Synthesis and characterization of magnesium hydroxide by batch reaction crystallization

Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl₂ and NaOH as reactive materials and NaCl as additive to improve the crystallization behavior of the product. The particle size distribution, crystal phase, morphology, and surface area of magnesium hydroxide were characterized by Malvern laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscope (SEM) and Branauer-Emmett-Teller (BET) method, respectively. The purity of products was analyzed by the chemical method. The effects of synthesis conditions on the particle size distribution and water content (filtration cake) of magnesium hydroxide were investigated. The results indicated that feeding mode and rate, and reaction temperature had important effects on water content and the particle size distribution of the product, and sodium chloride improved the crystallization behavior of magnesium hydroxide. The ball-like magnesium hydroxides with the particle size distribution of 6.0–30.0 μm and purity higher than 99.0% were obtained. This simple and mild synthesis method was promising to be scaled up for the industrial production of magnesium hydroxide.     

用氯化镁生产氢氧化镁和氧化镁的方法

采用一种精制原料和两次煅烧工艺克服在Aman法分步精制原料和三次煅烧等现有工艺路线长、能耗高、生产成本高等不足，将煅烧温度分为：600－800℃轻烧，800－1200℃重烧，1200－1800℃死烧3个温度段，可以分别制得高纯的轻质、重质氧化镁和镁砂。大幅度缩短了工艺路线和生产周期并降低生产成本，成功解决了从原料直接生产氧化镁的技术难题，创造了氧化镁生产的又一方法。     

活性氢氧化镁水热改性制备分散性氢氧化镁

探索了活性氢氧化镁经水热改性制备形貌规则、分散良好的片状氢氧化镁的方法。研究了焙烧-水化对活性氢氧化镁性质的影响及活性氢氧化镁水热改性制备分散性氢氧化镁的工艺规律,并用扫描电子显微镜（SEM）、X射线衍射仪（XRD）、物理吸附仪和激光粒度仪等对水热产物进行了表征。研究结果表明：通过低温焙烧及水化可将团聚态的工业氢氧化镁先转化为活性较高的氢氧化镁,再经温和水热改性即可制得形貌规则、分散性良好的片状氢氧化镁。     

Effects of magnesium hydroxide and its surface modification on crystallization and rheological behaviors of polypropylene

In this article, polypropylene composites filled with magnesium hydroxide (PP filled with MH) were prepared in corotating twin-screw extruder. The effects of MH particles content and types of treatment agents on the crystallization and melting behaviors, crystal structure, and rheological properties of PP/MH composites were studied by differential scanning calorimetry (DSC), a wide-angle X-ray diffraction, and dynamic rheological measurements. The DSC results show that MH particles act as a good heterogeneous nucleation effect on PP. Surface treatment of MH weakens its heterogeneous nucleation effect. The nucleating efficiency of MH on PP is found to depend strongly on its content and type of treatment agents. The dynamic rheological behaviors of MH filled PP is found that the complex viscosity (η*) increases with increasing MH content, whereas with increasing filler concentration the network structure becomes the prevailing process, which raises the η* values, especially at the low frequency zone. The η* values of the composites, however, decrease with the addition of various treatment agents. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The effect of grinding on precipitated magnesium hydroxide

Magnesium hydroxide, prepared by precipitation, was ground in a vibratory ball mill for 733 h. Samples were withdrawn at intervals, and examined by thermogravimetric analysis and by X-ray diffraction (the broadening of the lines being analysed using integral breadths), and their specific surfaces were determined by adsorption of nitrogen at —183°. The results indicate that the particles initially consist of small piles of plate-like crystallites and that they become progressively fractured across their (001) faces, until they are approximately equi-dimensional. By a process of shearing and re-adhesion, the piles become increasingly turbostratic in structure, but distortion of the lattice appears only after 350 h. Water is adsorbed on the surface temporarily exposed during grinding and some, at least, of it becomes buried in the interior of the particles.     

