磷酸镧除氟的H+,Zn2+,La3+∥SO2-4,PO3-4-H2O体系中Zn2+的间接络合滴定

采用镧盐除氟剂LaPO₄对锌电解液除F时,由于La³⁺和PO^3-₄的存在,H⁺,Zn²⁺,La³⁺∥SO^2-₄,PO^3-₄-H₂O体系中Zn²⁺不能直接用传统的滴定法测定。通过向待测液中加入适量NH₃·H₂O-NH₄Cl缓冲溶液络合Zn²⁺(Zn₃(PO₄)₂溶于氨性溶液),使La³⁺进入固相,抽滤、洗涤沉淀以分离Zn²⁺和La³⁺,收集滤液用EDTA(铬黑T作指示剂)滴定Zn²⁺,建立了间接络合滴定该体系中Zn²⁺的方法。实验结果表明:缓冲溶液采取较高的浓度配方、冲洗液采用稀释的缓冲溶液为宜。对于含0.1~1.0mmol Zn²⁺的样液,确定缓冲溶液为54g NH₄Cl溶于水,再加入350mL NH₃·H₂O,定容至1L,用量为20mL;冲洗液为缓冲溶液(1+2);为便于沉淀转移,加入沉淀La³⁺理论量1.1倍的F^-(La³⁺物质的量的3.3倍),可使沉淀转为不易于粘附玻璃的LaF₃。方法的定量限为0.01mol/kg。吸取含Zn²⁺在0.1~1.0mmol的H⁺,Zn²⁺,La³⁺∥SO^2-₄,PO^3-₄-H₂O体系平衡液,按照实验方法测定Zn²⁺,结果的相对标准偏差(RSD,n=6)小于0.1%,加标回收率为99%~100%。     

氧气反应模式-电感耦合等离子体串联质谱法测定土壤中砷和硒

采用电感耦合等离子体质谱法(ICP-MS)测定土壤中的As和Se时会受到严重的氩化物、氯化物、氧化物、双电荷等多原子离子干扰,从而导致测定土壤中As和Se难度加大。采用石墨消解仪以王水消解土壤样品,在串接模式下,分别设置第一级四极杆质量过滤器(Q1)质荷比(m/z)为75和80,在碰撞/反应池中通入氧气,⁷⁵As⁺、⁸⁰Se⁺和氧气反应生成⁷⁵As¹⁶O⁺和⁸⁰Se¹⁶O⁺,而干扰离子不能与氧气反应,分别设置第二级质量过滤器(Q3)m/z为91和96,使得⁷⁵As¹⁶O⁺和⁸⁰Se¹⁶O⁺通过并进入检测器中,从而避免了质谱干扰,据此建立了石墨消解-电感耦合等离子体串联质谱法(ICP-MS/MS)测定土壤中As和Se的方法。对氧气流速进行了优化,选择氧气流速为1.0 mL/min。实验表明:As和Se的线性范围均为0.500～100 μg/L,线性相关系数分别为0.999 93和0.999 98,检出限分别为0.008 mg/kg和0.001 mg/kg,定量限分别为0.032 mg/kg和0.004 mg/kg。采用所建立的实验方法对土壤标准物质和土壤样品中的As和Se分别进行测定,结果表明,对于标准物质,As和Se的测定值均在认定值的范围内,相对标准偏差(RSD,n=6)分别在2.0%~4.4%和2.6%~7.8%之间;对于土壤样品,实验方法对As和Se的测定结果与原子荧光光谱法基本一致,相对标准偏差(n=6)分别在2.3%~4.5%和3.7%~7.9%之间。     

