Sulfuric acid leaching kinetics of South African chromite

The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching con- ditions. The dimensionless change in specific surface area and the conversion rate of the chromite were observed to exhibit a proportional re- lationship. A modified shrinking particle model was developed to account for the change in reactive surface area, and the model was fitted to experimental data. The resulting model was observed to describe experimental findings very well. Kinetics analysis revealed that the leach- ing process is controlled by a chemical reaction under the employed experimental conditions and the activation energy of the reaction is 48 kJ.mol-1.

Kinetic study of high-pressure acid leaching of Mg and Ni from serpentine

Inner Mongolian serpentine ore was subjected to sulfuric acid leaching tests,and the effects of the leaching process parameters on the leaching efficiency of different metals were investigated.The leaching efficiency of Mg,Fe,Al,Ni,and Co reaches 93.98%,60.09%,82.08%,90.58%,and 94.06%,respectively,under the leaching conditions of 5 mol/L H_(2)SO_(4),liquid/solid ratio of 4 mL/g,and leaching temperature 100℃.Hence,the valuable metals in serpentine were effectively recovered by sulfuric acid leaching.The leaching behaviors of Mg,Fe,and a small amount of Al were analyzed using X-ray diffraction.The results show that the unreacted Mg and Fe remained as MgFe_(2)O_(4),and Al formed Al_(2)Si_(2)O_(5)(OH)_(4) in the leaching residue.The kinetics of Mg and Ni in the leaching process was studied respectively.The leaching kinetics of Mg conformed to the shrinking core model with an activation energy of 16.95 kJ/mol,which was controlled by the combination of the diffusion and chemical reaction.The leaching kinetics of Ni accorded with the Avrami equation with an activation energy of 11.57 kJ/mol,which was controlled by diffusion.In the study,the valuable metal elements were extracted from serpentine minerals with high efficiency and low cost,which possessed important practical values.

Leaching process and kinetics of manganese in low-grade manganese ore

Manganese was extracted from leaching low-grade manganese ore in sulfuric acid medium. The effects of granule diameter, leaching time, liquid/solid ratio (V/W) and the concentration of sulfuric acid were investigated through orthogonal and single factor experiments. The experimental results showed that the optimal leaching conditions are, size of 0.054mm, 120 minutes of reaction time, 3(V/W) of liquid/solid ratio and 30% of the concentration of sulfuric acid (g/g). Under those conditions, the leaching efficiency is 96.73%. The kinetics of the leaching process is in accordance with the characteristics of fractal reaction.

Kinetics of nickel leaching from roasting-dissolving residue of spent catalyst with sulfuric acid

Sulfuric acid leaching process was applied to extract nickel from roasting-dissolving residue of a spent catalyst, the effect of different parameters on nickel extraction was investigated by leaching experiments, and the leaching kinetics of nickel was analyzed. The experimental results indicate that the effects of particle size and sulfuric acid concentration on the nickel extraction are remarkable; the effect of reaction temperature is mild; while the effect of stirring speed in the range of 400-1 200 r/min is negligible. Decreasing particle size or increasing sulfuric acid concentration and reaction temperature, the nickel extraction efficiency is improved. 93.5% of nickel in residue is extracted under suitable leaching conditions, including particle size （0.074-0.100） mm, sulfuric acid concentration 30% （mass fraction）, temperature 80 ~C, reaction time 180 min, mass ratio of liquid to solid 10 and stirring speed 800 r/min. The leaching kinetics analyses shows that the reaction rate of leaching process is controlled by diffusion through the product layer, and the calculated activation energy of 15.8 kJ/mol is characteristic for a diffusion controlled process.

Extraction of Alumina from Coal Fly Ash with Sulfuric Acid Leaching Method

Coarse γ-Al2O3 powder was prepared through acid leaching,solid-liquid separation,crystallizing and aluminum sulfate decomposing processes using coal fly ash and concentrated sulfuric acid as raw materials.The metallurgy level Al2O3 can be obtained by disposing coarse γ-Al2O3 powder with Bayer process.The optimum conditions of acid leaching process were determined by experiments.The extraction rate of Al2O3 can be stabilized at about 87% under these conditions.The thermodynamics and kinetics of sulfuric acid leaching process were studied with irreversible thermodynamics.

