Surface functionalized mesoporous silicas as adsorbents for aromatic contaminants in aqueous solution.
A hexagonal mesoporous silica (HMS) and its postfunctionalized counterparts with propyl (P-HMS) and aminopropyl (AMP-HMS) were prepared and characterized by elemental analysis, N2 adsorption, powder x-ray diffraction, Fourier-transform infrared, and surface charge measurements. Batch experiments were further performed to systematically investigate adsorption properties of these materials toward two nonpolar aromatic compounds (pyrene and pentachlorobenzene) and three phenolic compounds (2,4-dichlorophenol, pentachlorophenol, and 4-methyl-2,6-dinitrophenol) in aqueous solutions. The adsorption isotherms were well described by the Freundlich model and varied in adsorption linearity. For HMS and P-HMS, the adsorption of pyrene and pentachlorobenzene was much stronger than that of pentachlorophenol at pH slightly greater than 6. Alternatively, for AMP-HMS, pentachlorophenol and 4-methyl-2,6-dinitrophenol showed comparable or stronger adsorption affinity than the other target compounds did, suggesting that a major role is played by electrostatic interactions of the two phenols. Furthermore, adsorption decreased with increasing pH for all adsorbate-adsorbent combinations except that of pentachlorophenol and 4-methyl-2,6-dinitrophenol on AMP-HMS, which showed bell-shaped curves with the maximum adsorption at pH close to the pK(a). The advantages of reversible adsorption and fast adsorption/desorption kinetics (<15 min), as compared to commercial microporous activated carbons, make AMP-HMS a promising candidate to remove selected phenolic compounds in water treatment.
Zhu
Dongqiang
D
State Key Laboratory of Pollution Control and Resource Reuse and School of the Environment, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, People's Republic of China.
Zhang
Hua
H
Tao
Qi
Q
Xu
Zhaoyi
Z
Zheng
Shourong
S
D000327:Adsorption; D006841:Hydrocarbons, Aromatic / Q000032:analysis*; D007700:Kinetics; D016062:Porosity; D017640:Silicates / Q000737:chemistry*; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification; D014961:X-Ray Diffraction
D006841:Hydrocarbons, Aromatic; D017640:Silicates; D012996:Solutions; D014874:Water Pollutants, Chemical