促进剂（TETD）在黄铁矿表面的电化学反应矿物工程等专业毕业设计外文翻译-中英文对照.doc

Electrodeposition of dixanthogen(TETD) on pyrite surfaceLI Wei-zhong(黎维中), QIN Wen-qing(覃文庆), SUN Wei(孙伟), QIU Guan-zhou(邱冠周) School of Mineral Processing and Bioengineering, Central South University, Changsha 410083, China Received 20 July 2006; accepted 28 October 2006Abstract: The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements. Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion, and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface. The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09106 cm2/s. Using the galvanostatic technique, the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as Ja=200 A/cm2, = 0.203 and J0=27.1 A/cm2Key words: electrochemical reaction; pyrrhotite; xanthate1 Introduction In the past decade, much progress has been made in understanding the reactions of sulfide mineral surfaces with xanthate reagents. It is widely recognized that the reactions in a flotation system involve electron transfer. Many electrochemical techniques have been employed to study the reaction mechanism of sulfide minerals (such as pyrite, galena and chalcopyrite) with xanthate reagents1. As well known, flotation of pyrite is an electrochemical process, and adsorption of collectors on the surface of mineral results from the electron transfer between mineral surface and oxidation-reduction composition in pulp. These investigations indicate that the oxidation of both the mineral and the collector plays an important role in the flotation process. It is generally believed that the reactions produce the hydrophobic particle surfaces required in flotation, and the dominant hydrophobic reactions are electrochemical in nature. Many distinct anode processes can produce hydrophobic products, such as the chemical adsorption reaction of xanthate ions, and the oxidation reaction of the xanthate ion to its disulfide compound. It is important in flotation to identify the different anodic reactions coupled to a cathodic process that is generally represented by the reduction of oxygen24. Pyrite(FeS2 ) is the most abundant sulfide mineral in crust of earth and an important raw material of chemical engineering process. The surface chemistry and surface reactivity of FeS2 have been extensively studied, particularly their importance in the processing of sulfide ores59. The electrochemical reaction on the surface of pyrite during flotation has been studied well, but there are only a few references available on the oxidation chemical kinetics and mechanism of the reaction on its surface1014. In this study, the electrochemical behavior of the pyrite electrode in a xanthate solution was investigated. Some advanced electrochemical techniques were employed to research the electrodeposit of dixanthogen on the pyrite surface.2 Experimental The pyrite used in this investigation consisted of 58.20% (mass fraction) Fe, 36.20%S, 3.1%SiO2 and was from Mengzi Mine of Yunnan Province, China. Sections cut from the highly mineralized pyrite were fashioned into the form of electrodes for electrochemical measurement. The cut section of mineral was mounted on the tip of a perspex tubule of d 7 mm using epoxy resin and