Recovery of nickel from spent catalyst from palm oil hydrogenation process using acidic solutions

In this study, recovery of nickel from spent catalyst from palm oil hydrogenation process is carried out via extractive leaching process using sulfuric and hydrochloric acids. The effects of acid concentration, solid-liquid ratio, temperature and digestion time on the recovery (acid dissolution) process are investigated. It is found that sulfuric acid is the better leaching solution as compared to hydrochloric acid for recovery (dissolution) of nickel from the spent catalyst. Results from speciation modelling using VMINTEQ further imply that nickel can form sulfate complexes which are more stable than chloride complexes at concentrations higher than 1 M. The optimum conditions for maximum recovery at 85% are achieved at 67% sulfuric acid concentration, digestion time of 140 min, solid-to-liquid ratio of 1:14 and reaction temperature of 80 °C. At solution temperatures higher than 80 °C, the percentage nickel extraction is reduced. The optimization study presented here is useful for spent catalyst generators in the palm oil industry intending to recover valuable metals which may assist in reducing palm oil processing costs.     

江西弋阳蛇纹石硫酸浸出过程工艺条件的优化研究

文章在常压、较低温度(<100℃)下,开展了江西弋阳蛇纹石硫酸浸出工艺条件的研究.以蛇纹石中氧化镁的浸出率为主要考察指标,通过单因素条件实验和正交实验,分别考察了蛇纹石酸浸反应温度、酸浸反应时间、硫酸溶液质量浓度、液固比等因素的变化对蛇纹石中氧化镁浸出率的影响,所得较佳的工艺条件为:酸浸反应温度95℃、酸浸反应时间5h...     

Selective recovery of valuable metals from partial silicated sphalerite at elevated temperature with sulfuric acid solution

The purpose of this work was to study the feasibility at laboratory-scale of a hydrometallurgical process for the selective recovery of valuable metals from partial silicated sphalerite in an oxygen pressure acid leaching system. The factors influencing dissolution efficiency of the ore were investigated and optimized. Under optimum conditions (i.e., temperature of 433 K, sulfuric acid concentration of 41.2 g/L, leaching time of 2.5 h, liquid/solid ratio of 6 mL/g, and pressure of 1.6 MPa) over 97% Zn was extracted into the leach liquor together with 0.3% SiO₂ and 2.9% Pb. The leaching slurry had good solid–liquid separation characteristics, and the filtration rate could be as high as 716 L/m² h. About 96% oxidation of sulfide sulfur to sulfate was achieved under these conditions. Analysis of the content of elemental sulfur in the leaching residues indicated that the fraction of sulfide sulfur determined as elemental sulfur was about 10% at 393 K, and that it decreased with temperature down to 0.5% at 453 K. Ultimate solid residues, which have been concentrated in silica and lead, can be oriented toward the lead smelter after alkali roasting-water washing pretreatment for metal recovery.     

尾矿砂的酸溶特性与镍的浸出研究

通过粉末X射线衍射（XRD）分析了金川尾矿砂的物相组成和脉石矿物的相对含量,利用热力学原理计算并分析了矿物在硫酸中的溶解难易程度。通过正交设计与实验, 得到浸出镍的最佳工艺条件：酸矿质量比为 0.9∶1、液固质量比为2∶1、反应温度为90 ℃、反应时间为4 h。在此酸浸条件下,尾矿砂中镍的浸出率可达93.3%,而蛇纹石和白云石可以完全溶解,并产生大量无定形二氧化硅。     

Catalytic dehydration of glycerol to acrolein over sulfuric acid-activated montmorillonite catalysts

