Arsenopyrite Oxidation with Ozone: Stoichiometry and Kinetics

When the recovery of precious metals by standard cyanidation is less than 80%, the ore is classified as refractory and needs an oxidizing pretreatment before cyanidation. Arsenopyrite is one of the main sulfide matrixes where occurs refractory gold. In this work, the arsenopyrite leaching in acid media was studied using ozone as an oxidizing agent. The results obtained show that arsenopyrite leaching is carried out in a stoichiometric way: one mole of Fe and one mole of S are leached by each mole of As leached. A maximum of 60% arsenopyrite leaching was obtained when 1 g (?25 µm) was submitted to acid leaching in 800 mL of 0.18 M acid solution (either chlorhydric, nitric, or sulfuric acid), mechanically stirred at 800 rpm and with the addition of 1.2 L/min oxygen gas containing 0.079 g O₃/L at 25° for 60 min. Although the apparent activation energy estimated was 4.07 kJ/mol, it is suggested that the system is controlled by chemical reaction.     

Pretreatment with Ozone for Gold and Silver Recovery from Refractory Ores

In this work ozonization was studied as pretreatment for two Mexican refractory ores in order to increase the gold and silver extraction. Two methods for contacting ozone with the mineral were studied (indirect and direct). The indirect method did not change the precious metals recoveries for mineral sample A, but increased those of mineral B (from 53 to 88% for gold and from 26 to 78% for silver). The direct pretreatment, only tested in mineral A, did not affect gold and silver recoveries but decreased the extraction time from 40 to 24 hours for maximum metal recovery.     

Intensification of ore concentration and sorption extraction of metals from technogenic raw material

A review of the research data on energy effect produced on the processing behavior of minerals and ores is presented. It is experimentally found that treatment of ores by accelerated electrons fosters the ore weakening and the selectivity of dissociation. Thermal modification of natural sorbents and ultrasonic effect application allow reaching the tenfold increase in sorption and kinetics of the mass-exchange processes and sorption technologies. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 129–139, May–June, 2007.     

Effect of the composition of some sulphide minerals on cyanidation and use of lead nitrate and oxygen to alleviate their impact

An investigation was carried out on synthetic ores containing high purity pyrite, pyrrhotite and chalcopyrite and on two gold ores currently processed to evaluate the impact of cyanicides on cyanidation and to improve the leaching performance by using a pre-leaching, injecting oxygen and adding lead nitrate. With regard to the synthetic ores, it was found that pyrrhotite did not generate a high cyanide consumption while pyrite and chalcopyrite were detrimental. Pre-leaching was deleterious for the ore containing chalcopyrite while pre-leaching with lead nitrate was very efficient to decrease the reactivity of the ore containing pyrite. The two gold ores studied had very different compositions. The low sulphide ore had a low sulphide content (1.36% S), present as pyrrhotite while the second had a very high sulphide content (20.2% S), in the form of pyrite, pyrrhotite and chalcopyrite. The efficiency of the process conditions was peculiar to the ores. The high sulphide ore required a stronger, longer pre-leaching period (12 h) with greater amounts of lime (7.0 kg/t) and lead nitrate (600 g/t) than the low-sulphide ore. The ore with a low sulphide content required a pre-leaching of only 1 h with a small quantity of Pb(NO₃)₂ (50 g/t) and leaching can be performed at 360 ppm NaCN to allow a recovery of 96.4% Au and a low cyanide consumption at 0.18 kg/t. As for the high sulphide ore, cyanidation had to be conducted at 560 ppm NaCN to recover 88.4% Au with a cyanide consumption of 0.80 kg/t. An increase in the amount of lime enhanced oxidation of soluble sulphides. Lead nitrate stabilized copper and iron dissolution by forming a passivation layer at the surface of sulphide minerals. Lead nitrate also prevented the formation of a passive layer at the surface of gold.     

ICP—AES techniques applied to analysis of precious metals in ores

A method for the simultaneous determination of precious metals and matrix elements in Fe and Cu ores is studied.The instrument used is ICAP-9000 polychromator and its accessory monochromator(N 1),Interferences of matrix are eliminated by matrix matching method,i.e.the influence of matrix was corrected by minus equivalent concentration method,The experiments show that the method is simple,sensitive and reliable;especially,suitable for determination of Au in Cu-Au ores.     

Use of Ozone for Gold Extraction from a Highly Refractory Concentrate

Precious metals are generally recovered from their ores by cyanide leaching. When the gold or silver are locked up in the mineral matrix, they remain unrecovered and the ore is classified as refractory to cyanidation. Ozonization in acidic media of an arsenopyritic-pyritic highly refractory gold concentrate (110 g Au/t) as a treatment prior to cyanidation was evaluated. While the conventional cyanidation of this concentrate recovers only 9% of the gold, a pretreatment with ozone before the cyanidation increases the gold recovery to 23%. The rest of the gold is in solid solution with the matrix. Even if this increase in gold extraction is not large enough to economically process this specific concentrate, it demonstrates that the gold locked up in pyrite or arsenopyrite could be recovered by ozonating the ore before cyanidation.     

电感耦合等离子体发射光谱法(ICP-AES)测定矿石中钼

本文报道了电感耦合等离子体发射光谱(ICP-AES)快速测定矿石中钼的方法 ,为了消除矿石的基体干扰,溶解国家一级标准样品制备成标准系列的标准溶液,制作校准曲线。钼的测定波长为202.030nm。本法检出限为0.094μg/mL,实际测定矿石中大于0.005%以上的钼。相对标准偏差(RSD)的范围:0.12%～1.4%。标样测定结果与国家标准样品值结果一致,矿石样品测定值与分光光度法测定结果一致。     

金堆城不同类型矿石选矿工艺及选别方法探讨

分析研究了辉钼矿在不同类型矿石中的嵌布特征对选矿回收率的影响，指出现行工艺不适应矿石性质变化是引起回收率波动的主要原因，确定了各类矿石的选矿工艺条件，推荐了配矿的处理方法。     

卷积溶出伏安法测定痕量金的研究及其应用

研究提出测定痕量金的卷积溶出伏安法。在0.05mol/L盐酸-0.05mol/L氯化钠底液中,2.5次微分阳极溶出法测定金,线性范围为1～10ng/mL,检出限达0.5ng/mL(2.5 x10~(-9)mol/L)。结合大孔巯基树脂或巯基棉富集分离,巳用于岩矿及铜系列物料的分析,取得了满意的结果。该法灵敏度高、准确,操作较简便、易掌握,所用仪器价廉,适于快速分析。     

难选氧化锌矿石中综合回收铁的试验研究

针对某低品位氧化锌矿石矿物组成复杂、嵌布粒度细和风化、泥化严重的特点,分别进行了浮选、磁选和焙烧-磁选三种流程的选矿工艺试验研究和比较。试验结果表明：利用焙烧-磁选联合流程处理该矿石,可获得铁品位60.95%、铁回收率80.55%的选矿指标。