高活性氧化镁的制备与吸附性能的研究

发布时间：2018-03-02 00:16

本文关键词： 氢氧化镁碳酸镁水热碳化活性氧化镁吸附　出处：《天津大学》2015年硕士论文　论文类型：学位论文

【摘要】：我国西部盐湖蕴含丰富的镁资源,由于技术等的限制,镁资源的利用率很低,研究开发高品质镁质产品(如活性氧化镁)是高效利用盐湖镁资源的重要途径,具有重要的经济和社会意义。活性氧化镁是一种重要的无机功能材料,在催化、橡胶、耐火材料、建筑材料、环保(如有毒气体的吸附、废水处理)等领域有着广泛的应用。本文以工业氢氧化镁为原料,研究不同形貌与活性的氧化镁的制备方法及其吸附性能。以氢氧化镁原料为前驱体,采用直接煅烧法制备无规则形貌的活性氧化镁,其制备的条件:煅烧温度450°C,保温时间4h,制得的氧化镁的柠檬酸值(CAA值)最小为48.47s,吸碘值最高为82.74mg/g。以氢氧化镁原料为原料,采用水热法制备了六角片状氢氧化镁前驱体,由其制备六角片状活性氧化镁的最佳工艺条件:煅烧温度为400°C,保温时间为5h,得到氧化镁的柠檬酸值(CAA值)最小为24.85s,吸碘值最高为161.42mg/g。以氢氧化镁原料为原料,与CO_2反应制备了Mg(HCO_3)_2溶液,通过未加入和加入柠檬酸钠添加剂制备了片层花状碱式碳酸镁和三水碳酸镁晶须前驱体,探究了两个前驱体制备活性氧化镁的最佳条件。由碱式碳酸镁制备活性氧化镁的最佳条件为煅烧温度650°C保温2h,在最优条件下制备了柠檬酸值(CAA值)为11.50s,吸碘值为216.72mg/g的活性氧化镁;以三水碳酸镁为前驱体制备活性氧化镁的最优条件为:煅烧温度为600°C,保温时间为2h,得到氧化镁产物的最小柠檬酸值为8.45s,最高吸碘值为262.14 mg/g。详细研究了结晶温度、柠檬酸钠添加量、反应时间及搅拌速率对镁离子的转化率和三水碳酸镁晶须的影响,并对柠檬酸钠在结晶过程中的作用进行了探讨。结果表明,在0.2%(w/w)柠檬酸钠的存在下,三水碳酸镁晶须的形成温度可以提高到90°C,镁离子转化率大幅提高到约80%。当结晶时间为30min,搅拌速率为200r/min时,制备出长径比达到28、尺寸均一、结晶度达99.19%、不含氯和钠离子的三水碳酸镁晶须。活性氧化镁对Pb~(2+)具有良好的吸附性能,详细研究了制备的四种活性的氧化镁产物的吸附性能,其中氧化镁晶须的吸附性能最好,其饱和吸附量可达364mg/g,其吸附过程可以用Langmuir吸附模型来描述。
[Abstract]:The salt lakes in the west of China contain abundant magnesium resources. Due to the limitation of technology, the utilization rate of magnesium resources is very low. The research and development of high quality magnesium products (such as active magnesium oxide) is an important way to efficiently utilize magnesium resources in salt lakes. Active magnesium oxide is an important inorganic functional material in catalysis, rubber, refractories, building materials, environmental protection (such as adsorption of toxic gases), In this paper, the preparation and adsorption properties of magnesium hydroxide with different morphology and activity were studied. Active magnesium oxide with irregular morphology was prepared by direct calcination. The preparation conditions were as follows: calcination temperature 450 掳C, holding time 4 h, the citric acid value and CAA value of the prepared magnesium oxide were 48.47 s, and iodine absorption value was 82.74 mg / g 路g. Hexagonal magnesium hydroxide precursor was prepared by hydrothermal method. The optimum technological conditions for the preparation of hexagonal active magnesium oxide are as follows: calcination temperature is 400 掳C, holding time is 5 h, the citric acid value and CAA value of magnesium oxide are 24.85 s, and iodine absorption value is 161.42 mg / g. The Mg(HCO_3)_2 solution was prepared by reacting with CO_2, and the floral basic magnesium carbonate and magnesium carbonate trihydrate whisker precursor were prepared by adding and without adding sodium citrate additive. The optimum conditions for the preparation of active magnesium oxide from two precursors were investigated. The optimum conditions for the preparation of active magnesium oxide from basic magnesium carbonate were calcined at 650 掳C for 2 h, and the citric acid value and CAA value were prepared under the optimum conditions of 11.50 s and iodine absorption value of 11.50 s. 216.72 mg / g active magnesium oxide; The optimum conditions for the preparation of active magnesium oxide using magnesium carbonate trihydrate as precursor are as follows: calcination temperature is 600 掳C, holding time is 2 h, the minimum citric acid value of magnesium oxide product is 8.45 s, and the highest iodine absorption value is 262.14 mg / g. The crystallization temperature is studied in detail. The effects of the amount of sodium citrate, reaction time and stirring rate on the conversion of magnesium ion and the whisker of magnesium carbonate trihydrate were discussed. The effect of sodium citrate on the crystallization process was discussed. The results showed that in the presence of 0.2w / w sodium citrate, The formation temperature of magnesium carbonate whisker can be raised to 90 掳C and the conversion rate of magnesium ion can be increased to about 80 掳C. when the crystallization time is 30 min and the stirring rate is 200 r / min, the ratio of length to diameter is 28 and the size is uniform. The crystallinity of magnesium carbonate whiskers without chlorine and sodium ions is 99.19. The active magnesium oxide has good adsorption properties for Pb~(2. The adsorption properties of the four active magnesium oxide products prepared are studied in detail. The adsorption capacity of magnesium oxide whisker is the best, its saturated adsorption capacity can reach 364 mg / g, and the adsorption process can be described by Langmuir adsorption model.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ132.2

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