钴镍渣中锌的溶出动力学研究

基于硫酸选择性溶出钴镍渣中金属锌的“腐蚀微电池”作用本质,推导了其溶出反应的动力学方程．建立了钴镍渣中金属锌溶出反应的实验装置,获取了反应温度为15℃时溶出的氢气体积随时间变化的数据．以所建立的动力学方程结合实验数据进行计算,结果表明,硫酸选择性溶出钴镍渣中金属锌并生成氢气的反应,在室温15℃条件下具有一级反应的动力学特征,其表观反应速率常数k＊=0．5617min^-1.     

负催化动力学光度法测定痕量镍的研究

本文研究了稀氨水溶液中,镍(Ⅱ)负催化过氧化氢氧化茜素褪色的新指示反应及其动力学条件,建立了动力学光度法测定痕量镍(Ⅱ)的新方法,证明了本反应为一级反应,速度常数 k=-0.100 min~(-1),半衰期 t_(1/2)=6.93 min,表观活化能既 E_a=252.7 kJ/mol,其 Sandell 灵敏度为2.27×10~(-5)μg/cm~2,线性范围0～0.10μg/25 ml.该法用于测定饮用水和人发中的痕量镍(Ⅱ)获得满意的结果.     

石油加氢废催化剂中钨和镍的提取及镍的酸浸动力学

研究了从石油加氢废催化剂中回收钨、镍的方法,通过正交试验考察了提取钨和镍的最佳工艺条件,并对镍的浸出过程动力学进行了研究.结果表明:当Na2CO3的用量是WO3理论量的6倍,在750℃下钠化焙烧4h,焙料在90℃下水浸2h,WO3的浸出率可达到95%以上;镍富集在浸出渣中,在硫酸质量分数为30%,固液比为1∶8,85℃下浸出4h,催化剂中镍的浸出率可达到98%以上;镍的浸出过程属于扩散控制模型,与扩散控制动力学方程式相吻合,浸出反应的表观活化能为15.95kJ/mol.     

CaO在红土镍矿直接还原焙烧中的作用机理

以Ni和Fe质量分数分别为1.46%和26.68%的红土镍矿为研究对象,进行直接还原焙烧-磁选试验研究,并对焙烧矿进行X线衍射(XRD)与扫描电镜(SEM)分析以研究CaO的作用机理。研究结果表明:使用含CaO的组合添加剂能够达到磁选精矿中镍质量分数为8.58%、回收率为88.15%的最佳试验效果。在直接还原焙烧过程中,添加的CaO能够在焙烧过程中与硅酸盐矿物反应生成辉石、提高含镍硅酸盐的反应活性、促进镍的还原并且能够降低还原过程中NiO与SiO2结合的概率,提高镍的回收率。     

热处理对黑色岩系镍钼矿富集的影响

为给镍钼矿的选-冶结合提供理论依据,通过对镍钼矿原矿与在800℃中性焙烧1.5 h后镍钼矿进行X线衍射(XRD)分析;在空气气氛与氩气气氛中对镍钼矿进行差热与热重分析,并对原矿和焙烧预处理矿进行浮选实验.研究结果表明:在300～800℃,有氧参与的空气气氛中,镍钼矿中有机质不断燃烧,差热分析(DTA)曲线产生很大的放热峰,质量损失率达20%;而在氩气气氛中,主要发生挥发、硫化、化合等反应,放热峰很小,质量损失率为18%;当温度高于800℃时,空气气氛中一直发生分解反应;而氩气气氛中,当温度超过1 320℃时,分解反应完成,开始出现化合反应;焙烧预处理后的镍钼矿更易于浮选,精矿钼品位提高0.88%,回收率提高7.91%.     

