分散剂对制备超细氢氧化镁影响的实验研究

以菱镁矿煅烧所得氧化镁为原料,水化制备超细氢氧化镁。在水化反应进行一段时间后加入分散剂,考察了分散剂种类和用量对氢氧化镁颗粒大小的影响。用偏光显微镜对氢氧化镁进行表征、扫描电镜观察产品微观大小与形貌,在添加适量分散剂条件下,可制得粒径为200～400nm、形状为六边形的片状氢氧化镁。     

工艺条件对制备超细氢氧化镁性能的影响

以菱镁矿为原料,经低温煅烧得到轻烧氧化镁,采用水化法制备氢氧化镁超细粉体.论文研究了水化温度、添加剂对水化产物颗粒大小的影响.利用XRD和SEM对合成氢氧化镁晶体特征、颗粒大小和形貌进行了表征.结果表明,制备的超细氢氧化镁为片状颗粒,颗粒大小约为200nm.     

氧化镁常压水合法制备氢氧化镁的过程分析

以活性氧化镁为原料,在碱性环境中用常压水合法制备纳米氢氧化镁,通过实时取样,结合扫描电子显微镜(SEM)和X射线衍射(XRD)表征其形貌和结构,探索氧化镁的水化合成过程和相关机理。结果表明:在水合时间2 h后,体系中氧化镁已经全部转化生成氢氧化镁,反应时间短。水合反应体系中OH-使氢氧化镁极性面稳定,未发生第Ⅱ类聚集生长,晶体呈片状结构。随着时间增长,氢氧化镁颗粒出现大颗粒长大,小颗粒缩小的现象,发生第Ⅰ类聚集生长,但平均粒径不变,为18.7 nm。     

用蛇纹石硫酸铵焙烧法制备超细氢氧化镁的研究

以蛇纹石为原料,通过硫酸铵焙烧法提取蛇纹石中的镁,并制备超细氢氧化镁.研究了温度对制备超细氢氧化镁性能的影响,得出适宜反应温度为40℃,SEM测试结果表明,制备的超细氢氧化镁颗粒间发生了较多团聚,比表面积较大.为克服氢氧化镁的团聚现象,降低比表面积,将氢氧化镁在反应釜中进行水热反应,得出适宜水热时间为3 h.化学分析以及粒度、比表面积、SEM测试结果表明,水热反应后氢氧化镁比表面积为13.79 m2/g,MgO含量为68.23%,晶型较好.     

熔盐法制备片状及多孔棒状形貌氧化镁

以MgCl₂、CaCO₃和NaCl、KCl为原料, 采用熔盐法制备了片状和多孔棒状形貌MgO粉体。借助XRD、FT-IR、SEM等手段对产物进行了分析和表征。结果表明: 原料在700 ℃热处理后, 经PEG溶液浸泡得到的氢氧化镁前驱物形貌为纤维状, 经EDTA-PEG溶液浸泡得到的氢氧化镁前驱物形貌为片状。纤维状氢氧化镁分解为氧化镁产物后呈多孔棒状形貌, 直径介于20～80 nm, 长径比介于40～100; 片状氢氧化镁分解为氧化镁产物后仍保持片状形貌, 厚度介于30～50 nm, 直径介于200～500 nm, 单片表面积最大可达1.0 μm²。     

低品位菱镁矿制备高纯氧化镁试验研究

随着耐火材料对氧化镁质量要求的提高,采用低品位菱镁矿制备高纯氧化镁引起广泛关注。对海城某菱镁矿矿石进行轻烧-氯化铵浸出,获得MgCl_2和CaCl_2等的浸出液,取等体积该浸出液采用氨水沉淀法制备氢氧化镁,在反应时间为60 min,反应温度为45℃,氨水浓度为8mol/L及搅拌速度为500 r/min的条件下,制备的氢氧化镁沉淀量达到最大值。将制备的氢氧化镁置于马弗炉中进行焙烧,在焙烧时间为30 min及焙烧温度为500℃的条件下,可制得纯度高达99.84%的氧化镁。激光粒度分析显示氧化镁的中位径(D50)为50.21μm,其中在0.500~100μm范围内粒径占95%,分散性好。     

