- Title
- Arsenic, antimony and phosphorus removal from contaminated waters using raw and modified biochars: insights into mechanism of redox transformation
- Creator
- Rahman, Md. Aminur
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Contamination of toxic metalloids including arsenic (As) and antimony (Sb) has become a major environmental concern worldwide due to its widespread presence in natural and wastewaters. Additionally, excessive discharge of phosphorus (P) to aquatic ecosystems can lead to eutrophication as P is an essential nutrient used in agriculture. Therefore, an efficient As, Sb and P removal technology from aqueous solutions must be developed. Adsorption is regarded as one of pioneer removal technologies used for the efficient removal of both inorganic and organic pollutants. Biochar-based materials are cost effective and biocompatible to terrestrial and aquatic environments, have the potential to remove As, Sb and P from aqueous solution. Currently, biochar functions as an excellent potential adsorbent and is widely applicable to research materials due to its extensive feedstock availability. Although biochar is effective in removing toxic elements, the sorption efficiency can be improved by activation or modification using single metals such as iron (Fe) or binary Fe-based materials such as Zirconium-Fe (Zr-Fe). Hence, this thesis investigated the ability of biochars and modified biochars to remediate As, Sb and P enriched waters. To this end, three types of biochars such as biosolid biochar (BSBC), cow manure biochar (CMBC) and horse manure biochar (HMBC) were synthesized and comprehensively evaluated for their removal efficiencies of few Group V elements. Biosolid biochar was further modified with Fe-chips (Fe-BSBC), Fe-salts (FeCl3-BBSC), Zr-salt (ZrOCl2.8H2O) and Zr-Fe (using Zr-salt and Fe-chips; and Zr-slats and Fe-salts in varying Zr to Fe ratios (1:1 to 1:100) for enhancing As, Sb and P removal capacities. Both pristine biochars (BSBC, CMBC and HMBC) and modified biochars (Zr-BSBC, Zr-FeBSBC and Fe-BSBC) were extensively characterized using a range of advanced techniques and subsequently applied for the removal of arsenate As(V), antimonate Sb(V) and P from aqueous solutions through sorption. The results indicated that Zr-Fe modified biochar composites removed the greatest amount of As, Sb and P from solution of the materials tested. The Freundlich model best fitted with the sorption data in removing As(V), Sb(V) and P which demonstrated that sorption occurred with multilayer onto heterogeneous surface on the biochars. It was also observed that the maximum sorption capacities for modified biochars were much higher than the pristine biochars for both As(V) and Sb(V). Kinetics data best fitted with the pseudo-second order model, indicating multiple reaction mechanisms are involved in removing As(V), Sb(V) and P with biochars. Contamination of toxic metalloids including arsenic (As) and antimony (Sb) has become a major environmental concern worldwide due to its widespread presence in natural and wastewaters. Additionally, excessive discharge of phosphorus (P) to aquatic ecosystems can lead to eutrophication as P is an essential nutrient used in agriculture. Therefore, an efficient As, Sb and P removal technology from aqueous solutions must be developed. Adsorption is regarded as one of pioneer removal technologies used for the efficient removal of both inorganic and organic pollutants. Biochar-based materials are cost effective and biocompatible to terrestrial and aquatic environments, have the potential to remove As, Sb and P from aqueous solution. Currently, biochar functions as an excellent potential adsorbent and is widely applicable to research materials due to its extensive feedstock availability. Although biochar is effective in removing toxic elements, the sorption efficiency can be improved by activation or modification using single metals such as iron (Fe) or binary Fe-based materials such as Zirconium-Fe (Zr-Fe). Hence, this thesis investigated the ability of biochars and modified biochars to remediate As, Sb and P enriched waters. To this end, three types of biochars such as biosolid biochar (BSBC), cow manure biochar (CMBC) and horse manure biochar (HMBC) were synthesized and comprehensively evaluated for their removal efficiencies of few Group V elements. Biosolid biochar was further modified with Fe-chips (Fe-BSBC), Fe-salts (FeCl3-BBSC), Zr-salt (ZrOCl2.8H2O) and Zr-Fe (using Zr-salt and Fe-chips; and Zr-slats and Fe-salts in varying Zr to Fe ratios (1:1 to 1:100) for enhancing As, Sb and P removal capacities. Both pristine biochars (BSBC, CMBC and HMBC) and modified biochars (Zr-BSBC, Zr-FeBSBC and Fe-BSBC) were extensively characterized using a range of advanced techniques and subsequently applied for the removal of arsenate As(V), antimonate Sb(V) and P from aqueous solutions through sorption. The results indicated that Zr-Fe modified biochar composites removed the greatest amount of As, Sb and P from solution of the materials tested. The Freundlich model best fitted with the sorption data in removing As(V), Sb(V) and P which demonstrated that sorption occurred with multilayer onto heterogeneous surface on the biochars. It was also observed that the maximum sorption capacities for modified biochars were much higher than the pristine biochars for both As(V) and Sb(V). Kinetics data best fitted with the pseudo-second order model, indicating multiple reaction mechanisms are involved in removing As(V), Sb(V) and P with biochars. In conclusion, the adsorption study suggests that Zr-BSBC, Zr-FeBSBC and FeBSBC could perform as favorable adsorbents for mitigating both As(V) and Sb(V) contaminated waters. However, the surface reduction of As(V) to As(III) and Sb(V) to Sb(III) under oxic conditions has important implications for the application of biochars in contaminated waters or soils, due to the difference in toxicity and sorption behavior.
- Subject
- arsenic; biochars; redox transformation; phosphorus removal
- Identifier
- http://hdl.handle.net/1959.13/1508276
- Identifier
- uon:56112
- Rights
- Copyright 2022 Md. Aminur Rahman
- Language
- eng
- Full Text
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