Application of microwave for promoting biooxidation of refractory high-sulphide concentrates: influencing factors analysis

ABSTRACT

To promote biooxidation efficiency of a refractory high-sulphide gold concentrate, microwave technology has been applied. Two factors were investigated in the microwave stage including initial solution pH and microwave irradiation time. The results show that biooxidation efficiency of the gold concentrate increases with the increasing initial solution pH. The effect of microwave irradiation on biooxidation efficiency becomes negligible after 300?s. The optimal experiment conditions were initial solution pH of 7.00 and microwave irradiation time of 300?s. Using the irradiated sulphide concentrate, the biooxidation period decreased and the biooxidation efficiency increased. After microwave irradiation, the mineral particle surface was destroyed and became bumpy. Microwave contributed to the decrease of mineral particle size and the increase of specific surface area. A mechanism model shows that the increasing mineral surface area caused by microwave irradiation leads to the enhancement of biooxidation efficiency.     

高砷高硫难处理金精矿预处理工艺研究

根据高砷高硫难处理金精矿的工艺矿物学特征,提出了二段焙烧-加压酸浸联合预处理工艺,重点讨论了该工艺对砷、硫和铁脱除效果的影响。研究结果表明,难处理金精矿经一段焙烧后,在焙烧温度700 ℃、焙烧时间120 min条件下,再经二段焙烧,所得焙砂中As含量仅为0.51%,S含量为0.34%,并且经过加压酸浸后As、S和Fe的脱除率都在95%以上,达到了很好的效果。     

Arsenic leaching from a gold bearing enargite flotation concentrate

The high arsenic content of the flotation concentrate obtained from a gold-bearing enargite ore for pyrometallurgical processing strongly diminishes its market value. An investigation has been carried out for selectively leaching arsenic from enargite–luzonite minerals using alkaline Na₂S solutions. By suitably adjusting the main reaction conditions almost 98% arsenic was leached, as well as part of the gold, particularly with high Na₂S concentrations. Copper was not lost from the solid phase in which the enargite is converted into a new species with the chemical formula Cu_1.5S.     

RECOVERY OF METAL VALUES FROM COPPER—ARSENIC MINERALS AND OTHER RELATED RESOURCES

Copper is often associated with arsenic in mixed sulphide minerals such as enargite (Cu₃AsS₄) and tennantite (Cu₁₂As₄S₁₃). Enargite, in particular, is the principal mineral in many deep epithermal copper–gold deposits. Most mining companies avoid exploiting such resources, because the arsenic can become a serious environmental liability or may considerably reduce the resource value due to hefty treatment charges. The few enargite deposits that have been exploited so far are usually rich in gold and silver. The first challenge in the exploitation of copper–arsenic sulphides is the effective separation of arsenic phases from other valuable minerals. In the last decade, though, it was shown that this is possible by pulp-potential adjustment (oxidative conditions) combined with pH adjustments (basic conditions) prior to flotation. In this way, two types of concentrate can be produced: one rich in arsenic and another low in arsenic but rich in other valuable metals. Arsenic-rich concentrates have traditionally been processed pyrometallurgically by reduction roasting to gaseous arsenic sulphide, which is then converted to arsenic trioxide. New pyrometallurgical technologies for the treatment of copper–arsenic sulphides include sulphidization roasting, sulphidization roasting and halogenation, and carbothermic reduction to copper arsenide. The hydrometallurgical treatment of copper–arsenic-antimony resources has been done by atmospheric leaching in alkaline sodium-sulphide solutions. Ultrafine grinding and ferric oxidation at atmospheric pressure, total pressure oxidation at temperatures above 220°C, and bacterial leaching have recently been tried on copper–arsenic sulphides, some with considerable success.     

