Copper ion removal from aqueous media using banana peel biochar/Fe₃O₄/branched polyethyleneimine

To address the severe pollution caused by heavy metals, adsorbents have attracted considerable attention based on the idea of energy conservation, emission reduction, and waste utilization. In this work, magnetic nanocomposites were employed as an adequate source for Cu²⁺ adsorption. Fe₃O₄ nanoparticles were modified using branched polyethyleneimine and biochar produced from banana peels. The magnetic nanocomposites (BPB/Fe₃O₄/BPEI) were prepared by chemical coprecipitation. The resulting adsorbents were characterized using SEM, TEM, EDS, XRD, and FTIR, and it was also indicated that BPB/Fe₃O₄/BPEI was successfully prepared by stepwise modification with BPB, Fe₃O₄, and branched polyethyleneimine. VSM result shows the BPB/Fe₃O₄/BPEI exhibit a paramagnetic behavior (21.22 emu/g). A mesoporous structure can be confirmed by BET analysis (BPB/Fe₃O₄/BPEI: 68.72 m²/g). The effects of contact time, pH, concentration of copper ions, and adsorbent dose on the efficiency of copper ion adsorption were investigated. The optimal adsorption efficiencies for BPB(81.99%), Fe₃O₄(20.18%), BPB/Fe₃O₄(82.15%), Fe₃O₄/BPEI(87.37%), and BPB/Fe₃O₄/BPEI(99.46%) were determined. Furthermore, D-R, Temkin, Freundlich, Langmuir, Redlich-Peterson, Toth, Sips, and Hill isotherm models, Weber-Morris intraparticle diffusion, and Elovich, PSO, PFO, and Boyd kinetic models were conducted to better understand the removal process. The BPB/Fe₃O₄/BPEI adsorbents fit the PSO kinetic model and the Sips isotherm model best. The maximum capacities for Cu2+ adsorption with BPB, Fe₃O₄, BPB/Fe₃O₄, Fe₃O₄/BPEI, and BPB/Fe₃O₄/BPEI are determined to be 15.14 mg/g, 2.75 mg/g, 24.65 mg/g, 32.66 mg/g, and 73.23 mg/g, respectively. Furthermore, the effect of other metal ions and the reusability of BPB/Fe₃O₄/BPEI were studied, indicating that BPB/Fe₃O₄/BPEI has good stability even in the presence of other influential heavy metal ions in solution and can be effectively reused for wastewater treatment. © 2022 Elsevier B.V.