The adsorption characteristics of fluoride on commercial activated carbon treated with quaternary ammonium salts (Quats)

Ching-Lung Chen; Sang-Won Park; Jenn Feng Su; Yu-Han Yu; Jae-Eun Heo; Kyung-Duk Kim; C P Huang

doi:10.1016/j.scitotenv.2019.133605

The adsorption characteristics of fluoride on commercial activated carbon treated with quaternary ammonium salts (Quats)

Sci Total Environ. 2019 Nov 25:693:133605. doi: 10.1016/j.scitotenv.2019.133605. Epub 2019 Jul 26.

Authors

Ching-Lung Chen¹, Sang-Won Park², Jenn Feng Su¹, Yu-Han Yu¹, Jae-Eun Heo³, Kyung-Duk Kim³, C P Huang⁴

Affiliations

¹ Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA.
² Department of Environmental Science, Keimyung University, Daegu, South Korea.
³ Center for Green & Convergence Technology, Keimyung University, Daegu, South Korea.
⁴ Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA. Electronic address: huang@udel.edu.

PMID: 31634998
DOI: 10.1016/j.scitotenv.2019.133605

Abstract

Commercial activated carbon was treated with six quaternary ammonium salts (Quats), namely, hexyltrimethylammonium (HTMA), octyltrimethylammonium (OTMA), decyltrimethylammonium (DCTMA), dodecyltrimethylammonium (DDTMA), Tetradecyltrimethylammonium (TDTMA), and hexadecyltrimethylammoium (HDTMA) as to enhance the fluoride adsorption capacity. In batch mode experiments, fluoride adsorption onto the Quats-treated activated carbon decreased dramatically with increase in solution pH. Fluoride removal by the Quats-treated activated carbons was closely related to the Quats chain length at less-than critical micelle concentration (CMC). Multi-site adsorption isotherm described fluoride adsorption characteristics well. Results showed that activated carbon treated with DDTMA exhibited the best fluoride adsorption density among all Quats investigated. DDTMA-treated activated carbons exhibited two-fold increase in the fluoride adsorption capacity compared to the untreated activated carbon. Results of regeneration, by alkaline desorption and/or Quats re-loading, showed fluoride-laden activated carbons have high reusability. DDTMA increased the positive surface charge of the activated carbon that enhanced fluoride adsorption. DDTMA-treated activated carbon was promising for fluoride removal from water with much enhanced removal capacity.

Keywords: Activated carbon; Fluoride; Multi-site Langmuir equation; Quaternary ammonium salts; Surface treatment.