Dissolution behavior of Caldag lateritic nickel ore subjected to a sequential organic acid leaching method

The dissolution behavior of Caldag lateritic nickel ore subjected to a sequential organic acid leaching method was investigated. The effects of the type of organic acid, acid concentration, leaching time, and leaching temperature on the lateritic nickel ore were examined. Organic acids were used individually prior to sequential leaching. Citric acid was more effective than the other two acids for the selective leaching of nickel and cobalt. An increase in the citric acid concentration negligibly affected the dissolution of the metals, whereas temperature exhibited a strong beneficial effect. Oxalic acid was determined to be the most appropriate organic acid for the second leaching step. After 8 h（4 h ＋ 4 h） of leaching with organic acids（0.5 M citric ＋ 0.5 M oxalic） in sequence at 90°C, 89.63% Ni, 82.89% Co, and 69.63% Fe were leached from the lateritic nickel ore. A sequential citric ＋ oxalic acid leaching method could represent a viable alternative for the dissolution of metals from lateritic nickel ore.

Reductive Acid Leaching of Low Grade Manganese Ores

Manganese recoveries from low-grade ores using organic acids as reducing agents were investigated in the present work. The acid leaching potential of both oxalic acid and citric acid were estimated. Manganese leaching amount were measured by using standard manganese curve and estimated by titration method. Effects of various acid concentrations on leaching efficiency were studied. The observed result suggested prominent manganese recovery of 66% by oxalic acid at 2 M concentration whereas citric acid had less effect on leaching showing leaching percentage upto 40% in 6 days. Acid leaching of manganese ore with both the acids gave a comparative data stating that oxalic acid leached better than citric acid.

宜宾某黏土型锂矿浸出工艺条件研究

对宜宾某地采集的Li2O品位为1.19%的黏土型锂矿,使用硫酸酸浸的方法,研究了浸出温度、浸出时间、硫酸浓度和液固比对锂的浸出率的影响,并以焙烧处理工艺和有机酸对实验进行了改进和优化。结果表明,该黏土型锂矿的浸出率受工艺条件影响,其中浸出温度的影响最大,其次分别是硫酸浓度、浸出时间和液固比;当浸出温度为150℃,浸出时间为90min,硫酸体积分数为50%,浸出液固比L/S=100(mL·g^(-1)),此时锂的浸出率较好,可达到65.08%;为了进一步提高浸出率,以700℃焙烧该黏土型锂矿30min,经焙烧处理后,锂的浸出率可以提高到79.79%。同时,从绿色环保、降低设备要求的角度,采用有机酸代替硫酸,该实验表明,当草酸质量分数为50%时,焙烧样锂的浸出率为61.20%,通过改进工艺和继续研究,草酸可以成为一种未来黏土锂提取工艺绿色环保化的浸出剂,具有很大的潜力。

柠檬酸-草酸体系处理红土镍矿可行性探索研究

研究了红土镍矿低温、绿色化提取的新工艺。传统冶金工业面临的主要压力是能源和环保问题,本研究利用自然界中存在的柠檬酸和草酸两种有机酸为提取试剂,力求在低温下实现红土镍矿的有效提取。研究以低品位红土镍矿为原料,采用与柠檬酸混合焙烧-水浸-草酸沉淀工艺实现镍钴的有效富集。考察了焙烧条件和浸出条件对红土镍矿中多种金属浸出率的影响,也探究了利用草酸从浸出液中直接沉淀镍离子的可行性。结果表明,当焙烧温度为140℃时,镍、钴、铁的浸出率分别为97.70%,97.94%,95.94%,当焙烧温度为100℃时,镍和钴浸出率均可以保持在87%以上,而铁浸出率降低到42.83%,这表明较低温度的焙烧对于红土镍矿中有价金属的浸出具有一定的选择性;利用超声浸出可有效地提高浸出效率;控制浸出温度在较低温度,焙烧产物中的金属浸出依然具有选择性,即镍钴浸出不受影响,而铁浸出率降低显著;以草酸为沉淀剂,无需要调节pH值即可从柠檬酸浸出液体系中沉淀金属,所得草酸盐沉淀为草酸镍和草酸镁混合物,铁几乎不沉淀。

用有机酸精制漂白高岭土细尾矿的研究

高岭土是多种矿物组成的含水铝硅酸盐的集合体，用途广泛。但由于大多数高岭土含有质量分数0．5％～3％的氧化铁或氢氧化铁，限制了它的使用。用还原和络合的方法对高岭土进行漂白，可有效降低高岭土中铁的含量。研究了在低pH下用有机酸（柠檬酸、萄糖酸、草酸）精制漂白煤系高岭土中高含量的氧化铁。结果表明，柠檬酸和萄糖酸的除铁效果差，不适应工业化生产，草酸能够除去高岭土中可浸铁，当pH低于1．2，浸取温度为80℃，白度达80％以上，使煤系高岭土适应工业应用的基本条件。同时，由于着色矿物的差异，不同矿源的高岭土漂白和白度稳定条件不同，实际生产中应根据具体的矿源，经试验后才能确定。