活化焙烧强化盐酸浸出红土矿的镍

通过X线衍射、红外光谱、差热、扫描电镜和液氮吸附等方法考察活化焙烧对红土矿矿相结构变化和有价金属浸出的影响。研究结果表明:该矿在277℃左右发生了针铁矿脱水转变为赤铁矿,在610℃发生蛇纹石去羟基化作用,该结果与通过XRD表征的在不同温度下进行焙烧的矿石中主要矿相的晶型转变结果一致;矿物在300℃焙烧时,比表面积为21.04 m2/g,在610℃焙烧时,比表面积为26.45 m2/g,比原矿的比表面积16.03 m2/g有较大提高,有助于后续的浸出过程;在300℃焙烧后,矿样浸出可以获得最大的镍浸出率,达93%,而铁的浸出减少,进一步升高焙烧温度不利于有价金属镍的浸出。     

红土镍矿选择性还原-熔分制备镍铁合金

以硅镁型红土镍矿为原料,采用金属化焙烧-熔分工艺,通过正交试验制备金属化球团,将所得金属化球团在1500℃条件下熔融分离30min提取镍铁合金,考察影响因素对实验结果的影响.结果表明:在选择性还原制备金属化球团过程中,对金属化率的影响程度从大到小的因素依次是C/O摩尔比、焙烧温度、焙烧时间和碱度;实验可获得镍品位19%的镍铁合金;在碱度为0.8~1.2范围内,S和P分配比随着碱度的升高而增大.利用X射线衍射和扫描电镜对金属化球团及熔融分离出的渣进行微观分析,发现加入的石灰石与复杂矿相反应可释放出简单镍氧化物和铁氧化物,促进还原反应的进行,当石灰石不足时,少量铁以Fe3+的形式存在于铁金属化率70%的金属化球团中.     

硫化镍精矿焙烧动力学研究

用沸腾床研究了金川硫化镍精矿和天然纯镍黄铁矿焙烧动力学。利用H_2O_2溶液吸收SO_2、测其电导率、自动记录焙烧曲线。求得两种矿物的表面活化能分别为174.4和109.6kJ/mol。焙砂经电镜检验表明:进行部分氧化焙烧时,两种矿的镍黄铁矿粒内都发生铁向外、镍向内的金属离子逆向迁移。铁的硫化物优先氧化,形成铁的氧化物壳层,而镍则富集在矿粒内部,与硫共存,不氧化。     

煤种对红土镍矿中镍选择性还原的影响机理

以某含镍1.86%(质量分数)、铁13.24%(质量分数)的红土镍矿为对象,分别采用石煤和无烟煤作为还原剂,考察了煤种对红土镍矿中镍的选择性还原的影响.结果表明,用石煤作为还原剂能够达到镍选择性还原的目的.X射线衍射及扫描电镜分析研究表明,还原过程中镍、铁先以镍纹石形式存在,随着煤用量增加,逐渐变为以铁纹石形式存在.同时随着煤用量的增加,焙烧后生成的含镍铁矿物中镍的比例逐渐递减,而铁的比例逐渐递增.石煤为还原剂时焙烧产物中主要以镍纹石的形式存在,同时金属铁的生成量比无烟煤作还原剂时低,因此采用石煤作还原剂比无烟煤作还原剂对镍还原具有更强的选择性,可以得到更高镍品位的镍铁精矿.     

红土镍矿镍和铁的综合回收试验

多米尼加某红土镍矿属强烈氧化的含镍酸性铁矿石,矿石中主要含有褐铁矿、石英、氧化铝和氧化镁等矿物.采用硫酸常压浸出-黄钠铁矾沉铁工艺对该红土镍矿进行湿法回收工艺研究.研究结果表明:镍、铁的浸出率分别为91.95％和67.96％;经黄钠铁矾法沉淀分离和焙烧工艺能够获得Fe品位为55.56％的氧化铁产品,且镍和铁的总回收率分别达到89.39％和67.46％.     

红土镍矿微波水热法浸提镍钴

采用微波水热盐酸浸出方法对腐泥土型红土镍矿提取镍钴进行了研究,详细探讨了焙烧预处理、微波水热浸出温度和浸出时间对镍钴浸出率的影响.对于300℃焙烧预处理后的红土镍矿,微波水热温度为50℃,浸出时间为1 h时,镍的浸出率高达93.65%,钴的浸出率为87.86%.红土镍矿的微波水热浸出体系与普通水热浸出体系相比,镍和钴的浸出效果更好.研究表明,扩散过程是镍、钴浸出过程的主要限制环节.     