For the development of efficient solid acid catalysts for the catalytic dehydration of glycerol to acrolein, catalysts made from montmorillonitic clay activated by sulfuric acid were investigated. Montmorillonite was activated in diluted sulfuric acid in the concentration range of 5–40 wt.%. The effects of sulfuric acid treatment on the structure of the montmorillonite were characterized by X-ray diffraction, measurements of acidity, N₂ adsorption–desorption isotherms, and Fourier transform infrared spectroscopy. The catalytic behavior of sulfuric acid-activated montmorillonite catalysts in the gas-phase dehydration of glycerol were investigated under varying conditions, including the reaction temperature, the feed rate, and the concentration of glycerol. After montmorillonitic clay was activated by sulfuric acid, the layered structural features of montmorillonite remained nearly intact. Ca^2 +-montmorillonite was changed to H⁺-montmorillonite by ion exchange reaction during activation. The optimal catalytic glycerol dehydration reaction conditions were found to be: temperature at 320 °C, liquid hourly space velocity (LHSV) = 18.5 h^− 1, concentration of glycerol solution = 10 wt.%, and the flow rate of N₂ carrier gas = 10 mL/min. A conversion of 54.2% of glycerol and a yield of 44.9 wt.% acrolein were achieved over the montmorillonite catalyst activated by an aqueous 10 wt.% sulfuric acid solution. The H⁺ in the interlayer space of acid-activated montmorillonite catalysts played a critical role in the catalytic dehydration of glycerol. The temperature, the LHSV, and the concentration of glycerol affected the performance of the catalysts through their influence on the reaction mechanism, the contact time, and the reaction equilibrium.     

低冰镍转炉渣中钴的氧压酸浸行为及其动力学

研究了转炉渣中钴氧压硫酸体系选择性浸出过程的行为及其动力学。通过改变搅拌速度、反应温度、硫酸浓度、氧分压、物料粒度以及反应时间等浸出条件,考察钴浸出率的变化及影响,获得转炉渣中钴的浸出动力学规律。结果表明,钴的浸出率随着温度、酸度、氧分压的增加而增加;硫酸质量浓度大于0.4 mol·L^-1会导致铁大量溶出;浸出过程符合未反应芯收缩核模型,前期受化学反应控制,然后转变为混合控制,后期受固体产物层扩散控制。化学反应控制和固体产物层扩散控制过程的活化能分别为43.19 kJ·mol^-1 和10.49 kJ·mol^-1。化学反应控制过程对硫酸浓度、氧分压及粒度的反应级数分别为0.79、0.85和 -0.95。     

Transformation of silica fume into chemical mechanical polishing (CMP) nano-slurries for advanced semiconductor manufacturing

Silica nanoparticles have been synthesized from silica fume using alkali dissolution–precipitation process. The dissolution efficiency of 99% at a temperature of 80 °C and a time of 20 min was achieved. Sodium silicate solution was obtained by dissolving the fume with NaOH solution. Then, silica nanoparticles were precipitated using sulfuric acid. Silica nanoparticles (175 nm) were achieved using 12% sulfuric acid at pH 7 and 200 ppm sodium dodecyl sulfate (SDS). The silica morphologies appeared as a spherical shape with narrow particle size distribution. The silica samples were used for the formulation and testing of chemical mechanical polishing (CMP) slurries. The morphology of the polished wafer surface and its roughness were examined by atomic force microscope (AFM).The results indicated that the surface roughness was greatly improved after application of CMP. It was found that the surface roughness of the polished wafer is 0.226 nm at an applied pressure of 7 psi. The removal rate was found to be 1200 Å. These values confirm the quality of polished wafers.     

Leaching kinetics of calcined magnesite in acetic acid solutions

The leaching kinetics of calcined magnesite by using acetic acid solutions was investigated in a batch reactor by using the parameters such as temperature, acid concentration and particle size. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for fluid–solid systems. It was concluded that the leaching of calcined magnesite was controlled by chemical reaction. In addition, the fact that leaching was controlled by the chemical reaction was also supported with the relationship between the reaction rate constant and the particle radius. The apparent activation energy of dissolution process was found as 34.60 kJ mol^?1.     

