- Title
- Biocompatible multifunctional clay-supported iron nanoparticles for arsenate and hexavalent chromium remediation from contaminated water
- Creator
- Uz-Zaman, Kh Ashraf
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Prolonged exposure to heavy metal(loid)s, including inorganic arsenic (As) and chromium (Cr) via drinking water is a major concern as it poses significant human health risks. Removal of these pollutants is crucial but requires effective and environment-friendly clean-up technology to avoid chance of the occurrence of secondary risk to the environment. Various conventional and smart technologies have been adopted to achieve the clean-up goals. To date, nano zero valent iron (nZVI) has showed prominent capacity as an adsorbent and reducing agent for decontamination and is capable to remediate both organic and inorganic contaminants from point of contamination. However, nZVI, if not modified shows aggregation into large particles, leading to the reduction of external surface areas. Also, aggregation caused quick settling down of the nZVI that prevents them from accessing sites of interest, and thus reduces its effectivity. Therefore, use of support material has been promising to avoid these technical infeasibilities, while envisaging enrichment of overall functionalities of composite. Clay minerals being one such support material. They are low cost and abundant in nature and possess stabilizing capacity/reactivity with other various co-materials, and improve the functionalities of both. In this study, a locally sourced smectite (smec)-supported nano zero-valent iron (nZVI) composite was developed for arsenate i.e., As(V).A range of tools was used, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersion X-ray (EDS), Brunauer-Emmett-Teller (BET) surface area analyzer to characterize the material. These show that the smectite layers were surrounded by a chain of iron nanobeads with even distribution on clay particles, which is quite exceptional among currently available clay-nZVIs. The specific surface area of smec-nZVI was 46.75 m2/g while the nZVI only had 7.29 m2/g. smec-nZVI composite also reached equilibrium within 4 h for As(V) sorption. The maximum As(V) sorption capacity of this composite was 23.12 mg/g in the ambient conditions. Using XPS the As and Fe chemical states before and after the sorption process were unveiled. Additionally, the release of iron nanoparticles from the composite at various pHs (3–10) were found negligible, which demonstrates the effectiveness of smec-nZVI to remove As(V) from contaminated water without posing any secondary pollutant. In the second experiment, nanobeads of nZVI nesting through nanosheets of acid activated clay (smectite) were developed for the removal of arsenate (As(V)) and Cr(VI). Materials were characterised using a range of tools, likewise, mentioned in the experiment. Nanoscale imaging and elemental mapping of the composite show the presence of nZVIs on the surfaces of nanosheets of smectite, including that in the interlayers. The mild acid treatment improved the BET surface area of smec (47.5 m2/g) and reached 67.14 m2/g while after incorporating nZVI it was escalated to 91.09 m2/g in ASmec-nZVI composite. The maximum As(V) and Cr(VI) sorption capacities of this composite were 39.15 and 5.13 mg/g respectively, with the initial solution pH 5. The XPS-derived chemical states of Fe, As, Cr were interpreted to reveal the enhanced removal process. Also, the composite was not harmful to soil bacteria, as a proxy of biocompatibility of spent material. Considering the above, the unique clay sheet-supported nZVI can be considered as multifaceted and safe adsorbent. The subsequent study reports a surfactant 3-(N,N-dimethylpalmityl-ammonio) propane sulfonate (SB16) modified smectite (SbSmec) supported iron nanoparticles composite (SbSmec-FeNP) for sorption of As(V) and Cr(VI). Like the other experiments in this thesis, the state-of-the-art instrumentation and analytical techniques revealed two different arrangements of iron nanoparticles found in SbSmec-FeNP, including nanobeads or in chain of nanobeads (nZVI) while the others were Fe-complex blended with the template and forming network of complexes. The maximum As(V) and Cr(VI) sorption capacity of SbSmec-FeNP was 70.57 and 7.66 mg/g, respectively, with initial solution pH ~5. Chemical states of Fe, As, Cr after the sorption process were interpreted using XPS to understand the mechanism of adsorption. Likewise, in test as a proxy of spent material’s biocompatibility, the soil bacterial growth was not much affected by the fresh composite. Taking the above into account, this novel surfactant modified clay sheet-supported nZVI can be considered as a resourceful and secure adsorbent.
- Subject
- biocompatible; clay-supported; iron nanoparticles; contaminated water
- Identifier
- http://hdl.handle.net/1959.13/1473263
- Identifier
- uon:48986
- Rights
- This thesis is currently under embargo and will be available from 01.03.2024., Copyright 2023 Kh Ashraf Uz-Zaman
- Language
- eng
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