黄药体系下铅离子诱导异极矿强化硫化浮选及其机理

针对异极矿难以硫化的问题,采用铅离子(Pb²⁺)对其进行预先活化,研究黄药体系下的浮选行为和强化硫化机理。结果表明:与常规硫化(硫化+重金属活化)相比,添加适量Pb²⁺的预处理对异极矿硫化有强化作用,不但可以提高异极矿回收率,还能降低硫化钠用量,而脉石矿物石英几乎不受影响;Pb²⁺的活化机理表现在Pb²⁺可吸附在异极矿表面增加硫化活性位点,当加入硫化钠以后可迅速生成硫化铅(PbS),并对后续PbS的形成具有诱导结晶作用,使得表面生成更多的PbS晶体,从而达到强化硫化目的。     

CaF_2催化真空碳热还原异极矿制备金属锌(英文)

通过异极矿真空碳热还原试验,研究添加CaF2和对碳热还原硅酸锌的的影响。结果表明:CaF2能催化硅酸锌的碳热还原,降低还原温度,缩短反应时间;温度越低,催化效果越好;CaF2的添加量越多,催化效果越明显。CaF2催化真空碳热还原异极矿的较佳工艺条件是:CaF2的添加量约10%,还原蒸馏温度1373K,C/Zn总的物质的量比2.5,系统压强低于20kPa,反应时间约40min。在较佳工艺条件下,异极矿中约93%的锌被还原蒸馏出来。     

硫代硫酸盐溶液浸取硫化金精矿中银的动力学研究

含铜的氨性硫代硫酸铵溶液浸取含铜硫化金精矿中银的动力学特征与浸取金类似，可分为前期反应、后期反应。只是初期溶解速度慢些，最终浸取率低些。浸取过程除与黄铁矿腐蚀过程有关外，银的络合与沉淀对浸取过程也有影响。比值控制最终浸取率。     

硫压对Fe40Mo高温硫化行为的影响

观察分析了Ｆｅ４０Ｍｏ合金在１０￣５０ｋＰａ的硫蒸气中的高温硫化动力学规律和硫化产物层结构变化。结果表明，硫压对Ｆｅ４０Ｍｏ的硫化动力学规律和硫化速度有一定影响，５０ｋＰａ时比１０ｋＰａ硫化还慢些；高硫压及较高温度下合金硫化由其中Ｆｅ的硫化控制，而不象低硫压时只受Ｍｏ的硫化控制。这些表现与Ｆｅ２０Ｍｏ的相近，表明在高温和高硫压的苛刻环境中，合金中添加Ｍｏ的作用被削弱了。合金硫化动力学表现与产物层结     

硫酸根存在下硫代硫酸铵溶液浸出硫化金精矿中金的动力学研究

含铜的氨性硫代硫酸铵溶液浸取合铜硫化金精矿中金的反应过程分为前期反应、后期反应两个阶段。前期为界面反应控制,后期为反应剂通过固体反应产物层的扩散过程控制。整个浸取过程都受载金矿物腐蚀反应所控制。体系中硫酸铵可能有两种作用:①NH_4~ 与NH_3组成缓冲液;②SO_4~(2-)抑制S_2O_3~(3-)氧化分解。体系中Cu~(2 )作为氧化剂,氧气使Cu~(2 )再生。     

由粉煤灰水热合成方钠石及其表征

利用粉煤灰通过水热合成反应合成了单一方钠石,并对其进行了表征.经XRD分析,合成产物为单一方钠石,理想的结构式为Na8Al6Si6O24Cl24,晶胞参数为a0 =0.889 nm,z=1.经SEM观察,合成产物为规则球形,球形颗粒表面粗糙,紧密连接;合成的方钠石与原料粉煤灰化学组成最明显的变化是硅含量减少,S/A(SiO2与Al2O3质量比)由2.3降低至2.0.红外光谱和差热分析均显示了合成产物中自由水的存在.     

