机械活化强化矿物浸出过程的研究进展

综述了近10年来国内外关于机械活化强化矿物浸出的研究工作,包括机械活化对矿物原料性质的影响,对强化矿物浸出的效果及作用机理,强化矿物浸出反应动力学.最后对机械活化的研究发展前景进行了展望.     

机械活化方式对攀枝花钛铁矿浸出强化作用

对滚筒球磨、行星球磨和搅拌球磨不同设备机械活化攀枝花钛铁矿及其浸出反应进行了研究.结果表明,机械活化可以强化钛铁矿的浸出过程,搅拌磨强化浸出的效果最好,行星磨次之,滚筒磨最差.活化后的钛铁矿浸出活性与其晶胞在c轴方向的显微应变增大有关,而与a轴和b轴方向的显微应变关系不大.搅拌磨活化时能产生更细小的矿物颗粒,在c轴方向有更大的显微应变以及在颗粒表面有更高的表面活性,浸出活性更高.钛铁矿的浸出效果与有效的活化效果有关,而活化效果与机械力的强度和类型都有关.     

机械活化对氧化锌矿碱法浸出及其物化性质的影响

研究了不同活化时间、活化方式对云南兰坪低品位氧化锌矿碱法浸出的影响. 结果表明,当浸出液NH4Cl浓度2.0 mol/L、NH3×H2O浓度1 mol/L、温度30℃、浸出液与浸出矿样液固比为10 L/g时,未活化矿样浸出90 min浸出率仅为60.08%,而活化90 min矿样浸出90 min的浸出率为69.36%,为可浸出含锌物相的103.97%;先磨后浸的强化效果优于边磨边浸. 不同活化时间、活化方式不仅造成矿物的形貌、粒度分布不同,而且使矿样在球磨过程中的物相转化存在差异：活化与浸出步骤分离时,球磨过程发生了机械化学反应,矿样中ZnS被氧化成利于浸出的物相,从而比两步骤合并的浸出效果好.     

锂辉石-氧化钙烧结法提锂的物相重构与动力学

对锂辉石-氧化钙烧结过程进行热力学分析,绘制了各反应Gibbs自由能与温度的关系图。结果表明,Al₂O₃会优先和Na₂O、Li₂O、K₂O反应,然后与CaO反应生成CaO·Al₂O₃,而且烧结温度需高于1060℃以保证LiAlSi₂O₆能够完成晶形转变。并探讨了锂辉石-氧化钙烧结法提锂的反应机理。考察了不同烧结条件对锂浸出率的影响并对熟料进行X射线衍射（XRD）分析表征。实验结果表明,在配料比为1∶1.25、烧结温度1150℃、烧结时间60min时,锂的浸出率达到92.14%,熟料中的主要物相为Ca₂SiO₄与LiAlO₂。利用XRD和扫描电镜-能谱联用仪（SEM-EDS）对熟料与浸出渣的物相、显微形貌及元素分布情况进行了分析表征。为了确定烧结反应的控制性步骤,在最优烧结条件的基础上对烧结过程进行动力学分析,结果表明,锂辉石-氧化钙烧结体系属于球形颗粒三维界面化学反应控制,烧结过程的动力学拟合方程为\mathrm{1}-{(\mathrm{1}-x)}^{\mathrm{1}/\mathrm{3}}=\mathrm{0.00677}t。     

