ICATC 2023

Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/27835

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Author: search.filters.author.Alahakoon, Yasmitha A

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    Lignin Based Embedded and Surface Deposited Nanoscale Zero Valent Iron for Cd(II) Remediation
    (Faculty of Computing and Technology, University of Kelaniya Sri Lanka., 2023) Arachchi, Uthsara Malaweera; Hettige, Ayesha L; Alahakoon, Yasmitha A; Peiris, Chathuri; Mlsna, Todd; Gunatilake, Sameera
    Vast industrialization occurring throughout the world has led to a drastic increase in water pollution by heavy metals. Cd is a heavy metal that has garnered significant concern due to its toxicity and adverse health effects on humans and other living organisms. Recent studies have focused on the application of Biochar (BC) supported carbothermally produced Nanoscale Zero Valent Iron (nZVI) for the remediation of a variety of contaminants. However, only limited research has been carried out to assess and compare the mechanisms of Cd removal and remediation efficiency by different types of carbothermally prepared nZVI. To address this issue, the present study investigated the application of two nanocomposites, Lig-eG@nZVI and Lig-sG@nZVI, produced through two carbothermal reduction routes at 1000 °C. In Lig-eG@nZVI, nZVI was embedded in the Lignin Biochar (Lig-BC) matrix while in Lig-sG@nZVI, nZVI was deposited on the Lig-BC surface. In this study, enhanced uptake of Cd(II) was observed with increasing pH with maximum uptake at pH 6. Cd sorption at 30 °C was evaluated using the Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, Toth and Jossens adsorption isotherm models. The experimental data was best fitted to Sips isotherm model, with a maximum Sips capacity of 9.688, 8.102 and 6.665 mg g-1 at 30 °C and pH 6 for Lig-eG@nZVI, Lig-sG@nZVI and Lig-BC, respectively. The two composites showed enhanced remediation due to the synergistic effect of remedial mechanisms of both nZVI and Lig-BC components. Possible adsorption mechanisms for BC include cation-π interactions, electrostatic attractions and surface complexation precipitation with minerals. Owing to the nearly identical standard redox potential of Cd with zero valent iron, the feasibility of Cd(II) remediation through reduction is very low and the only viable removal mechanism is sorption or surface complex formation. Fast remediation kinetics were observed for the three materials. According to thermodynamic studies conducted, the overall adsorption processes of all three materials were confirmed to be physisorptive, endothermic and spontaneous in nature. This study bridges the existing knowledge gap by conducting a comprehensive evaluation on the application of Lig-eG@nZVI, Lig-sG@nZVI and Lig-BC for the remediation of Cd(II) in aqueous media.
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    Carbothermally Synthesized, Lignin-Based, Embedded And Surface Deposited Nano Zero- Valent Iron for Water Purification: Characteristics and Applications
    (Faculty of Computing and Technology, University of Kelaniya Sri Lanka., 2023) Alahakoon, Yasmitha A; Wilson, Shine; Ranasinghe, Yohara K; Peiris, Chathuri; Mlsna, Todd; Gunatilake, Sameera
    Synthesizing tailor-made materials for remediating wastewater polluted with contaminants of emerging concerns, has become a major concern of the scientific community. Nanoscale zero valent iron (nZVI) together with a biochar (BC) support provide advantageous materials for wastewater purification via adsorption, reduction, complexation and advanced oxidation mechanisms. Two approaches to nZVI-composite engineering have been reported: embedding in support matrix and surface depositing, where the latter being more common. Nonetheless, the behavior of embedded material towards contaminant remediation has not yet been sufficiently studied. Furthermore, the remediation capability of these two materials has not been comparatively evaluated. The present study focuses on preparing and extensively characterizing two materials; nZVI embedded in (Lig-e-nZVI) and surface deposited (Lig-s-nZVI) on lignin BC with subsequent comparative analysis of remedial action of the two materials. SEM, SEM/EDX, XRD, FTIR, proximate and ultimate analysis, point of zero charge, iron leaching and regeneration studies were carried out using pristine lignin BC as the control material. Porous and non-porous structures of the carbothermally prepared materials where crystalline iron was embedded or surface coated were compared along with their surface and bulk elemental compositions. It was evident that although the surface iron content is high in Lig-s-nZVI, the total iron content in both the materials were same. Loaded iron was confirmed to be in the zero valent state as per the observed XRD peak patterns. Surface functional groups and overall surface charge of the materials and iron leaching and depletion of remediation capacity were also analyzed. Pharmaceutical precursors p-nitroaniline (pNA) and p-nitrophenol (pNP) were used as sample molecules in this study due to their toxicity and health effects owing to persistence and bioaccumulation. Synergistic adsorptive and degradative behavior of the materials towards pNA and pNP showed an optimum pH of 3.0 and an optimum contact time of 60 minutes. Higher initial adsorption capacity was observed for Lig-s-nZVI and high sustainability and stability was portrayed by Lig-e-nZVI over the regeneration cycles. Both materials showed comparatively increased adsorption capacities in a simulated wastewater matrix. Therefore, it is conclusive that Lig-s-nZVI is of improved remedial capacity towards organic contaminants whereas, Lig-e-nZVI is a better candidate in action over time. Providing a thorough comparison of the properties and remediation performance of nZVI-BC composites synthesized using two commonly employed methods is expected to offer fresh insights to the scientific community.