水化条件对氢氧化镁颗粒尺寸的影响

研究了水化温度、水化时间、悬浮液浓度和水化介质配比对氢氧化镁颗粒尺寸的影响。结果表明，有添加剂存在时，氢氧化镁颗粒尺寸随着水化温度的提高先增加后降低然后又有明显增加，水化温度为70℃时得到的产物颗粒最为细小；水化2h，产物粒径最小；改变悬浮液浓度和水化介质配比。对生成的氢氧化镁颗粒尺寸影响不大。     

天然高岭土水热合成纳米莫来石粉体的研究

以天然高岭土为原料,联合氧化-还原工艺和黄铁矾法去除有机质和杂质,采用常压、开放水热晶化法制得了主晶相为莫表石的复相纳米晶.实验利用XRD、SEM对在不同条件下制得样品的晶相组成、形貌进行了表征.研究结果表明:前驱体精矿粉(一次莫来石、二次莫来石)的选择是影响主晶相为莫来石复相纳米晶水热合成的主要原因之一;在煅烧温度为1170℃、水热晶化温度为75℃、NaOH浓度为3mol/L、晶化时间为5h时,制得的纳米粉体含有莫来石和二氧化硅,颗粒形貌为类球形,少部分呈针状,颗粒平均粒径约为100nm.     

盐湖氧化镁制备氢氧化镁的研究

研究以盐湖资源的综合利用为背景,青海某盐湖的氧化镁产品为原料,研究采用水合法制备氢氧化镁的工艺条件。通过单因素条件试验研究反应温度、反应时间和原料固液比等反应参数对原料转化率及产品粒径的影响规律,探索氧化镁水合法制备氢氧化镁的制备机理,初步确定最佳制备条件为反应温度180～200℃、反应时间5～7 h,原料固液比1∶40条件时,可制得产品d₅₀为20 μm左右、粒度分布比较均匀且结晶良好的片状氢氧化镁产品。     

水热法制备阻燃剂氢氧化镁

硫酸镁溶液添加氢氧化钠沉淀出氢氧化镁凝胶,再用水热法改性制得阻燃剂级氢氧化镁,研究试验条件(氢氧化钠浓度、水热处理温度、水热处理时间)与水热产物性能的关系.水热改性后的氢氧化镁颗粒为针状,粒度均匀.在试验条件下,氢氧化钠浓度越高.水热改性效果越显著.水热处理的最佳条件为[OH-]=4mol·L-1,[MgSO4]=2mol·L-1,温度200℃,改性时间40～60min.搅拌充分,陈化时间小于18h.     

Alkaline digestion of dunite for Mg(OH)2 production: An investigation for indirect CO2 sequestration

The sequestration of CO₂ by carbonating natural minerals has a great potential for secure reduction of net CO₂ emissions. Feedstock Mg–silicate minerals are usually converted into Mg rich solutions or Mg(OH)₂ before the carbonation process, due to the slow reaction kinetic of direct carbonation. The present work studied the alkaline digestion of Mg–silicate minerals into Mg(OH)₂ for CO₂ sequestration. Powdered dunite containing ∼73 ± 2 wt% of forsterite (Mg₂SiO₄) was dissolved using highly concentrated NaOH aqueous systems at 90 and 180 °C with varied NaOH concentration and duration of reaction. Thermal analysis and Rietveld Refinement Quantitative Phase Analysis (QPA) confirmed that an effective digestion of dunite was possible at 180 °C achieving 80 wt% of Mg(OH)₂. It was found that NaOH concentration in solution, temperature and duration of reaction significantly influence the progress of digestion.     

