Recovery of valuable metals from a low-grade nickel ore using an ammonium sulfate roasting-leaching process

Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process.The nickel ore was mixed with ammonium sulfate,followed by roasting and finally leaching with water.During the process the effects of the amount of ammonium sulfate,roasting temperature,and roasting time on the leaching recovery of metal elements were analyzed.The optimum technological parameters were determined as follows:ammonium sulfate/ore ratio,0.8 g/g;roasting temperature,400°C;and roasting time,2 h.Under the optimum condition the leaching recoveries of Ni,Cu,Fe,and Mg were 83.48%,76.24%,56.43%,and 62.15%,respectively.Furthermore,the dissolution kinetics of Ni and Mg from the nickel ore was studied.The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ·mol-1,which were consistent with the values of diffusion control reactions.Therefore,the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.     

Pilot scale test of producing nickel concentrate from low-grade saprolitic laterite by direct reduction-magnetic separation

The enrichment of Ni from a low-grade saprolitic laterite ore,which has been pre-treated by high pressure grinding roller（HPGR） to be 74% passing 0.074 mm and contains 0.92% Ni,18.47% Fe,10.61% MgO and 42.27% SiO2,was conducted by using pelletizing,rotary kiln reduction and magnetic separation process on a semi industrial scale,and the effects of reduction duration,mass ratio of coal to pellets（C/P）,the types of magnetic separator,the sections of grinding-separation and the grinding fineness on the recovery of Ni and Fe were examined.It is shown that nickel concentrate containing 3.13 % Ni and 59.20 % Fe was achieved at recoveries of 84.36 % and 71.51% for Ni and Fe,respectively under the following conditions：reducing at （1120±40） ℃ for 120 min,C/P being 1.0,wet grinding of reduced pellets up to 70%-87% passing 0.074 mm and a magnetic field intensity of 238.8 kA/m during the first section of grinding-magnetic separation,and a grinding fineness of 84%-91% passing 0.045 mm and a magnetic intensity of 39.8 kA/m during the second section of grinding-magnetic separation.The enriched Ni containing concentrate has a low content of S and P,and can be used for further processing to produce high-grade ferronickel alloy.     

红土镍矿干燥焙烧工艺条件选择研究

以红土镍矿为原料,用热重分析(TG)和X射线衍射分析(XRD)等方法,对红土铁矿干燥焙烧条件进行研究.结果表明,在矿石粒度为0~3 mm且小于180目颗粒占25%,配焦粉量8%,焙烧温度850℃,焙烧时间90 min,干燥焙烧效果最佳.     

Soda decomposition of low-grade tungsten ore through mechanical activation

Leaching of low-grade refractory tungsten ore was carried out through mechanical activation. The effect of temperature, amount of Na₂CO₃, addition of NaOH, ratio of liquid to solid and leaching time on the recovery of WO₃ was studied. The WO₃ recovery upto 96%–99% has been achieved when the tungsten ore was digested by soda not more than three times stiochiometric amount at 185–195 °C for 1.0–2.0 h. The WO₃ recovery can increase 10%–15% compared to that of conventional soda autoclave process. Project supported by the Key Program of the 8th Five-year Plan of China Synopsis of the first author Zhao Zhongwei, born in 1966, received Ph D degree in 1995. Major research field: hydrometallurgy, seperation science and mechanochemistry.     

Application of response surface methodology in optimizaing the sulfation-roasting-leaching process of nickel laterite

Nickel was recovered from nickel laterite using a sulfation-roasting-leaching process and the effects of operation parameters in-cluding acid addition,roasting temperature,and roasting time on nickel extraction and iron dissolution were investigated using response surface methodology(RSM).Two second-order polynomial models of high significance were presented to show the relationship between the responses and the variables.The analysis of variance(ANOVA) showed high coefficients of determination(R2) of 0.894 and 0.980 for the two models,respectively.Optimum areas of ≥80% Ni extraction and ≥5% Fe dissolution were obtained by the overlaid contours.Verification experiments in the optimum areas were conducted and the results indicate a close agreement with the predicted values obtained from the models.     

