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Low-pollution expandable graphite preparation and stability of

Author: ChenXiaoWei
Tutor: MouChunBo
School: Qingdao University
Course: Materials Science
Keywords: expandable graphite nitrate preparation stability
CLC: TQ127.11
Type: Master's thesis
Year: 2009
Downloads: 248
Quote: 3
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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.

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CLC: > Industrial Technology > Chemical Industry > Non-metallic elements and their inorganic compounds, the chemical industry > Part Ⅳ family of non-metallic element and its inorganic compounds > Carbon and its inorganic compounds > Carbon
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