The effects of pH on the precipitation of rice straw lignin from An Giang, Vietnam

Authors

  • Thuy-An Ngo*
  • Dao-Chi Vo Thi
  • Nhan-Tanh Nguyen Tran
  • Thien-Khanh Nguyen Tran
  • Minh-Nguyet Doan Thi
  • Mai-Linh Duong
  • Lan-Tuyen Nguyen

Abstract

This research aimed to extract lignin from rice straw and reveal the pH value of diluted acid at which the most effective yield of lignin was precipitated. In this study, rice straw obtained from local fields in the An Giang province of Vietnam and sodium hydroxide 2 M was employed to extract lignin from rice straw. Hydrochloric acid was used to adjust the sample pH values to be in the range of 1.5-3.5. Fourier-transform infrared spectroscopy (FTIR) analysis was used to characterize the functional groups of the lignin materials. Thermogravimetric analysis (TGA) analysis was employed to supply information on the thermal decomposition of the lignin samples. Herein, the results showed that lignin precipitated at different pH values affected its thermal properties. At 700oC, the yield of the remaining lignin components were 56% at pH 2.0, but the weight loss of lignin agglomerate samples precipitated at pH 3.5 dropped to 85% because many non-lignin substances existed in the samples. The yield of the crude lignin samples obtained were 16.51, 17.66, 15.27, 14.33 and 13.26% for pH of 1.5, 2.0, 2.5, 3.0 and 3.5 respectively. The crystallite regions played an important role in the lignin structures. The spectrum peaks at pH 1.5, 2.0 and 2.5 were broader than the peaks at pH 3.0 and 3.5. The results demonstrated the highest percentage of lignin precipitate was collected at pH 2.0.

Keywords:

agglomerate, crystallinity region, decomposition, lignin, precipitate, redissolve, rice straw, thermal

DOI:

https://doi.org/10.31276/VJSTE.64(3).03-07

Classification number

2.2

Author Biographies

Thuy-An Ngo

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Dao-Chi Vo Thi

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Nhan-Tanh Nguyen Tran

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Thien-Khanh Nguyen Tran

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Minh-Nguyet Doan Thi

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Mai-Linh Duong

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

Lan-Tuyen Nguyen

An Giang University, Vietnam National University - Ho Chi Minh City, 18 Ung Van Khiem Street, Dong Xuyen Ward, Long Xuyen City, An Giang Province, Vietnam

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Published

2022-09-15

Received 7 July 2021; revised 21 September 2021; accepted 5 October 2021

How to Cite

Thuy-An Ngo, Dao-Chi Vo Thi, Nhan-Tanh Nguyen Tran, Thien-Khanh Nguyen Tran, Minh-Nguyet Doan Thi, Mai-Linh Duong, & Lan-Tuyen Nguyen. (2022). The effects of pH on the precipitation of rice straw lignin from An Giang, Vietnam. Vietnam Journal of Science, Technology and Engineering, 64(3), 3-7. https://doi.org/10.31276/VJSTE.64(3).03-07

Issue

Section

Physical Sciences