改質多壁奈米碳管吸附水溶液中重金屬離子之探討

由於奈米碳管表面官能基化可提高吸附水溶液中的重金屬之能力，且可解決奈米碳管在溶液中易凝聚的問題，故本研究利用奈米碳管表面接枝COOH官能基吸附水溶液中二價銅離子。改質後之奈米碳管於水溶液之溶解度約2500 mg/L，經由FTIR、TGA、反滴定之分析結果可知經改質後碳管表面產生羧基，其熱重損失約為13%，而表面接枝酸根量為1.25mmol/g。在改質碳管吸附銅離子之部分，探討實驗變數包括：反應時間、二價銅離子濃度、pH、離子強度、碳管劑量、溫度等，以尋求吸附系統之最佳條件，並利用Langmuir、Frendlich模式來討論其吸附機制。實驗結果顯示改質碳管吸附水溶液中銅離子之反應中，pH及碳管劑量主要為影響吸附量之因素，而由離子強度實驗中可推測兩者間反應包括離子交換。碳管鹼化使接枝的高分子鏈舒展開後，動力平衡時間在1分鐘內即可達平衡。相對於未接枝前碳管幾乎不吸附銅離子的情況，在30℃反應條件下，奈米碳管對銅離子的吸附量由3.77 mg/g增加為16.72 mg/g，奈米碳管對水溶液中銅離子去除效率明顯增加。吸附模式可符合Langmuir模式為單層吸附反應，由所求得之熱力參數指出此吸附為一自發吸熱反應。吸附後之銅離子可利用0.5 mM硝酸回收，而碳管再利用5次後，效率為84％，具有良好的再生效率。

關鍵字

奈米碳管；接枝；二價銅離子；吸附

並列摘要

In this work, pure multiwalled carbon nanotubes (MWCNTs) were grafted poly acrylic acid to adsorb effectively Cu(II) ions from aqueous solution. The solubility of functionalized MWCNTs was 2500 mg/L in aqueous solution. Identified by FTIR, TGA, and titration, the surface grafted carboxyl groups were 1.25 mmol/g MWCNTs ,and weight loss was 13%. The adsorption of Cu(II) onto functionalized MWCNTs was studied as a function of contact time, pH, ionic strength, MWCNT dosage, and temperature. The results show that Cu(II) adsorption onto MWCNT depends strongly on pH and MWCNT dosage. Cu(II) ions can easily adsorb onto MWCNTs prepared in alkaline solution. Kinetic data show that the adsorption process achieved equilibrium within less than 1minutes. The effect of ionic strength indicated that the Cu(II) adsorption onto functionalized MWCNT might include ion exchange. The Cu(II) adsorption capacity of functionalized MWCNTs was 17.62 mg/g, which is greater than that of pure CNTs, 3.4 mg/g. This reflects that functionalized MWCNT are more effective sorbents. The adsorption data fit Langmuir isotherm well. The thermodynamic analysis revealed the adsorption of Cu(II) ions onto functionalized MWCNTs is an endothermic and spontaneous process. Results of desorption study showed that Cu(II) ions could be removed from MWCNTs by 0.5 mol/L nitric acid and 84% sorption capacity of MWCNTs remained after 5 cycles.

並列關鍵字

Carbon nanotube ； Grafting ； Copper(II) ion ； Adsorption

參考文獻

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改質多壁奈米碳管吸附水溶液中重金屬離子之探討

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