Chitosan/poly(2-(diisopropylamino)ethyl methacrylate-based pH-sensitive magnetic composite for application in avermectins adsorption in aqueous medium

A new composite material with magnetic and pH-responsive properties, composed of chitosan/ poly(2-diisopropylamino)ethyl methacrylate (Fe₃O₄/SiO₂/CS/PDPA) was developed with the purpose of removing avermectins in aqueous media. The material was characterized by different techniques to evaluate its characteristics. The adsorption process was investigated through the optimization of some parameters, with the most favorable results at pH 8.0, using 20 mg of adsorbent and stirring for 5 min. Under such conditions, the material showed adsorption efficiency of around 80.5, 69.9, and 74.8% for eprinomectin, doramectin and ivermectin, respectively. The adsorption mechanism was investigated using the pseudo-second order kinetic model and the Langmuir-Freundlich dual site isotherm model. Thermodynamic analysis indicated that the adsorption process is exothermic and spontaneous. The material also showed good regenerative capacity, allowing several reuse cycles. The results obtained suggest that the synthesized material has potential application as an adsorbent in the removal of avermectins from aqueous samples. (author)