Preparation, characterization, adsorption performance and mechanism of Fe₃O₄@PANI-PG boron adsorbent

In this paper, the traditional difficult problem of separation between adsorbent and water phase was effectively solved by a kind of magnetic polyols boron adsorbent, which were designed and prepared based on the principle of magnetic separation. Firstly, the polyaniline compound Fe₃O₄ (Fe₃O₄@PANI) composites with core-shell structure were prepared by the in-situ polymerization reaction at the presence of aniline and Fe₃O₄ nanoparticles, which were prepared by ourselves. Then propylene glycol modified polyaniline compound Fe₃O₄ (Fe₃O₄@PANI-PG) boron adsorbent was successfully prepared by the ring-opening reaction between polyaniline terminal active —NH₂ and glycidyl. After that, the micro-structure, composition and functional groups were analyzed by the SEM, TEM, EDS, XRD, XPS and FTIR, respectively. The adsorption time, initial concentration of boric acid, pH and other factors of Fe₃O₄@PANI-PG were investigated by the single factor experiment. On this basis, the optimal adsorption conditions (time t=10 h, initial concentration C₀=1309 mg/L, pH=9.93) were obtained by response surface method, and the corresponding optimal adsorption capacity up to Q_e=0.1181 mmol/g. In addition, it was found that the adsorption process was in accordance with the quasi-second-order adsorption kinetics and Langmuir adsorption isotherm based on the adsorption kinetics and adsorption isotherm fitting. Finally, the adsorption mechanism of Fe₃O₄@PANI-PG was explored and the results indicating the complex reaction between the hydroxyl group at the end of the adsorbent and B(OH)₄⁻ in the aqueous phase formed a stable five-membered ring chelate.