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標題: | 環境友善生物碳材料於水中污染物之去除:材料製備、特性分析及其應用 Eco-friendly biochar-based materials in removal of contaminants from aqueous solutions: Fabrication, characterization and applications |
作者: | Dinh Viet Cuong 丁越強 |
指導教授: | 侯嘉洪(Chia-Hung Hou) |
關鍵字: | None, Biochar-based material,hierarchical porous carbon,MnO2-biochar composite,adsorption,electrosorption,redox transformation, |
出版年 : | 2020 |
學位: | 博士 |
摘要: | None This thesis aims to develop eco-friendly biochar (BC)-based materials for water treatment. The BC-based materials can be controlled and enhanced their properties, e.g., physical, chemical, or/and electrochemical properties. The improvement of these properties can be beneficial for surface or interface-related or ionic transport processes, resulting in efficient water treatment. Firstly, the application of high-quality meso/micropore-controlled hierarchical porous carbon (HPC) was synthesized by a hard template method utilizing BC and then used to adsorb copper ions from an aqueous solution. The preparation procedure included two main steps: base leaching and physicochemical activation. During the activation process, porosity characteristics (i.e., specific surface area (SSA) and mesoporosity) were controlled by altering the KOH impregnation ratio, activation time, and temperature under the CO2 atmosphere. As evidenced, HPC material has a very high SSA of 2330 m2 g–1 with an 81% mesoporosity. Besides, a copper adsorption study was performed using the HPC samples with different pore structures and characteristics. The most obvious finding to emerge from this study was that a high adsorption capacity (265 mg g–1) and fast removal of copper ions can be obtained by HPCs synthesized from activated BC. The large SSA ensures a high adsorption capacity, while the mesopores are preferable for faster ion removal during the adsorption process. Secondly, HPC as an eco-friendly electrode material was fabricated from BC for electrosorption of ions. The porous structure in the HPC can be controlled by different activation times to optimize the material physicochemical and electrochemical properties. The HPC achieved a high SSA (1839 m2 g−1), large PV (1.21 cm3 g−1), and mesoporosity (58%). The HPC electrode exhibited excellent electrochemical properties with a high specific capacitance of 120.5 F g−1 at 5 mV s−1 in a 1 M NaCl solution as well as good reversibility for capacitive charge storage. The large ion-accessible SSA, interconnected pore structure among micropores and mesopores, and high mesoporosity of the HPC electrode played crucial roles in the enhancement of the electrosorption performance. The HPC electrode exhibited a high electrosorption capacity of 8.11 mg g−1 and a mean deionization rate of 0.92 mg g−1 min−1 for 20 mM NaCl in single-pass capacitive deionization. The associated charge efficiency and energy consumption were 48.1% and 0.064 kWh mol−1, respectively, indicating a low energy requirement of water desalination. Furthermore, the HPC electrode showed good regeneration ability in consecutive cycles for the removal of inorganic pollutants, i.e., NH4+, Mg2+, and Cu2+, with electrosorption capacities of 1.54, 1.53 and 0.52 mg g−1, respectively. Consequently, HPC from tailored activated rice husk BC can provide a new opportunity to achieve high-performance electrosorption in various water and wastewater treatment processes. As(III) species, accounting for a predominant proportion in groundwater, is more toxic, and difficult in adsorption than As(V) species. Thirdly, an active MnO2/rice husk BC composite (MBC) was successfully prepared to enhance the As(III) removal for groundwater remediation. MBC achieved an improved porosity structure (i.e., SSA, PV, and mesoporosity), providing abundant reaction or interaction sites for surface or interface-related processes such as redox transformation and adsorption of arsenic. As a result, the significant enhancement of the arsenic removal capacity can be achieved by using MBC. More specifically, MBC showed a great removal capacity of As(III), which was tenfold higher than that of BC. It can be ascribed to the redox transformation of As(III) via MnO2, resulting in more effectively adsorbed As(V) species. In addition, pH was an important factor, which influenced the As(III) removal capacity. Under the alkaline condition, the As(III) removal capacity of MBC was lower than that of under acidic and neutral conditions due to the negative effects of electrostatic repulsion. Importantly, a powerful transformation capability of As(III) via MBC was presented, namely, only 5.9% As(III) has remained in the solution under neutral condition. The As(III) adsorption was governed by surface complexation mechanisms of functional groups, i.e., COOH, OH, and Mn-OH. Most interestingly, the application of the MBC in the treatment of simulated groundwater demonstrated an efficient arsenic removal of 94.6% and the concentration of arsenic as low as the 10 µg L–1 WHO guideline. The results of this thesis provided strong evidence that BC-based materials can be efficiently applied in water treatment (e.g. heavy metal and ammonium removal, desalination, water softening, and redox transformation of As(III)). The applications of these BC-based materials demonstrated great flexibility through various treatment processes such as adsorption, electrosorption, and integrated process of transformation and adsorption. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69916 |
DOI: | 10.6342/NTU202003877 |
全文授權: | 有償授權 |
顯示於系所單位: | 環境工程學研究所 |
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