Biosorption of 2,4-D, 2,4-DP, and 2,4-DB from Aqueous Solution by Using Thermophilic Anoxybacillus flavithermus and Analysis by High-Performance Thin Layer Chromatography: Equilibrium and Kinetic Studies Sadin Ozdemir, a Fatma Matpan Bekler, b Veysi Okumus, a Abdurrahman Dundar, a and Ersin Kilinc c a Department of Biology, Faculty of Arts and Science, University of Siirt, 56100-Siirt, Turkey; sadin77@hotmail.com (for correspondence) b Department of Biology, Faculty of Science, University of Dicle, 21280-Diyarbakir, Turkey c Department of Chemistry, Faculty of Science, Laboratory of Chemical Analysis, University of Dicle, 21280-Diyarbakir, Turkey Published online 15 July 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.10576 In this study, the potential biosorption characteris- tics of the thermophilic Anoxybacillus flavithermus (A. flavithermus) was investigated for the removal of the chlorophenoxy acid derivates, namely, 2,4-dichloro- phenoxy acetic acid (2,4-D), 2,4-dichlorophenoxy pro- panoic acid (2,4-DP or dichlorprop), and 2,4-dichlor- ophenoxy butyric acid (2,4-DB). The experiments were performed for the simultaneous biosorption of the stud- ied pesticides. Optimum biosorption conditions were determined as a function of contact time, pH of the so- lution, amount of biomass, and initial pesticides con- centrations. The concentrations of the pesticides in the remaining solutions were simultaneously analyzed by high performance thin layer chromatography. The op- timum parameters were found as pH: 4.0 for biosorp- tion medium, 60 min of contact time, 50 mg of bacte- ria, and 50 mg L 21 of initial pesticides concentrations. Langmuir and Freundlich models were applied to describe the biosorption isotherm of the pesticides by A. flavithermus as biomass. Biosorption of pesticides on to A. flavithermus showed pseudo first-order rate kinetics at different initial concentration of pesticides and dif- ferent temperatures. The experimental adsorption data were fitted both the Langmuir and Freundlich adsorp- tion models. Fourier-transform Infrared spectroscopy was used to understand the bonding mechanism of pesticides to biosorbent and surface functionality of the biosorbent The highest pesticide uptake was calculated from Langmuir isotherm and found to be 24.15 mg g 21 for 2,4-D. Among the studied pesticides, Ó 2011 American Institute of Chemical Engineers 544 December 2012 Environmental Progress & Sustainable Energy (Vol.31, No.4) DOI 10.1002/ep