｗｅｒｅｏｂｔａｉｎｅｄ[1～ 4 ] .Ｔｈｅｉｒｔｈｅｒｍａｌｄｅｃｏｍｐｏｓｉｔｉｏｎｂｅｈａｖｉｏｒｈａｄｂｅｅｎｒｅ ｐｏｒｔｅｄｉｎｐｒｅｖｉｏｕｓｐａｐｅｒｓ[5～ 8] .…     

氧化球团烟气中SO2和H2O(g)对SCR脱硝的影响

选择性催化还原(SCR)具有效率高、技术成熟的优势,但处理球团烟气需要加热才能达到SCR脱硝的反应温度,导致能耗和运行成本高.氧化球团预热Ⅱ段(PH段)烟气温度在300℃以上,满足SCR反应所需温度,但是烟气中含有的SO2和H2O(g),会对催化剂的脱硝性能产生影响.研究了 PH段烟气中SO2和H2O(g)对V/Ti催...     

Kinetic studies on the removal of extracellular hydrogen peroxide by cultured fibroblasts

To investigate the function of antioxidant enzymes in intact cells, we examined the removal of extracellular H2O2 by cultured fibroblasts (IMR-90). H2O2 concentration dependence of the reaction rate was interpreted as that the process involves two kinetically different reactions (referred to as reactions 1 and 2). Reaction 1 was characterized by a relatively low Km value (about 40 microM), and reaction 2 by linear dependence of the rate up to 500 microM H2O2. The magnitude of reaction 1 was reduced by treatment of the cells with diethyl maleate or 6-amino-nicotinamide, while reaction 2 was inhibited by 3-amino-1,2,4-triazole treatment. It was concluded that reactions 1 and 2 are principally due to GSH peroxidase and catalase, respectively. The values of kinetic parameters were estimated by curve-fitting, and it was inferred that 80 to 90% of H2O2 is decomposed by GSH peroxidase at H2O2 concentrations lower than 10 microM. The contribution of catalase increases with the increase in H2O2 concentration. The intact cells showed a low catalase activity (about 15%), as compared with the activity found in the solubilized cells. The low catalase activity was ascribed to the latency of the enzyme caused by localization in peroxisomes. Fibroblasts also removed intracellular H2O2 generated by menadione. Treatment with diethyl maleate greatly impaired the H2O2-removing capability and caused H2O2 efflux into the medium.     

Catalase-free photosystem II: the O2-evolving complex does not dismutate hydrogen peroxide

A photosystem II (PSII) membrane-associated heme catalase has been identified as a major source of the dark H2O2-dismutation reaction in PSII membrane samples [Sheptovitsky, Y. G., and Brudvig, G. W. (1996) Biochemistry 35, 16255-16263]. Based on this finding, a catalase-free PSII membrane sample was prepared by using mild heat treatment to deplete most of the PSII membrane-associated heme catalase followed by inhibition of the residual catalase with 50 mM 3-amino-1,2,4-triazole, a specific heme catalase inhibitor that binds covalently to compound I. After these treatments, the PSII membrane sample exhibited only 0.02% of the original H2O2-dismutation activity when assayed in the presence of 20 mM 3-amino-1,2,4-triazole. This small residual H2O2-dismutation activity is attributed to adventitious metal ions or the non-heme iron in PSII because the activity was still present in a Mn-depleted PSII sample but was completely suppressed by adding 5 mM ferricyanide to the assay buffer; the effect of ferricyanide is attributed to oxidation of H2O2-dismutating cations. Although the H2O2-dismutation activity was completely eliminated by these treatments, the light-induced O2-evolution activity was retained. A single saturating flash given to catalase-free PSII membranes did not induce any H2O2-dismutation activity. These results demonstrate that the S1/S-1 and S2/S0 cycles of the O2-evolving complex of PSII do not occur in the presence of H2O2, as proposed by Velthuys, B., and Kok, B. [(1978) Biochim. Biophys. Acta 502, 211-221]. The light-induced O2-evolution activity in catalase-free PSII was found to be irreversibly impaired by micromolar concentrations of H2O2. Thus, it is possible that the PSII membrane-associated heme catalase plays an important role in protection of the O2-evolving complex from damage by H2O2.