Arsenic in Gold Processing

Abstract

The processing of gold bearing sulphide minerals which contain arsenopyrite and other complex arsenic sulphide minerals results in arsenic containing emissions and effluents which must be given careful consideration in relation to clean air and clean water standards. The sources of arsenic and the various process options for treating arsenical gold ores and concentrates are briefly reviewed

The problem relating to the removal of arsenic from gaseous emissions from roasting processes is considered

Residues from aqueous processing contain a variety of arsenical materials which have not been characterised, and the long-term stability of these is suspect

The use of lime to stabilise aqueous residues as cither calcium arsenate or calcium arsenite has been shown to be inadequate for long term disposal since both compounds are converted into calcium carbonate due to the influence of carbon dioxide in the atmosphere

Ferric ion solutions have been used to precipitate ferric arsenate or to form ferric hydroxide which binds the arsenic for short term disposal. The long term stability of these ferric materials is poor, but could lead to the acceptance of a slow release option rather than complete containment of residues.     

含砷高硫金精矿焙烧—氰化工艺研究

按焙烧—氰化方案对某含砷高硫金精矿的提金工艺进行了试验研究, 结果表明, 金精矿在模拟工业窑炉操作制度下焙烧氧化, 硫、砷脱除率和综合氧化率分别达９５％ 、９２％ 和９５％以上, 焙砂经细磨—碱洗后氰化, 金的浸出率超过９１％ 。     

提高含砷金精矿二段焙烧-氰化工艺金浸出率的试验研究

在试验研究基础上,提出了一种提高含砷金精矿二段焙烧-氰化浸出工艺金浸出率方法.试验结果表明,含砷金精矿经一段焙烧(450～500℃)除砷后,加入一定量的添加剂SR,再进行二段焙烧(630～650℃),然后经稀硫酸除铜后进行氰化浸出,可使金的氰化浸出率提高4.65%.该方法可获得较好的经济效益和社会效益.     

焙烧氧化处理对含金硫精矿工艺矿物学特性的影响研究

基于矿物解离分析仪,结合X射线全自动衍射仪、扫描电子显微镜和激光粒度分析仪,对湖南某矿山浮选铅锌矿后的难处理含金硫精矿焙烧氧化处理前后的矿物性质、粒度、裂纹和孔隙及金矿物解离度和连生情况进行了测试分析.结果显示:焙烧氧化处理使该含金硫精矿中毒砂和黄铁矿氧化转变为赤铁矿,氧化过程会导致矿物碎裂,颗粒粒度变细,颗粒表面疏松...     

Upgrading of iron ores using microwave assisted magnetic separation followed by dephosphorization leaching

This paper describes the development of a flowsheet using a combination of sample preparation, magnetic separation (in a range 0.4–1?T), microwave treatment (in a range 0.54–0.9?kW), and leaching operations (HCl, in a range 0.25–1.25?M) for the beneficiation of iron ores (Total Fe [T_FE]: 55.48%). The work was aimed at recovering T_FE from the non-magnetic product by increasing its magnetic susceptibility through microwave treatment. It was found that goethite mineral in the non-magnetic product at a temperature of around 200^oC was converted to paramagnetic (hematite) or ferromagnetic minerals (maghemite and magnetite) by microwave treatment and overall beneficiation recovery was improved. The phosphorus (P) content in the final product was then removed by leaching in 0.25?M HCl. The iron loss from the final concentrate during leaching was found to be 0.78%, which was negligible. Overall, a final concentrate assaying 61.78% T_FE with a recovery of 94.97%, and containing 0.04% P with 94.73% removal was obtained providing satisfactory results for use in the industry. This study gives an alternative way for possible future studies to produce an iron concentrate with a high recovery from problematic iron ores, which can be categorised due to its P content.     