氧气反应模式-电感耦合等离子体串联质谱法测定土壤中砷和硒

采用电感耦合等离子体质谱法(ICP-MS)测定土壤中的As和Se时会受到严重的氩化物、氯化物、氧化物、双电荷等多原子离子干扰,从而导致测定土壤中As和Se难度加大。采用石墨消解仪以王水消解土壤样品,在串接模式下,分别设置第一级四极杆质量过滤器(Q1)质荷比(m/z)为75和80,在碰撞/反应池中通入氧气,⁷⁵As⁺、⁸⁰Se⁺和氧气反应生成⁷⁵As¹⁶O⁺和⁸⁰Se¹⁶O⁺,而干扰离子不能与氧气反应,分别设置第二级质量过滤器(Q3)m/z为91和96,使得⁷⁵As¹⁶O⁺和⁸⁰Se¹⁶O⁺通过并进入检测器中,从而避免了质谱干扰,据此建立了石墨消解-电感耦合等离子体串联质谱法(ICP-MS/MS)测定土壤中As和Se的方法。对氧气流速进行了优化,选择氧气流速为1.0 mL/min。实验表明:As和Se的线性范围均为0.500～100 μg/L,线性相关系数分别为0.999 93和0.999 98,检出限分别为0.008 mg/kg和0.001 mg/kg,定量限分别为0.032 mg/kg和0.004 mg/kg。采用所建立的实验方法对土壤标准物质和土壤样品中的As和Se分别进行测定,结果表明,对于标准物质,As和Se的测定值均在认定值的范围内,相对标准偏差(RSD,n=6)分别在2.0%~4.4%和2.6%~7.8%之间;对于土壤样品,实验方法对As和Se的测定结果与原子荧光光谱法基本一致,相对标准偏差(n=6)分别在2.3%~4.5%和3.7%~7.9%之间。     

焦炭在H2O+CO2气氛中的溶损反应特性

 为了研究富氢高炉内焦炭的溶损反应特性,开发了连续进水的全自动焦炭反应性测定装置,分别利用CO₂和N₂载带不同比例H₂O(0%～30%)提供H₂O+CO₂(H₂O和CO₂混合气体)和H₂O+N₂(H₂O和N₂混合气体)的含水气氛进行焦炭溶损试验,通过红外气体分析仪实时记录出口气体中CO和H₂的摩尔分数,研究了焦炭在H₂O+CO₂气氛下的溶损反应过程以及碳溶反应(C+CO₂=2CO)和水煤气反应(C+H₂O=CO+H₂)的动力学过程。研究表明,随着H₂O+CO₂混合反应气氛中H₂O比例的增加,焦炭的碳素溶损率和溶损速率均逐渐增大,而且水煤气反应的溶损速率逐渐变大、碳素溶损率逐渐升高,但是碳溶反应的溶损速率则逐渐减小、碳素溶损率也逐渐降低,这说明H₂O+CO₂反应气氛中H₂O和CO₂同时与焦炭反应存在显著的竞争作用。通过分析碳素溶损率和水蒸气含量线性关系的拟合斜率发现,焦炭在H₂O+CO₂混合反应气氛中发生的碳溶反应和水煤气反应的斜率均小于单纯单一气氛下的碳溶反应和水煤气反应的斜率,并提出基于斜率差值的抑制因子α表征H₂O和CO₂对碳溶反应和水煤气反应互相影响程度,CO₂对水煤气反应的抑制因子α_<sub>CO₂/H₂O为0.253,H₂O对碳溶反应的抑制因子α_<sub>H₂O/CO₂为0.179,α_<sub>CO₂/H₂O为α_<sub>H₂O/CO₂的1.41倍,CO₂对水煤气反应的抑制程度强于H₂O对碳溶反应的抑制程度。     

高炉富CO2鼓风的煤气量及热平衡综合分析

为了探析高炉富CO₂条件下炉缸煤气量及热量损失,本文通过计算不同富CO₂率鼓风的炉缸煤气量,明确了炉缸煤气量各成分随富CO₂率的变化规律,在此基础上,根据CO₂+C=2CO的吸热反应,分析了富CO₂鼓风对燃料比、理论燃烧温度、冶炼强度及热平衡的影响。结果表明,按照1 kg燃烧碳量计算,鼓风CO₂含量提升1%（需要鼓风中带入0.0434 m³的CO₂）,炉缸煤气量中CO提高0.0868 m³,N₂下降0.1251 m³,总煤气量下降0.0817 m³。同时,带入的0.0434 m³的CO₂,其分解热量为306.20 kJ。     

