Adsorption of linear alkylbenzene sulfonates on carboxyl modified multi-walled carbon nanotubes
Zhuo Guan1, Xiang-Yu Tang2, Taku Nishimura3
1Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China; Laboratory of Soil Physics and Soil Hydrology, Department of Biological and Environmental Engineering, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.
Abstract:
Understanding of the adsorption behavior of organic pollutants on carbon nanotubes (CNTs) and its governing factors are crucial for the assessment of transport and fate of organic pollutants. This study explored adsorption characteristics of linear alkylbenzene sulfonates (LAS) on carboxyl modified multi-walled carbon nanotubes (CMMWCNTs) and the effect of solution chemistry and temperature on LAS sorption. Results indicted LAS adsorption isotherms to display five distinct regions of sorption at 25°C and 60°C. Regardless of temperature, the adsorption isotherm of LAS on the CMMWCNTs was well described using the Freundlich equation. This result indicated heterogeneous distribution of adsorption sites on the CMMWCNT surface. At low initial LAS concentrations, below the critical micelle concentration, (2, 10 and 50mgL-1) LAS adsorption on the CMMWCNTs followed pseudo second-order kinetics. The highest LAS adsorption was observed at ionic strengths of 1.0molL-1 for NaCl; and 0.2molL-1 for both CaCl2 and MgCl2. However, LAS sorption was greatest in the presence of sodium-divalent anion salts and at higher temperatures. These findings are of relevance to the fate and environmental risk of LAS in the presence of CMMWCNTs in high salinity wastewaters or effluents and brackish receiving surface water bodies (e.g., at estuaries).