草酸对珊瑚砂的溶蚀作用及其机制研究

营造热带吹填陆域的宜居生态环境,构建植被生态系统必不可少,其中,研究植被分泌小分子有机酸对岛礁母质珊瑚砂的风化作用对于岛礁生态建设至关重要。通过研究不同浓度草酸对珊瑚砂的溶蚀动力学,建立动力学模型,研究珊瑚砂溶蚀的主要影响因素,探讨草酸对珊瑚砂的溶蚀机制。结果表明,在不同草酸溶液中,反应初始阶段珊瑚砂中Ca^2+、Mg^2+迅速溶出,随后大量Ca^2+被草酸固定生成草酸钙沉淀。随着草酸浓度的增加,溶液中Ca^2+浓度逐渐降低,Mg^2+浓度逐渐升高,c(Ca^2+)最大值为0.65 mmol·L^-1,c(Mg^2+)最大值为2.87 mmol·L^-1。通过Mg^2+溶出动力学拟合发现其溶出动力学符合Stumm模型,主要受扩散过程的影响。此外,高浓度草酸会抑制珊瑚砂中Ca^2+的溶解流失。XRD和SEM分析结果表明,高浓度草酸与珊瑚砂反应生成草酸钙沉淀相互胶连附着在珊瑚砂表面,且溶蚀过程中优先溶蚀珊瑚砂组分中镁方解石,其次是文石和方解石。

Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils

Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions(0.063–0.25, 0.25–0.5, and 0.5–2 mm) of both rocks were studied by citric acid solution at p H 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size,leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased,corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases: 1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.

持续淋溶条件下有机酸对土壤磷素释放及无机磷组分的影响

采用土柱模拟试验,研究了柠檬酸、草酸和乙酸在持续淋溶条件下土壤磷的动态释放特征及淋溶前后无机磷组分的变化情况。结果表明:相同浓度条件下三种有机酸对供试土壤磷的活化能力大小顺序为:柠檬酸>乙酸>草酸,且不同有机酸淋溶过程中磷的释放特征各不相同。乙酸的最大释磷量及释磷率虽不及其它有机酸处理,但表现出了较好的持续活化能力。持续淋溶条件下,三种有机酸均能显著地活化土壤无机磷,其中柠檬酸和乙酸处理对无机磷的活化效果较好,草酸相对较弱,且有机酸的淋溶使土壤磷素形态构成发生变化;柠檬酸和乙酸作用下各形态无机磷变化率大小顺序为:Ca-P>Fe-P>Al-P>O-P;草酸处理下变化率顺序为:Ca-P>Al-P>O-P>Fe-P,说明三种有机酸对Ca-P的活化最为明显,其次为Fe-P或Al-P,而O-P在淋溶前后变化很小。

柠檬酸、草酸和苹果酸对高岭石的溶解作用

采用间歇法(batch method)模拟研究高岭石在柠檬酸、草酸和苹果酸溶液中的长期溶解效应。研究表明:柠檬酸、草酸和苹果酸三种低分子量有机酸能显著促进高岭石的溶解,它们对高岭石的溶解能力都是随其浓度的升高而增强,其溶解能力的顺序为:草酸>柠檬酸>苹果酸;苹果酸导致了高岭石Si的优先释放,而柠檬酸和草酸则导致了Al的优先释放。对于柠檬酸而言,高岭石一般在反应中期趋于同步溶解,且其同步性随其浓度的升高而增强。对于草酸而言,高岭石通常是在反应后期才趋于同步溶解;而对于苹果酸而言,1 mmol L-1时,在整个实验期间,高岭石都是非同步溶解;5 mmol L-1和10mmol L-1时,高岭石是以Al/Si小于1的一定速率比溶解;20 mmol L-1时,高岭石是在反应96 h后才表现为趋于同步溶解。

两种低分子量有机酸对磷酸铵镁溶解的影响

实验室采用间歇法,模拟研究作物根系分泌的两种低分子有机酸(柠檬酸和草酸)对磷酸铵镁溶解的影响。结果表明:低分子量有机酸对磷酸铵镁中养分的释放有明显促进作用,促进N和P等营养元素的释放,而且溶解的过程有利于提高根际土壤的缓冲性能。常温下两种酸的溶解作用效果为:草酸>柠檬酸。有机酸对磷酸铵镁的溶解与温度的升高呈正相关,并且随着浸提时间的延长,养分释放量增大至稳定,这一平衡与温度有关。进一步说明了磷酸铵镁是一种理想的缓释性肥料,有利于作物生长。