热分解法制备三水碳酸镁晶须及其结晶动力学研究

利用菱镁矿制备重镁水溶液,以此为前驱溶液,采用热分解法制备三水碳酸镁晶须。借助X射线衍射分析（XRD）和扫描电镜（SEM）探究热解时间、重镁水溶液浓度和搅拌速率对产物组成和形貌的影响,并研究结晶动力学。结果表明,在温度50 ℃、热解时间120 min、重镁水质量浓度为2.75~3.39 g/L时,热分解法制备得到平均直径为6.0 μm、平均长度为100 μm的棒状MgCO₃·3H₂O晶须。随着时间和浓度增加,MgCO₃·3H₂O晶体表面或整个棒状结构会发生溶解重新形成无定形颗粒,并逐渐形成多孔棒状4MgCO₃·Mg（OH）₂·3H₂O。搅拌速率影响MgCO₃·3H₂O晶须的产率。MgCO₃·3H₂O晶体中,[MgO₆]正八面体通过Mg-O键以共顶点的方式紧密相连,沿化学键作用力较强的[010]方向无限连接形成长链。结晶动力学线性拟合结果表明重镁水溶液浓度增大,诱导期时间缩短。      

Gold losses from cyanide solutions part II: The influence of the carbonaceous materials present in the shale material

Gold was found to be mainly adsorbed onto the carbonaceous particles in the Beatrix shale material with possible minor loss of gold due to co-precipitation of gold with Mg(OH)₂ and Fe(OH)₃.Two types of carbonaceous material were present in low concentrations in the Beatrix shale and resembled kerogen. The one type can be described as filamentous particles and the other as roundish particles. Rank measurements done on the carbonaceous particles in the shales showed that they fall in the anthracite range. Adsorption of gold on carbonaceous material of similar rank showed that anthracite has the highest propensity to adsorb gold. This suggests that the carbonaceous particles would have similar gold adsorption properties as anthracite. The lack of an obvious correlation between the propensity of a shale to adsorb gold and its carbon content is probably due to the fact that not all the carbonaceous particles are liberated during milling so that they can be brought into contact with' the gold cyanide solution.     

连二亚硫酸钠还原制备纳米银粉

通过向银的乙二胺四乙酸络合溶液中滴加还原剂连二亚硫酸钠溶液制备了纳米尺寸的银粉。考察了硝酸银浓度、络合剂用量、还原剂浓度、pH值、反应温度、搅拌速度、还原剂溶液滴加速度对所制得银粉粒径的影响, 用X射线衍射和场发射扫描电镜对所制银粉的晶体结构和形貌进行了表征。试验结果表明, 在Ag-EDTA络合溶液浓度为0.005 mol/L, EDTA过量10%, pH值为11.5, 还原剂浓度为0.0075 mol/L, 搅拌转速为400 r/min, 反应温度为50 ℃, 还原剂滴加速度为0.06 mL/s的条件下, 所得银粉的平均粒径为58 nm。     

氯化钠对氧化镁水化产品形貌的影响

为考察以NaCl为晶型诱导剂,常压下水化反应制备一维状氢氧化镁的可行性,以六水氯化镁低温煅烧生成的活性氧化镁为原料,常压下水化合成氢氧化镁。结果表明:NaCl浓度为0.034 mol/L时,水化反应产品主要呈片状;NaCl浓度为0.171 mol/L时,水化产品呈槽沿的凹槽状;NaCl浓度为0.342 mol/L时,形成半管状产品,且分散性较好。即随着NaCl浓度的提高,水化产品逐渐向一维状趋势发展。当NaCl浓度较低时,新生成的氢氧化镁只能任意吸附在已生成的氢氧化镁晶体上,生成分散性较好的规则片状氢氧化镁;当NaCl浓度较高时,NaCl能够选择性地吸附在氢氧化镁的特定晶面上,使片状颗粒沿着垂直的晶面优先生长,最终发生定向排列形成槽状;随着NaCl浓度的进一步提高,Na~+易于扩散到[Mg(OH)_6]~(4-)八面体中,取代部分Mg~(2+)的位置,降低氢氧化镁生长的梯度能量,进而改变氢氧化镁晶体在不同方向的生长速率,有利于诱导晶体沿一维方向生长,可快速诱导生成一维管状产品。     