Process development for the direct solvent extraction of nickel and cobalt from nitrate solution: aluminum,cobalt, and nickel separation using Cyanex 272

A direct solvent extraction (DSX) process for purifying nickel and cobalt from the nitric acid leach solution of nickel laterite ores was conceived and experimentally probed. The proposed process consists of two solvent extraction (SX) steps but with only one extractant-bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex® 272)-used in both steps. The first extraction step involved the removal of aluminum and zinc, whereas the second extraction step involved the separation of cobalt along with manganese from nickel. The experimental results showed essentially quantitative removal of aluminum (>97%) and zinc (>99%) in a single extraction stage using 20vol% Cyanex 272 at pH 2.1. Some cobalt (32%) and manganese (55%) were co-extracted but were easily scrubbed out completely from the loaded organic phase using dilute sulfuric acid at pH ≤ 1.38. Cobalt and manganese in the first extraction raffinate were extracted completely in four extraction stages at staggered pH values of 4.0, 4.4, 4.5, and 4.0 in the first, second, third, and fourth stages, respectively, using also 20vol% Cyanex 272. A small amount of nickel (up to 6.6%) was co-extracted but was easily scrubbed out completely with dilute sulfuric acid at pH 2.0. A flow diagram showing the input and output conditions and the metals separated under the deduced optimum conditions is presented.     

蛇纹石型红土矿常压酸浸实验研究

主要探讨了常压下盐酸对蛇纹石型红土镍矿进行浸出的工艺条件。考察了酸矿比、液固比、反应温度、反应时间等对蛇纹石型红土镍矿浸出的影响。通过实验得出最佳工艺条件:酸矿比为2.5∶1、液固比为5∶1、反应时间为0.5 h、反应温度为100℃。在此条件下镍、钴、铁浸出率分别为100%、100%和90%。     

5709萃取镍(Ⅱ)的宏观动力学研究

采用改进的恒界面池进行了异己基磷酸（１－甲基－庚基）酯（国内代号５７０９）－正庚烷体系从硫酸介质中萃取镍（Ⅱ）的动力学研究，以实现钻、镍的萃取分离。研究了水相中镍浓度， ｐＨ值和有机相中 ５７０９的浓度，两相内搅拌器的转速，两相界面积和操作温度对镍（Ⅱ）萃取传质的影响。采用热力学方法处理了实验数据，并建立了相应的数学模型。结果表明，水相中镍离子的扩散和镍的１－２络合物生成的界面化学反应为主要控制步骤。     

红土镍矿非自由水脱除热分析动力学

在升温速率分别为10、15、20和25℃·min-1的条件下,利用差示扫描量热仪对红土镍矿非自由水脱除过程进行了测试.针对测试数据,分别采用Flynn-Wall-Ozawa ( FWO)法、胡荣祖-高红旭-张海( HuGZ)法、Boswell法、Starink法、Friedman-Reich-Levi ( Friedman)法等不同的转化率法计算其活化能,利用Malek法计算指前因子( A)以及确定机理函数,最后利用所得的动力学公式推导出等温下反应进度与时间的关系并对不同温度下的能耗进行分析比较.红土镍矿非自由水脱除过程的平均活化能为181.50 kJ·mol-1;指前因子lnA为21.95 min-1;机理函数符合Z-L-T方程,即脱除过程为三维扩散控制机制;干燥温度越高所需的平均功率越小.     

Synthesis and characterization of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> prepared from atmospheric pressure acid leach liquors of nickel laterite ores

A chemical precipitation-thermal decomposition method was developed to synthesize Co₃O₄ nanoparticles using cobalt liquor obtained from the atmospheric pressure acid leaching process of nickel laterite ores. The effects of the precursor reaction temperature, the concentration of Co2+, and the calcination temperature on the specific surface area, morphology, and the electrochemical behavior of the obtained Co₃O₄ particles were investigated. The precursor basic cobaltous carbonate and cobaltosic oxide products were characterized and analyzed by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, specific surface area analysis, and electrochemical analysis. The results indicate that the specific surface area of the Co₃O₄ particles with a diameter of 30 nm, which were obtained under the optimum conditions of a precursor reaction temperature of 30℃, 0.25 mol/L Co2+, and a calcination temperature of 350℃, was 48.89 m2/g. Electrodes fabricated using Co₃O₄ nanoparticles exhibited good electrochemical properties, with a specific capacitance of 216.3 F/g at a scan rate of 100 mV/s.     