黄色长余辉材料Ba6Al18Si2O37∶Eu2+, RE3+的制备及发光性质

采用高温固相法以碱土硅铝酸盐体系Ba₆Al₁₈Si₂O₃₇为基质,选取Eu²⁺为激活剂,通过不等价取代的方式引入稀土离子RE³⁺调节基质内部缺陷,成功制备了一系列黄色长余辉材料Ba₍(6-x-y))Al₁₈Si₂O₃₇∶xEu²⁺,yRE³⁺(RE=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Tm, Ho, Er, Lu)。以Ba₍(6-x-y)) Al₁₈Si₂O₃₇∶Eu²⁺, Tm³⁺为代表详细研究其结构、发光、余辉、缺陷及热释光谱,利用X射线粉末衍射仪对样品的结构进行了表征,证明所得到的荧光粉具有单一结构,掺杂离子的加入并没有改变晶体结构。在366 nm紫外光激发下,样...     

水热臭葱石固砷过程Na+和K+的影响

水热臭葱石沉砷体系中Na⁺、K⁺碱金属离子对沉砷渣物相组成影响显著,Fe(Ⅲ)与As(Ⅴ)共沉淀生成臭葱石(FeAsO₄·2H₂O)、次水合砷酸铁(FeAsO₄·0.75H₂O)砷铁共沉淀物,同时Fe(Ⅲ)还以黄钠铁矾(NaFe₃(SO₄)₂(OH)₆)、黄钾铁矾(KFe₃(SO₄)₂(OH)₆)、碱式硫酸铁(Fe(OH)SO₄)形态竞争析出,从而影响沉砷渣的稳定性。在Na₂SO₄-(K₂SO₄)-FeSO₄-H₃AsO₄-H₂O体系中研究了Na⁺、K⁺     

Preparation of Eu2+,Dy3+,Zr4+ ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu²⁺,Dy³⁺ and Zr⁴⁺ ions co-doped strontium aluminate(i.e.,SrAl₂O₄:Eu²⁺,Dy³⁺,Zr⁴⁺)/molybdate(i.e.,Ho₂MoO₆ or Nd₂MoO₆) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron...     

拜耳法生产氧化铝过程铝酸钠溶液中S2-和S2O2-3的测定

采用拜耳法利用高硫铝土矿生产氧化铝时,矿石中的硫在溶出后主要以S^2-和S₂O^2-₃等形式进入生产过程中的铝酸钠溶液,对生产造成一系列的危害。实验通过设计的特殊装置,在含硫的铝酸钠溶液中添加氯化亚锡的盐酸溶液,以氮气为保护气体和载体,生成的硫化氢气体与醋酸镉溶液反应生成硫化镉沉淀,再采用间接碘量法测定S^2-含量;加入硝酸银溶液生成硫代硫酸银、亚硫酸银和硫酸银沉淀,再添加氨水溶解亚硫酸银和硫酸银沉淀,根据硫代硫酸银水解后的硫化银沉淀量计算S₂O^2-₃含量。试验研究了氮气流速、氨水加入量和淀粉指示剂加入量对测定结果的影响。实验方法用于测定3种模拟铝酸钠溶液中S^2-和S₂O^2-₃,S^2-和S₂O^2-₃的回收率均为95%,S^2-和S₂O^2-₃测定结果的相对标准偏差(RSD,n=5)分别为0.12%~0.34%和0.27%~0.57%。按照实验方法对3份贵州某铝厂拜耳法生产氧化铝过程铝酸钠溶液中S^2-和S₂O^2-₃进行测定,S^2-和S₂O^2-₃测定结果的RSD(n=5)分别为0.28%~0.35%和0.32%~0.46%,加标回收率为94%~95%。     

硫酸高铁铵滴定法测定制备金属钛的电解质熔盐中Ti2+和Ti3+

利用TaσakoBa（硫酸高铁铵滴定法）的基本原理,在CO₂保护气氛下,分两步测定出金属钛电解质中的Ti²⁺、Ti³⁺,以及低价钛的合量（Ti²⁺+ Ti³⁺）。文中采用HCl-HF溶解试样,用H⁺氧化Ti²⁺为Ti³⁺,用硫酸高铁铵氧化Ti²⁺和Ti³⁺为Ti⁴⁺,用三氯化钛标准滴定溶液滴定过量的Fe³⁺。文中对影响测定结果的关键因素,如硫酸高铁铵加入量、反应酸、标准滴定溶液、氧气干扰等进行了试验,确定最佳反应条件。在优化的条件下,测定了两个金属钛电解质中的低价钛,结果的相对标准偏差（RSD,n=8）均小于10%。纯物质Ti₂O₃和TiO的加标回收率在97%以上,满足分析要求。     