A kinetic study on hydrochloric acid leaching of nickel from Ni–Al2O3 spent catalyst

Hydrochloric acid leaching of nickel from spent Ni–Al₂O₃ catalyst (12.7% Ni, 39.2% Al and 0.68% Fe) has been investigated at a range of conditions by varying particle size (50–180 μm), acid concentration (0.025–2 M), pulp density (0.2–0.4%, w/v) and temperature (293–353 K). Nickel was selectively leached from the catalyst, irrespective of the different conditions. Under the most suitable conditions (1 M HCl, 323 K, stirring at 500 rpm, 50–71 μm particle size), the extent of leaching of Ni and Al after 2 h was 99.9% and 1%, respectively. The XRD pattern of the spent catalyst corresponded to crystalline α-Al₂O₃ along with elemental Ni. The peak due to elemental Ni was absent in the residue sample produced at the optimum leaching conditions, confirming the complete dissolution of Ni from the spent catalyst. The leaching results were well fitted with the shrinking core model with apparent activation energy of 17 kJ/mol in the temperature range of 293–353 K indicating a diffusion controlled reaction.     

硫酸浸出硼泥制备片状氢氧化镁实验研究

对硫酸浸出硼泥制备氢氧化镁进行了研究,考察了反应温度、反应时间、硫酸用量和硫酸初始浓度等因素对硼泥中镁浸出率的影响。结果表明：在浸出硫酸足量的条件下,反应温度对镁浸出率影响最大。实验得到酸浸条件：反应温度为95 ℃、反应时间为3 h、硫酸质量分数为40%、硫酸用量为理论量的1.2倍。在此条件下,硼泥中镁的浸出率为95.62%。反应完成后,得到初级硫酸镁浸出液,通过进一步梯度碱析和水热反应,制得纯度为99.35%的片状氢氧化镁。SEM和XRD测试表明,片状氢氧化镁具有形貌均一、颗粒分散性好和结晶度高的特征。     

高硫镁肥的制备与评价

利用不同配比的物料(蛇纹石、石灰石、橄榄石)与硫酸反应,并添加硫黄造粒制备高硫镁肥。分析了肥料制备过程以及肥料总硫含量和颗粒分级硫含量受物料种类、硫酸浓度、反应温度及水分添加量等的影响。确定了在110~118℃下反应,硫能够均匀分散于肥料中,且石灰石肥料与蛇纹石肥料相比,易于造粒,硫含量高。     

钛石膏硫酸浸取法提取铁质氧化物及石膏的物相变化

硫酸法生产钛白粉副产大量钛石膏，因其含有较多杂质而无法直接利用，目前可采用硫酸酸浸处理提高钛石膏的品质。本文以硫酸为浸取剂，研究钛石膏中铁质氧化物在不同硫酸浓度、反应温度、固液比、反应时间条件下的溶出规律以及酸浸产物的物相变化；采用XRD、XRF、SEM等分析手段，对钛石膏酸浸前后样品的物相、化学成分、形态等进行分析。结果表明，硫酸酸浸可以有效去除钛石膏中铁质氧化物，最佳工艺条件下去除率可达93.14%，白度由原来的8.1提高至54.4。在酸浸过程中随着硫酸浓度、反应温度、固液比等浸取条件的改变，钛石膏中的二水石膏脱水形成半水石膏和无水石膏。采用硫酸酸浸法处理钛石膏，滤液经处理可获得Fe(OH)₃，废液可循环利用，将为钛石膏的资源化利用提供新途径。     

富硼渣硫酸浸出实验研究

以硼铁精矿含碳球团还原熔分得到的富硼渣为原料,研究了其物相成分,并进行硫酸浸出实验,探究了硫酸用量、反应温度、反应时间及液固比对硼浸出率的影响。结果表明,该富硼渣中三氧化二硼的质量分数达到20%,主要含遂安石相和橄榄石相。硫酸浸出实验中,硼浸出率随着硫酸用量、反应温度和反应时间的增加而增大,随着液固比的增大而减小。当硫酸用量为理论用量的80%、液固体积质量比为8 mL/g、反应温度为40 ℃、反应时间为60 min时,富硼渣中硼的浸出率达到93.56%。     

煤灰渣酸浸提铝试验

为实现煤炭资源化分级利用,对东北某热电厂循环流化床锅炉灰渣进行提铝研究。用硫酸在不同的反应条件下酸浸,以获得较高的铝浸出率和合适的酸浸条件,产品为富含硫酸铝的酸浸液和高硅提铝残渣。酸浸实验结果表明,较为合适的酸浸条件为:5mol/L的硫酸、105～110℃的酸浸温度、2h的反应时间和1:3的固液比,此时铝浸出率为91.5%,提铝残渣中SiO₂含量高达87.6%。X射线衍射分析(XRD)和扫描电镜(SEM)分析表明,原始煤灰渣中的铝元素主要以非晶态的化合物形式存在,而非晶态物质具有较高的化学反应活性,促成了较高的铝浸出率。因此,这种循环流化床锅炉的灰渣酸浸提铝提硅较为合适。     