Preparation of nanometer yttrium oxide

The nanometer yttrium oxides were obtained through precipitation in aqueous solution by reaction with ammonium bicarbonate. The reaction between yttrium chloride and ammonium bicarbonate, the effect of surfactants on particle size and the methods of controlling agglomeration were studied. Compared to other methods, the method of controlling the agglomeration by adding surfactant is one of the best methods for controlling the agglomeration of nanometer particles in wetchemical process. Increasing surfactants in process of precipitation deduced particle size, obtained narrow size distribution of primary particles. As for the concentration range studied, excess surfactants increased the particle size on the contrary. Characteristics of the thermal decomposition of yttrium carbonate were studied. It indicated that the approximate chemical composition of the precipi tate was Y(OH)Clx (CO3)(1-x/2) · 3H2O,the cubic Y2O3 was obtained above 600℃ , the specific surface and the remain chloride of nanometer Y2O3 was decreased with calcinating temperature rising. The spherical nanometer yttrium oxide was gained with primary particles＜50 nm,agglomerate distribution D50 ＜ 150 nm, BET＞ 35 m2/g, agglomerate constant (D50/DBET ) ＜6.     

由低品位菱镁矿制备高纯碳酸镁的研究

以低品位菱镁矿为原料, 经轻烧、消化, 在不同条件下进行碳酸化, 将消化料浆转化为碳酸氢镁进入液相而制得重镁水, 采用活性炭为吸附剂脱除钙、铁等杂质, 并研究了不同添加剂对重镁水热解产物形貌的影响。研究表明, 随着碳酸化温度升高, 氧化镁的收得率降低; 随着碳酸化时间的延长, 氧化镁的收得率增加; 随CO₂气体流量的增大, 氧化镁的收得率稍有增加, 但增加幅度很小。XRD分析表明重镁水热解产物的主要成分是3MgCO₃·Mg(OH)₂·3H₂O 和MgCO₃·3H₂O。经过提纯处理后, 热解产物纯度很高, CaO含量小于0.04%, TFe含量小于0.02%。SEM分析表明, 无添加剂时, 热解产物为片状; 加入酸性添加剂磷酸二氢钾时, 热解产物为花瓣状; 加入碱性添加剂碳酸铵时, 热解产物为球状; 加入可溶性镁盐时, 热解产物为晶须状。     

Preparation of magnesium hydroxide from serpentinite by sulfuric acid leaching for CO2 mineral carbonation

Carbon capture and storage (CCS) by mineral carbonation is a promising way for CO₂ emissions mitigation that has been under studied for decades. In this work, the preparation of magnesium hydroxide from Finnish serpentinite using sulfuric acid leaching as the first step of a CO₂ mineral carbonation process was studied. Some details of leaching behavior of the ore were revealed and a valuable metal was recovered in this study. It was found that leaching yield of magnesium increased with sulfuric acid dosage, limited by a product layer formed on the ore particles, resulting in incomplete serpentinite decomposition. Agitation and ultrasonication were demonstrated to be effective in controlling the thickness of product layer. About 95% of iron was recovered from the leachate and leaching residues and valuable Fe-rich substances were obtained as by-products. After the iron extraction, a fine Mg(OH)₂-rich powder could be prepared from the Mg-rich solution by precipitation using sodium hydroxide solution.     

钛铁矿制备纳米钛基材料的研究

以廉价易得的天然钛铁矿为原料,采用"机械球磨活化+碱浸"工艺制备FeTiO_3纳米花,采用"机械球磨活化+碱浸+酸浸"工艺制得TiO_2/FeTiO_3纳米微粒。首先通过机械球磨活化减小钛铁矿的物理尺寸,使其化学性质变得活泼,然后通过碱浸的方法得到呈三维花瓣状的FeTiO_3纳米花,最后纳米花进一步酸浸得到规则的TiO_2/FeTiO_3纳米微粒。通过分析FeTiO_3纳米花和TiO_2/FeTiO_3纳米微粒的形貌和物相组成,得出结论碱浸时较优的NaOH浓度为1mol/L,碱浸时间为2h,酸浸时较优的HCl浓度为2mol/L,酸浸时间为8h。较优条件下获得的FeTiO_3纳米花厚度在25nm左右,长度在200～400nm之间,TiO_2/FeTiO_3纳米微粒直径在30nm左右。通过分析碱浸和酸浸的机理,可知反应过程中都有不稳定液相中间产物的生成,运用溶解和中间体水解产生沉淀的机理进行了解释,中间体的生成和水解平衡受酸或者碱浓度的影响。