纳米氢氧化镁的卤水—碱法合成与分析及重质氧化镁的制备

发布时间：2018-06-02 00:01

  本文选题：纳米氢氧化镁 + 活性氧化镁　； 参考：《华东师范大学》2015年硕士论文

【摘要】：我国卤水资源丰富,多以镁离子形式存在。近来,海水淡化、制盐工业和通过盐湖来提取钾元素也产生大量卤水废液,一定程度上造成污染,所以合理利用卤水,将其变废为宝意义重大。纳米材料是21世纪的新型材料,由于具有粒径小、比表面积大、形貌多样等特点而在光电、化学等方面表现出特异性,所以有关镁化合物纳米材料的生产受到广泛关注。纳米氢氧化镁是一种重要的无机材料,由于其受热分解成氧化镁和水,可将其作为一种无烟无毒的防燃填充材料,此外它中和能力强,在医药等方面也有广泛应用。高活性氧化镁粒径一般小于2000nm,通常柠檬酸活性测定值在25s以下,由于颗粒细微其光电磁等特性异于一般氧化镁。在医药上可用作治疗肠胃疾病药品的辅佐添加剂；环保上可作为高效解离吸附剂,吸附酸性气体和含氯烃、有机磷的有毒化学物质等。本文采用卤水-碱法在不同实验条件下制备纳米氢氧化镁和活性氧化镁,同时也探索了制备堆积密度大于0.5g/ml的重质氧化镁。主要的研究内容有：1.卤水-烧碱直接沉淀法制备纳米氢氧化镁粉体以卤水、烧碱为原料制备目标粉体氢氧化镁,制备时考察了反应温度、反应时间、浓度、干燥方式等因素对粉体粒度D50(平均粒度,下同)的影响。用激光粒度仪测量不同实验条件下制得粉体的平均粒度D50,并对粉体进行XRD、SEM和TG-DTG表征分析。最终在最优条件下制得纯度高、粒度小、疏松分散的片状纳米氢氧化镁,其厚度约为10nm、直径约150nm。2.不同条件下卤水-碱法制备氧化镁并考察其活性以卤水、烧碱为原料制备氧化镁前驱体,煅烧得氧化镁后柠檬酸法测其活性。改变反应温度、浓度和干燥方式等考察其与粉体活性的关系,确定最优反应条件；分别考察了正向滴加、反向滴加和双注滴加法对所制备出的氧化镁活性的影响,以确定滴加方式；最后对产物进行XRD、SEM表征分析。研究发现：当卤水稍过量,最佳的反应条件和煅烧温度下能够制备出粒度小、分散性高、表面多孔的片状活性氧化镁,其柠檬酸活性检测(CAA值)约8s。3.卤水-混碱直接沉淀法制备重质氧化镁以卤水、烧碱、纯碱为原料采用直接沉淀法制备氧化镁前驱体,首先分别以纯碱、烧碱及二者混合为沉淀剂制备氧化镁,测出其堆积密度,并进行XRD、SEM表征分析,以判断出最佳碱性沉淀剂；然后控制混碱的总量一定,通过改变混碱摩尔比、制备时温度、浓度等条件制备氧化镁前驱体,再煅烧制氧化镁粉体,得目标粉体后测出其堆积密度,确定最佳制备条件。研究发现：纯碱、烧碱以摩尔比1：3与卤水在T=60℃时反应,850℃下煅烧2.5h得氧化镁堆积密度最大,约1.527g/ml。
[Abstract]:Brine resources are abundant in China, and most of them exist in the form of magnesium ions. Recently, seawater desalination, salt industry and the extraction of potassium from salt lakes also produce a large amount of brine waste liquid, which causes pollution to a certain extent, so it is of great significance to make rational use of brine and turn it into a treasure. Nanomaterials are new materials in the 21st century. Because of their small particle size, large specific surface area and various morphologies, nanomaterials show specificity in photoelectricity and chemistry, so the production of magnesium nanomaterials has been paid more and more attention. Nanocrystalline magnesium hydroxide is an important inorganic material, which can be used as a kind of smokeless and non-toxic combustion-proof filling material because of its thermal decomposition into magnesium oxide and water. In addition, it has strong neutralization ability and has been widely used in medicine and so on. The particle size of highly active magnesium oxide is generally less than 2000nm, and the determination value of citric acid activity is less than 25s, which is different from that of ordinary magnesium oxide because of its fine photoelectric and magnetic properties. It can be used as adjuvant additive in medicine for treating gastroenteric diseases, environmental protection can be used as high efficient dissociation adsorbent, adsorption of acid gas and chlorinated hydrocarbon, toxic chemicals of organophosphorus and so on. In this paper, nanocrystalline magnesium hydroxide and active magnesium oxide were prepared by brine-alkali method under different experimental conditions. At the same time, the preparation of heavy magnesium oxide with bulk density greater than 0.5g/ml was also explored. The main content of the study is: 1. Magnesium hydroxide nanoparticles were prepared by brine and caustic soda direct precipitation method. The reaction temperature, reaction time, concentration, drying method and other factors on the particle size D50 (average particle size) were investigated during the preparation of magnesium hydroxide, which was prepared from brine and caustic soda. The same as below. The average particle size D50 of the powder was measured by laser particle size analyzer under different experimental conditions. The powder was characterized by XRD SEM and TG-DTG. Finally, the high purity, small particle size and loose dispersion of flake magnesium hydroxide were obtained under the optimum conditions, the thickness of which was about 10 nm and the diameter of magnesium hydroxide was about 150 nm.2. Magnesium oxide was prepared by brine alkali method under different conditions. The activity of magnesium oxide precursor was studied by using brine and caustic soda as raw materials. The activity of magnesium oxide was measured by citric acid method after calcination. The optimum reaction conditions were determined by changing the reaction temperature, concentration and drying method, and the effects of direct drop, reverse drop and double drip addition on the activity of the prepared magnesium oxide were investigated, respectively. Finally, the products were characterized by XRDX SEM. It is found that when the brine is slightly excessive, the best reaction conditions and calcination temperature can be used to prepare the flake active magnesium oxide with small particle size, high dispersion and porous surface. The CAA value of its citric acid activity is about 8s. 3. Preparation of heavy magnesium oxide by direct precipitation of brine, caustic soda and soda, magnesium oxide precursor was prepared by direct precipitation method. First, magnesium oxide was prepared by using soda, caustic soda and their mixture as precipitators, respectively. The bulk density was measured and analyzed by XRDX SEM to determine the best alkaline precipitator, and then the magnesium oxide precursor was prepared by changing the molar ratio of the mixed base, temperature and concentration of the mixed alkali, and then controlling the total amount of the mixed alkali. After calcining the magnesium oxide powder, the stacking density of the target powder was measured and the optimum preparation conditions were determined. The results show that the maximum bulk density of magnesium oxide can be obtained by calcination of soda and caustic soda at 850 鈩，

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