粗MnSO4溶液中MnS2O6的去除条件研究

用软锰矿吸收SO₂生成MnSO₄时会伴随有副产物MnS₂O₆生成。产品中MnS₂O₆的存在会降低硫酸锰产品质量，同时会缓慢释放出SO₂气体污染环境。本文用单因素实验方法研究了粗MnSO₄溶液中MnS₂O₆的最优去除条件。研究结果显示，软锰矿用量为12.2 g，硫酸加入量为20 mL、反应温度100℃、反应时间3 h、搅拌速度500 r/min，MnS₂O₆的去除率可达91%以上。其最终产品能达到GB1622-1986一级品标准。     

软锰矿浆催化氧化烟气SO2的动力学初探

对高液固比软锰矿浆与烟气SO2产酸过程进行了研究,在考察液固比、氧浓度和pH值等对反应过程影响的实验基础上,认为高液固比下主要发生的是软锰矿浆对烟气SO2的催化氧化生成硫酸的反应,并认为在[O2]控制区内,反应可以分为线性阶段和幂函数2个反应阶段.     

软锰矿浆催化氧化烟气SO2的动力学初探

对高液固比软锰矿浆与烟气SO2产酸过程进行了研究，在考察液固比、氧浓度和pH值等对反应过程影响的实验基础上，认为高液固比下主要发生的是软锰矿浆对烟气SO2的催化氧化生成硫酸的反应，并认为在[O2]控制区内，反应可以分为线性阶段和幂函数2个反应阶段。     

砷华生产废渣中硫的回收利用研究

高温下氧化焙烧细磨后的砷华生产废渣，利用软锰矿浆吸收产生的SO2气体，吸收液经净化除杂、浓缩结晶等工序可制备工业产品硫酸锰。适宜的焙烧条件如下：焙烧温度为650℃，焙烧时间为60min，废渣粒度为-97μm。选择合适的吸收工艺，Mn的浸出率可达96．20％，此时SO2脱除率为87．20％。     

砷华生产废渣中硫的回收利用研究

高温下氧化焙烧细磨后的砷华生产废渣,利用软锰矿浆吸收产生的SO2气体,吸收液经净化除杂、浓缩结晶等工序可制备工业产品硫酸锰.适宜的焙烧条件如下:焙烧温度为650℃,焙烧时间为60 min,废渣粒度为-97μm.选择合适的吸收工艺,Mn的浸出率可达96.20%,此时SO2脱除率为87.20%.     

软锰矿浆烟气脱硫动力学研究

研究了软锰矿浆烟气脱硫工艺SO2与软锰矿反应的动力学特征,考察了搅拌强度、温度和SO2浓度等因素对反应速率的影响,计算出反应活化能和反应级数,建立了揭示SO2与软锰矿反应动力学特征的锰浸出速率方程.     

软锰矿浆烟气脱硫动力学研究

研究了软锰矿浆烟气脱硫工艺SO2与软锰矿反应的动力学特征,考察了搅拌强度、温度和SO2浓度等因素对反应速率的影响,计算出反应活化能和反应级数,建立了揭示SO2与软锰矿反应动力学特征的锰浸出速率方程.     

软锰矿催化氧化脱除烟气中的SO2

对软锰矿催化氧化法去除烟气中SO2的方法进行了探索，研究了各工艺参数对烟气中SO2去除率的影响。结果表明：MnO2与Mn^2 的催化效果较好，传质过程对脱硫过程的影响较大，软锰矿浆在合适条件下能有效吸收低浓度的SO2。     

低浓度软锰矿浆烟气脱硫过程中的催化作用

通过对SO2-4浓度的分析,研究了低浓度软锰矿浆烟气脱硫过程中的液相和固相催化作用.研究表明:低浓度软锰矿浆中Fe(Ⅱ,Ⅲ)的浸出率很低(＜ 7%),致使Fe(Ⅱ,Ⅲ)离子的液相催化作用和Mn(Ⅱ)、Fe(Ⅱ,Ⅲ)离子间的液相协同作用不明显.该过程中实际生成的so2-4主要来自3个方面:MnO2的直接氧化还原作用,Mn(Ⅱ)的液相催化作用以及软锰矿固相组分的催化作用.其中,Mn(Ⅱ)的液相催化作用始终占据主导地位;MnO2的直接氧化还原作用与固相催化作用相比,在20 min前有明显的优势,而20 min后则几乎可以忽略不计.     

