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چکیده
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In recent decades, remediation of polluted water has shifted towards the enhancement of environmentally friendly adsorbents with robust stability. In this regard, a biosorbent was designed and synthesized by anchoring carboxylated pineapple peel cellulose and ethylenediaminetetraacetic acid onto aminosilane modified Fe 3O4 nanoparticles. A vast number of carboxyl and amino active groups in the structure of the biosorbent led to the efficient adsorption of Cu2+ and Zn2+ from polluted water. The biosorbent was characterized by FE-SEM, TEM, EDX, XRD, FT-IR, BET, VSM and TGA techniques. The influence of pH, temperature and biosorbent dosage on the ion removal was investigated by Central Composite Design. The maximum uptake% was 93.18 and 96.30% for Cu2+ and Zn2+, respectively. Coordination and electrostatic attraction were proposed as the main reasons for the removal of heavy metal ions. Astonishingly, the adsorption of Zn2+ was ultrafast and completed within 40 s and it took 420 s for removal of Cu2+. The external surface biosorption, intra-particle diffusion and diffusion through the smaller pores and slits, in sequence, were the dominant steps in the adsorption of each ion. Modified pseudo-n-order and modified Langmuir–Freundlich were the best models to describe kinetics and equilibrium results. The maximum adsorption capacity of the biosorbent for Zn2+ was higher than one for Cu2+ (153.9 vs. 149.4 mg g-1). What’s more, thermodynamics study confirmed that the adsorption of Zn2+ was exothermic in spite of the adsorption of Cu2+ at the higher concentration of the biosorbent and the entropy change of adsorption was positive for each cation. Besides, the regenerating of the biosorbent was successfully accomplished for five cycles using a solution of EDTA in the presence of ultrasonic waves.
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