机械活化强化锌焙砂中锌的浸出

锌精矿焙烧阶段产生的铁酸锌(ZnFe₂O₄)是一类具有尖晶石结构的复合氧化物,性质稳定,不溶于稀酸和碱,在常规浸出条件下,仍有20%的锌以铁酸锌的形式存在于锌浸渣中,导致锌精矿焙烧产物的锌浸出率不高,一般为80%左右。机械活化具有使矿物晶格产生缺陷,降低反应对温度、酸浓度等条件依赖程度的优点。因此,本文采用机械活化对锌焙砂进行预处理,以硫酸为浸出剂,研究了机械活化时间、球料比、硫酸浓度、液固比、温度对锌的浸出率及其他杂质离子的影响规律。结果表明：锌的浸出率随机械活化时间的延长呈现出先增大后降低的趋势。机械活化(H₂C₂O₄·2H₂O与锌焙砂的质量比为3.60%,球料比为2∶1,球磨时间10min)-酸浸(70g/L H₂SO₄,液固比为10∶1,温度为35℃)工艺结果表明,锌的浸出率为87.61%,与未机械活化时相比(82.59%),锌的浸出率提高5个百分点。机理分析表明,机械活化使锌焙砂颗粒粒径变小,产生晶格畸...     

机械活化强化二氧化硫脲漂白高岭土的试验研究

以星子高岭土为原料,在常温弱碱(T=25℃,p H=8)条件下采用机械活化强化二氧化硫脲(TD)漂白高岭土。考察了活化时间、行星磨转速和TD用量对高岭土除铁效果的影响。采用X射线衍射、扫描电镜表征试样,结果表明:机械活化强化TD漂白高岭土中的最佳条件为:TD用量为高岭土质量的0.6%,转速为400 r/min的行星磨球磨处理时间120 min。此时,铁的去除量可达2.51 mg/g,烧成白度可达75.18%,比原矿提高10.95%。     

铜尾矿浮选明矾石精矿中有价元素直接碱浸动力学及过程强化

作为一种多元素矿物,紫金山铜尾矿浮选明矾石精矿有望成为铝、钾和镓等元素的替代资源。相对于传统工艺,KOH溶液直接浸出明矾石精矿可以避免高能耗的热分解过程,同时降低杂质离子的干扰。本工作研究了铜尾矿浮选明矾石精矿在KOH溶液中的直接浸出行为特性,重点研究了不同碱浓度和温度下精矿中多元素浸出率随时间的变化规律,并结合动力学分析阐明了精矿直接碱浸反应的控制步骤;在此基础上,引入机械活化促进精矿中有价元素的高效浸出。结果表明,在实验条件下精矿直接碱浸过程中仅发生明矾石相的分解;提高KOH浓度和浸出温度可使元素浸出速率快速增加;根据经典的液-固反应收缩核模型的动力学理论,分析发现浸出反应符合化学反应步骤控制。机械活化使精矿粒径降低、比表面积增加、非晶化程度提高,从而使精矿的反应活性增强,使铝、钾和镓的浸出速率提高。     

机械活化固相共反应剂法制备硬脂酸淀粉酯

以木薯淀粉为原料,硬脂酸为酯化剂,乙酸酐为共反应剂,采用机械活化共反应剂法制备硬脂酸淀粉酯。以取代度为评价指标,考察共反应剂用量、酯化剂用量、预反应温度、预反应时间、酯化反应时间等对酯化反应的影响,并用红外光谱(FTIR)、核磁共振氢谱(1H NMR)对产物进行表征。实验表明,硬脂酸和乙酸酐摩尔比1∶1. 5,酯化剂用量为30%淀粉干基,预反应温度80℃,预反应时间1 h,机械活化温度60℃,机械活化时间1 h,得到淀粉酯最高取代度为0. 086 7。红外光谱与核磁表明淀粉成功酯化,并同时含有乙酰基与硬脂酸基两种不同长度的碳链。     

机械活化固相共反应剂法制备硬脂酸淀粉酯

以木薯淀粉为原料,硬脂酸为酯化剂,乙酸酐为共反应剂,采用机械活化共反应剂法制备硬脂酸淀粉酯。以取代度为评价指标,考察共反应剂用量、酯化剂用量、预反应温度、预反应时间、酯化反应时间等对酯化反应的影响,并用红外光谱(FTIR)、核磁共振氢谱(1H NMR)对产物进行表征。实验表明,硬脂酸和乙酸酐摩尔比1∶1. 5,酯化剂用量为30%淀粉干基,预反应温度80℃,预反应时间1 h,机械活化温度60℃,机械活化时间1 h,得到淀粉酯最高取代度为0. 086 7。红外光谱与核磁表明淀粉成功酯化,并同时含有乙酰基与硬脂酸基两种不同长度的碳链。     