Lead and nickel distribution in the Cup-PbO-SiO2 and the Cup-NiO-SiO2 Systems equilibrated with liquid copper

The distribution of lead and of nickel between molten copper and a ternary cuprous oxide-metal oxide-silica saturated slag was measured at 1498 K. The results are correlated using ion fractions, calculated either according to Temkin’s method, or as electrically equivalent ion fractions. The simpler method suggested by Temkin correlates slightly better than the other giving the following relations between the ionic concentration quotients and impurity concentration in the metal: logN _Pb ⁺⁺/N ² _Cu ⁺ = logX _Pb + 2.40 ± 0.05, valid up toX _Pb = 0.003 logN _Ni ⁺⁺/N ² _Cu ⁺ = 0.44 logX _Pb + 0.15 ± 0.07, valid up toX _Ni = 0.004. In the nickel systems, an Ni rich phase, identified as NiO, separates from the metal at X_Ni = 0.04 (0.4 wt pct). A tentative phase diagram of the Cu₂O-NiO-SiO₂ system at 1498 K is presented. The data found in this investigation explain why the impurities Pb or Ni cannot be practically reduced to low levels by oxidation. This results from the large amounts of copper that are oxidized in going to low impurity levels. Use of a two-slag refining process is shown to cut slag losses of copper to less than half those encountered with a single slag operation.     

Isotope exchange studies of the rate of dissociation of CO2 on liquid iron oxides and CaO-saturated calcium ferrites

Measurements of the rates of dissociation of CO₂ on liquid iron oxides and CaO-saturated liquid calcium ferrites have been made by the¹⁴CO₂-CO isotope exchange technique. For temperatures up to about 1550 °C, the apparent first order rate constants for both melts are essentially inversely proportional to the equilibrium CO₂/CO ratio over the range studied (≈0.4 to 12). Evidence is presented that the rate limiting step in the interfacial oxidation of these melts by CO₂ is the dissociation of CO₂- Rates of oxidation, in mol cm^?2 s^?1, in CO₂-CO atmospheres are deduced to be given by the equations:v =( _p CO ₂ a _o ^{? 1} ? _p CO) exp(?15,900/T ? 2.03) andv = (pCO₂ α _o ^-1 ?pCO) exp(?3800/T ? 6.93) for the iron oxides and CaO-saturated calcium ferrites, respectively, wherea ₀ is the oxygen activity of the melt expressed as the equilibrium CO₂/CO ratio and the pressures are in atmospheres. The strong dependence on the CO₂/CO ratio is shown to be consistent with the need to transfer two charges to the adsorbing or dissociating CO₂ molecule. Correlation with the existing surface tension data is inconclusive.     

The interfacial kinetics of the reaction of CO2 with liquid nickel

Measurements of the rate of dissociation of CO2 on liquid nickel have been made by the¹⁴CO2-CO isotope exchange technique between 1490 and 1670 °C at CO2/CO ratios between 0.01 and 7. Apparent first order rate constants are given by the expression:ka = (1 + 2pCO₂/pCO)⁻¹exp(−12700/T - 0.65) mol cm⁻² s⁻¹ atm⁻¹. It is shown that the results are consistent with blockage of the surface by oxygen which exhibits ideal Langmuirian adsorption over the conditions of the experiments. The adsorption coefficient of oxygen with respect to the infinitely dilute solution with 1 wt pct as the standard state is deduced to be given by the equation: logK′_o = 11880/T - 4.6. It is deduced that the interfacial rate of oxidation of nickel by CO₂ is given by the rate of dissociative chemisorption of CO₂. Measurements of the rate of decarburization of liquid nickel are reexamined in the light of the present results.     