水热合成法制备HfO_2薄膜(英文)

以HfOCl2·8H2O为前驱体采用水热合成法制备了HfO2溶胶,采用旋涂法制备了HfO2-PVP薄膜。利用透射电镜和粒度分析仪观察和表征HfO2溶胶的微观结构和粒度分布。实验发现,通过调整不同的水热合成温度、反应物前驱体浓度、溶液的pH值和水热合成时间等制备条件,可以在3～100nm范围内对HfO2溶胶颗粒的大小进行控制。分别采用椭偏仪,原子力显微镜,傅里叶红外变换光谱对HfO2–PVP薄膜的形貌和结构进行了表征和测量。结果表明,旋涂法制备的HfO2-PVP薄膜的粗糙度小于0.5nm,折射率达1.75左右。实验还发现,HfO2薄膜的激光损伤阈值达到15J/cm3(1064nm,1ns),HfO2-PVP薄膜的激光损伤阈值可高达20J/cm3(1064nm,1ns)。还对HfO2-PVP薄膜中有机粘结剂PVP在激光诱导损伤过程中的作用机理进行了初步探讨。     

二氧化钛纳米粉体的可控水热合成研究

采用TiCl_4为原料,用水热法合成了二氧化钛纳米粉体,讨论了水热反应条件对二氧化钛粉体结构和微观形貌的影响.结果表明:在0.5～1.0 mol/L TiCl_4, 130～190 ℃, 3～9 h的水热条件下,合成的TiO_2纳米粉体属于金红石相;TiO_2的形貌和尺寸与原料浓度、反应时间和反应温度密切相关,随着原料浓度的增加、反应温度的升高以及反应时间的延长,TiO_2形貌由球形纳米粒子向纳米棒转变,其尺寸也随之增大.     

水热合成法制备纳米级CuWO_4·2H_2O粉体及其合成机理(英文)

选用Cu(NO3)2·3H2O和Na2WO4·2H2O分析纯作为反应原材料,通过水热合成法制备了纳米级的Cu WO4·2H2O粉体。讨论了前驱体Cu2WO4(OH)2的生成过程,并且建立了在水热合成过程中前驱体Cu2WO4(OH)2向Cu WO4·2H2O转变的机理。利用HRTEM以及XRD分析了前驱体和水热反应产物的物相及微观结构和形貌。结果表明:水热反应产物Cu WO4·2H2O粉体呈球形,粒径分布范围为20~30 nm。Cu WO4·2H2O粉体的生成过程符合原位结晶机制。在长时间的高热高压的水热环境中,WO42-离子在前驱体Cu2WO4(OH)2表面吸附扩散,通过脱水和原子重排,Cu WO4·2H2O在Cu2WO4(OH)2表面异相形核。WO42-离子通过Cu WO4·2H2O层与Cu2WO4(OH)2发生反应,直到WO42-离子被耗尽。     

嗜酸硫氧化细菌作用下元素硫化学形态的研究进展

嗜酸硫氧化细菌是生物冶金过程中研究最为广泛的细菌,广泛分布在含硫和硫化物丰富的环境中。嗜酸硫氧化细菌作用下,单质硫及其它还原型硫化物（包括金属硫化矿）经过一系列形态转换使得硫在其细胞体内、体外和环境沉积物中存在着不同形态分布。单质硫经细菌细胞活化后在细胞体内以硫球形式积累;还原型硫化物可被细菌氧化至硫酸盐,其氧化中间态多为单质硫或连多硫酸盐等。有关嗜酸硫氧化细菌作用下硫的形态研究十分缺乏,进一步开展嗜酸硫氧化细菌作用下元素硫化学形态的研究可以为这类细菌的硫氧化机制及对硫化矿的浸出机理的阐明提供理论依据。     

含单质硫的硫化砷渣水热稳定化的过程及机理

提出一种水热处理方法以稳定硫化砷渣.在最优条件(160℃、2 h、液固比1:1、初始pH 2)下,水热处理后As和Cd元素的浸出毒性分别由504.0和12.0 mg/L降低至1.23和0.03 mg/L.硫化砷渣的稳定化主要通过颗粒转化成块状的结构转变及As和Cd化学形态的转变来实现.此外,硫化砷渣中具有熔融和聚合特性...     

Kinetics and mechanism of high-temperature sulfur corrosion of Fe-Cr-Al alloys

The influence of aluminium on the kinetics and mechanism of high-temperature sulfidation of Fe-Cr alloys containing 20 at.% chromium has been investigated. It has been found that the addition of aluminum greatly improves the scaling resistance of Fe-Cr alloys against attack by sulfur vapors at high temperatures.     

