Adsorption of picloram herbicide on montmorillonite: Kinetic and equilibrium studies

JOSE L. MARCO-BROWN; MARIA MAR ARECO; ROSA MARÍA TORRES SÁNCHEZ; MARIA DOS SANTOS AFONSO

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 449 p. 121 - 128

0927-7757

tThe kinetics of the adsorption of picloram (PCM) onto montmorillonite (Mt) was studied in situ byattenuated total reflectance Fourier-transform infrared spectra (ATR-FTIR). Pseudo-first-order, pseudo-second-order, intra-particle diffusion and mixed surface reaction intra-particle diffusion-controlledkinetic models were applied to the experimental results. The latter was the model that best representedthe experimental results. The adsorption equilibrium isotherms revealed the presence of two indepen-dent adsorption processes on different surface sites. The adsorption isotherms normalized by the surfacearea were fitted with the Langmuir and Freundlich models to obtain the respective parameters.Due to the anionic form of PCM, the adsorption onto the external clay mineral surface sites followed bythe entrance of the PCM molecule into the Mt basal space in a less energetically favorable pathway wasproposed. The interaction of PCM with montmorillonite surface sites through nitrogen of the pyridinering and carboxylic group by forming an inner sphere complex was confirmed by ATR-FTIR.