Premium
Site‐Specific Adsorption of 1,3‐Dinitrobenzene to Bacterial Surfaces: A Mechanism of n –π Electron‐Donor‐Acceptor Interactions
Author(s) -
Qu Xiaolei,
Xiao Lin,
Zhu Dongqiang
Publication year - 2008
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2007.0236
Subject(s) - chemistry , sorption , electron acceptor , biosorption , electron donor , deprotonation , protonation , adsorption , aqueous solution , bacillus subtilis , acceptor , photochemistry , organic chemistry , bacteria , catalysis , ion , physics , biology , genetics , condensed matter physics
Surface and subsurface contamination with nitroaromatic compounds (NACs) has drawn considerable attention, and biosorption may play an important role in the fate and transport of these compounds in the environment. We studied the sorption of polar 1,3‐dinitrobenzene (DNB) as a representative NAC and 2,6‐dichlorobenzonitrile and nonpolar phenanthrene and 1,2,4,5‐tetrachlorobenzene from the aqueous phase to two common bacteria, gram‐negative Escherichia coli and gram‐positive Bacillus subtilis. Sorption of DNB is highly nonlinear and is well described by the Langmuir model and shows the highest capacity among all tested solutes (up to 2.4% of E. coli biomass and 7.6% of B. subtilis biomass by weight) despite the lowest solute hydrophobicity. These results indicate that strong specific sorptive interactions exist between DNB and bacterial surfaces. We propose a mechanism of n –π electron‐donor‐acceptor interactions between the oxygen electron pairs of deprotonated carboxyl groups (electron donors) of bacterial surfaces and DNB (electron acceptor). Biosorption of DNB increases with deprotonation of functional groups as pH increases, which rules out hydrophobic effects and H‐bonding as major sorption driving forces because they are both favored by protonation of functional groups as pH decreases.