Generation process of FeS and its inhibition mechanism on iron mineral reduction in selective direct reduction of laterite nickel ore

Numerous studies have demonstrated that Na₂SO₄ can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na₂SO₄ is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that Na₂S formed by the reaction of Na₂SO₄ with CO reacts with SiO₂ at the FeO surface to generate FeS and Na₂Si₂O₅. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.     

红土镍矿焙烧过程中的矿相转变及其对气体还原的影响

研究了印度尼西亚红土镍矿焙烧过程中的矿相转变过程以及焙烧温度对混合气体 (V (CO) : V (O₂)=50 : 50)还原的影响. 采用差热/热重分析(differential scanning calorimeter/thermal gravimetric, DSC/TG)、比表面积分析法(Brunauer Emmett Teller, BET)、X射线衍射(X-ray diffraction, XRD)、扫描电镜(scanning electron microscope, SEM)等方法综合考察了各因素对红土镍矿焙烧过程及其对后续还原的影响. 结果表明: 在焙烧阶段, 红土镍矿中的针铁矿在 300°C 左右脱除结晶水形成赤铁矿, 600~700 °C时蛇纹石分解形成无定形态硅镁酸盐, 且当温度继续升高时无定形态硅镁酸盐会结晶形成橄榄石; 利用混合气体 (V (CO) : V (O2)=50 : 50)还原红土镍矿时, 随着焙烧温度的升高, 镍和铁的金属化率也逐渐升高, 经700°C焙烧后, 还原产物镍的金属化率最高可达86.81%, 但是当焙烧温度超过橄榄石结晶温度时则不利于红土镍矿的还原, 镍的金属化率降至66.73%.     

Dechlorination of 2,4-dichlorophenol by nickel nanoparticles under the acidic conditions

Metal nanoparticles are effective for remediation of contamination with a range of compounds including chlorinated organics.However,the sorption process of the passivation oxide layers on the metal nanoparticle surfaces may result in incomplete degradation of contaminants.This phenomenon can be prevented by an acidic washing procedure or reaction in an acidic medium.In this paper,nickel nanoparticles manufactured via the carbonyl powder process were analyzed using scanning electron microscopy,transmission electron microscopy,X-ray diffraction and energy-dispersive X-ray spectroscopy.The sorption and degradation of 2,4-dichlorophenol (2,4-DCP) by nickel nanoparticles under acidic conditions was then investigated.Transmission electron microscopy and XRD results showed that the nickel nanoparticles range in size from 10 to 20 nm,and a thin passivation layer of NiO is present on the surface.This oxide layer can be removed by pretreatment washing with acidic solutions.It was indicated that dechlorination was the key reaction pathway for degradation of 2,4-DCP by nickel nanoparticles under acidic conditions.The main degradation products were 4-Chlorophenol,2-Chlorophenol,and Phenol,and among these,Phenol was dominant.The acidic medium promoted degradation by providing an appropriate pH,and H+ may be involved in the reaction.Dechlorination of 2,4-DCP by nickel nanoparticles under the acidic condition follows the second order kinetic model,and the rate constants at 298,306,316 K are 0.02,0.2 and 0.3 (g L h)-1,respectively.     

CaF2强化红土镍矿自还原过程中金属相聚集长大行为

针对高镁高硅型中低品位红土镍矿,采用煤基自还原-细磨-磁选工艺制备镍铁粉,研究了内配碳比对红土镍矿中铁、镍氧化物自还原的影响,CaF_2对红土镍矿自还原过程中氧化物的还原、金属相的析出及聚集长大的影响规律。研究表明在CaF_2作用下通过降低内配碳比可抑制氧化铁的还原,从而获得镍品位较高的镍铁粉,但相应牺牲镍的回收率;CaF_2能与红土镍矿中高熔点的硅酸盐脉石通过固相反应生成低熔点的透闪石(Ca_2Mg_5(Si_4O_(11))_2F_2),使硅酸盐矿物结构由岛状转变为链状,提高硅酸盐矿物反应活性,促进镍、铁氧化物的还原;通过降低红土镍矿脉石相的熔化性温度,CaF_2能明显强化红土镍矿自还原过程中金属相的析出、聚集和长大,促进镍铁与脉石的有效分离,从而大幅度提高镍铁粉中镍和铁的品位及金属元素的回收率。