- Title
- Halloysite templated nano functional materials for the remediation of pollutants from wastewater
- Creator
- Deb, Amal Kanti
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Due to increasing industrial operations for goods and services to meet the global demands, tonnes of toxic waste materials are also generated that become gradually alarming for environmental quality and health burden for humans. Depending on the industrial sector, wastes contain toxic metal(loid)s, dyes and other organic pollutants, and often a mixture of them poses a potential risk to environmental and human health. The major environmental problem is the impact of disposing of wastewater and other residues in superficial and underground water bodies. Consequently, the rapid global contamination of freshwater systems with such toxic chemicals is one of the significant environmental problems faced by humanity. Therefore, sustainable remediation of such wastewater using efficient and biocompatible materials is an emerging issue in the twenty-first century. To date, nanotubes are the most promising among the high-aspect-ratio nanomaterials for advanced applications, including environmental remediation. However, the toxicity of these nanotubes’, particularly carbon nanotube (CNT), is a big concern. Conversely, clay nanotubes such as halloysite nanotube (HNT) outperform this and can be safely utilized in environmental applications. Currently, there is a considerable demand for a multifunctional, cost-effective, stable and eco-friendly nanohybrid material in sustainable remediation technology. HNT has tunable surface structures, high-aspect-ratio and large surface areas with low cost and biocompatibility, making it the best emerging support material for metal and metal oxide nanoparticles (NPs) to design multifunctional nanohybrids. On the other hand, ultra-small metal nanoparticles (NPs), in the form of nanoclusters (NCs) with a core size less than 3 nm, are the prime class of materials in modern nanotechnology. Therefore, this research has developed new methodologies for synthesizing multifunctional and biocompatible nanohybrids following green chemistry principles. Ultra-small copper nanoclusters (CuNCs, < 3 nm) have been synthesized using biocompatible glutathione (GSH) and seeded them into the surfaces of HNT to produce CuNCs@HNT nanohybrid. In another methodology, ultra-small magnetite (Fe3O4) NPs (4.52 ± 1.63 nm) were synthesized and selectively loaded them into the inner surface (lumen) of HNT through an eco-friendly synthesis approach. The nanohybrid, Fe3O4NPs@HNT, was further tuned with biocompatible polymers, sodium alginate and poly (vinyl alcohol) to produce beads (SPHM). After intensive characterizations using advanced and sophisticated analytical tools, the materials were utilized as nanocatalysts and nano adsorbents in the sustainable remediation of multiple aqueous contaminants. The nanohybrid, CuNCs@HNT provide faster catalytic degradation of contrasting organic azo dyes, methylene blue (MB) and methyl orange (MO), than the bare CuNCs. CuNCs@HNT degrades 100% cationic MB (30 mg/L) within only 17.5 ± 2.5 s with an extremely low catalyst dose (1 μg Cu equivalent/mL). In contrast, it takes 75 ± 3.15 m for over 90% degradation of anionic MO (10 mg/L) with the same dose. However, in terms of catalyst-to-dye mass ratio and the more persistent nature of MO, CuNCs@HNT outperforms those. Furthermore, the catalyst is highly reusable and stable since it potentially performs in consecutive eight cycles of MB catalysis. On the contrary, CuNCs are not reusable due to their self-aggregation in the aqueous media. In addition, the biocompatibility investigation reveals that CuNCs@HNT is biocompatible and nontoxic to the soil environment, which complies with sustainable remediation. To further prove the multifunctional property, CuNCs@HNT was additionally utilized in the remediation of carcinogenic hexavalent chromium [Cr(VI)] from water. The result shows that CuNCs@HNT has a high Cr(VI) adsorption capacity (79.14 ± 6.99 mg/g) at pH 5 with an increment at lower pH values. The mechanistic insights evidence that CuNCs@HNT can reduce 80% of highly toxic Cr(VI) to less toxic Cr(III) during adsorption through the redox reaction and the coordinated oxo-chrome-complex formation. The adsorbent was regenerated and reused up to five successive adsorption-desorption cycles with excellent adsorption capacity and without losing its structural integrity. The nanohybrid also removed 99.5% Cr(VI) from contaminated surface water [10 mg Cr(VI)/mL], indicating that coexisting anions, cations and other interferences of natural surface water did not impact the performance of the material during Cr(VI) adsorption. Moreover, cost evaluation suggests that the material’s cost per litre of Cr(VI) effluent is only 0.03 USD; thus, the remediation of Cr(VI) using CuNCs@HNT is cost-effective. The nanohybrid, Fe3O4NPs@HNT has good magnetic properties, which enable it to magnetically separate after treatment. The material efficiently removed arsenate [As(V)] from water within 8 h with 12.73 ± 1.16 mg/g adsorption capacity, which is higher than its bare counterpart Fe3O4NPs (7.92 ± 0.98). Mechanism study suggests that As(V) adsorption occurred through the formation of outer-sphere (OS) bidentate binuclear (BB) and inner-sphere (IS) BB and bidentate mononuclear (BM) complexes. The material was regenerated and reused in five adsorption-desorption cycles with similar adsorption capacity and without losing significant structural integrity. Fe3O4NPs@HNT can also remediate 99.5% As(V) from the contaminated groundwater [5 mg As(V)/L]. Hence, the groundwater composition does not affect the material’s activity. The preparation cost of Fe3O4NPs@HNT is extremely low, i.e., the material cost for 100 m3 wastewater remediation is only 10.40 USD. Furthermore, the biocompatibility test confirms its biocompatibility to the soil environment. The SPHM has a spherical shape with a mesoporous structure and magnetic properties. SPHM was utilized for enhanced removal of an emerging micropollutant, streptomycin (STR), from water. The SPHM beads show a synergistic effect in the remediation of STR with exceptionally high adsorption capacity, 235.71 ± 13.98 mg/g, which is much higher than its counterpart, Fe3O4NPs@HNT (33.15 ± 2.38 mg/g). The mechanistic study reveals that pore filling, intra-particle diffusion and chemisorption occurred during the adsorption of STR by SPHM. X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToF-SIMS) analyses confirm that NH+ of guanidine and N-methyl-glucosamine groups and OH- group of STR electrostatically interacted with the opposite functional groups of SPHM. In addition, SPHM performed exceptionally well in recycling and reusing up to ten consecutive adsorption-desorption cycles without losing its structural morphology. Moreover, SPHM proved its potential in the remediation of STR from surface stream water, while cost evaluation indicates that the material cost is only 0.38 USD per litre of wastewater treatment. Overall, all newly developed materials proved their multifunctional potential in the sustainable remediation of both organic and inorganic contaminants from surface and groundwater with their biocompatibility and cost-effectiveness. Therefore, these multifunctional and biocompatible materials are the potential to scale up at the industrial level for wastewater treatment.
- Subject
- nano functional materials; pollutants; wastewater; azo dyes; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1505464
- Identifier
- uon:55670
- Rights
- Copyright 2022 Amal Kanti Deb
- Language
- eng
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