摘要:本研究計畫的重要性在於面對氣候變遷所帶來的衝擊下,研發出低能耗、對環境友善的水淡化脫鹽技術,以增加水資源的供給多樣性,並從過去提供額外電能來進行水處理的方式,轉變成為從廢水中擷取電能的觀念。因此,本計畫將製備新穎的三維通道之碳電極材料,將其應用在電容去離子技術與微生物脫鹽電池中,並結合兩項電化學技術各自的特點,同步處理污水、產生電能,以及進行淡化鹽水之工作。
本研究計畫分成三部分:(1)以硬式模板式結合軟式模板法,與化學氣相沉積方法來研發新穎的三維通道碳電極材料,從而掌握控制孔洞結構與分佈的關鍵技術;(2)使用三維通道之階層孔洞(巨孔洞、中孔洞、微孔洞)碳材於電容去離子技術中,增加離子的電容儲存能力與電吸附效能。另外,發展三維通道之巨孔洞碳材,作為微生物脫鹽電池中之陽極材料,降低系統內電阻,提昇電子傳遞速率,以及增加電能的輸出效率;(3)整合以上兩個電化學系統,利用微生物脫鹽電池,對海水進行脫鹽,並在代謝有機污染物質時,提供穩定的直流電,來驅動電容去離子程序,從而進行二次脫鹽的工作。本研究成果將建立一個綠色之產電-脫鹽水處理技術,並可應用於海水淡化、處理高導電度廢水或水再生利用程序,極具有學術研究價值與發展潛力。
Abstract: Due to climate change and unsustainable use of natural water resource, water shortage has become a critical problem throughout the world. Alternative water sources such as brackish water and seawater desalination have been introduced as the strategic solutions to secure fresh water supply. However, large quantities of energy is needed to produce potable water. Noteworthy, capacitive deionization (CDI) that follows the concept of capacitive ion storage offers a new opportunity by increasing energy efficiency and delivering clean water. Also, microbial desalination cell (MDC), referred to a new bioelectrochemical system, is proposed to be a promising technology for seawater desalination with simultaneous electricity generation. Furthermore, carbon electrode materials play a key role to determine the performance of these electrochemical processes (i.e., desalination capability and power output). Most recently, three-dimension carbon electrodes have been considered as ideal porous electrode materials for electrochemical applications such as electrical double layer capacitors and lithium-ion batteries.
In this study, we propose a new energy-sustainable process for water desalination by coupling capacitive deionization with a microbial desalination cell. Three-dimensional hierarchical porous carbon electrodes are synthesized by hard-soft template method for electrosorption of slat ions in capacitive deionization. By taking structural advantages of macropores, mesopores, and micropores, the synthesized carbon electrodes can exhibit high specific capacitance, good pore accessibility for ion diffusion, large ion-accessible surface area, and thereby, the desalination performance can be improved. Additionally, for microbial desalination cell, three-dimension carbon nanotube-coated electrodes with macroporous channels are fabricated by using a chemical vapor process. The use of carbon electrodes associated with three-dimensional continuous and macroporous structure is an effective way to enhance microbe colonization, decrease inner resistance, and then increase bio-electron transfer efficiency, suggesting an increase in volumetric power density.
Furthermore, we investigate the microbial desalination cell-driven capacitive deionization (MDC-CDI) technology. In this systemic integrated process, microbial desalination cell is performed to generate electricity by using bacteria to degrade organic contaminants, and to remove salt ions from seawater. Because of the same level of open circuit voltage and current, capacitive deionization can be further driven by the microbial desalination cell, and as the downstream desalination process to further desalinate salt water (i.e., brackish water). The results of this study can demonstrate the feasibility of the integrated electrochemical MDC-CDI system as a energy-sustainable process for simultaneous wastewater treatment, power production, and water desalination.