含钴三元硫化物常压硫酸浸出钴的动力学研究

开展含钴三元硫化物常压硫酸浸出的实验研究。考察搅拌速度、浸出温度、硫酸浓度和粒度对钴浸出率的影响,并分析从含钴三元硫化物中浸出钴的动力学。结果表明,在最佳条件下,钴和铁被选择性浸出,且浸出率均大于99%,而钼和铜则富集于浸出渣。通过对实验数据的分析可知,钴的浸出符合由固体产物层产生的收缩核模型,且浸出过程受内扩散控制。浸出反应的活化能为49.86k J/mol,硫酸浓度和粒度的反应级数分别为0.57和-1.4。

拜耳法赤泥中钪、钇浸出行为及动力学研究

采用两步酸浸法浸出赤泥中的钪和钇,用磷酸对赤泥进行一段酸浸,实现脱碱和脱硅并富集稀土金属钪、钇;用硫酸对磷酸浸出渣进行二段酸浸,考察了硫酸浓度、液固比、反应温度、反应时间对钪、钇浸出过程的影响,并进行了浸出动力学分析。结果表明,赤泥经磷酸浸出后,脱碱和脱硅效果较好,K、Na、Si浸出率分别为75.62%、87.82%、80.25%;在硫酸浓度2.5 mol/L、液固比7∶1、反应温度70℃、反应时间45 min条件下进行二段硫酸浸出,Sc、Y平均浸出率分别为74.49%、80.02%。Sc和Y的硫酸浸出过程均符合多相液固区域反应模型,受扩散控制,表观反应活化能分别为18.50 kJ/mol和16.74 kJ/mol。

废旧磷酸铁锂电极粉中Li和Fe同步浸出动力学研究

废旧磷酸铁锂中有价组分高值化回收和利用具有资源循环和环境保护双重意义。对废旧磷酸铁锂电极粉的浸出过程进行了条件优化和动力学研究,系统探究了硫酸浓度、反应温度、电极粉粒径及搅拌速度对Li和Fe浸出行为的影响,并阐明了Li和Fe的浸出动力学机理。结果表明:在硫酸浓度2.5 mol/L、浸出温度75℃、粒径0.14 mm左右、搅拌速率400 r/min的条件下,Li和Fe的浸出率均在99.8%以上。动力学研究表明浸出过程受外扩散控制,浸出动力学方程符合Avrami模型,浸出过程中Fe和Li的表观活化能分别为11.03、8.45 kJ/mol。废旧磷酸铁锂电极粉中Li和Fe的浸出动力学机理结果可为有价元素的同时提取提供理论指导。

电解锰渣中锰的浸出行为与动力学分析

研究了用硫酸浸出电解锰渣中的锰,通过单因素试验和正交试验优化了工艺参数,并对电解锰渣浸出前后的物相、结构、形貌,以及浸出锰动力学进行了分析,建立了锰浸出模型,探究了浸出机制。结果表明:在粒径200目、搅拌速度为400 r/min、浸出温度95℃、硫酸浓度1.5 mol/L、浸出时间120 min、液固体积质量比11/1优化条件下,Mn浸出率达97.90%;锰浸出动力学符合液-固未反应收缩核模型,受化学反应控制;在浸出锰过程中,可以通过控制液固体积质量比、温度提高Mn浸出率。