the exposed outer surface was well polished. The exposed surface area of the electrode was about 1 cm2. The reference and auxiliary electrodes were saturated calomel electrode(SCE) and graphite rods, respectively. All potential in this study were quoted in volts, with respect to a standard hydrogen electrode (SHE). The electrochemical measurements were performed with a conventional three-electrode cell using a electronics potentiostat/galvanostat model EG&G 273A and a model 636 Electrode Rotator. Both were operated by a computer. The EG&G corrosion measurement system (Princeton Applied Research Model 352) and Analysis Software (Model 270) were used in the experiment. The studies were carried out using the pyrite as electrode in a 0.5 mol/L KCl solution in the presence of butyl xanthate.3 Results and discussion 3.1 Two stages of electrochemical reaction on pyrite surface in butyl xanthate solution While the potentiostat applies a constant current on the pyrite electrode for a specified duration, the overall consumed charge Q can be calculated by the following equation: Q=Q+Qc (1) where Qc is the charge consumed by the diffusion of xanthate ion on the pyrite surface, and Q is the charge consumed by the electrochemical adsorption of xanthate ion. According to the Sand formula15: Q=Q0+3.14n2F2Dc02/4J (2)where n is the number of transfer electrons in reaction,F is the Farady constant, D is the diffusion coefficient of xanthate, c0 is the initial concentration of butyl xanthate ion, and J is the current density.If the electrochemical adsorption of butyl xanthate ion on the pyrite surface did not occur, the charge consumed by the electrochemical adsorption of xanthate ion (Q ) would be zero. The value of Q can be verified using galvanostatic technique. Table 1 lists the results of galvanostatic experiments for a pyrite electrode at different currents. The Q value is linearly related with 1/J. Based on the results in Table 1, the plot of the consumed charge Q as a function of the reciprocal of current density (Ja-1 ) is drawn in Fig.1. From this figure, we calculate the charge consumed by the electrochemical adsorption of butyl xanthate ion (Q) to be equal to 0.242 mC/cm , not zero which means that an electrochemical adsorption of buty xanthate ion takes place on the pyrite surface. The electrochemical absorption reaction of butyl xanthate ion on pyrite surface can be written as X-X(ads)+e (3)Fig.1 Relationship between overall charge and current density in galvanostatic experiment (BX=10-4mol/L, pH=9.18, 25) Fig.2 shows the voltamograms in pH 9.18 buffer for a pyrite electrode starting from 0.4V (vs SHE) in the positive direction. There is an anodic peak appeared at 0.1 V, which indicates that an electrochemical reaction occurs. The possible reaction is the oxidation of butyl xanthate ion on the pyrite surface:2X-X2+2e (4)=0.1280.059logX- , X- =10-4 mol/L, =0.108V. So we can think that the oxidation of butyl xanthate ion on the pyrite surface is a consecutive charge transfer eaction. The electrochemical reaction can be divided into two stages: the first step is electrochemical adsorption of butyl xanthate ion, and then the adsorbed ion associates with a butyl