Mechanism of gold dissolving in alkaline thiourea solution

Reaction mechanism of gold dissolving in alkaline thiourea solution was studied by electrochemical methods,such as cyclic voltammetry,chronopotentiometry,AC impedance,linear sweep voltammetry.Apparent activation energy of anodic process of gold electrode dissolving in alkaline thiourea solution is 14.91 kJ/mol.Rate determining step is the process of gold thiourea complex diffusing away from electrode surface to solution.The results of AC impedance and chronopotentiometry indicate that thiourea adsorbs on gold electrode surface before dissolving in solution.There does not exist proceeding chemical reactions.Formamidine disulfide,the decomposed product of thiourea,does not participate the process of gold dissolution and thiourea complex.Species with electro-activity produced in the process of electrode reaction adsorbs on the electrode surface.In alkaline thiourea solution,gold dissolving mechanism undergoes the following courses:adsorption of thiourea on electrode surface;charge transfer from gold atom to thiourea molecule;Au[SC(NH2)2]ads receiving a thiourea molecule and forming stable Au[SC(NH2)2]2 ;and then Au[SC(NH2)2]2 diffusing away from the electrode surface to solution,the last step is the rate-determining one.     

Electrochemical kinetics of gold dissolving in alkaline thiourea solution

1 INTRODUCTIONEssentially , determination of electrode reac-tion mechanism is just the determination of thecourse of electrode reaction and the rate-determi-ning step[1 5]. Based on the previous results[6 11],gold dissolution mechanism undergoes the follow-ing courses in alkaline thiourea solution: adsorp-tion of thiourea on active points of electrode sur-face and formation of Au[SC(NH2)2]ads; chargetransfer fromactive gold atomto thiourea moleculeand formation of Au[SC(NH2)2]a+ds; Au-…     

Study on mechanism of gold leaching by thiourea in the presence of sodium sulphite

Ｃｙａｎｉｄａｔｉｏｎｈａｓｂｅｅｎｕｓｅｄｆｏｒｍｏｒｅｔｈａｎｏｎｅｈｕｎ ｄｒｅｄｙｅａｒｓｉｎｇｏｌｄｉｎｄｕｓｔｒｙｓｉｎｃｅｔｈｅｆｉｒｓｔｐａｔｅｎｔｂｙＭａｃＡｒｔｈｕｒａｎｄｔｈｅＦｏｒｒｅｓｔｓｉｎ 1889[1] ,ａｎｄｓｔｉｌｌｒｅｍａｉｎｓｔｈｅｍｏｓｔｐｏｐｕｌａｒｏｐｔｉｏｎｆｏｒｐｒｏｃｅｓｓｉｎｇｇｏｌｄｏｒｅｓｂｅｃａｕｓｅｏｆｉｔｓｐｒｏｃｅｓｓｓｉｍｐｌｉｃｉｔｙａｎｄｏｐｅｒａｔｉｏｎｅｃｏｎｏｍｙ .Ｎｅｖｅｒｔｈｅ ｌｅｓｓ,ａｐｐｌｉｃａｔｉｏｎｏｆｔｈｅｔｅ…     

Optimization of efficient stable reagent of alkaline thiourea solution for gold leaching

1　INTRODUCTIONThiourea ,asanontoxic goldleachingreagentsubstitutingcyanide ,hasattractedtheinterestofmanyresearchersallovertheworldsincethedissolu tionofgoldinthioureasolutionwasfirstreportedin194 1,andaseriesofstudiesonthetheoryandtech nologyforleachinggoldbythioureahavebeencon ducted[1 3] .Mostreportson golddissolutioninthioureasolutionwereconcernedwithacidicmedia .Itwasdifficultforgoldtodissolveinalkalinesolutionbecauseofthepassivationofelementsulfurproducedbytheirreversibledecompositi…     