Study on SO42−/ZrO2-MoO3 in the integrative transformation of cottonseed oil deodorizing distillate

With the integrative transformation of non α-tocopherols, glycerides, free fatty acids, and methyl alcohol in cottonseed oil deodorizing distillate as the target reaction, we prepared highly catalytic SO₄^2?/ZrO₂-MoO₃ solid acid catalyst by precipitation–wet impregnation. The optimal conditions for catalyst preparation were then determined by varying sulfuric acid concentration, MoO₃ loading factor, calcination temperature, and calcination time. The structure of SO₄^2?/ZrO₂-MoO₃ solid acid catalyst was then examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurements, scanning electron microscopy, and other methods. Results show that the MoO₃ loading factor (percentage weight ratio of MoO₃ to ZrO₂), impregnation concentration of sulfuric acid, and calcination temperature were the most important factors that influenced catalytic activity. The optimal conditions for catalyst preparation were an MoO₃ loading factor of 20%, a sulfuric acid impregnation concentration of 0.75 mol/L, a calcination temperature of 550 °C, and a calcination time of 6 h. The obtained catalyst exhibited the highest catalytic activity under these conditions.     

Extraction of boric acid from colemanite mineral by supercritical carbon dioxide

The use of H₂SO₄ in boric acid production from colemanite mineral has several problems, related to product impurities, corrosion and environmental discharge limits. To overcome these problems and to increase extraction efficiency of boric acid, heterogeneous reaction between colemanite and CO₂ dissolved in H₂O was studied at and above supercritical CO₂ conditions. Supercritical conditions enhanced the extraction efficiency of boric acid from colemanite mineral, with 96.9% boric acid extraction efficiency being obtained from CO₂–colemanite reaction at 60 °C, for 2 h of reaction time for particles in the range of +20–40 μm. A powder crystallized from filtrate of reaction was determined as H₃BO₃ and the solid formed at the end of reaction was characterized mostly as CaCO₃ according to FTIR, XRD, TGA and SEM analyses. The use of supercritical CO₂ as a leaching agent in colemanite does not only produce boric acid but also helps to reduce the amount of CO₂ in the atmosphere. Based on these facts, supercritical CO₂ as extractant makes this process green and sustainable for recovering boric acid from boron minerals.     

Comparison of red,brown and green seaweeds on enzymatic saccharification process

The production of bioethanol from seaweeds using acid hydrolysis and the enzymatic saccharification was studied. Red seaweed (Gelidium amansii), brown seaweed (Laminaria japonica), and green seaweed (Codium fragile) were selected, and the characteristics of their conversion to bioethanol were analyzed. The optimum conditions of the dilute acid hydrolysis preprocessing for bioethanol production from the seaweed were a reaction temperature of 150 °C, sulfuric acid content of 5.0 wt.%, and reaction time of 60 min. The seaweeds listed in order of bioethanol conversion performance are red seaweed > brown seaweed > green seaweed. The optimum dosage of enzyme was 2.0 mL per 10 g of seaweed. The optimal fermentation conditions for bioethanol production using seaweed included a commercial yeast dosage of 30 wt.% and a fermentation time of 3 days.     

磷尾矿硝酸脱镁制取氢氧化镁工艺研究

实验采用硝酸对磷矿浮选尾矿进行化学脱镁,讨论了温度、pH和时间3个因素对脱镁率和磷溶解率的影响.发现在液固比为3∶1的前提下,最佳酸浸条件为:温度50℃,pH=2.5,时间150 min,在上述条件下脱镁率达到94.26％,磷溶解率为5.94％.脱镁后的酸浸液实现了Mg2+与其他金属离子的分离,并通过XRD和化学分析得知产品Mg(OH)2中MgO质量分数为64.45％.