Water, Vol. 18, Pages 371: Boosting Adsorption of Organically Complexed Ni onto Thin-Layered Porous Biomass-Derived Carbon
Water doi: 10.3390/w18030371
Authors:
Zarak Mahmood
Yuting Yuan
Shikha Garg
Yong Chen
Xiao Li
Tao Cui
Christopher Miller
Muhammad Haris
Yuan Wang
T. David Waite
Ni removal from waste streams wherein it is present in organically complexed forms remains a major industrial challenge since organically bound Ni does not readily precipitate and is poorly removed by conventional adsorbents. In this work, two effective adsorbents, namely thin-layered porous carbon (TLPC) and MnO2-decorated TLPC (i.e., MnO2-TLPC), were developed for the removal of both inorganic and organically complexed Ni(II) from synthetic and real waste streams. Both adsorbents removed inorganic Ni(II) as well as Ni(II) present in organically complexed forms, achieving up to ~80% removal from both real and synthetic electroplating wastewater. Critically, Ni removal efficiencies were maintained over five adsorption–desorption cycles, demonstrating excellent regeneration and reuse potential. The Ni removal by TLPC was pH-dependent, whereas MnO2-TLPC showed minimal pH sensitivity. TLPC relies on outer-sphere, charge-driven adsorption, whereas MnO2-TLPC achieves stronger Ni binding through inner-sphere complexation promoted by oxygen- and nitrogen-based functional groups. The sorbents also reduced dissolved organic carbon, with TLPC displaying higher organic removal efficiency. Mechanistic analysis indicates that Ni uptake is primarily governed by sorption of both complexed and inorganic Ni(II) present in equilibrium with the complex, combined with sorption of the free ligand itself. The sorption of the free ligands and inorganic Ni(II) drive Ni–ligand decomplexation in the solution phase, enabling further Ni removal. Overall, TLPC provides a low-cost, high-performance option for treating alkaline wastewaters with elevated Ni and organic loadings, while MnO2-TLPC offers robust, pH-resilient removal under circumneutral conditions. These findings position both materials as promising candidates for practical wastewater treatment applications targeting complexed metal contaminants.
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