Kinetics study of leaching arsenic from Ni-Mo ore roasting in dust mixture of hydrochloric and sulfuric acids

The kinetics of leaching arsenic from Ni-Mo ore roasting dust was investigated. The effects including leaching temperature, particle size of the smelter dust, stirring speed, the coefficient β（the molar ratio of sodium chlorate to arsenic in the smelter dust） and the initial H＋ concentration on leaching arsenic were studied. The results indicate that the leaching of arsenic increases sharply with the decrease of particle size. The orders of reaction with respect to H＋ concentration and particle size are determinted to be 1.136 and 1.806, respectively. The leaching of arsenic reaches 99% under experimental conditions, the apparent activation energy is determined to be 11.157 kJ/mol, which is consistent with the values of activation energy for diffusion model The kinetics equation of leaching arsenic from the roasting dust could be expressed by a semi-empirical equation as 1-2/3η （1 -η）^2/3 = k0（c[H＋]）^1.136ro^-1.806 exp[（-11157 /RT）t].     

Ferronickel enrichment by fine particle reduction and magnetic separation from nickel laterite ore

Ferronickel enrichment and extraction from nickel laterite ore were studied through reduction and magnetic separation. Reduction experiments were performed using hydrogen and carbon monoxide as reductants at different temperatures （700-1000℃）. Magnetic separa- tion of the reduced products was conducted using a SLon-100 cycle pulsating magnetic separator （1.2 T）. Composition analysis indicates that the nickel laterite ore contains a total iron content of 22.50wt% and a total nickel content of 1.91wt%. Its mineral composition mainly con- sists of serpentine, hortonolite, and goethite. During the reduction process, the grade of nickel and iron in the products increases with in- creasing reduction temperature. Although a higher temperature is more favorable for reduction, the temperature exceeding 1000℃ results in sintering of the products, preventing magnetic separation. After magnetic separation, the maximum total nickel and iron concentrations are 5.43wt% and 56.86wt%, and the corresponding recovery rates are 84.38% and 53.76%, respectively.     

Leaching kinetics of low-grade copper ore with high-alkality gangues in ammonia-ammonium sulphate solution

The leaching kinetics of low-grade copper ore with high-alkality gangues was studied in ammonia-ammonium sulphate solution. The main parameters, such as ammonia and ammonium sulphate concentrations, particle size, solid-to-liquid ratio and reaction temperature, were chosen in the experiments. The results show that the increase of temperature, concentrations of ammonia and ammonium sulphate is propitious to the leaching rate of copper ore. The leaching rate increases with the decrease of particle size and solid-to-liquid ratio. The leaching rate is controlled by the diffusion through the ash layer and the activation energy is determined to be 25.54 kJ/mol. A semi-empirical equation was proposed to describe the leaching kinetics.     

Activation pretreatment of limonitic laterite ores by alkali-roasting using NaOH

Activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting to remove Cr,Al,and Si,as well as its effect on Ni and Co extraction in the subsequent pressure acid leaching process w...     

Recovery of zinc from low-grade zinc oxide ores by solvent extraction

1　INTRODUCTIONZincoxideoresarethemainsourceofzincmetalaf terzincsulfideores .Withtheescalatingdepletionofzincsulfideores,zincoxideoresincludingwillemite(Zn2 SiO4 ) ,hemimorphite[Zn4 (Si2 O7) (OH)·H2 O]andsmithsonite (ZnCO3) ,becameanimportantsourceofzinc[1] .InChina,zincoxideoresarerelativelyabundant,whicharemainlystoredinsouthwestandnorth westChi na,suchasYunnan ,Sichuan ,GuangxiandGansuprovince[2 ] .Manystudieshavebeendoneontheconcentrationofzincoxideores,yettheprogressesaresli…     

Nickel extraction from low grade laterite by agitation leaching at atmospheric pressure

This research work deals with the extraction of nickel from a low grade nickel laterite ore, taken from a deposit located in southwestern of Iran, through agitation leaching at atmospheric pressure. The assaying and mineralogical studies carried out on the nickel laterite sample, showed the 0.88% Ni, and principally consisted of oxide and silicate crystalline phases i.e. dolomite, quartz, magnetite, and goethite. Among numerous factors affecting such process, four major parameters i.e. temperature, agitator speed (r/min), leaching agents and their concentration were considered in a two-level full factorial experimental design. The agitation leach tests showed that the ore could be leached at atmospheric pressure with sulfuric acid while citric acid was almost unpromising. Analysis of variance (ANOVA) using DX7 software was employed to identify effective parameters. Sulfuric acid concentration and temperature were the most effective parameters on Ni extraction. Furthermore, the factorial models for experiment responses were developed. The results showed 83% Ni extraction after 4 h leaching, under optimized conditions i.e. temperature at 95 °C, acid concentration at 5 N and agitator speed at 1000 r/min. This study revealed that factorial experimental design can be implemented to identify effective parameters on the agitation leaching process of nickel laterite.     

