Formation of silicon carbide from microsilica waste by means of lignite semicoke

The formation of silicon carbide from briquetted batch consisting of microsilica waste from silicon and silicon-alloy production is investigated. The batch is treated at 1873, 1923, and 1973 K, for 5–30 min, with various reducing agents: lignite semicoke, coal semicoke, coke breeze, and coke dust. The best results are obtained when using lignite semicoke from the Berezovsk deposit in Kansko-Achinsk Basin: the yield of silicon carbide is 97.00–97.62%; it constitutes 82.52–84.90% of the products obtained. The optimal treatment temperature and time are determined: 1923–1973 K for 15–20 min. The products consist predominantly of cubic silicon carbide (β SiC). Chemical enrichment increases the SiC content in the products to 90–91%; this is higher than in abrasive micropowder of grain size 1–2 μm. The effectiveness of enrichment in terms of oxide and iron impurities is high: 87–95%. The silicon carbide is characterized by a high silica content: more than 7%. Accordingly, it may be regarded as a promising material for the production of siliconcarbide refractories used in silica binder. Silicon carbide is obtained as micropowder with irregular particles in the size range 0.2–1.0 μm.     

Production of silicon carbide from microsilica waste by reduction with lignite semicoke

Silicon carbide may be produced from fine-grain batch consisting of two main components: microsilica waste; and semicoke obtained from Berezovsk lignite (Kansko-Achinsk Basin). The physicochemical properties of the silicon carbide are certified in the present work. Two forms of microsilica are considered: (1) microsilica formed in the production of silicon (containing 93.41–95.33% SiO₂; 1.96–3.28% C_free; 0.30–0.34% Si_free; and 1.25–1.45% CaO + Fe₂O₃ + MnO); (2) microsilica formed in the production of high-silica ferrosilicon: (containing 91.72–93.63% SiO₂; 0.56–1.18% C_free; 0.18–0.20% Si_free; and 1.38–2.32% CaO + Fe₂O₃ + MnO). Its specific surface is 21000–24000 m²/kg. The microsilica is inclined to form spherical aggregates measuring 200–800 nm. The aggregates consist of spherical particles ranging in size from 30 to 100 nm. The lignite semicoke contains 94.05% carbon, 9.2% ash, 0.2% sulfur, and 0.007% phosphorus; its specific surface is 264000 m²/kg. The composition of the silicon carbide is investigated, along with its specific surface; the size and shape of the carbide particles are determined. In both cases, the predominant phase is cubic silicon carbide (β-SiC), with an accompanying glassy phase consisting of silicates of calcium, magnesium, and iron. When the batch containing microsilica from ferrosilicon production, the silicon carbide is accompanied by α iron. In synthesis at 1923 and 1973 K for 50 and 90 min, respectively, polymorphic conversion of β-SiC to α-SiC_p is observed. The content of silicon carbide in the products is 82.52–84.90%. Chemical enrichment of silicon carbide proves expedient. The optimal enrichment conditions are as follows: the action of hydrochloric acid (concentration no less than 35%) at 353 K for 3 h, with a 1:2 solid/liquid ratio. The enrichment characteristics are as follows: the content of silicon carbide in the products is 90.42–91.10%; and 87–95% of the impurities (metal oxides and iron) are removed. The silicon carbide is obtained as micropowder consisting of irregular particles (size 0.2–1.0 μm) with specific surface 8000–9000 m²/kg.     

Reaction mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust

Abstract

The experiments in this paper were performed to research the mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust. The reduction potential of zinc during cementation was determined to investigate the morphology of products. Residues after the cementation process from zinc sulphate solution were analyzed by SEM and EPMA to investigate the morphology of products. Different temperature will cause different structure of particles. The reaction mechanism of cobalt removal by zinc dust is thought to be as follows: first, the Co2+ forms Co–Zn alloy with zinc particles, and the reaction reaches equilibrium quickly; second, the Co–Zn alloy continues reacting to Co with Co2+, which is the control process of the whole reaction.     