Determination of the Rate of CO2–CO Reaction with Magnetite by Isotope Exchange Technique

To clarify the mechanism and get the accurate kinetic parameters of CO₂–CO reaction with magnetite, ¹³CO₂–CO isotope exchange technique was used to determine the rate constants of CO₂ dissociation on the surface of magnetite from 1073 to 1373 K. The real interfacial rate constant was estimated by considering the gas phase mass transfer along a plate. The relationship of the rate constant and CO₂/CO ratio was expressed by the formula of k_c = k₀ (CO₂/CO)^?1?m, m represents the effect of CO₂/CO ratio on the activity of oxygen in iron oxide. The apparent activation energy of the reaction between CO₂–CO gas and magnetite was calculated to 161, 175 ± 15, 198, and 197 ± 16 kJ mol^?1 for CO₂/CO ratios of 4.0, 5.0, 6.0, and 10.0, respectively. This dependence relationship may be caused by the decrease of free electron in magnetite phase with the increase of CO₂/CO ratio.     

Effect of water vapour content in H2–H2O–CO–CO2 mixtures on activity of iron oxide in slags relevant to novel flash ironmaking technology

Abstract

As an integral part of developing a novel flash ironmaking technology at the University of Utah, the activity of iron oxide in the slag was studied under three different gas atmospheres: H₂/H₂O (H₂), CO/CO₂/H₂/H₂O (reformed natural/coal gas), and CO/CO₂. The conditions of the slags investigated were MgO-saturated CaO–FeO–Al₂O₃–SiO₂–MnO (0·2–0·8 wt-%)–P₂O₅ (0·1–0·9 wt-%) in the temperature range 1550–1600°C with wt-% CaO/wt-% SiO₂ of 0·8 to 1·2, and under pO₂?=?2×10^?10–2×10^?9 atm. Water increased the activity coefficient of FeO in the slag and accordingly lowered the FeO content. The average FeO content was found to be 10, 11 and 16 wt-% under H₂/H₂O (H₂), CO/CO₂/H₂/H₂O (reformed natural/coal gas), and CO/CO₂, respectively. An empirical correlation for γ_FeO in slags under H₂/H₂O atmospheres was formulated to givelog γ_FeO?=??3·0623 X_FeO?3·1421 X_CaO?2·5068 X_MgO+2·1957     

Kinetics of the Reaction between CO2—CO and Liquid Copper

Direct determination of the rate of the reaction between CO₂—CO and pure liquid copper in the interfacial reaction regime and an examination of the effect of oxygen has been made by using the ¹⁴C isotope exchange technique. The first order rate constant for the dissociation of CO₂ on clean, oxygen-‘free’ surfaces is found to be described by the equation:

log K⁰(mol/cm².s.atm) = ? 3510/T ? 2.36

between 1150 and 1400°C, to within an uncertainty of +60%. The first order rate constant for the dissociation (k₂) and that for the formation (k₁) of CO₂ on oxygen-doped surfaces are related through the equation:

k1 = k²a⁰

where a_o the oxygen activity in liquid copper with the standard state defined by pCO₂Sol;pCO = 1. Full consistency is found between experiments with ¹⁴C-labelled C0₂ and CO. The effect of a₀ on the rate of dissociation of CO₂ is in agreement with the site-blocking model and the rate constant (k₂) is found to be consistent with the equation:

with a₀ between 0.015 and 50 at 1200°C. In comparison, the magnitude of the reaction rate is significantly greater than those suggested by earlier studies. Possible causes for the discrepancy are discussed.     

Modelling Decarburization in Electrical Steels

A model is presented to predict the decarburization rate of electrical steels during reactive annealing. In a first step, the warm annealing atmosphere composition is calculated as function of the composition of the cold gas containing N₂‐H₂‐H₂O‐CO‐CO₂‐CH₄‐O₂. In a second step, the decarburization kinetics, which is controlled both by the surface reaction and by the diffusion of carbon towards the surface, is calculated. The model is then used to study the balance between surface reaction and the diffusion control of the decarburization process. We could conclude that for low sheet thickness and/or low H₂O/H₂ ratio in the annealing atmosphere, the decarburization is surface reaction controlled, while for commercial thicknesses and industrially applied dew points, the process is diffusion controlled. Furthermore, we looked at the difference in decarburization between complex N₂‐H₂‐H₂O‐CO‐CO₂ atmospheres used in industrial application, and N₂‐H₂‐H₂O atmospheres typically used in lab annealing. We could conclude that the decarburization rate is influenced by the addition of CO and CO₂ and that the final carbon level is increased if CO and CO₂ are added to the gas.     