电解质种类对电催化氧化降解苯酚的影响

研究了不同电解质对有机物电催化氧化性能的影响。以高温热解法制备了Ti/SnO2+Sb2O3阳极,用SEM和XRD对电极结构进行了表征。以苯酚为目标有机物,考察了Na2SO4、NaCl和NaNO33种不同电解质对苯酚降解效果的影响。用循环伏安法研究了苯酚在不同支持电解质条件下的电化学行为。采用碘量法测定了在不同电解质溶液中氧化性物质的生成量。研究结果表明,电极的活性涂层主要由SnO2和微量的Sb2O3组成,均匀完整地覆盖住了Ti基体表面。以NaCl为支持电解质时苯酚降解效果明显优于用Na2SO4、NaNO3为支持电解质,并且苯酚的降解主要以电极表面电化学生成的HClO和ClO-的间接化学氧化为主。以Na2SO4为支持电解质时有利于降低和稳定槽电压。在3种电解质条件下,苯酚的降解均遵循一级反应动力学规律。在降解过程中NaCl溶液中生成的氧化性物质浓度最大,且随降解时间延长逐渐增大。     

Determination of sulfur oxides formed during the S(IV) oxidation in the presence of iron

The reaction products (i.e., sulfate (SO4(2-)) and dithionate (S2O6(2-))) of S(IV) oxidation in the presence of iron(III) under different experimental conditions were investigated. Ion-interaction chromatography was used for the separation of sulfate and dithionate using tetrabutylammonium hydroxide (TBAOH) as an ion-pair reagent. The chromatographic method was optimized by varying the composition of the mobile phase (i.e., concentration of TBAOH, acetonitrile and Na2CO3) and by varying the flow rate of the mobile phase. The method was successfully applied to the determination of dithionate formed during the S(IV) oxidation in the presence of Fe(III). In air-saturated solutions sulfate was observed as the only product, while in N2-saturated solutions dithionate was also determined, but it is the minor reaction product and represents about 4% of the total amount of oxidized HSO3- under the studied conditions.     

The formation of dithionate during the iron(III)-catalysed autoxidation of sulfur(IV)-oxides

The iron(III)-catalyzed autoxidation of sulfur(IV)-oxides results in the formation of two different oxidation products of sulfur(IV): dithionate, S₂O₆²⁻, and sulfate, SO₄²⁻. The yield of these reaction products depends on the experimental conditions. Under the studied conditions ([Fe(III)] : [SIV)] = 1:10, pH = 2–4) dithionate is the minor reaction product. The formation of dithionate is influenced by the initial pH but not by the initial O₂ concentration. The presence of CO²⁺, Mn²⁺, and Ni²⁺ have no influence on the yield of dithionate, whereas in the presence of Cr³⁺ less and, in the presence of Cu²⁺, no dithionate is formed.     

软锰矿浆烟气脱硫反应机理研究

利用软锰矿浆吸收烟气中SO2 ,该方法不仅可脱硫 ,还可副产具有工业价值的硫酸锰产品 ,是一种较好的脱硫资源化方法。通过对软锰矿浆与SO2 的反应机理的分析和实验验证 ,确定该体系的主要反应 ,为该工艺过程可行性研究提供理论和实践依据     

微氧环境下无色硫细菌和硫酸盐还原菌脱硫

通过间歇曝气形成微氧环境让SRB和CSB实现共生,使含硫酸盐有机废水中硫酸根最终转化成单质硫达到脱硫目的.研究考察了曝气量对SRB还原和CSB氧化的影响,确定了合适的曝气强度和水力停留时间,使得单质硫占系统内总硫比值最大.实验结果显示,在进水COD/SO42-=2000/1500 mg/L、曝气开关时间为2 s/2 min、生化时间为10 h时,单质硫产率最大,为89.53％,SO42-浓度降至最低值72.7 mg/L,还原率达95.1％,此时脱硫效果较好.     

Formation of estrogenic products from environmental phthalate esters under light exposure

Phthalate esters (PEs) have been suspected to be environmental endocrine disruptors and the detailed mechanism remains unclear. The activities of these chemicals can be enhanced through chemical modification under the environmental conditions. We demonstrate that PEs acquire unequivocal estrogenic activity by light exposure. Through UV exposure of an aqueous PE solution, one active photoproduct, identified as 4-hydroxyPE (PE-4OH) based on its characteristic UV and mass spectra, was detected in an estrogen receptor alpha-dependent transactivation assay. PE-4OH was effectively generated by UV 290 nm. The PE-4OH production accompanied H2O2 generation in a UV dose-dependent manner. Both PE and UV irradiation were indispensable in the generation of H2O2. Addition of H2O2 to the PE solution increased PE-4OH production under UV irradiation. The PE-4OH production was also observed in the PE reaction with the Fenton reagent generating hydroxyl radical without UV irradiation. The proposed mechanism for PE-4OH production based on these results is such that by PE-mediated photosensitization H2O2 is generated from O2 and H+ and decomposed to hydroxyl radical, thus oxidizing the PE benzene ring. The PEs-4OH are remarkably active estrogenic products of PEs and would be involved in ER-mediated endocrine disruption.     

