Effect of purification methods on the quality and morphology of plastic waste-derived carbon nanotubes

Abstract

Recent innovative research efforts on the usage of plastic wastes as a cheap carbon source for carbon nanotubes (CNTs) production have emerged as a low-cost and sustainable means of producing CNTs. However, plastic waste-derived CNTs are rarely used in some purity-sensitive and high-alignment needed applications due to the poor quality of CNTs resulting from the abundance of impurities such as non-crystalline amorphous carbon, metallic nanoparticles, and other impurities. Therefore, purification is a crucial issue to be addressed to fully harness all potential applications of CNTs derived from waste plastic materials. Here, the effect of employing different purification methods on the morphology and purity of waste plastic-derived CNTs was investigated. CNTs were synthesized using waste polypropylene plastic as carbon feedstock via a single-stage catalytic chemical vapour deposition (CVD) technique. As-produced CNTs were purified using liquid-phase oxidation (chemical oxidation in nitric acid), gas-phase oxidation in air, and a combination of both liquid- and gas-phase oxidation methods. The synthesized and purified CNTs were characterized for morphology, purity, surface functional groups, thermal stability, and crystallinity using Transmission electron microscopy (TEM), Raman spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD), respectively. Results obtained showed that a combination of both liquid and gas phase oxidation purification techniques resulted in purer, better quality, and less defective CNTs with an IG’/IG value of 0.89 and ID/IG value of 0.86, while chemically treated CNTs (CNT-PC) presented more structurally defective CNTs and shortened nanotubes compared to other investigated treatment methods with an ID/IG value of 0.96. CNTs purified by a multi-step protocol (CNT-PAC) showed the highest weight loss of 72.3% indicating the highest quality and the presence of filamentous carbon. This study confirms that the choice of purification techniques influences the morphology and quality of plastic-derived CNTs.

Keywords

• Plastic waste derived carbon nanotubes
• purification methods
• chemical oxidation
• air oxidation
• morphology
• quality

References

1. L. Yaqoob, T. Noor, and N. Iqbal, “Conversion of plastic waste to carbon-based compounds and application in energy storage devices,” ACS Omega, Vol. 7, pp. 13403–13435, 2022. [CrossRef]
2. R. Rao, C. L. Pint, A. E. Islam, R. S. Weatherup, S. Hofmann, E. R. Meshot, ... and A. J. Hart, “Carbon nanotubes and related nanomaterials: Critical advances and challenges for synthesis toward mainstream commercial applications,” ACS Nano, Vol. 12, pp. 11756–11784, 2018. [CrossRef]
3. U. P. M. Ashik, W. M. A. W. Daud, and J. Hayashi, “A review on methane transformation to hydrogen and nanocarbon: Relevance of catalyst characteristics and experimental parameters on yield,” Renewable and Sustainable Energy Reviews, Vol. 76, pp. 743–767, 2017. [CrossRef]
4. R. Das, M. E. Ali, S. B. Abd Hamid, M. S. M. Annuar, and S. Ramakrishna, “Common wet chemical agents for purifying multiwalled carbon nanotubes,” Journals of Nanomaterials, Vol. 2014, pp. 237–237, 2015. [CrossRef]
5. X. Jia, and F. Wei, “Advances in production and applications of carbon nanotubes,” Topics in Current Chemistry, Vol. 375, Article 18, 2017. [CrossRef]
6. H. U. Modekwe, M. A. Mamo, K. Moothi, and M. O. Daramola, “Effect of different catalyst supports on the quality, yield and morphology of carbon nanotubes produced from waste polypropylene plastics,” Catalysts, Vol. 11, Article 692, 2021. [CrossRef]
7. A. F. Ismail, P. S. Goh, J. C. Tee, S. M. Sanip, and M. Aziz, “A review of purification techniques for carbon nanotubes,” Nano, Vol. 3(3), pp. 127–143, 2008. [CrossRef]
8. P.-X. Hou, C. Liu, and H.-M. Cheng, “Purification of carbon nanotubes,” Carbon, Vol. 46, pp. 2003–2025, 2008. [CrossRef]