超细氢氧化镁制备工艺研究

用摩尔比为1∶2的硫酸镁溶液与氨水反应(氨水稍过量),通过一步沉淀法制取超细氢氧化镁,经正交试验选出适宜条件,并用表面改性剂Z17对氢氧化镁进行表面改性,利用超声波分散,制得粒度在0.1μm左右,分布均匀的超细氢氧化镁。     

纳米片状氢氧化镁的制备

纳米Mg(OH)_2(氢氧化镁)是一种聚合物用环保高效无卤阻燃剂,但采用常规法制得的纳米Mg(OH)_2因极易团聚而分散性较差。以氧化镁/HCl(盐酸)制备的氯化镁、NH_3·H_2O(氨水)和NaOH(氢氧化钠)为原料,在PEG(聚乙二醇)存在的情况下,采用水热法合成了3种不同尺寸的纳米片状Mg(OH)_2。研究结果表明:所得产物均为纳米片状结构,并且均具有较强的光致发光特性,而且1 mol/L NaOH/Mg(OH)_2、1 mol/L NH_3·H_2O/Mg(OH)_2、2 mol/L NH_3·H_2O/Mg(OH)_2的厚度分别为20、10、6 nm;随着纳米Mg(OH)_2片层厚度的减小,其表面极性增强,发射峰位置红移,发射峰强度减弱。     

氢氧化镁的表面处理研究

为了解决氢氧化镁与聚合物相容性不好等问题，表面改性是有效的途径之一。分别采用稀土偶联剂、硬脂酸钙偶联剂，以及其联合偶联剂，以干法和湿法对4种不同的氢氧化镁进行了表面包覆工作。包覆后的氢氧化镁真密度都有下降，而表观密度和灼烧失重都有所增加。通过对比得出了以稀土为偶联剂，采用干法对氢氧化镁进行处理得到的效果最好。     

Sintering of magnesium hydroxide obtained from magnesium chloride solutions

Conclusions We studied two batches of magnesium hydroxide obtained by precipitating out (using dolomite milk) from magnesium chloride solution formed when processing potassium ores.The effect of the compaction pressure, the firing temperature, and prior heat treatment on the sintering process of magnesium hydroxide was investigated.The experimental samples of magnesium hydroxide exhibit high sinterability and facilitate the production of periclase powders (powder bodies) having a porosity of 6.8–9.9% at a firing temperature of 1600°C. The degree of sintering of magnesium hydroxide increases with increasing compaction pressure and firing temperature. Prior heat treatment of the material at 800–1000°C intensifies the sintering process with simultaneous reduction of shrinkage.The studies conducted on the specimens prepared from a fired briquette established that the periclase (magnesite) powder obtained from magnesium hydroxide is suitable for the production of magnesia refractories.A. V. Kushchenko and G. G. Eliseeva (UkrNIIO) participated in this investigation.Translated from Ogneupory, No. 2, pp. 7–10, February, 1988.     

Fire-retarding polypropylene with magnesium hydroxide

Four types of magnesium hydroxide with different particle and crystallite sizes and different degrees of agglomeration were added at amounts up to 60% by weight to polypropylene to obtain a series of composites. The burning characteristics, tensile yield strength, flexural modulus, notched Izod impact strength, and melt flow index of the resulting composites were measured. Magnesium hydroxide coated with sodium stearate was found to give an increased melt flow index and impact strength to the composites as compared to values obtained with uncoated magnesium hydroxide. Incorporation of not less than about 57% by weight of magnesium hydroxide made the composite nonflammable, but at the same time considerably reduced its impact, flexural, and tensile yield strengths. As the amount of magnesium hydroxide filler was increased, the tensile yield strength and flexural strength of the composite proportionally decreased while the flexural modulus increased. The impact strength reached a maximum value when the amount of incorporation was 30% by weight. The lower the degree of agglomeration of the magnesium hydroxide filler and the greater the crystallite size within the range to about 2μm, the better were the mechanical properties of the composite.     

