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低污染可膨胀石墨的制备及稳定性研究
【作者】 陈小伟；
【导师】 牟春博；
【作者基本信息】 青岛大学 ， 材料学， 2009， 硕士
【摘要】 为了减少现行工业制备可膨胀石墨方法中锰离子的排放,本文在硫酸酸性条件下用硝酸钠和硝酸铵作为氧化剂及插入剂。探讨了一种无重金属离子污染、低成本的可膨胀石墨制备方法。本文主要讨论了硫酸用量、插入剂种类、插入剂与石墨的配比、反应温度和时间等不同因素对制备可膨胀石墨的膨胀体积的影响规律。采用正交试验方法分析并确定分别用硝酸钠和硝酸铵作插层剂制备可膨胀石墨的最佳工艺条件是:石墨（g）:硝酸钠（g）:浓硫酸（mL）=5:5:22;反应温度50℃;反应时间50min,在此条件下制备的可膨胀石墨膨胀体积可达到330 mL·g-1;石墨（g）:硝酸铵（g）:浓硫酸（mL）=10:1.5:28;反应温度40℃;反应时间45min在此条件下采用两次加料法制备的可膨胀石墨的膨胀体积可达400 mL·g-1,生产过程无重金属离子参与,杜绝重金属离子的污染,同时可以对废液进行回收利用。在改进可膨胀石墨制备工艺的同时本文还讨论了可膨胀石墨的稳定性:通过用水、酸、碱以及盐溶液对可膨胀石墨进行浸渍处理后测定样品的膨胀体积,以此来观察可膨胀石墨的稳定性。实验发现新制备的可膨胀石墨稳定性较差,用酸、碱以及硝酸盐、磷酸盐等各种试剂对新制备的可膨胀石墨进行处理后,会影响到产品的稳定性。酸碱性的强弱和盐离子浓度对可膨胀石墨的稳定性影响不大;当溶液中存在合适的离子时可膨胀石墨可以继续生长,其中溴化钾对其膨胀体积的提高作用最大。制备完成后,随着时间的推移脱夹层反应趋于停止,可膨胀石墨的稳定性增强,各种处理对其膨胀体积将不再产生明显影响。另外,对可膨胀石墨进行浸渍处理时,发现所得膨胀石墨的硫含量也发生了变化,当浸渍试剂为碱性或者存在碱金属离子时,会使产品的含硫量增加,特别是当试剂中存在钠离子时所得膨胀石墨的含硫量大大增加。而经过盐酸浸渍处理后所得膨胀石墨的含硫量有所减少。
【Abstract】 In order to reduce the emission of heavy metal ions of the existing industrial methods of producing of expandable graphite,this paper researched a low-cost preparation method for producing expanded graphite without heavy metal ions pollution:in sulfuric acid medium with sodium nitrate and ammonium nitrate as an insertion agent to produce expandable graphite.This article discussed the amount of sulfuric acid,the insert agent type,the ratio of insert agent and graphite,reaction temperature and time on the effects of expanded volume.And then used orthogonal test method to determine the optimum reaction conditions:graphite（g）:sodium nitrate（g）:concentrated sulfuric acid（mL） = 5:5:22; reaction temperature 50℃;reaction time 50min,in this condition the expanded volumes of the production can be reached 330mL·g-1;graphite（g）:ammonium nitrate（g）:concentrated sulfuric acid（mL）= 10:1.5:28;reaction temperature 40℃; reaction time 45min,using two feed methods can prepared expandable graphite with 400mL·g-1,the production process with no heavy metal ions pollution,as well as recycling of waste.At the same time this article also discussed the stability of expanded graphite.We steeped the expandable graphite in water,acid,alkali,salt solution and then test its expanded volume,so we can get its stability state.We discovered that new prepared expandable graphite is less stable.The stability of new prepared expandable graphite can be changed after steeped in acid,alkali,as well as nitrate,phosphate and other reagents. Acid-base and salt ion concentration have little effect on the stability of expandable graphite;when there are suitable ions appears in the reagent the expandable graphite can get a further growth,which KBr can greatly increase its expanded volume.With the passage of time the stability of expanded graphite can be enhanced.In addition,we found that the sulfur content of the expandable graphite got changed after being steeped.When the impregnating reagent are alkali or contains alkaline metal ion,the sulfur content of the product will increase,especially when the reagent have sodium ions from the sulfur content of expanded graphite will greatly increased.After steeped in hydrochloric acid the expanded graphite’s sulfur content get decreased.