紫外分光光度法测定金硫脲浸出液中的铜

确定了在硫脲 ( Tu)介质中用紫外分光光度法测定铜的条件 .在λ=30 0 nm处 ,Cu2 +-Tu络合物具有较强吸收 ,而 Tu无紫外吸收 .当硫脲含量在 5 0 0 mg/ L,p H2 .0 ( HCl)时 ,Cu2 +质量浓度在 0 .5～ 1 0 mg/ L范围内遵守比尔定律 .Na+、K+、Ca2 +、Mg2 +、Cl-、NO- 3 、SO42 -、F-等不干扰测定 ,Au3 +、Ag+干扰较小 ,Fe3 +的干扰可用 F- 离子掩敝 .应用该法测定了几种金矿硫脲浸出液中铜的含量 ,与原子吸收法进行比较 ,相对偏差不大于± 3% .     

一步法合成硫脲的研究

采用含氮量≥20％的石灰氮(CaCN2)水解物和H2S直接反应，一步法生成硫脲．该反应分两个阶段完成：反应的第一阶段为HzS的吸收过程，受其溶解度的影响，常压下有利反应的温度为35C左右，反应液中除了溶解的H2S和未水解的CaCN2外，主要有Ca(SH)2和H2CN2以及少量副反应生成的尿素；第二阶段主要是Ca(SH)2和H2CN2继续反应，生成CS(NH2)2(硫脲)，反应主要受硫脲生成速度的影响，温度宜控制在80～85℃，时间不得超过5h．该法所得硫脲按ZBG17013-88分析为合格产品．     

ANODIC OXIDATION OF THIOSULFATE IONS IN GOLD LEACHING

Oneofthemainproblemsconcerninggoldextractionwiththiosulfateisthatthiosulfateisunsta'bleandinclinedtobedecomposedbyoxidation,whichleadstoitshighconsumption.AmericanresarcherKerleygotpatents["'jforaddingsulphiteasstablizingagent,buthisdetailedreportisnotyetavailable.Ourstudiesshowthatsulphiteisofnonoticeableeffectonimprovingthestabilityandreducingtheconsumptionofthiosulfate,whiletheeffeetofammonismuchmoresignificant.Therefore,investigationontheregularitiesofanodicoxidationofthiosulfateisimportan…     

硫脲结晶工艺中搅拌器参数的优化

采用冷却结晶的方式,通过改变搅拌器形式、搅拌器搅动速牢、搅拌器相对于结晶器内壁的间距大小等结晶器装置的工艺参数,以提高硫脲堆密度。实验结果表明,三层三叶片的桨式搅拌器对于硫脲溶液有均匀的搅拌效果,选择搅拌器速率最佳值为135r／min,硫脲晶体可以达到0．75g／ml的堆密度。     

硫脲法提取金银试剂消耗研究

在定量研究硫脲（ＴＵ）法提取金银中硫脲、硫酸、氧化剂及添加剂的消耗基础上，考查体系中三价铁对硫脲的氧化还原反应过程、红外光谱分析流脲在矿物表面的吸附状态及杂质配位影响等硫脲的主要消耗夫向。探讨了消耗机理，提出了优化工艺。在不加氧化剂条件下，金的浸出率可达９８％以上，各试剂消耗可降到常规硫脲法的１／３到１／５以下。     

Kinetics of the electrochemical process of galena electrodes in the diethyldithiocarbamate solution

The electrochemical process of galena in a pH 12.8 buffer solution was investigated using chronoamperometry and chronopotentiometry. To establish kinetic parameters on the surface of galena in the diethyldithiocarbamate solution, the exchange current density and the dependence of current density on reaction time were determined. Experimental results demonstrate that the exchange current density of galena is 1.585×10?2 A/m2 in the diethyldithiocarbamate-free solution. In the diethyldithiocarbamate solution, ...     