Separation of arsenic and antimony from dust with high content of arsenic by a selective sulfidation roasting process using sulfur

The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process. The factors such as roasting temperature, roasting time, sulfur content and nitrogen flow rate were investigated using XRD, EPMA and SEM–EDS. In a certain range, the sulfur addition has an active effect on the arsenic volatilization because the solid solution phase ((Sb,As)₂O₃) in the dust can be destroyed after the Sb component in it being vulcanized to Sb₂S₃ and this generated As₂O₃ continues to volatile. In addition, an amorphization reaction between As₂O₃ and Sb₂O₃ is hindered through the sulfidation of Sb₂O₃, which is also beneficial to increasing arsenic volatilization rate. The results show that volatilization rates of arsenic and antimony reach 95.36% and only 9.07%, respectively, under the optimum condition of roasting temperature of 350 °C, roasting time of 90 min, sulfur content of 22% and N₂ flow rate of 70 mL/min. In addition, the antimony in the residues can be reclaimed through a reverberatory process.     

Gold leaching with elemental sulfur in alkaline solutions under oxygen pressure

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A new thermobalance for studying the kinetics of high-temperature sulfidation of metals

A new thermobalance for studying the high-temperature sulfidation of metals and alloys is described. Results of preliminary investigations of the sulfidation kinetics of iron confirm that this apparatus is entirely suitable for such gravimetric measurements. The weight gains of the sample are recorded exact to 10^–5. The application of the membrane manometer makes possible direct measurements of the sulfur vapor pressure with an accuracy of ±0.2 (tr). Owing to a special construction of vacuum valves, easy access to the reaction chamber is secured, thus eliminating any necessity of cutting the reaction tube.     

The sulfidation of manganese at low sulfur pressures at 700–950°C

The kinetics of manganese sulfidation has been studied in H ₂-H₂ S gas mixtures as a function of temperature (973–1223 K) and sulfur pressure (7×10 ^–9 to 3×10 ^–4 Pa), using a thermogravimetric technique. The sulfidation of manganese at low pressures follows the parabolic rate law similar to the behavior at high sulfur pressures (10 ^–4–10⁵ Pa), although an initial nonparabolic incubation period, longer at lower sulfur pressures, was observed. The sulfidation rate constant increased with sulfur pressure and temperature according to the following empirical equation: k_P=const P(S ₂)^1/n exp(–E/RT)However, in disagreement with the results at high sulfur pressures, the exponent 1/n and the activation energy changed considerably with temperature and sulfur pressure. The results are analyzed in terms of a point-defect model of the single corrosion product—MnS—and of the possibility of a doping effect of MnS by hydrogen.     

Kinetics and mechanism of high-temperature sulfidation of an Fe-23.4Cr-18.6Al Alloy in H2S-H2 atmospheres

Sulfidation of an Fe-23.4Cr-18.6Al (at.%) alloy was investigated in H₂S-H₂ atmospheres, Pa, at 973 K. It was found over this pressure range that sulfidation after an early transient period followed the parabolic rate law, being diffusion controlled. An investigation was carried out of the scales formed during early transient sulfidation over the sulfur pressure range Pa. Fully developed scales were multilayered consisting of an inner compact layer of equiaxed grains, an intermediate layer of equiaxed and columnar grains exhibiting a small degree of porosity, and an outer porous layer of distinct plates and needles. The grains of the inner and intermediate layers contained quarternary sulfide phases. The following phases were identified: spinels (CrFe)Al₂S₄ and (FeAl)Cr₂S₄, hexagonal (FeCr)Al₂S₄, (CrAlFe)₂S₃, and (CrAlFe)₅S₆. The plates and needles were composed of hexagonal (FeCr)Al₂S₄ and (CrAlFe)₂S₃ at and 10^–5 Pa from which pyrrhotite, FeS, grew at .     

Kinetics and mechanism of the sulfidation of Fe-Mo alloys

Iron-molybdenum alloys containing up to 40 wt.% molybdenum were exposed to sulfur vapor at a partial pressure of 0.01 atm at temperatures of 600–900°C. Sulfidation kinetics were measured over periods of up to 8 hr using a quartz-spring thermogravimetric method. The sulfidation kinetics of all alloys studied obeyed the parabolic rate law. The sulfidation rate of iron was found to be reduced by factors of 60 at 900°C and 120 at 600°C by the addition of 40 wt.% molybdenum. Duplex sulfide scales formed on all alloys at all temperatures, the scales consisting of an inner layer of mostly MoS₂ and an outer layer of FeS. Platinum markers were located at the interface between the outer and inner scales, showing that outward iron diffusion and inward sulfur diffusion through the inner layer occurred. The improved sulfidation resistance was attributed to the formation of the MoS₂, which acted as a partially protective barrier to the diffusion of the reacting species. Sulfidation activation energies were found to range from 24.3 to 28.5 kcal mole for the alloys compared to 20.6 kcal/mole, for pure iron. The rate-controlling step was outward iron diffusion through the outer iron sulfide layer.     