含砷银铜精矿中有价金属回收技术综述

本文分析了对含砷银铜精矿利用的技术方案,简述了对这一精矿进行的低温焙烧、化学除砷、浸铜以及浸银等实验研究以及取得的技术指标。     

Decomposition of mixed rare earth concentrate by NaOH roasting and kinetics of hydrochloric acid leaching process

A new clean extraction technology for the decomposition of Bayan Obo mixed rare earth concentrate by NaOH roasting is proposed.The process mainly includes NaOH roasting to decompose rare earth concentrate and HCl leaching roasted ore.The effects of roasting temperature,roasting time,NaOH addition amount on the extraction of rare earth and factors such as HCl concentration,liquid-solid ratio,leaching temperature and leaching time on the dissolution kinetics of roasted ore were studied.The experimental results show that when the roasting temperature is 550℃ and the roasting time is 60 min,the mass ratio of NaOH:rare earth concentrate is 0.60:1,the concentration of HCl is 6.0 mol/L,the ratio of liquid to solid(L/S) 6.0:1.0,and the leaching temperature 90℃,leaching time 45 min,stirring speed 200 r/min,and the extraction of rare earth can reach 92.5%.The relevant experimental data show that the process of HCl leaching roasted ore conforms to the shrinking core model,but the control mechanism of the che mical reaction process is different when the leaching temperature is different.When the leaching temperature is between 40 and 70℃,the chemical reaction process is controlled by the diffusion of the product through the residual layer of the inert material.The average surface activation energy of the rare earth element is E_a=9.96 kJ/mol.When the leaching temperature is 75-90℃,the chemical reaction process is controlled by the interface transfer across the product layer(product layer interface mass transfer) and diffusion.The average surface activation energy of rare earth elements is E_a=41.65 kJ/mol.The results of this study have certain significance for the green extraction of mixed rare earth ore.     

The soda-ash roasting of chromite minerals: Kinetics considerations

Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate during the soda-ash roasting reaction depends on the oxygen partial pressure and availability of oxygen at the reaction front. The effects of temperature, oxygen partial pressure, charge composition, and their roles on the overall roasting reaction were studied in order to analyze the reaction mechanism. The influence of process parameters such as the addition of alkali and process residue as the filler material on the overall reaction rate is discussed. The rate-determining steps for the soda-ash roasting reaction are analyzed. The importance of the binary Na₂CO₃-Na₂CrO₄ liquid phase during the reaction in determining its speed is also examined. It is shown that the experimental results for the roasting reaction can be best described by the Ginstling and Brounshtein (GB) equation for diffusion-controlled kinetics. From the measured kinetics data, the apparent activation energy for the roasting reaction was calculated to be between 180 and 190 kJ · mol⁻¹ in the temperature range from 1023 to 1210 K and between 35 and 40 kJ · mol⁻¹ above 1210 K.     

加压氧化浸出工艺的机理研究

加压浸出法具有流程短、砷浸出率高、浸出时间短及无SO2等有毒物质产生的优点,是预处理含硫、砷金矿石或金精矿的有效手段.在酸性介质中,硫化物、铁化合物与砷化物发生高温氧化的主要反应包括3种形式:硫化物全部被氧化成硫或硫酸盐,反应过程中产生的Fe2+被氧化成Fe3+,砷被氧化成砷酸盐.随着易处理矿石资源日益减少,加压浸出法...     

碳热焙烧还原砷酸钙制备金属砷

致力于碳热焙烧还原砷酸钙制备具有商业价值的金属单质砷,为推进砷危废物无害化处理向砷资源化回收利用前进展开科学研究。其中热重分析表明,砷酸钙与碳粉混合热解的质量损失分为3个阶段,阶段1和阶段2为失水过程,阶段3为碳还原砷酸钙生成CaO和砷蒸气过程。且研究发现,可以利用相边界反应动力学模型解释阶段3反应机制。而单因素条件实验结果表明:在温度1000 ℃、碳配入系数1.4、恒温时长60 min条件下砷挥发率高达99.94%。X射线衍射仪(XRD)、扫描电镜能谱仪(SEM?EDS)对反应体系中有关产物表征表明,较优条件下产品砷主要为片状金属砷和粉末非晶体砷,焙烧残渣为CaO。      