机械活化强化锌精矿焙烧脱硫的研究

分析了机械活化强化焙烧脱硫的机理，并对锌精矿进行了试验研究。结果表明，机械活化对锌精矿焙烧脱硫的强化效果非常显著。     

锂辉石浸出液提锂除杂规律研究

碳酸锂是一种基础锂盐, 不仅广泛应用于传统化工行业, 也是生产锂电池的重要原料, 近年来锂电产业蓬勃发展, 极大推动了原料碳酸锂的提取与制备研究。为了提取锂辉石中的锂来制备碳酸锂, 利用沉淀溶解-平衡理论分析锂浸出液的除杂规律。对锂辉石进行转型焙烧、酸化焙烧、浸取, 锂辉石中98%左右的锂可进入液相, 得到锂浸出液, 然后根据溶解平衡理论确定3步除杂净化条件：1）中和pH至6.5除大部分Al ³⁺和Fe ³⁺;2）加入氧化剂将Fe ²⁺氧化成Fe ³⁺, 调 pH 至8.0除Fe ³⁺;3）调pH至10.0, 加入理论量碳酸钠（以液相Ca ²⁺计）, 最终Al ³⁺、Fe ³⁺、Mg ²⁺ 等浓度低于10 ^-6 mol/L, Ca ²⁺质量分数约为2×10 ^-5。     

铜尾矿机械活化试验研究

基于机械活化原理对铜尾矿性能进行了试验研究,结果表明粉磨10 min的铜尾矿掺入水泥后,水泥标准稠度需水量随着掺加量的增加而减小,继续延长粉磨时间水泥标准稠度需水量随着掺量增加而增加,而粉磨时间对掺有铜尾矿的水泥凝结时间几乎没有影响。在12%～16%范围内,延长粉磨时间对铜尾矿28 d活性指数较为有利,其余掺量并不明显,并且掺入铜尾矿的水泥流动性损失加剧。     

Tetragonality enhancement in BaTiO3 by mechanical activation of the starting BaCO3 and TiO2 powders: Characterization of the contribution of the mechanical activation and postmilling calcination phenomena

By‐products including unwanted phase formation and/or unreacted starting materials are normally seen in the outcome of solid‐state synthesis approaches used in the literature for powder processing of advanced materials; this drawback requires critical attention and must be addressed in the new synthesis pathways in order to obtain quality powder products. A high energy mechanical milling approach was developed in this work. Addressing the drawback, the starting materials were mechanically activated by a high energy ball mill before their mixing step. It was found that highly pure barium titanate nanopowders with high tetragonality character are obtained using the approach developed here. The work also characterized tetragonality, role of the mechanical activation and postmilling thermal treatment on structure, phase formation and morphology of the obtained powder products. It was found that the mechanical activation accelerates the kinetic of formation of barium titanate and enhances the purity and tetragonality of the final products. The mechanism behind this achievement and the related reaction pattern are disclosed in this work. In order to obtain highly pure tetragonal barium titanate, a calcination temperature of 1173 K (900°C) after 30 hours mechanical activation is necessary; if these requirements are not satisfied, the final powder product contains impure phases and/or unreacted starting materials. The results also indicated that the processing conditions result in enhancement of tetragonality character of the final powder products. It seems that the method developed here can be used as a generalized methodology for obtaining the quality highly pure monosized nanocrystals of the mixed oxides for assembling in nanotechnology.     

