以α-纖維素製備高純度石墨烯及其於水中氯離子的高效率吸附去除

Thermal Conversion of α- Cellulose to High Purity Graphene and its Application for the High Efficiency Removal of the Chloride Ions in Water

羅嫚琳(Man-Lin Luo)

指導教授 ： 黃武章 ； 張國慶

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2015年)

https://doi.org/10.6346/NPUST.2015.00092

摘要

石墨烯為單(少)層石墨結構的物質，其具有比矽高的遷移力、特殊光電特性與熱傳導等特性。目前石墨烯的合成方法有物理剝離法、化學氣相層積法、超臨界二氧化碳剝離法[5]以及濕式化學氧化(還原)法等。本研究室於2012至2014年間針對生質物製備石墨烯材料進行了一系列的詴驗並成功製備具高導電效率之石墨烯材料，同時提出碳材料中所含石墨烯純度之定量方式，並發現石墨烯含量與生質物所含的α-纖維素含量呈正相關。因此本研究將延續先前之研究，並以α-纖維素合成高純度之石墨烯材料，藉以提出高純度、低成本之石墨烯製程，同時將其作為水中色度與氯離子的處理劑。
由結果可知，冺用α-纖維素原料以二階段熱處理程序製備之高純度石墨烯材料是可行的。且其在熱裂解溫度1500 oC、處理時間48 hr所製備之石墨烯，其純度最高可達98.95 %，而帄均導電度與電阻率分冸為95.69 S/cm與0.0104 Ω〄cm，且亦可藉由30 %之H2O2與超音波震盪將其分離出單層之石墨烯片。且由XRD分析發現，第二階段熱裂解程序之時間增加，其石墨結晶層訊號(2 θ degree = 26o)之強度並未隨之增加且有減弱之趨勢。推測是由於第一階段炭化程序已有少許石墨微晶生成且其表面部分氧化，使其進入第二階段熱裂解程序時抑制了石墨晶層的發展並造成其能量散射而產生之淬冷現象。
由產業分析可知人造石墨與以CVD製程製備之石墨烯之成本分冸為1,450 USD/ton與28.57 USD/g，而本研究所用之α-纖維素原料成本約為40 USD/kg，且以α-纖維素製備石墨烯之帄均產率約為12.30 %，且其純度約為92.85 %，其製程成本約為0.11 USD/g。因此以α-纖維素製備石墨烯可望大幅降低其製程之成本。 將自製石墨烯(~ 90 %)用於甲基藍與飛灰水洗液之氯離子的去除。由結果可知，其具有快速、高穩定性且無(低)二次污染物產生等優點。且其經光活化後作為高氯含量(~ 177,000 ppb)之飛灰水洗液的處理劑測詴結果可知，其作為高氯含量之飛灰水洗液的處理劑效果最穩定。且其添加量為0.1 g時，於處理時間5 min時，水中氯離子之去除率為66.67 %々而將其添加量增加為1.25 g，於處理時間5 min時，其去除率可達100 %。而將其作為三維不對稱式電化學系統之工作電極進行甲基藍之脫色測詴中可知於於處理時間5 min時，其色度之去除率其去除率已可達100 %。因此未來可望將其應用於工業廢(污)水之處理單元上使用。

關鍵字

生質物 ； α-纖維素 ； 石墨烯 ； 氯離子 ； 去氯

並列摘要

Graphene is a monolayer graphite that has higher electron mobility than silicon, high heat conduction and special optical properties. Many graphene fabrications have been proposed, such as chemical vapor deposition, chemical reduction of graphene oxide, and the exfoliation method. However, these processes are unfeasible due to high cost and the difficulty of removing byproducts. Since 2012 to 2014, our research group identified a feasible method of characterizing graphene sheet content quantitatively in carbon materials and processes for the preparation of high graphene sheet content carbon materials (GSCCMs) from biochar. From these results, we observed a formation of graphene sheet containing α-cellulose content of woody biomass materials. Therefore, in this study we investigated an economic route to mass production of graphene from α-cellulose materials, and its application to remove methyl blue and chloride from MSWI fly ash washing wastewater by graphene.
It was found that the efficiency of XRD quenching on GSCCMs increased with the changing of heat-treatment temperature due to the increment in the size of graphene sheets. The highest graphene sheet content of graphene from α-cellulose has 98.95 % at 1500 oC for 48 hr, with an average conductivity and resistivity of 95.69 S/cm and 0.0104 Ω‧cm, respectively. The highest graphene sheet was separated into a monolayer graphene after it was immersed in 30 % of H2O2 solution at room temperature. According to the industry reports, the cost of artificial graphite and graphene for a CVD process is 1,450 USD/ton and 28.57 USD/g, respectively, and the cost of α-cellulose is 40 USD/kg. In this study, the production cost of GSCCMs from α-cellulose was about 0.11 USD/g, and graphene yield was 12.3 %. Therefore, preparing graphene from biomass materials could highly reduce the cost. Homemade graphene from α-cellulose (the graphene content ~ 90 %) removed approximate 177,000 ppb of methylene blue and high chloride content from MSWI fly ash waste water using washing processes. From results, using optical activation homemade graphene from α-cellulose has the advantage of high stability and fast, non (or low) - secondary pollutants etc. When the treatment time was set at 5 minutes, the removal ratio of chloride was achieved at 66.67 % and has 2.22 times higher removal ratio of chloride than other carbon materials. When the treatment time was set at 20 minutes, the removal ratio of chloride was achieved at 100 %. The removal ratio of methyl blue was achieved 100 % at 5 min by using homemade graphene from α-cellulose as working electrode of 3D- asymmetric electrochemical system. The utilization of homemade graphene from α-cellulose is promising, and can be applied as a treatment unit for industrial wastewater in the future.

並列關鍵字

Biomass ； α-cellulose ； Graphene ； Chloride ions ； Dechlorination

參考文獻

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