Intercalation of rigid molecules between carbon nanotubes for adsorption enhancement of typical pharmaceuticals

Abstract

A nucleophilic aromatic substitution reaction was proposed to synthesize porous carbon nanotubes (CNTs) to avoid their aggregation in solution. Hydroxylated carbon nanotubes (CNTs-OH) were reacted with different concentrations of rigid decafluorobiphenyl (DFB) to form the different CNTs-based adsorbents (CNT-DFB0.9, CNT-DFB1.8, CNT-DFB2.7 and CNT-DFB3.6). Among them, CNT-DFB1.8 exhibited the highest adsorption capacity for carbamazepine (CBZ) and tetracycline (TC) due to its higher specific surface area and pore volume than powdered CNTs. The proposed reaction was verified and the textural properties of the CNT-DFB adsorbent were characterized. The CNT-DFB1.8 adsorbent exhibited faster adsorption for CBZ than TC, and the maximum adsorption capacities for CBZ and TC were 403.0 and 456.5μmol/g respectively, according to the Langmuir fitting. With the increase of solution pH, TC adsorption on CNT-DFB1.8 decreased while CBZ adsorption increased. In addition, a simple thermal method was applied to regenerate the spent CNT-DFB1.8 by heating in air at 400°C, and the adsorption capacity changed little in the five adsorption cycles. This study provided a novel method to increase the dispersion of CNTs in the prepared adsorbent, showing the potential application for the removal of pharmaceuticals in water or wastewater treatment.