Adsorption of acidic pesticides 2,4-D, Clopyralid and Picloram on calcined hydrotalcite

Calcined hydrotalcite, HT500, a Mg–Al mixed oxide with NaCl-structure of composition Mg3AlO4.5 was shown to be an effective adsorbent for the acidic pesticides: 2,4-D, Clopyralid and Picloram. Adsorption experiments were conducted using three procedures: time-dependent (kinetic), pH-dependent and concentration-dependent (isotherm). Results indicate that the intensity of the adsorption is related to the acidity of the pesticides. The characterization of the adsorption products by XRD and FT-IR spectroscopy confirm the adsorption of the three pesticides in the anionic form in the hydrotalcite interlayer by reconstruction of the layered structure. There was evidence of the adsorption of Picloram also in molecular form.