Polyethylenimine-Crosslinked 3-Aminopropyltriethoxysilane-Grafted Multiwall Carbon Nanotubes for Efficient Adsorption of Reactive Yellow 2 from Water

This research intended to report amine-functionalized multiwall carbon nanotubes (MWCNTs) prepared by a simple method for efficient and rapid removal of Reactive Yellow 2 (RY2) from water. EDS analysis showed that the N content increased from 0 to 2.42% and from 2.42 to 8.66% after modification by 3-Aminopropyltriethoxysilane (APTES) and polyethylenimine (PEI), respectively. BET analysis displayed that the specific surface area, average pore size, and total pore volume were reduced from 405.22 to 176.16 m(2)/g, 39.67 to 6.30 nm, and 4.02 to 0.28 cm(3)/g, respectively. These results proved that the PEI/APTES-MWCNTs were successfully prepared. pH edge experiments indicated that pH 2 was optimal for RY2 removal. At pH 2 and 25 °C, the time required for adsorption equilibrium was 10, 15, and 180 min at initial concentrations of 50, 100, and 200 mg/L, respectively; and the maximum RY2 uptake calculated by the Langmuir model was 714.29 mg/g. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic. Moreover, 0–0.1 mol/L of NaCl showed negligible effect on RY2 removal by PEI/APTES-MWCNTs. Five adsorption/desorption cycles confirmed the good reusability of PEI/APTES-MWCNTs in RY2 removal. Overall, the PEI/APTES-MWCNTs are a potential and efficient adsorbent for reactive dye wastewater treatment.