Adsorption of mono- and di-butyltin by a wheat charcoal: pH effects and modeling.
Understanding adsorption processes of butyltins (BTs) such as monobutyltin (MBT) and dibutyltin (DBT) by black carbons is important for the evaluation of BT exposure risks to organisms and humans. However, relevant knowledge is scarce. In this study, the acidity constants pK(a,1)=2.3, pK(a,2)=3.5 and pK(a,3)=5.9 for MBT and pK(a,1)=3.0 and pK(a,2)=5.1 for DBT are estimated via potentiometric titration. Additionally, adsorption isotherms of BTs to a wheat charcoal were determined. The adsorption behavior was observed to be pH-dependent due to BT speciation and the pH-dependent surface charge of the charcoal. MBT adsorption to the charcoal decreases with increasing pH from 4 to 8, while the highest adsorption occurs at pH 6 for DBT. Adsorption of the BTs is successfully described in the pH range of 3-10 by using a newly developed pH-dependent Dual Langmuir model. The model has the potential to predict the interaction of BT species with charcoal, which can contribute to the risk assessments of BTs in the environment.
Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark. fang@life.ku.dk
Liping
L
Fang
Ole K
OK
Borggaard
Jan H
JH
Christensen
Peter E
PE
Holm
Hans Christian Bruun
HC
Hansen
D000327:Adsorption; D002606:Charcoal / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009947:Organotin Compounds / Q000737:chemistry*; D014908:Triticum / Q000737:chemistry
D004785:Environmental Pollutants; D009947:Organotin Compounds; C516409:mono-n-butyltin; C056189:di-n-butyltin; D002606:Charcoal