Immobilised tannin: Efficient trap for nickel and lead ions in aqueous solution
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Date
2021
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Environmental Challenges - ELSEVIER
Abstract
Quantity of water is a major concern, but the quality is of more urgent concern due to heavy metal pollution.
In this study, the focus was to develop adsorbents (tannin resin (TR) and iron-doped tannin resin (Fe-TR)) from
invasive Acacia mearnsii for Pb 2 + and Ni 2 + in solution. The developed TR and Fe-TR were prepared directly
by crosslinking and iron-grafting; respectively with thermal stable at ≤ 350 °C. Surface functionality analysis
revealed the presence of chelating groups at ≈ 1688 and 3661 cm − 1 . The crystallite sizes of the adsorbents were
smaller compared to tannin; however, the % carbon and nitrogen were significantly higher. Also, the Brunauer
Emmet–Teller study revealed that iron-grafting of tannin after crosslinking increases the surface area, pore volume
and pore size. Furthermore, the surface morphology of adsorbents indicated a well-defined structure with the
formation of a whitish deposit and rough lump-like after ion uptake. Both adsorbents showed a type II isotherm
with adsorption capacities of 40.650 mg/g and 13.763 mg/g for Pb 2+ and 120.63 mg/g and 110.74 for Ni 2 +
ion by TR and Fe-TR; respectively. The absorbate-adsorbent interactions were observed to be endothermic with
negative and positive Gibb’s free energy values for the adsorption of Pb 2 + and Ni 2 + ; respectively. The adsorption
kinetics of Ni 2 + is governed by several models; however, Pb 2 + interaction is regulated by Pseudo-second-order
model. Furthermore, the data generated offered the possibility of both chemisorption and physisorption processes;
highlighting the flexibility and multifunctionality of tannin traps for the erasure of ion impurities in wastewater.
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