On the interfacial rate of reaction of CO2 with a calcium ferrite melt

Measurements of the rate of dissociation of CO₂ have been made by the¹⁴CO₂-CO isotope exchange technique on calcium ferrite melts with Ca/Fe = 0.30 at 1300 °C. Studies have also been made of the interfacial rates of oxidation of calcium ferrite melts with an average CaO content of 19.45 wt pct (CaJFe ≃0.33) in CO₂-CO atmospheres at 1362 °C. It is shown that the rates of oxidation are consistent with the rates of isotope exchange, indicating a common rate determining step. Measurements of the equilibrium Fe³⁺/Fe²⁺ ratio as a function of the CO₂/CO ratio for 19.3 wt pct CaO melts at 1360 °C and for 28.7 and 18.6 wt pct CaO melts at 1300 °C are found to be in close agreement with the deductions of Takeda, Nakazawa, and Yazawa. Combination of the equilibrium data with the results of the isotope exchange studies indicate that the apparent first order rate constant for the dissociation of CO₂ is inversely proportional to the square of the Fe³⁺JFe²⁺ ratio of the melt, as has been previously found for liquid iron oxide, lime-saturated calcium ferrites, silicasaturated iron silicates, and an equimolar “FeO”-CaO-SiO₂ melt.     

Reduction of Sn-Bearing Iron Concentrate with Mixed H<Subscript>2</Subscript>/CO Gas for Preparation of Sn-Enriched Direct Reduced Iron

The development of manufacturing technology of Sn-bearing stainless steel inspires a novel concept for using Sn-bearing complex iron ore via reduction with mixed H₂/CO gas to prepare Sn-enriched direct reduced iron (DRI). The thermodynamic analysis of the reduction process confirms the easy reduction of stannic oxide to metallic tin and the rigorous conditions for volatilizing SnO. Although the removal of tin is feasible by reduction of the pellet at 1223 K (950 °C) with mixed gas of 5 vol pct H₂, 28.5 vol pct CO, and 66.5 vol pct CO₂ (CO/(CO + CO₂) = 30 pct), it is necessary that the pellet be further reduced for preparing DRI. In contrast, maintaining Sn in the metallic pellet is demonstrated to be a promising way to effectively use the ore. It is indicated that only 5.5 pct of Sn is volatilized when the pellet is reduced at 1223 K (950 °C) for 30 minutes with the mixed gas of 50 vol pct H₂, 50 vol pct CO (CO/(CO + CO₂) = 100 pct). A metallic pellet (Sn-bearing DRI) with Sn content of 0.293 pct, Fe metallization of 93.5 pct, and total iron content of 88.2 pct is prepared as a raw material for producing Sn-bearing stainless steel. The reduced tin in the Sn-bearing DRI either combines with metallic iron to form Sn-Fe alloy or it remains intact.     

Interfacial reaction between CO2-CO gas and molten iron oxide containing P2O5

The interfacial reaction between CO₂-CO gas and molten iron oxide containing P₂O₅ was investigated by the ¹³CO₂-CO isotope exchange technique at 1773 K with CO₂/CO=1.0. The apparent rate constant rapidly decreased with the addition of P₂O₅ up to 2.86 mol pct PO_2.5 and the Fe³⁺/Fe²⁺ ratio kept constant at approximately 0.2. By the classic site blockage model, in which the reaction only occurs on the vacant sites, and the modified site blockage model, in which the reaction occurs on the vacant sites and the sites occupied by phosphorus simultaneously, the effect of the addition of P₂O₅ was analyzed and the reaction mechanism of CO₂ dissociation was discussed. It may be concluded that the dissociation of the adsorbed CO₂ molecule is reasonable as a rate-determining step and that the effect of phosphorus on the interfacial reaction is caused by the decrease in the number of active sites with the increase of phosphorus content as a surface active element in molten iron oxide.