Adsorption behavior and mechanism of glufosinate onto goethite.
The adsorption of glufosinate (GLU), a widely used herbicide similar to glyphosate (GLY), onto goethite was investigated as a function of the pH, ionic strength, background cations and anions, heavy metal ions and fulvic acids (FAs) by using batch adsorption experiments. In situ ATR-FTIR spectroscopy and density functional theory (DFT) calculations were carried out to characterize the molecular interactions between GLU and goethite surfaces. The macroscopic results indicated that an increasing pH exerted an adverse effect on GLU adsorption because of the electrostatic repulsion, and the adsorption was not sensitive to ionic strengths or background cation types, indicating that an inner-sphere surface complex was involved. GLU adsorption can be considerably depressed by PO4(3-), SO4(2-), and a high level of FA because of the competitive effect, while being enhanced by Cu(2+) with a maximum adsorption at approximately pH5 because of the metal ion bridging effect. Other examined divalent metal cations (Cd(2+), Zn(2+), and Pb(2+)) showed almost no effect on GLU adsorption, indicating weak interaction between them. ATR-FTIR spectra and the DFT calculations further proved that GLU was bonded to goethite surfaces through the formation of a monodentate mononuclear inner-sphere complex between the phosphinic moiety and surface Fe(III) centers under an acidic condition. The results showed that GLU had a similar adsorption mechanism to that of GLY onto goethite, but with a lower adsorption affinity, possibly exerting higher mobility and risk in soils.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China; Department of Environmental Science and Engineering, Nanjing University Jinling College, 8, Xuefu Road, Nanjing, 210089, PR China. Electronic address: xj_tank@163.com.
Jian
J
Xu
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China. Electronic address: xygu@nju.edu.cn.
Xueyuan
X
Gu
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, 1, Xikang Road, Nanjing, 210098, PR China. Electronic address: guoyong@hhu.edu.cn.
Yong
Y
Guo
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China. Electronic address: tongfei_nju@163.com.
Fei
F
Tong
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163, Xianlin Ave., Nanjing, 210023, PR China. Electronic address: chenly@nju.edu.cn.
Liangyan
L
Chen
D000327:Adsorption; D000613:Aminobutyrates / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D008956:Models, Chemical; D012989:Soil Pollutants / Q000737:chemistry*
D000613:Aminobutyrates; D006540:Herbicides; D058085:Iron Compounds; D008903:Minerals; D012989:Soil Pollutants; C094886:goethite; C003121:phosphinothricin
ATR-FTIR; Adsorption; Glufosinate; Goethite; Soil