过硫酸铵氧化沉淀法富集净化钴渣中钴的试验研究

某公司生产初期采用α-亚硝基-β-萘酚除钴工艺回收湿法炼锌净化钴渣中的钴,存在药剂消耗量大、钴渣含钴低、生产亏损的问题,后采用过硫酸铵氧化沉淀法富集钴,形成了一种钴的富集倍数高,成本低、流程短、易操作、环保的净化渣回收钴的实用方法.该方法分三个阶段:酸浸阶段包括稀酸选择性浸出和逆流酸性浸出,在较优工艺参数下,钴的浸出率...     

Separation of cobalt and nickel by ozone oxidation

The utilization of ozone for the separation of cobalt from nickel sulfate was investigated by determining the oxidation rate for Co(II) and Ni(II) ions under various ozonation conditions at 60°C. The oxidation reaction was observed to follow a first order rate with respect to the ozone partial pressure of the O₃-O₂ mixture gas and to be promoted considerably by vigorous agitation. The oxidation rates were virtually constant down to a fairly low concentration of the oxidizable ions. Nickel ion was found to be oxidized more easily at lower pH in the mixed sulfate solutions than in solutions of a single sulfate. At pH 2.5–5.0, ozone oxidation seems to be effective to separate cobalt ions selectively from nickel sulfate solutions, due to the extremely slow oxidation of the nickel ion in comparison with cobalt.     

含锗褐煤的利用现状

概述了我国含锗褐煤的资源状况，分析了我国从含锗褐煤中提取锗的方法和特点，对国外含锗煤的利用现状进行了评述，提出了含锗褐煤利用的发展方向。     

含锗褐煤的利用现状

概述了我国含锗褐煤的资源状况,分析了我国从含锗褐煤中提取锗的方法和特点,对国外含锗煤的利用现状进行了评述,提出了含锗褐煤利用的发展方向。     

Adsorption of 1,1,1,2-Tetrafluoroethane by Various Adsorbents

Experiments have been conducted to investigate gas-phase adsorption characteristics of 1,1,1,2-tetrafluoroethane (HFC-134a) by activated carbon fiber, extruded activated carbon, granular activated carbon, activated alumina, and molecular sieve. HFC-134a is currently regarded as an excellent replacement for chlorofluorocarbon-12, a refrigerating and cooling agent extensively used previously in all automobiles and many cooling systems. Performances of HFC-134a adsorption were characterized by the equilibrium adsorption capacity, time to reach equilibrium, and desorption efficiency of exhausted adsorbent. A simple thermal treatment process with proper operating temperature and treatment duration was found to be effective for the regeneration of exhausted adsorbents. Adsorption isotherms of the empirical Freundlich and Jossens types were observed to adequately represent the equilibrium adsorption data. A mass transfer model based on the pseudo steady state squared driving force was adopted to describe the mass transfer process of HFC-134a adsorption.     

沉淀—电吸附联合处理氰化提金废水

采用沉淀—电吸附联合工艺处理高铜高铁提金氰化废水,对处理过程的反应原理和工艺流程进行了系统的分析说明,同时对关键处理结果进行了讨论。研究表明,采用沉淀—电吸附联合工艺处理高浓度氰化提金废水是可行的。经Zn SO4沉淀处理后,废水中Fe2+、Cu2+及游离CN-的沉淀率分别达到100%、85.89%和99.43%。电吸附处理后,废水中的Cu2+、SCN-与游离CN-的去除率分别为98.68%、43.60%和99.57%。经X射线衍射(XRD)分析表明,硫酸锌沉淀后的沉淀物主要由Zn2[Fe(CN)6]、Zn(CN)2和Cu CN组成,而电吸附处理后得到的沉淀物90%以上为Cu SCN,沉淀物及饱和阳极板可经综合处理回收氰化物与金属,同时废水可返回浸出系统循环利用。     