xanthate ion from the solution and forms a dixanthogen on the sulfide mineral.The oxidation process of xanthate ion is as X(ads)+X-1(aq)X (ads)+e (5)Fig.2 Voltammogram curves of pyrite electrode in presence of xanthate (BX=10-4mol/L, pH=9.18, 25 )3.2 Determination of diffusion coefficient of butyl xanthate on pyrite surfaceIn potentiostatic experiment, the potentiostat applies a constant potential for a special duration and monitors the resulting current density, which can be used to investigate electrode process and to determine the diffusion coefficient of butyl xanthate. From Fig.2, there is a space of 0.70 V between the anodic shoulder and cathodic shoulder, and we can determine the production of dixanthogen(BX2) on pyrite surface is an irreversible reaction. Fig.3 shows the plot of current density versus time for pyrite electrode in butyl xanthate solution in response to potentiostatic step of 0.10 V. The relationship between current density and time can be ascertained by the following equation: J-1=4.1610-6+1.5710-2t0. 5 (6)Fig.3 Current and time changes in response to potentiostatic step for pyrite electrode (BX-=10-4mol/L, pH=9.18, 25 )From an electrochemical reaction in the electrolyte solution, the suppositions are given as follows. 1) Diffusion of reactant obeys the second Fick law; the current caused by diffusion of reactant is in direct proportion to the superficial area of electrode surface; 2) The electrode process is controlled by diffusion of reactant; and 3) The electromigration and convection are neglected.The boundary conditions are determined as follows. 1) The concentration of butyl xanthate in the system is equal to the initial concentration, ie. cx(x,0)=c0x; 2) The concentration of butyl xanthate at indefinite position away from the electrode is equal to the initial concentration, which is described by Cx(, t)=c0x; and 3) The concentration of butyl xanthate on the surface of electrode is zero, expressed by cx(0, t)=0. The current density caused by diffusion can be given byJ=nFDdcx(x, t)/dxx=0 (7) According to the second Fick law, the following equation can be given: Cx(x, t)= c0xerf(x/2(Dt)0.5 (8) J=nFc0x (D/t)0.5 (9) J1=(nF c0x )-1(t/D)0.5 (11)where D is the diffusion coefficient of butyl xanthate,c0x is the initial concentration of butyl xanthate, t is the reaction time, n is the number of transfer electrons in reaction, F is the Farady constant, and is 3.141 6.From Eqn.(5), the intercept is 4.1610-6. It is small enough, so the relationship between current density and time in Eqn.(5) can be simplified as follows:J-1=1.5710-2t0. 5 (12)According to the Eqns.(10) and (11), the diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined, and it is about 1.0910-6cm2/s.3.3 Kinetics of electrochemical reaction on pyrite electrode surface The oxidation of butyl xanthate ion on the pyrite electrode surface is an irreversible reaction, so there are suppositions given as follows. 