A new extraction process of refractory gold arsenosulfide concentrates

A new hydrometallurgical process for the refractory gold arsenosulfide concentrates under normal temperature and pressure was presented. The experimental results of a refractory gold concentrate show that the total consumption of NaOH in alkaline leaching is only 40% of those theoretically calculated under the conditions of full oxidization at the same oxidation of arsenic to ar-senate and sulfur to sulfate. After alkaline leaching, cyanidation and adsorption were carried out for 24 h. The dissolution of gold by NaCN is increased to 95.3% from 12.8% before pretreatment, and meanwhile 99.3% of the adsorption of gold by activated charcoal. The consumption of NaCN for one ton ore is 10 kg, which is 1.2 times less than that before pretreatment. As it is carried out under normal temperature and pressure, the investment of installations is also decreased.     

高温高压解吸电解工艺中粉炭金的回收

通过对高温高压解吸电解工艺中生成的粉炭进行研究,分析了粉炭产生及其品位高的原因,采用了科学处理粉炭的方法,降低了渣中金的含量,提高了金的回收率,对氰化厂的金属平衡和经济效益有着重大意义。     

001A强酸性树脂吸附硫脲金的研究

研究了强酸性苯乙烯系阳离子交换树脂００１－Ａ在ｐＨ＝ ２．０的Ｈ２ＳＯ４－ ＣＳ（ＮＨ２）２－ Ｈ２Ｏ２ 体系中,吸附、富集硫脲金的性能。结果表明,该树脂对硫脲金离子Ａｕ（Ｔｕ）＋２ （Ｔｕ＝ 硫脲）具有吸附率高,吸附容量大等优异性能。Ａｕ 负载柱可用Ｎａ２Ｓ２Ｏ３ 溶液定量洗脱,用过的树脂可再生。     

硫脲类三唑衍生物结构与活性的密度泛函理论研究

硫脲类三唑衍生物类化合物在农药创新中占有重要地位,为了揭示其结构与活性之间的关系,为新型杀菌剂的制备和筛选提供理论依据,本研究运用Gaussian 03程序,运用密度泛函理论(DFT)B3LYP方法在6-311G的基组水平上对6种甲酰基硫脲三唑衍生物进行研究, 对这6种化合物的几何构型进行了优化,得到其优化几何、原子净电荷以及分子轨道能量参数。根据优化结果分析了6种化合物的结构特点以及结构和活性之间的关系。计算了6种化合物的红外光谱数据,与实验数据吻合良好。分析结果表明:S(9)原子在化合物的杀菌活性中所起的作用最大,S(9)原子上的电荷越多,化合物的活性越高。     

Synthesis and adsorption properties for Au（Ⅲ） of alkoxycarbonyl thiourea resin

A novel alkoxycarbonyl thiourea resin（ATR） was synthesized by monomer polymerization of oxydiethane-2,1-diyl dicarbonisothiocyanatidate and polyethylene polyamine, and characterized by FT-IR. The adsorption properties of ATR were investigated by batch test. The adsorption capacities for Au（Ⅲ）, Ag（Ⅰ）, Cu（Ⅱ）, Zn（Ⅱ, Fe（Ⅲ）, Ca（ Ⅱ ） and Mg（ Ⅱ ） are 4.65, 4.40, 0.40, 0.90, 0.86, 0.0080 and 0.016 mmol/g, respectively, when the adsorption condition is as follows： contact time 24 h, temperature 30 ℃, initial concentration of Au（Ⅲ） 5.08 mmol/L and that of other metals 0.10 mol/L, and concentration of acid 1.0 mol/L. The adsorption capacity for Au（Ⅲ） increases with the increase of contact time, temperature and initial concentration of Au（Ⅲ）. The capacity after five adsorption-desorption cycles remains 90% that of the first time, and the separation factors of ATR for binary metal ion solutions are larger than 995, indicating that ATR is of good regeneration property and selectivity. XPS results show that the functional atoms of ATR supply electrons for Au and coordinate with Au during the adsorption.     

