Adsorption Behavior of Basic Red 46 by Single-Walled Carbon Nanotubes Surfaces

In this study, the adsorption behavior of Basic Red 46 (BR 46) in aqueous solutions by single-walled carbon nanotube (SWCNTs) and functionalized SWCNTs having covalent attachments of carboxylic group (SWCNT-COOH) surface as adsorbents were investigated. The adsorption equilibrium data were analyzed using various adsorption isotherms, and the results have shown that adsorption behavior of BR 46 could be described reasonably well by a generalized isotherm. Kinetic studies indicated adsorption of BR 46 by SWCNTs and SWCNT-COOH surfaces follows a pseudo-order model. The maximum adsorption capacities of BR46 by SWCNTs and SWCNT-COOH surfaces are reported at 298 K, 38.35 and 49.45 mg/g, respectively. The adsorption of BR 46 depends on the initial pH of the solution with maximum uptake occurring at about pH 9. Decrease in the absolute value of Delta G(0) with increasing temperature indicates that higher temperatures hardship the adsorption. The negative value of Delta H-0 reflects an exothermic adsorption and indicates that the adsorption is favored at low temperature. The negative entropy states that the adsorption of BR 46 by SWCNT-COOH and SWCNTs surfaces are orderly adsorbed by the surfaces.