含砷、汞金矿提金工艺展望

指出了常规的浮选一焙烧 /细菌 /加压等预氧化流程处理含砷、汞金矿石存在的问题 ,介绍了原矿沸腾焙烧提金新工艺特点及处理含砷、汞金矿石所具有的独特优势     

含砷难处理金矿预处理研究——（Ⅱ）加石灰焙烧法

本文研究了用加石灰焙烧法对含砷难处理金矿进行预处理，该法可有效地消除砷和硫可能对环境造成的污染，对含砷为３．７６％，硫６．２３％，金２３．３ｇ／ｔ的金精矿进行焙烧后，金的浸出率可达９０％左右，而未经焙烧预处理的金直接浸出率仅５６．９６％。     

含砷、锑、碳难处理金精矿焙烧氰化提金工艺研究

镇沅含砷、锑、碳难处理金精矿直接氰化金浸出率小于 10 % ,采用常规焙烧 -焙砂氰化提金工艺金浸出率仅达到 73 2 % ,而采用先行除锑 ,再焙烧脱除硫、碳、砷的提金工艺方案 ,金氰化浸出率达到90 4 % ,同时锑可作为锑精矿外售 ,经济效益明显。     

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For the problem of desulfurization from sulphur concentrate, the reaction kinetics process of low grade sulphur concentrate roasting under oxygen enrichment was studied, and the changes of mineral phases in sulphur concentrate roasting during the course of oxidation were analyzed by SEM, XRD and EDS. At the same time, according to DSC and TG curves, the kinetic parameters of desulfurization reaction were calculated by Achar- Brindley- Sharp- Wendworth differential method and Coats- Redfern integral method, and the desulfurization mechanism of sulphur concentrate was determined at different temperature stages. The results show that with the rising temperature, the complex sulphur concentrate gradually becomes hematite, accompanied by the formation or the decomposition of the intermediate ferric sulfate; and sulfur content of roasting ores decreases. The kinetics calculation results show that in the temperatures of 430??975??, oxidation roasting of sulfur concentrate has four temperature stages. In the first three stages, desulfurization reaction mechanisms all accord with Avrami- Erofeev equation, belonging to the chemical reaction control of the random nucleation and then growth, only the reaction order and the apparent activation energy of reaction vary in different temperature stages; In the fourth stage, the desulfurization reaction mechanism accords with Z- L- T equation, belonging to the reaction control of the three- dimensional diffusion of the residual sulphide. In addition to this, the apparent activation energies of reaction are 10. 812 and 9. 920kJ/mol respectively, and are the lowest in four temperature stages.     

某碳质金精矿富氧焙烧—氯化浸出试验研究

某碳质金精矿直接氰化浸出金浸出率很低,小于30%,为进一步提高金浸出率,针对碳质金精矿性质,进行了富氧焙烧—氯化浸出试验研究。结果表明:与常规氧化焙烧相比,富氧焙烧降低了焙烧温度,缩短了焙烧时间;富氧焙烧最佳焙烧温度550℃~600℃,氧气体积分数50%,焙烧时间2.0 h,在此条件下,碳、硫去除率均在95%以上;焙砂采用M-NaCl氯化浸出,在最佳浸出条件为固液比1∶6,浸液pH=3,浸出剂用量8 kg/t,试样粒度62~75μm,浸出时间4 h时,金浸出率可达92.50%,相对于试样直接氯化浸出时有显著提高;表明富氧焙烧—氯化浸出工艺是可行的。     

某含砷金精矿加氯化剂氧化焙烧探索试验

对某含砷金精矿加入氯化剂进行氧化焙烧与单一氧化焙烧进行了比较试验,试验结果表明,加氯化剂焙烧能较大幅度提高焙砂的金氰化浸出率,可提高9.27%~11.61%。