Application of amine-functioned Fe₃O₄ nanoparticles with HPEI for effective humic acid removal from aqueous solution: Modeling and optimization

Humic acids are one type of natural organic matter and precursors of chloro organic compounds that cause a major problematic issue for water treatment plants. In the present study, Hyperbranched polyethylenimine (HPEI) was grafted onto Fe₃O₄ nanoparticles for HA adsorption from aqueous solution. Fe₃O₄@HPEI nanoparticles were characterized via TEM, SEM, FTIR, XRD, VSM, and BET analysis. The effects of various operational parameters including initial HA concentration, pH, adsorbent dose, contact time and ionic strength on the HA removal were assessed. According to the obtained statistical model, the optimal condition was acquired at the initial HA concentration 79 mg/L, adsorbent dose 0.128 g/L, pH 3 and contact time 29 min, which up to 97.27% HA were adsorbed by Fe₃O₄@HPEI that was close to the predicted result by the model (95.6%) that confirmed the validity of the selected model. The adsorption data were fitted to the pseudo-second-order kinetic and Freundlich isotherm. Thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The fabricated Fe₃O₄@HPEI nanoparticles could be repeatedly utilized as a suitable adsorbent to remove HA from the aqueous environment.