Application of self-propagating high-temperature synthesis and mechanical activation for obtaining nanocomposites

A new method is developed for obtaining powder nanocomposites consisting of a metallic or intermetallic matrix and ceramic nanometer particles as a reinforcing phase. This method involves the following consecutive processes: short-time mechanical activation of the mixture of powder reagents in a high-energy planetary ball mill, self-propagating high-temperature synthesis, and additional mechanical activation of the synthesis products. Specific features of the reinforcing phase synthesis in matrices are examined by an example of TiB₂-Cu and TiB₂-TiNi systems. Compaction conditions that allow obtaining volume nanostructural materials with high strength characteristics are found. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 58–71, March–April, 2007.     

Preparation of porous rutile titania from ilmenite by mechanical activation and subsequent sulfuric acid leaching

Synthesis of porous titania via mechanical activation of natural ilmenite and subsequent simultaneous dissolution and hydrolysis in dilute solutions of sulfuric acid was investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), N₂ adsorption/desorption measurements, energy-dispersive X-ray spectrometry (EDX) and thermogravimetric analysis (TG). This is a novel template-free approach for synthesis of microporous, mesoporous and micro–mesoporous TiO₂ materials. Effects of sulfuric acid concentration and calcination temperature on physicochemical properties of the TiO₂ materials were examined systematically. The results show that both the factors considerably affected the porosity of the materials. In a 15% acid solution a microporous TiO₂ hydrolysate with BET surface area 109.3 m²/g was prepared. With a 10% H₂SO₄, we obtained a more pure micro/mesopore TiO₂ hydrolysate with BET area of 257.6 m²/g. Calcining the hydrolysate at 500 °C led to the formation of a mesopore TiO₂. The mesoporous TiO₂ generated at 600 °C still has a BET area of 92.1 m²/g. The high thermal stability is probably related to the presence of H₂SO₄ in the channel walls of hydrolysate. The XRD analysis indicated all the TiO₂ materials prepared in this study being rutile. The mechanism for formation of the porous rutile TiO₂ is mainly via in situ hydrolysis and precipitation of the dissolved titanium on the un-reacted ilmenite surface, where H₂SO₄ may play a very important role.     

Effect of mechanical activation on SHS: Physicochemical mechanism

Mechanically activated SHS (MASHS) is currently a subject of extensive investigation but up to now a mechanism of strong influence of mechanoactivation (MA) on subsequent SHS is not well understood. In this work, a system of relatively simple estimates is developed to analyze the physicochemical mechanism of the effect of preliminary MA on SHS, in particular, the role of the stored energy of cold plastic deformation and that of accumulated point defects. Brief analysis of the known MASHS theories is presented. A qualitative explanation of the effect of MA on SHS is proposed based on the modern theory of deformation-enhanced interdiffusion during MA and state-of-the-art conceptions of solid-state nucleation in the field of concentration gradient.      

Effects of mechanical activation on the digestion of ilmenite in dilute H2SO4

The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using spend acid to leach ilmenite can cut the waste emission and save fresh feeding acid. However, the leaching reaction with dilute acid is very slow and the digestion efficiency is fairly low. This paper describes a wet-milling process to enhance the dilute-acid leaching of ilmenite that makes it possible to produce TiO_2 pigment in a more environmentally benign routine. The leaching kinetic study of unmilled ilmenite, dry milled 60 min ilmenite and wet milled 60 min ilmenite was conducted by revision of the shrinking core model(SCM), incorporation of particle size distribution(PSD) into SCM. The results revealed that mechano-chemical activation method significantly increased the leaching efficiency of titanium from 36% to 76% by reducing the particle size and increasing the reaction contact area. On the other hand, the milling process increased the lattice deformation and amorphization of crystalline, which lowered the activation energies in the leaching process. Compared with dry milling operation, wet milling is more effective, the particle size distribution of wet-milled ilmenite was much narrower, smaller, and more uniform. Wet milling of ilmenite makes the leaching reaction with dilute acid(60 wt% H_2 SO_4) practicable and the re-use of spend acid becomes possible and economical.