Enhanced adsorptive removal of methyl orange and methylene blue from aqueous solution by alkali-activated multiwalled carbon nanotubes.
An alkali-acitvated method was explored to synthesize activated carbon nanotubes (CNTs-A) with a high specific surface area (SSA), and a large number of mesopores. The resulting CNTs-A were used as an adsorbent material for removal of anionic and cationic dyes in aqueous solutions. Experimental results indicated that CNTs-A have excellent adsorption capacity for methyl orange (149 mg/g) and methylene blue (399 mg/g). Alkali-activation treatment of CNTs increased the SSA and pore volume (PV), and introduced oxygen-containing functional groups on the surface of CNTs-A, which would be beneficial to improving the adsorption affinity of CNTs-A for removal of dyes. Kinetic regression results shown that the adsorption kinetic was more accurately represented by a pseudo second-order model. The overall adsorption process was jointly controlled by external mass transfer and intra-particle diffusion, and intra-particle diffusion played a dominant role. Freundlich isotherm model showed a better fit with adsorption data than Langmuir isotherm model. Adsorption interactions of dyes onto CNTs-A from aqueous solutions were investigated using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) method. The remarkable adsorption capacity of dye onto CNTs-A can be attributed to the multiple adsorption interaction mechanisms (hydrogen bonding, π-π electron-donor-acceptor interactions, electrostatic interactions, mesopore filling) on the CNTs-A. Results of this work are of great significance for environmental applications of activated CNTs as a promising adsorbent nanomaterial for organic pollutants from aqueous solutions.
State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Jie
J
Ma
Fei
F
Yu
Lu
L
Zhou
Lu
L
Jin
Mingxuan
M
Yang
Jingshuai
J
Luan
Yuhang
Y
Tang
Haibo
H
Fan
Zhiwen
Z
Yuan
Junhong
J
Chen
D000327:Adsorption; D000468:Alkalies / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry / Q000302:isolation & purification*; D008751:Methylene Blue / Q000737:chemistry / Q000302:isolation & purification*; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D016062:Porosity; D012996:Solutions; D014462:Ultrafiltration / Q000379:methods; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
D000468:Alkalies; D001391:Azo Compounds; D037742:Nanotubes, Carbon; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; C100258:methyl orange; D008751:Methylene Blue