Studies of the kinetics of nickel sulfidation in H2S-H2 mixtures in the temperature range 450–600°C

The reaction between pure nickel and H₂S-H₂ mixtures containing 1–65% H₂S has been studied over the temperature range 450–600°C. The sulfidation of nickel in the temperature range 560–600°C has been found to follow a linear rate law at low concentrations of H₂S and a parabolic rate law at higher concentrations (10% and 65% H₂S); X-ray examination of the scale formed on the metal showed it to be almost entirely -Ni₃S₂. On the basis of the kinetics and marker studies it can be concluded that the sulfide scale on nickel is formed by the outward transport of the metal and the inward transport of sulfur. In the temperature range 450–500°C the sulfidation of nickel follows a parabolic rate law. In mixtures containing 10% H₂S the scale formed contains voids, the occurrence of which is connected with formation of Ni₇S₆. It has also been shown that the rate of transport through the Ni₃S₂ layer has an essential influence on the formation of a continuous layer of Ni₇S₆. Marker studies have shown that both nickel and sulfur appear to be mobile in -Ni₃S₂.     

Influence of temperature and the role of chromium on the kinetics of sulfidation of 310 stainless steel

The sulfidation of 310 stainless steel was studied over the temperature range from 910 to 1285° K. By adjusting the ratio of hydrogen to hydrogen sulfide, variations in sulfur potential were obtained. The effect of temperature on sulfidation was determined at three different sulfur potentials: 39 N·m^–2, 1.4×10^–2 N·m^–2, and 1.5×10^–4 N·m^–2. All sulfide scales contained one or two surface layers in addition to a subscale. The second outer layer (OL-II), furthest from the alloy, contained primarily Fe-Ni-S. The first outer layer0 (OL-I), nearest the subscale, contained Fe-Cr-S. The subscale consisted of sulfide inclusions in the metal matrix. Two different phases were observed in OL-II depending on the temperature and sulfur potential. Below 1065°K OL-II is composed of a mixture of monosulfides of iron and nickel (Fe Ni)_1–xS and pentlandite (Fe_4.5Ni_4.5S₈) with the pentlandite phase exsolved as lamellae upon cooling. At temperatures higher than 1065°K only the pentlandite phase was formed, which melted above 1145°K at sulfur potentials greater than 10^–2 N·m^–2, yielding metal-rich iron-nickel-sulfur. Above 1145°K, and at sulfur potentials less than 10^–2 N·m^–2, OL-II ceased to exist (this temperature is termed transition temperature). Below the transition temperature, where OL-II exists, OL-I could be represented by the general composition (Fe, Cr)_1–xS. This phase on cooling transformed into an array of structures differing in FeCr ratio. These substructures, however, were not observed in quenched samples. Above the transition temperature OL-I changed to a chromium-rich sulfide composition and was associated with a sudden decrease in reaction rate. Subscale formation was found to be due to the dissociation of OL-I at the scale-metal interface, and the extent of subscale growth was found to depend on the temperature and the sulfur potential, as well as the composition of OL-I. At a given temperature and sulfur potential the weight-gain data obeyed the parabolic rate law after an initial transient period. The parabolic rate constants obtained at the sulfur potential of 39 N·m^–2 did not show a break when the logarithm of the rate constant was plotted as a function of the inverse of absolute temperature. Sulfidation carried out at a sulfur potential below 2 × 10^–2 N·m^–2, however, did show a break at 1145°K. This break was found to be associated with the changes which had occurred in the FeCr ratio of OL-I. Below the transition temperature the activation energy was found to be approximately 125 kJ · mole^–1. Above the transition temperature the rate of sulfidation decreased with temperature but depended on the FeCr ratio in the ironchromium-sulfide layers of the OL-I. A reaction mechanism consistent with the experimental results has been proposed in which the diffusion of cations through OL-I is the rate-controlling step. Below the transition temperature the diffusion of Fe and Ni through OL-I contributes to the scale formation, whereas above the transition temperature the diffusion of Cr through OL-I controls the scale formation. Existing literature on the Fe-Ni-S system is compared with the present results.