Pesticides adsorption–desorption on Mg–Al mixed oxides. Kinetic modeling, competing factors and recyclability

The adsorption of the ionizable pesticide Nicosulfuron and the ionic pesticide Mecoprop-P on a calcined Mg–Al hydrotalcite (HT-500) in the presence and absence of various anions was studied with a view to assessing the potential of regenerating the adsorbent. Kinetic tests showed the adsorption of both pesticides to involve intraparticle diffusion, and the rate constant of intraparticle diffusion for Nicosulfuron to increase with increasing concentration of the compound by effect of its increased molecular size relative to Mecoprop-P. Application of the Langmuir and Dubini–Radushkevich equations to the adsorption isotherms for the two pesticides revealed easy adsorption of both via an ion-exchange process. Adsorption and desorption of the two pesticides were both affected by the presence of other anions. The adsorbents and their adsorption products were characterized by X-ray diffraction and FT-IR spectroscopies. Based on the results of regeneration tests, calcined hydrotalcite is an effective adsorbent for the removal of Nicosulfuron and Mecoprop-P from contaminated water.