Aggregation kinetics of single walled carbon nanotubes influenced by the frequency of ultrasound irradiation in the aquatic environment

Chang Min Park; Yasir A J Al-Hamadani; Jiyong Heo; Namguk Her; Kyoung Hoon Chu; Min Jang; Sangho Lee; Yeomin Yoon

doi:10.1016/j.ultsonch.2017.06.003

Aggregation kinetics of single walled carbon nanotubes influenced by the frequency of ultrasound irradiation in the aquatic environment

Ultrason Sonochem. 2017 Nov:39:750-757. doi: 10.1016/j.ultsonch.2017.06.003. Epub 2017 Jun 7.

Authors

Chang Min Park¹, Yasir A J Al-Hamadani¹, Jiyong Heo², Namguk Her², Kyoung Hoon Chu¹, Min Jang³, Sangho Lee⁴, Yeomin Yoon⁵

Affiliations

¹ Department of Civil and Environmental Engineering, University of South Carolina, Columbia, 300 Main Street, Columbia, SC 29208, USA.
² Department of Civil and Environmental Engineering, Korea Army Academy at Young-Cheon, 495 Hogook-ro, Kokyungmeon, Young-Cheon, Gyeongbuk 38900, South Korea.
³ Department of Environmental Engineering, Kwangwoon University, 447-1 Wolgye-Dong Nowon-Gu, Seoul, South Korea.
⁴ School of Civil and Environmental Engineering, Kookmin University, 77 Jeongneung-ro, Seoul 02707, South Korea.
⁵ Department of Civil and Environmental Engineering, University of South Carolina, Columbia, 300 Main Street, Columbia, SC 29208, USA. Electronic address: yoony@cec.sc.edu.

PMID: 28733002
DOI: 10.1016/j.ultsonch.2017.06.003

Abstract

The colloidal stability of single-walled carbon nanotubes (SWNTs) sonicated at three different ultrasonication (US) frequencies (28, 580, and 1000kHz) were investigated under environmentally relevant conditions. In particular, correlations between surface chemistry, electrokinetic potential, interaction energy, and the aggregation kinetics of the aqueous SWNTs were studied. We observed that H₂O₂ production is negatively correlated with the yield of hydroxylation and carboxylation of SWNTs, which was dependent on the generation of ultrasonic energy by cavity collapse during US process. The SWNTs sonicated at relatively high US frequencies (580 and 1000kHz) aggregated rapidly in synthetic surface water, whereas alkalinity affected the stability of SWNTs insignificantly. This was because the SWNTs became less negatively charged under such conditions and were captured in deep primary energy wells, according to the Derjaguin-Landau-Verwey-Overbeek theory. Critical coagulation concentration values for the ultrasonicated SWNTs were determined to be 102mM NaCl for 28kHz, 22mM NaCl for 580kHz, and 43mM NaCl for 1000kHz. Suwannee River humic acid decreased the aggregation rate of SWNTs due to the steric hindrance, because of adsorbed macromolecules. Our findings show that the aggregate stability of SWNTs is controlled largely by a complex interplay between the evolution of surface functional groups on the SWNTs during US and solution chemistry.

Keywords: Humic acid; Single-walled carbon nanotubes; Sonication frequency; Synthetic surface water; Ultrasonication.