Correspondence pubs.acs.org/IECR
Comments on “Hollow Carbon Fibers Derived from Natural Cotton as Effective Sorbents for Oil Spill Cleanup” Vinitkumar Singh and Seshadri Ramkumar* Nonwovens & Advanced Materials Laboratory, Texas Tech University, Lubbock, Texas 79409, United States Sir: We would like to thank Wang et al.1 for presenting a detailed study on the use of natural materials for cleaning-up an oil spill, which from an environmental perspective is important. Furthermore, the field is currently evolving due to recent oil and toxic spill scenarios. Although Wang et al. have compared oil sorption capacities of natural cotton and carbon fibers synthesized using cotton, we beg to bring to your kind attention the need for specifying the type of cotton used in this study. The structure, physical, and chemical characteristics of cotton vary with the type of chemical processing and finishes applied to it. Depending on the type of cotton and processing variations, its oil absorption also varies.2 Therefore, from a scientific point of view, it is important to clearly delineate the characteristics of the type of cotton used. Wang et al. report that the cotton used was 100% Banitore cotton, which is not a raw cotton fiber but a cotton chemically processed with a bleaching agent. It is clear from the information available in the public domain such as supplier information, that Banitore cotton is an absorbent cotton. The hydrophilic and hydrophobic characteristics of raw and chemically processed cotton such as Banitore vary significantly as raw cotton is hydrophobic due to its natural wax.3 As the crux of the work carried out by Wang et al. is to quantify the oil absorption by cotton and its derivatives, any variation in the type of cotton used will affect the results. This is evident from their results on the poor selectivity of oil for the particular type of cotton used by them. As the cotton used by Wang et al. is absorbent cotton, it is hydrophilic in nature. This is evident from the zero contact angle values for water obtained by the authors, and hence this cotton exhibits poor oil absorption characteristics. However, the authors have used a generalized statement mentioning that cotton showed poor selectivity in absorbing oil in an oil−water system (section 3.3, Contact Angle Measurement; last line in the paper). This generalized statement may lead to some confusion as raw cotton is hydrophobic and therefore should have more selectivity for oil. The result obtained by Wang et al. fits well for the absorbent cotton they have used in their study, which is hydrophilic. However, without specifying the type of the cotton, the results may be misleading. We humbly request the authors to specify the nature of the cotton as absorbent cotton so that there will be no ambiguity with the usage of the statement on the poor oil selectivity of cotton as reported. We again, thank the authors for the timely and useful study.
■
Notes
The authors declare no competing financial interest.
■
REFERENCES
(1) Wang, B.; Karthikeyan, R.; Lu, X.; Xuan, J.; Leung, M. K. H. Hollow carbon fibers derived from natural cotton as effective sorbents for oil spill cleanup. Ind. Eng. Chem. Res. 2013, 52, 18251−18261, DOI: 10.1021/ie402371n. (2) Singh, V.; Kendall, R. J.; Hake, K.; Ramkumar, S. Crude oil sorption by raw cotton. Ind. Eng. Chem. Res. 2013, 52 (18), 6277− 6281. (3) Hsieh, Y. L.; Thompson, J.; Miller, A. Water wetting and retention of cotton assemblies as affected by alkaline and bleaching treatments. Text. Res. J. 1996, 66 (7), 456−464.
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. © 2014 American Chemical Society
Published: January 14, 2014 3412
dx.doi.org/10.1021/ie4041498 | Ind. Eng. Chem. Res. 2014, 53, 3412−3412