蛇纹石酸浸渣碱溶脱硅反应动力学

以蛇纹石酸浸渣为原料,系统研究了碱溶脱硅反应动力学。通过X射线衍射(XRD)、X射线荧光(XRF)、热重-差热(TG-DTA)和场发射扫描电镜-能谱(FESEM-EDS)对蛇纹石酸浸渣物相、化学组成、热稳定性及形貌结构进行了详细分析。利用单因素变量法对蛇纹石酸浸渣碱溶脱硅反应过程进行了研究,详细讨论了NaOH质量分数、反应温度、液固比、搅拌速度和粒度对酸浸渣中SiO_(2)溶出率的影响,并分别采用收缩核模型及Avrami方程拟合动力学,并建立了反应动力学方程。结果表明:在该体系中,蛇纹石酸浸渣碱溶过程动力学不符合传统的收缩核模型,而符合Avrami方程且拟合相关性较高;整个溶出过程受扩散控制,模型特征参数n_(1)=0.21,反应表观活化能E_(a)=8.62 kJ/mol。

废三元锂离子电池正极材料脱锂渣的淀粉还原浸出动力学

以淀粉为还原剂从废三元锂离子电池(LIBs)正极材料脱锂渣中回收Ni、Co和Mn,并研究其浸出动力学和机理。系统地研究搅拌速率、浸出温度、H_(2)SO_(4)浓度和淀粉用量对Ni、Co和Mn浸出率的影响。结果表明,在搅拌速率为500 r/min、硫酸浓度为1.5 mol/L、淀粉用量为6 g/L、浸出温度为80℃和浸出时间为60 min的优化条件下,Ni、Co和Mn的浸出率分别达到98.07%、96.52%和98.06%。根据冶金过程液固反应动力学模型,脱锂渣的浸出动力学可以用化学反应控制的未反应收缩核模型很好地进行描述。在浸出反应中,Ni、Co和Mn的表观反应活化能分别为93.32、102.84和95.68 k J/mol,H_(2)SO_(4)的表观反应级数分别为0.9225、1.0335和1.1285。淀粉容易制取、成本低,可取代传统还原剂用于从废三元锂电池中提取有价金属。

含氟助浸剂对石煤提钒酸浸动力学的影响

在石煤酸浸提钒工艺中,添加助浸剂可明显改善钒的浸出效果。采用液-固多相反应的未反应核收缩模型研究含氟助浸剂对石煤焙烧样中钒浸出动力学的影响,采用X射线衍射仪、扫描电镜以及比表面积测定仪对试样浸出前后结构进行表征。动力学试验与计算结果表明:加入含氟助浸剂后钒浸出反应的表观活化能由58.25 kJ/mol降为22.77 kJ/mol,硫酸反应级数由1.047 1降为0.535 7。结构分析表明含氟助浸剂的加入加剧了对矿物结构的破坏,增大试样的比表面积及孔隙通道,从而使钒更容易浸出。

蛇纹石硫酸浸出过程动力学研究

首先确定了蛇纹石硫酸浸出过程中影响浸出速率的主要因素，以此为条件，对蛇纹石中ＭｇＯ的浸出速率进行了研究．结果表明：ＭｇＯ的浸出动力学能适用容积反应模型，其浸出速率可表示为样品中残留ＭｇＯ量的二级反应，其表观活化能约为９３．２０ｋＪ／ｍｏｌ，属化学反应控制．

石煤灰渣酸浸提钒工艺中钒的浸出动力学

采用液-固多相反应的缩芯模型研究了石煤灰渣中V2O5的浸出动力学,考察了酸浸温度、硫酸浓度对V2O5浸出反应速率的影响.结果表明,在实验温度范围内,V2O5的浸出过程为固膜扩散控制,浸出反应的表观活化能为29.96kJ/mol.当硫酸浓度小于6mol/L时,浸出属化学反应控制过程;当硫酸浓度大于6mol/L时,浸出过程为固膜扩散控制,其表观反应级数为1.199.提高酸浸温度可提高V2O5的浸出率;在硫酸浓度小于6mol/L时提高硫酸浓度,可提高V2O5的浸出率;而高于该值提高硫酸浓度对V2O5浸出率的提高无明显作用.