1) The electromigration and convection are neglected; and 2) The variations in the concentration of xanthate are caused by diffusion. The relationship between over potential of anodic reaction and the reaction time can be ascertained by the following equation:=(8.314T/nF)ln(Ja/J0)(8.314T/nF)ln1(t/)1/2 (12)where is the over potential of the anodic reaction, T is the temperature, Ja is the galvanostatic current density, J0 is the exchange current density, is the transition time, t is the time of reaction, and is the transmission coefficient. In chronopotentiometry experiment, the potentiostat applies a constant current (200 A/cm2) for a specified duration and monitors the resulting potential of pyrite electrode. Fig.4 shows the resulting curve of chronopotentiometry in butyl xanthate solution. From this plot, the transition time () of the oxidation of xanthate ion on the pyrite surface can be determined as 4.73 s.Fig.4 Potential and time changes in response to galvanostatic step for pyrite electrode (BX=10-4mol/L, pH=9.18, 25 )The oxidation of butyl xanthate ions on a pyrite surface is given in the following reaction: 2X-X2+2e The thermodynamic potential() of this reaction can be calculated by the Nernst equilibrium:=00.059logX-, X-=10-4mol/L (13)=twhere t is the value of the potential at time t.As the function of log1(t/4.73)0.5, the change othe over potential() of the oxidation of butyl xanthate ion on pyrite surface can be plotted as Fig.5. From Fig.5, it can be seen that the over potential is linearly related to the log1(t/)1/2, and the relationship can be represented by following equation:=0.1260.063log1 (t/4.73)1/2 (14)According to the Eqns.(12) and (14), because the value of R, T, F and are certain, the electrochemicalFig.5 Relationship between over potential of pyrrhotite electrode and log1(t/)1/2 (BX=10-4mol/L, pH=9.18, 25)kinetic parameters can be calculated as J = 200 A/cm2, =0.203, J =27.1 A/cm24 Conclusions 1) The first step in the electrodeposit of butyl xanthate ion on the pyrite surface is the electrochemical adsorption of xanthate ion, and then the adsorbed ion associates with a xanthate ion from the solution and forms dixanthogen on the sulfide mineral. 2) The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.0910-6 cm2/s. 3) The oxidation of the butyl xanthate ion on the pyrite surface produces dixanthogen. The kinetic parameters are calculated as Ja=200 A/cm2, =0.203, J0=27.1 A/cm2. 4) For an effective flotation separation of pyrite from polysulfide minerals containing Pb, Cu, Zn, etc, it is important to control the formation of dixanthogen on the pyrite surface.References 1 KELSALL G H, YIN Q, VAUGHAN D J. Electrochemical oxidation of pyrite (FeS2) in aqueous electrolytes J. Journal of Electroanalytical Chemistry, 1999, 471(2): 116125. 2 FINKELSTEIN N P. The activation of sulphide minerals for flotation a review J. International Journal of Mineral Processing, 1997,52(2/3): 81120. 3 PATRICK R A D, ENGLAND K E R, CHARNOCK J M. Copperactivation of sphalerite and its reaction with xanthate in relation toflotation: An X-ray absorption spectroscopy (reflection extended X-ray absorption fine structure) investigation J. International Journal of Mineral Processing, 1999, 55(4): 247265. 4 ZHANG Qin, HU Yu-hua, GU Guo-hua, NIE Zhen-yuan.Electrochemical flotation of ethyl xanthate-pyrrhotite system J.Trans Nonferrous Met Soc China, 2004, 14(6): 11741179. 