Decomposition of phorate in aqueous solution by ozonation

Phorate (O,O-diethyl S-ethylthiomethyl phosphorodithioate) dissolved in aqueous solution was almost completely decomposed by ozonation to form various species within 10 minutes of reaction time for the experimental conditions examined in this research. The generation rate of sulfate was found to be fairly independent of solution pH value. However, the formation of phosphate and carbonate was more favorable for alkaline solutions where hydroxyl free radical is the primary oxidative species. The reaction rates increased with initial gaseous ozone concentrations, indicating the reaction was mass transfer-controlled within the experimental range of this research. Combining the analytical results by various instruments, including gas chromatograph equipped with an electron ionization detector (GC-EID), high performance liquid chromatography (HPLC), ion chromatography (IC), and total organic carbon (TOC), the temporal sequence of phorate ozonation was proposed in this study. The oxidation of sulfur atoms on the phosphorus-sulfur double bond or carbon-sulfur-carbon bond by ozonation was found to occur at first to form sulfate and various intermediates.     

Studies on a New Method of Simultaneously Removing Sulfur Dioxide and Oxides of Nitrogen from Combustion Gases

Simultaneous reduction of SO₂ and NO by catalyzed reaction with carbon monoxide at space rates approaching 10⁴ vol/vol/hr has been shown. The reaction of sulfur dioxide with carbon monoxide results in the formation of carbon dioxide and elemental sulfur. Nitric oxide reacts with carbon monoxide to form carbon dioxide and molecular nitrogen. Metals supported on alumina appear to be the preferred catalysts. Among the effective metals are copper, silver, and palladium. A side reaction of carbon monoxide with elemental sulfur to form carbonyl sulfide requires that the initial amount of carbon monoxide be stoichio-metric for the amount of sulfur dioxide plus nitric oxide present. A furnace employing this method would have to be operated at low excess air, near stoichiometric fuel/air, or possibly slightly on the rich side.     

Flow rates of ions in waters percolating through a model ecosystem with forest trees

From 1983-88 the long-term effects of low level exposure with O(3), SO(2) and simulated acid rain on mineral cycling in model ecosystems with spruce, fir and beech seedlings were investigated. Systems consisting of open-top chambers built above lysimeters were protected against the intrusion of ambient rain and dust. As part of the investigations on mineral cycling the fluxes of elements with water input and output of the canopy and soil compartments are presented. During the 5 year duration of the experiment, pronounced effects on canopy deposition and cation leaching were observed. Most noticeable were throughfall enrichment with sulfate through dry deposition of SO(2) as influenced by duration of needlewetting and factors promoting SO(2) oxidation. Depending on sulfur deposition, leaching of calcium, magnesium, manganese, zinc and ammonium from canopies was elevated, in total leading to enhanced soil input of acid. After 15 months, the water percolating the soils in the lysimeters of these treatments was acidified, with elevated flowrates of sulfate, manganese, calcium and magnesium. The results on canopy/soil leaching are compared to those from old conifer stands in the field.     

Comparison of titania nanotubes and titanium dioxide as supports of low-temperature selective catalytic reduction catalysts under sulfur dioxide poisoning

A series of iron–manganese oxide catalysts supported on TiO₂ and titanium nanotubes (TNTs) were studied for low temperature selective catalytic reduction (SCR) of NO with NH₃ in the presence of SO_2. The results showed that the specific surface area and the amount of Brønsted acid sites were highly correlated. The results also demonstrated that higher Mn⁴⁺/Mn³⁺ ratios and larger specific surface areas might be the main reasons for the excellent performance of MnFe-TNTs catalyst after SO₂ poisoning. The SO₂ poisoning effect could be minimized by reducing the GHSV, increasing the reaction temperature, or increasing the [NH₃]/[NO] molar ratio. The results also indicated that the formation of ammonium sulfate had a stronger effect on the NO conversion efficiency as compared to the formation of metal sulfate. Thus operating the low temperature SCR at above 230 ^oC to avoid the formation of ammonium sulfate would be the priority choice when SO₂ poisoning is a concerned issue.?Implications: Low-temperature selective catalytic reduction (SCR) has attracted increasing attention due to that it can reduce the energy consumption for the SCR process employed in industries such as steel plants and glass manufacturing plants. However, it also suffers from the sulfur dioxide (SO₂) poisoning problem. This study investigates the possibility of using titania nanotubes (TNTs) as the support of Mn/Fe bimetal oxide catalysts for low-temperature SCR to reduce the SO₂ poisoning. The results indicated that the MnFe-TNT catalyst can tolerate SO₂ for a longer time as compared with the MnFe-TiO₂ catalyst.