热酸浸出黄钠铁矾渣工艺

以黄钠铁矾渣为原料,研究硫酸浸出过程的工艺条件,分析浸出过程的热力学和动力学机理.实验结果表明,在液固比为5∶1,搅拌速率为350 r/min条件下,浸出黄钠铁矾渣的最佳工艺条件为:硫酸质量浓度为225 g/L,反应温度为95℃,反应时间为2.5 h,该条件下多组实验的渣中Fe、Zn浸出率均大于96%.黄钠铁矾渣硫酸浸出过程在动力学上属于收缩核模型,受化学反应控制.

硫化铟常压硫酸浸出动力学研究

用人工合成的硫化铟模拟实际硫化铟,通过测定不同物料粒度、不同反应温度、不同硫酸浓度和不同浸出时间下铟的浸出率,进行了硫化铟常压硫酸浸出的动力学研究。结果表明:硫化铟常压硫酸浸出过程符合晶粒参数n为0.576的Avrami模型,受化学反应和扩散混合控制;由于化学反应较快,因此要提高铟的浸出效率,应设法强化扩散效应。

废催化剂焙烧水浸渣中硫酸浸取钴的动力学研究

以废催化剂处理过程中得到的镍钴渣为研究对象,采用硫酸浸出镍钴渣,使钴和镍得到有效回收,并对硫酸浸出钴的动力学进行探讨。研究结果表明:搅拌速度为400～1200r/min时对钴浸出率的影响非常小,物料粒度、硫酸浓度和反应温度等因素对钴浸出率则有较大影响;当反应温度为80℃,反应时间为180min,原料粒度为(0.074～0.100)mm,H2SO4浓度为6mol/L,搅拌速度为800r/min,固液比为1:10时,钴的浸出率为94.2%,镍的浸出率则为93.5%;硫酸浸出镍钴渣的反应受产物层内扩散控制,表观活化能为16.34kJ/mol。

硫酸浓度对蛇纹石中氧化镁浸出反应速率的影响

研究了硫酸浓度对蛇纹石中 Mg O浸出反应速率的影响 ,并建立蛇纹石中 Mg O的浸出反应速率表达式 :(1 )当硫酸用量大量过量时 ,浸出反应速率方程式为 r Mg O=k1 · cm H· cn Mg O,其中反应级数 m、n分别为 m=0 .2 0～ 0 .2 4、n=2 ,反应的表观活化能在 85～ 95k J/ mol范围 ;(2 )工艺浸出条件下 ,其浸出反应速率方程式可表示为 dr Mg O/ dt=k2 · (7.1 4 4 -3 .4 0 r Mg O) 0 .2 2 6· (1 -r Mg O)

蛇纹石硫酸浸出过程工艺条件的优化研究

硫酸浸出过程是蛇纹石综合利用过程中的关键因素之一 ,在单因素条件实验的基础上 ,采用 L16( 4 4)正交实验法对蛇纹石硫酸浸出过程的优化工艺条件进行了研究。结果表明 :当以矿粒粒径 <75μm、搅拌速率 >2 0 0 r/min、活化剂 FS-1加入量为 1.5 %为固定因素时 ,其优化工艺条件为 :浸出温度 10 0℃ ,浸出时间 3h,硫酸质量浓度为 45 % ,液固比 4.0。

高硅低品位氧化锌矿的酸浸动力学

针对高硅天然氧化锌矿常规处理时存在的矿浆难压滤、液固比过小、Zn浸出回收率低等问题，试验探讨了酸度、加酸方式、固液比、粒度及温度因素对锌浸出率的影响。结果表明：固液比1：6时，0．15～O．212mm粒级在常温下与浓度为8％的H2SO4反应120min，锌的浸出率可达96．07％。升高温度，Zn的浸出率可提高至99．02％。浸出过程可用收缩未反应核模型来解释，即浸出率与动力学方程1-（1-α）^1/3～k·t相吻合。浸出动力学显示反应过程中可通过控制矿物表层的扩散来控制反应过程的速率。活化能是控制扩散过程的特征，其值约为6．385kJ／mol。