Relationship between attachment probability and surface energy in adhesion process of gold particles to oil-carbon agglomerates

1　INTRODUCTIONInflotationfield ,someattentionshavebeenpaidtomodelingtheprocessofflotationinordertoobtainadeepunderstandingofhowamineralparticleisat tachedtoabubble .Schulze[1] analyzedtheelementaryprocessesofflotationintermsofphysico chemistry .Anfrunsetal[2 ] studiedthebubble particleattachmentexperimentallyinthecaseofpotentialflow .Solarietal[3] investigatedtheeffectofbubblesizesonadhesionprobability .Polatetal[4 ] estimatedthetruedistribu tionofflotationrateconstantsforafirst orderkin…     

超声波对亚硫酸与氢氧化钙中和反应的影响

研究了不同超声作用方式和功率对亚硫酸与氢氧化钙中和反应的影响。实验结果表明,一定超声功率可以缩短亚硫酸钙成核时间,提高中和反应速度,能有效的降低溶液中Ca2 和SO32-的残留量。为研究超声强化蔗汁硫薰中和反应提供参考。     

冀东地区中生代花岗岩、深部过程与金矿

冀东是中国东部重要的金矿富集区之一,是滨太平洋地区构造－岩浆及成矿作用的重要组成部分,在马兰峪背斜的北冀及其核部形成了一条近NE向的金矿带。按其寄主岩特征主要成为3种类型,从深层至浅层分别是：（1）产于基底－太古宙变质岩中的金厂峪式金矿;（2）产于中生代花岗岩中及其接触带中的峪耳崖式金矿;（3）产于盖层－元古宇长城系和蓟县系灰岩中的冷口式（或万庄式）金矿。这3种金矿的寄主岩石虽然不同,但却有许多相似之处。这些金矿均形成于中生代,空间上与燕山期花岗岩密切相关,矿化特征非常相似之处。边些金矿均形成于中生代,空间上与燕山期花岗岩密切相关,矿化特征非常相似。硫同位素和铅同位素成分显示,金来源于地幔和下地壳,与中生代的岩浆作用有关。金矿在不同地质体中的分布受断裂带的控制,此外,万庄金矿还受喀斯特古溶洞的控制。氢氧同位素资料表明,该地区的成矿流体来源于大气水和岩浆水。该地区的金矿被认为是壳幔物质交换的产物,并且是多阶段金矿化的结果。最后,建立了冀东地区的金矿成矿模式。     

一步法合成硫脲的研究

采用含氮量≥20%的石灰氮(CaCN2)水解物和H2S直接反应,一步法生成硫脲.该反应分两个阶段完成:反应的第一阶段为H2S的吸收过程,受其溶解度的影响,常压下有利反应的温度为35 ℃左右,反应液中除了溶解的H2S和未水解的CaCN2外,主要有Ca(SH)2和H2CN2以及少量副反应生成的尿素;第二阶段主要是Ca(SH)2和H2CN2继续反应,生成CS(NH2)2(硫脲),反应主要受硫脲生成速度的影响,温度宜控制在80～85 ℃,时间不得超过5 h.该法所得硫脲按ZBG17013-88分析为合格产品.     

活性炭从硫脲溶液吸附金的等温线

测定了20,30,40℃条件下活性炭从硫脲原始溶液吸附金的等温线,应用气相吸附的Langmuir方程和Clausius-Clapeyron方程分别计算了饱和吸附量和吸附热。结果表明:(1)在20,30,40℃金的饱和吸附量分别是6.00,9.17,15.4mmol/g,随温度升高而增加;(2)吸附热随活性炭覆盖率增加呈对数关系下降,起始微分吸附热和积分吸附热分别为-9.82和-9.61kJ/mol;(3)被吸附的络离子主要是Au[CS(NH_2_2]~+和Au[CS(NH_2)_2]_2~+,本体系具有化学吸附的性质。