不同温度热解残余生物质半焦对磷的吸附

[目的]研究生物质热解制备生物油的残余半焦对水中磷的吸附性能.[方法]研究了不同温度(550、650和750 ℃)热解半焦吸附磷的动力学和等温线,分别采用准一级、准二级和颗粒内扩散3种模型及Langmuir、Freundlich等温吸附方程对实验数据进行拟合.[结果]结果表明准二级动力学模型能较好描述磷在半焦表面的吸附行为,平衡吸附量和吸附速率随着热解温度的升高而增加.此外,等温吸附过程能较好地用Freundlich吸附等温线方程描述,表明磷在半焦表面的吸附受多种机制影响.3种温度下热解所得半焦对磷的吸附活化能分别为10.86、11.27和10.95 kJ/mol,说明该吸附过程主要为物理吸附.[结论]生物质热解半焦对水中磷具有良好的吸附去除效果.     

China''''s imports and exports of nickel and cobalt by category

~~China's imports and exports of nickel and cobalt by category~~     

The separation of manganese from cobalt by D2EHPA

The separation of manganese from cobalt in sulphate solution by D2EHPA diluted with kerosene is reported. Manganese can be separated by controlling the aqueous and organic pH in the neighborhood of 4.2 and 2.0, respectively. A continuous separation process is proposed. Results indicate that a high degree of separation between manganese and cobalt can be achieved.     

Gold Adsorption by Activated Carbon and Resin

Activated carbon and resins readily adsorb gold from cyanide leach solutions. The main advantages of carbon are its high selectivity towards gold, its ease of elution and its large particle size. On the other hand, resins do not suffer from the problems of pore blocking by fine particles in the slurry and show superior adsorption kinetics and higher loading capacity for gold. In addition, when resins are used in the form of fibre-reinforced sheets, many of the problems associated with beads are overcome. The experimental results are shown to fit the homogeneous surface diffusion model with certain modifications when pore blocking occurs. The Fritz and Schluender isotherm is used to describe the equilibrium behaviour of adsorbed species. This reduces to the well-known Freunlich isotherm when only one component (eg. Gold) need be considered.     

Stoichiometry of liquid-liquid extraction of nickel and cobalt by LIX63

Distribution and spectrophotometric studies were conducted in order to characterize and identify the nickel and cobalt complexes extracted by LIX63 (H₂Ox). The extraction of these metals was found to proceed by a varied and complicated process. Nickel is initially extracted as Ni(HOx)₂ which subsequently converts to Ni(HOx) (H₂Ox) ₂ ⁺ . The equilibrium position between these two complexes depends upon the pH of the adjacent aqueous phase. Formation of Ni(HOx)₂ is favored at pH > 4.5 and conversion to Ni(HOx) (H₂Ox) ₂ ⁺ is favored at lower pH. These two extractable species may fit into a reaction scheme that also involves the complexes Ni(HOx)₂(H₂Ox) and Ni(H₂Ox) ₃ ²⁺ . The extraction of cobalt by LIX63 first forms Co(HOx)₂ which apparently slowly oxidizes to Co(HOx)₂(H₂Ox)⁺. Formerly Graduate Assistant, The Pennsylvania State University     

Electrowinning of cobalt I. Winning from pure cobalt sulphate bath

Electrowinning of cobalt from a pure cobalt sulphate bath was carried out. Effects of current density, cobalt concentration in the bath, temperature, etc. on current efficiency and on the nature of the deposit were studied. The results indicate that bath pH and temperature play major roles in the cobalt deposition. A high current efficiency can be achieved at relatively low temperature and relatively high bath pH (pH > 4.0). Further, at relatively low bath pH and high temperature (～60°C), a high current efficiency can also be obtained; however, in the former case the deposited cobalt is dull and brittle and malleable in nature.