5 HUNG A, MUSCAT J. Density functional theory studies of pyrite FeS2 (111) and (210) surfaces J. Surface Science, 2002, 520(12): 111119. 6 OPAHLE I, KOEPERNIK K, ESCHRIG H. Full potential band structure calculation of iron pyrite J. Computational Materials Science, 2000, 17(24): 206210. 7 EDELBRO R, SANDSTR J M A, PAUL J. Full potential calculations on the electron band structures of sphalerite, pyrite and chalcopyrite J. Applied Surface Science, 2003, 206(14): 300313. 8 QIN Wen-qing, QIU Guan-zhou. Electrodeposition of dixanthogen on surface of pyrrhotite electrode J. Trans Nonferrous Met Soc China, 2000, 10(Special Issue): 6163. 9 QIN Wen-qing, LI Quan, QIU Guan-zhou, XU Ben-jun. Electrochemical oxidation of pyrrhotute in aqueous solution J. Trans Nonferrous Met Soc China, 2005, 15(4): 922925. 10 WANG Hui-xiang, WANG Dian-zuo, LI Bo-dan. Improved methods to determine the electrochemical Peltier heat using a thermistor I: Improved heat-sensor electrodes and lumped-heat-capacity analysis J. Journal of Electroanlytical Chemistry, 1995, 392(Issues促进剂（TETD）在黄铁矿表面的电化学反应黎维中 覃文庆 孙伟 邱冠周矿物加工与生物工程学院，中南大学，长沙410083，中国2006年7月20日收到，2006年10月28日接受摘要：采用循环伏安，计时和旋转圆盘电极测量对黄铁矿表面的黄药进行了电化学反应研究，。实验结果表明，在反应的第一步是电化学离子吸附黄药，然后吸附离子与药水中的黄药离子结合在黄铁矿电极表面形成一个促进剂。黄铁矿电极表面丁基黄药的扩散系数可确定为约1.09 10-6 cm2/s。采用恒流技术，对丁基黄药离子在黄铁矿表面氧化反应的动力学参数的计算是Ja = 200A/cm2，= 0.203和J0 = 27.1A/cm2关键词：电化学反应，磁黄铁矿，黄药1 简介在过去的十年中，了解黄药试剂与硫化矿物表面的反应已取得很大进展。人们普遍认识到，在浮选系统涉及电子转移反应。已采用许多电化学方法用黄药试剂研究硫化物矿物反应机制（如如黄铁矿，方铅矿，黄铜矿）1。众所周知，黄铁矿浮选是一个电化学过程，在矿物表面的吸附收藏者造成矿物表面和氧化还原成分的矿浆之间的电子转移。这些调查表明，矿物和收藏者的氧化都在浮选过程中具有重要作用。人们普遍认为，反应产生疏水粒子表面的需要浮选，主导疏水的反应是电化学的本性。许多不同的阳极过程可以产生疏水产品，如黄药离子化学吸附反应，以及黄药离子与其二硫化合物的氧化反应，。在浮选重要的是鉴定不同阳极反应耦合到阴极过程它通常是由氧还原为代表的。2-4硫铁矿（硫化铁）是地壳最丰富的硫化物矿物，也是重要的化工过程的原料。表面化学和表面硫化铁反应已被广泛研究，特别是它们在硫化物矿石加工中的重要性5-9。对浮选过程中黄铁矿表面电化学反应进行了很好研究，但在氧化的化学动力学和在其表面的反应机制中只有很少的一部分可参考10-14。 在这项研究中，对黄铁矿电极在黄药作用下的电化学行为进行了研究。采用一些先进的电化学技术来研究对黄铁矿表面促进剂的电沉积。2 实验在本次调查采用黄铁矿包括58.20（质量分数）的Fe，36.20的S，从3.1SiO2来自中国云南省蒙自矿井。从高矿化的黄铁矿切断的部分进入电极形式塑造了电化学测量。矿产的削减部分安装在一个半径7毫米，使用环氧树脂其裸露外表面被很好抛光的有机玻璃细管的顶端。该电极表面的暴露面积约1 cm2。参考和辅助电极分别是饱和甘汞电极（SCE）和石墨棒。在本研究中关于电极对于标准氢所有可能被引述为伏（SHE）。 使用电子电位/恒电流模式的EGG 273A条和模型636电极转子细胞的常规三电极得到了电化学测量结果。两者都是由电脑操作。EGG公司的腐蚀测量系统（普林斯顿应用研究模型352）和分析软件（型号270）在实验中被使用用。 这些研究利用黄铁矿作为电极在丁基黄药存在的0.5mol/ L KCl溶液中进行。3 结果与讨论3.1两个阶段的电化学反应在黄铁矿表面的丁基黄药解决方案 虽然电位应用于黄铁矿电极恒流为指定的持续时间，整体消费的电荷，可以通过下列公式计算：Q=Q+Qc (1)其中Qc的是由黄药离子对黄铁矿表面扩散消耗的电荷，Q是由黄药离子电化学吸附消耗的电荷。根据砂公式15：Q=Q0+3.14n2F2Dc02/4J (2)其中n是在反应转移电子数，F是法拉第常数，D为黄药的扩散系数，c0的是丁基黄药离子初始浓度，J是电流密度。 如果在黄铁矿表面丁基黄药离子电化学吸附没有发生，消耗在黄药离子（Q）的电化学吸附将是零。 Q值可以验证使用恒流技术。表1列出了黄铁矿电极在不同电流下的恒电流实验结果。 Q值与1 / j呈线性相关。根据表1，对消耗Q作为电流密度(Ja-1 )等功能是绘制在图1。从这个数字，我们计算由丁基黄药离子(Q)电化学吸附所消耗的费用要等于0.242的MC /厘米，不为零，这意味着一个丁基黄药离子就在黄铁矿表面的地方电化学吸附。黄铁矿表面丁基黄药离子对电化学反应的吸收，可写为X-X(ads)+e (3)图1恒电流试验中总体电流和恒流电流密度之间的关系 (BX=10-4mol/L, pH=9.18, 25) 图2显示了的伏安在pH 9.18缓冲区黄铁矿电极从-0.4V（vs SHE）的正方向开始。有一氧化峰出现在0.1 V，这表明电化学反应发生。可能的反应是丁基黄药离子在黄铁矿表面氧化：2X-X2+2e (4)=0.1280.059logX- , X- =10-4 mol/L, =0.108V. 因此，我们可以认为，丁基黄药离子在黄铁矿表面氧化是一个连续的电荷转移反应。电化学反应可分为两个阶段：第一个步骤是丁基黄药离子电化学吸附，然后吸附离子结合溶液中的丁基黄药离子，对硫化物矿物形成了促进剂。 黄药离子的氧化过程是X(ads)+X-1(aq)X (ads)+e (5)图2黄药在黄铁矿电极存在伏安曲线(BX=10-4mol/L, pH=9.18, 25 )3.2测定黄铁矿表面丁基黄药的扩散系数在电位实验中，特殊的时间电位适用一个恒电位，监测所产生的电流密度，它可以用于研究电极过程，并确定丁基黄药的扩散系数。在图2中，有一个0.70 V之间的阳极和阴极肩空间，我们可以决定促进剂生产条（BX2）是一个不可逆转的反应。图3显示了丁基黄药在黄铁矿电极溶液中反应的0.10V电位步骤电流密度随时间变化的曲