氢氧化镁在工业废水处理中的应用

推荐了一种被称为“环境友好型”绿色安全废水处理剂－氢氧化镁。由于其具有缓冲性,活性大,吸附能力强,不具腐蚀性,安全,无毒,无害,近年来在工业废水处理系统得到了广泛的应用。主要包括：作酸性废水中和处理剂,重金属离子脱除以及废水中氮磷和其他有害物质的脱除等。     

Manufacturing of magnesium hydroxide from natural magnesium chloride sources

Various processes for manufacturing magnesium hydroxide have been considered and tested in order to decide whether they can be employed to the full-scale production of this product from natural sources (bischofite and magnesium chloride brines). The process for the synthesis of magnesium hydroxide from magnesium chloride using sodium hydroxide has been improved.     

一维氢氧化镁材料的制备研究

以氯化镁和氨水为原料,实验室自制了条带状碱式氯化镁作为一维氢氧化镁材料的前驱体。在乙醇溶液中,以氢氧化钠为转化剂,将前驱体转化为氢氧化镁。采用扫描电子显微镜及X射线衍射光谱对产品的结构及微观形貌进行表征,对比研究了静置转化、水浴搅拌转化、水热转化3种转化方式对产品的影响。结果表明,采用水热转化法制备的氢氧化镁材料,具有良好的一维形貌,尺寸均匀,长径比大,材料表面极性小,且反应耗时短,更利于工业化生产。     

氢氧化镁吸附性能研究

采用氢氧化镁乳液对富含重金属离子废水、印染废水以及海水中的微量硼实施吸附处理。研究结果表明:氢氧化镁对废水中各类重金属离子均有很好的吸附效果,去除率最高达到98%;对印染废水的脱色率与COD去除率分别达到97.5%和80%;对海水中硼的吸附率达到74%。     

纳米银材料绿色制备及其在水处理中的应用进展

针对纳米银粒子最常用的制备方法化学还原法中化学试剂的大量使用及其对环境的污染,结合近几年国内外的研究成果,介绍了纳米银的绿色制备方法,包括二糖法、多糖法、微生物合成法、植物提取物法等。同时介绍了纳米银离子在净水处理和废水处理方面的应用进展。分析认为,糖类作为还原剂可生成具有良好催化及杀菌性能的纳米银粒子。纳米银的形貌可控制备以及生物合成法中微生物及植物的选择技术等是今后纳米银绿色制备的发展方向。     

氢氧化镁阻燃剂发展概述

介绍Mg(OH)2阻燃剂的优势以及阻燃抑烟机理,评述了Mg(OH)2阻燃剂的制备方法,提出了新的制备工艺以及有针对性的发展方向与建议。     

高纯纳米氢氧化镁制备工艺

引言我国是镁资源大国,西部盐湖镁资源尤为丰富,主要以水氯镁石(MgCl2·6H2O)形式存在,成本十分低廉.我国镁资源利用处于较低水平,主要是以MgCl2·6H2O形式直接出口,造成资源的浪费.氢氧化镁具有分解温度高、热稳定性好、无毒、无烟及抑烟等特点,可作为高性能无机阻燃剂应用于高分子材料中.环境友好的阻燃剂氢氧化镁受到了各国重视,有关研究[1～3]、生产活动十分活跃,尤其是高纯、超细氢氧化镁阻燃剂已成为目前国内外开发与研究的热点.国内外超细Mg(OH)2粉体制备方法主要有沉淀合成法[4]、水热法[5]、反向沉淀法[6]、沉淀共沸蒸馏法[7]…     

花瓣状纳米氢氧化镁及氧化镁的微波辅助合成

在微波辅助下,以硫酸镁、NH₃•H₂O-NH₄Cl缓冲溶液为原料,通过均相沉淀反应制备了纳米氢氧化镁,经煅烧又得到了纳米氧化镁。采用X射线衍射（XRD）、透射电镜（TEM）、扫描电镜（SEM）、热重分析（TG）等分别对纳米氢氧化镁和氧化镁的结构、形貌及热稳定性进行了分析测试。结果表明,纳米氢氧化镁的结晶性能较好,其形貌为由厚度约40 nm的纳米片团聚而成的花瓣状;纳米氧化镁亦保持了氢氧化镁花瓣状形貌。并对微波辅助下纳米氢氧化镁形成的可能机理进行了初步探讨。