微乳液萃取分离镍和钻的研究

对曲拉通X-100、正丁醇、正庚烷、水、P204、NaOH微乳液体系进行萃取分离钴和镍的研究。确定了萃取分离钴和镍的最佳工艺条件,在此条件下,钴的萃取率高达87．4％,而钴只有10．87％,镍钴离子浓度的最佳分离范围为1：2．5—1：4,镍和钴的分离效果令人满意。     

Span80-TBP-NaOH体系乳状液膜法富集红土矿浸出液中镍的研究

采用Span80-TBP-NaOH体系乳状液膜法,提取红土矿浸出液中的Ni（Ⅱ）;测定了表面活性剂含量、载体含量、内相试剂浓度、外水相酸度、温度等对提取速率的影响.根据温度对提取速率的影响求出反应的表观活化能,确定了该反应过程的速控类型.在最适分离条件下,做二级提取实验,其提取效果可达90%以上.     

Techniques of copper recovery from Mexican copper oxide ore

Mexican copper ore is a mixed ore containing mainly copper oxide and some copper sulfide that responds well to flotation. The joint techniques of flotation and leaching were studied. The results indicate that an ore containing 19.01% copper could be obtained at a recovery ratio of 35.02% by using sodium sulfide and butyl xanthate flotation. Over 83.33% of the copper oxide can be recovered from the tailings by leaching in suitable conditions, such as 1 h stirring at a temperature around 25 ℃ with a mixing speed of 500 r/min, an H2SO4 concentration of 1.0 mol/L and a mass ratio of the ore-slurry-liquid to solid (mL/mS) of 3. The overall yield of refined ore after flotation and leaching is over 89.18% of the copper, which is much better than sole flotation or leaching. A copper product containing more than 99.9% copper was obtained by using the process: flotation-agitation leaching-solvent extraction-electro-winning.     

Extraction of vanadium from vanadium slag by high pressure oxidative acid leaching

To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw s...     

Technological conditions and kinetics of leaching copper from complex copper oxide ore

The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H₂SO₄ concentration, particle size of crude ore and agitation rate on the leaching efficiency of copper were also evaluated. And the kinetic equations of the leaching process were obtained. The results show that the leaching process can be described with a reaction model of shrinking core. The reaction can be divided into three stages. The first stage is the dissolution of free copper oxide and copper oxide wrapped by hematite-limonite ore. At this stage, the leaching efficiency is very fast (leaching efficiency is larger than 60%). The second stage is the leaching of diffluent copper oxides, whose apparent activation energy is 43.26 kJ/mol. During this process, the chemical reaction is the control step, and the reaction order of H₂SO₄ is 0.433 84. The third stage is the leaching of copper oxide wrapped by hematite-limonite and silicate ore with apparent activation energy of 16.08 kJ/mol, which belongs to the mixed control.     

Carburization of ferrochromium metals in chromium ore fines containing coal during voluminal reduction by microwave heating

Chromium ore fines containing coal (COFCC) can be rapidly heated by microwave to conduct the voluminal reduction, which lays a foundation of getting sponge ferrochromium powders with a lower content of C. Under the conditions of COFCC with n(O):n(C) (molar ratio) as 1.00:0.84 and n(SiO₂):n(CaO) as 1.00:0.39, the samples were heated by 10 kW microwave power to reach the given temperatures and held for different times respectively. The results show that the low-C-Cr ferrochromium metal phase in the reduced materials forms before the high-C-Cr ferrochromium metal phase does. With increasing temperature the C content of ferrochromium metals is in a positive correlation with the content of Cr. The C content of ferrochromium metal in reduced materials is 0–10.07% with an average value of 4.68%. With the increase of holding time the Cr content in ferrochromium metals is in a negative correlation with the content of C, while the content of Fe changes in the contrary way. In the microwave field the kinetic conditions of carburization are closely related with the temperature of microwave heating, holding time and carbon fitting ratio. Foundation item: Project(50474083) supported by the National Natural Science Foundation of China; Project supported by the Baoshan Iron & Steel Co. Ltd. of China