9. P. Mahalingam, B. Parasuram, T. Maiyalagan, and S. Sundaram, “Chemical methods for purification of carbon nanotubes- A Review,” JJournal of Environmental Nanotechnology, Vol. 1(1), pp. 53–61, 2012.
10. S. Boncel, and K. K. K. Koziol, “Enhanced graphitization of c-CVD grown multi-wall carbon nanotube arrays assisted by removal of encapsulated iron-based phases under thermal treatment in argon,” Applied Surface Science, Vol. 301, pp. 488–491, 2014. [CrossRef]
11. A. H. Hammadi, A. M. Jasim, F. H. Abdulrazzak, A. M. A. Al-Sammarraie, Y. Cherifi, R. Boukherroub, and F. H. Hussein, “Purification for carbon nanotubes synthesized by flame fragments deposition via hydrogen peroxide and acetone,” Materials (Basel), Vol. 13, Article 2342, 2020. [CrossRef]
12. I. Pelech, U. Narkiewicz, A. Kaczmarek, and A. Jedrzejewska, “Preparation and characterization of multi-walled carbon nanotubes grown on transition metal catalysts,” Polish Journal of Chemical Technology, Vol. 16(1), pp. 117–122, 2014. [CrossRef]
13. J. C. Goak, S. H. Lee, and N. Lee, “Effect of purification on the electrical properties of transparent conductive films fabricated from single-walled carbon nanotubes,” Diamond and Related Materials, Vol. 106, Article 107815, 2020. [CrossRef]
14. A. Ahamed, A. Veksha, K. Yin, P. Weerachanchai, A. Giannis, and G. Lisak, “Environmental impact assessment of converting flexible packaging plastic waste to pyrolysis oil and multi-walled carbon nanotubes,” Journal of Hazardous Materials, Vol. 390, Article 121449, 2020. [CrossRef]
15. H. U. Modekwe, M. A. Mamo, M. O. Daramola, and K. Moothi, “Catalytic performance of calcium titanate for catalytic decomposition of waste polypropylene to carbon nanotubes in a single-stage CVD reactor,” Catalysts, Vol. 10(9), Article 1030, 2020. [CrossRef]
16. H. U. Modekwe, M. Mamo, K. Moothi, and M. O. Daramola, “Synthesis of bimetallic NiMo/MgO catalyst for catalytic conversion of waste plastics (polypropylene) to carbon nanotubes (CNTs) via chemical vapour deposition method,” Materials Today: Proceedings, Vol. 38, pp. 549–552, 2021. [CrossRef]
17. M. S. Dresselhaus, G. Dresselhaus, R. Saito, and A. Jorio, “Raman spectroscopy of carbon nanotubes,” Physics Reports, Vol. 409, pp. 47–99, 2005. [CrossRef]
18. E. M. Elsehly, N.G. Chechenin, A. V. Makunin, H. A. Motaweh, E. A. Vorobyeva, K. A. Bukunov, E. G. Leksina, and A. B. Priselkova, “Characterization of functionalized multiwalled carbon nanotubes and application as an effective filter for heavy metal removal from aqueous solutions,” Chinese Journal of Chemical Engineering, Vol. 24, pp. 1695–1702, 2016. [CrossRef]
19. H. U. Modekwe, M. Mamo, K. Moothi, and M. O. Daramola, “Polypropylene waste-derived carbon nanotubes (CNTs) via single-stage CVD technique: Determination of crystallinity,” IOP Conference Series: Materials Science and Engineering, Vol. 1107, Article 012067, 2021. [CrossRef]
20. R. Yudianti, H. Onggo, Sudirman, Y. Saito, T. Iwata, and J. Azuma, “Analysis of functional group sited on multi-wall carbon nanotube surface,” The Open Materials Science Journal, Vol. 5, pp. 242–247, 2011. [CrossRef]
21. A. Cao, C. Xu, J. Liang, D. Wu, and B. Wei, “X-ray diffraction characterization on the alignment degree of carbon nanotubes,” Chemical Physics Letters, Vol. 344, pp. 13–17, 2001. [CrossRef]
22. J. Dore, A. Burian, and S. Tomita, “Structural studies of carbon nanotubes and related materials by neutron and X-ray diffraction,” in Proceedings of the International Conference. Condensed Matter Physics, Vol. 98(5), pp. 495–504, 2000. [CrossRef]
23. D. K. Singh, P. K. Iyer, and P. K. Giri, “Diameter dependence of interwall separation and strain in multiwalled carbon nanotubes probed by X-ray diffraction and Raman scattering studies,” Diamond and Related Materials, Vol. 19, pp. 1281–1288, 2010. [CrossRef]
24. H. Yusa, and T. Watanuki, “X-ray diffraction of multiwalled carbon nanotube under high pressure : Structural durability on static compression,” Carbon, Vol. 43, pp. 519–523, 2005. [CrossRef]
25. R. Das, S. B. A. Hamid, M. E. Ali, S. Ramakrishna, and W. Yongzhi, “Carbon nanotubes characterization by X-ray powder diffraction – A Review,” Current Nanoscience, Vol. 11(1), pp. 1–13, 2015. [CrossRef]