Cadmium ion sorption from aqueous solutions by high surface area ethylenediaminetetraacetic acidand diethylene triamine pentaacetic acid-treated carbon nanotubes

Abstract

A novel and rapid microwave-assisted approach along with Friedel–Crafts acylation has been successfully<br><br>introduced for functionalization of carbon nanotubes (CNT) via aliphatic and aromatic carboxylic acids.<br><br>This green and efficient route may play an essential role for realizing miscellaneous functionalizations<br><br>of CNT, which were successfully functionalized via ethylenediaminetetraacetic acid (EDTA) and<br><br>diethylenetriaminepentaacetic acid (DTPA). Qualitative (FT-IR) and quantitative (TGA, Raman, XPS)<br><br>characterization has been employed to investigate the degree of functionalization. The N2 adsorption<br><br>isotherm shows significant increases of 270% and 262% in specific surface area in the low partial<br><br>pressure region after functionalization of CNT with EDTA and DTPA, respectively, which resulted from<br><br>eliminating the tube ends or caps. By looking at the potential of EDTA and DTPA for sequestering metal<br><br>ions, EDTA- & DTPA-treated CNT were used to evaluate the aqueous cadmium(II) adsorption efficiency.<br><br>Then, the effects of solution temperature, pH and contact time on the adsorption of Cd2+ ions onto<br><br>the treated samples and pristine CNT were investigated. The adsorption performance of Cd2+ ions by<br><br>functionalized samples showed dramatic growth when compared with the pristine sample, which was<br><br>effectively pH dependent. The pseudo second-order model precisely captured the kinetic analyses of<br><br>adsorption. This study suggested that the functionalization method not only enhanced the effective<br><br>surface area including active adsorption sites on the CNT structure, but also decreased the<br><br>functionalization time and cost significantly and proposed a promising material for capacitive<br><br>deionization.