本文選題：電容去離子 + 脫鹽�。� 參考：《東北大學》2015年博士論文

【摘要】：電容去離子(Capacitive deionization, CDI)脫鹽是一種新興的、環(huán)境友好型水處理技術。與蒸餾、反滲透等傳統脫鹽技術相比,CDI是在電場力的作用下,直接將水中離子吸附分離出來,而不是把水從原水中分離出來,無需高溫、高壓,因而具有低能耗、低污染、低成本等技術優(yōu)勢,越來越受到國內外學者的關注。針對目前CDI技術脫鹽效率不高、提升CDI脫鹽性能的機理尚不完善等不足,首先構建了流通式電吸附除鹽實驗裝置,并利用該裝置進行了傳統CDI脫鹽性能、工藝條件的優(yōu)化等實驗研究。在此基礎上,進行了傳統CDI脫鹽技術的強化與改進,以及提升CDI脫鹽效率與降低能耗的實驗研究與機理分析。研究結果對完善CDI脫鹽技術體系,提高CDI脫鹽效率及CDI大規(guī)模開發(fā)利用有所裨益。主要研究內容與結果如下：將活性炭粉末、粘結劑PVDF和導電劑石墨粉的組分按85：10：5的質量配比,在石墨板(集流板)上涂覆制備CDI用活性炭涂層電極。經BET和DFT材料比表面積與孔徑分布測試后,測試結果表明電極涂層材料活性炭的比表面積為1770m2/g,中孔分布約占總孔徑分布的35%；對所制備電極的SEM圖像與EDX分析表明,粘結劑PVDF與活性炭粉末完整地粘結在集流板上,電極性能穩(wěn)定。通過Box-Behnken實驗設計,分別以電吸附量和能耗為評價指標,根據響應面(RSM)理論構建了二次響應面優(yōu)化模型；方差分析表明模型顯著性、準確度和可信度均較高；根據RSM法優(yōu)化結果,選擇電源工作電壓1.57 V、溶液初始濃度1000 mg/L、溶液流速25 mL/min、極板間距2 mm,在此條件下可獲得最大的電吸附量為10.53 mg/g,而選擇電源工作電壓1.38 V、初始濃度900 mg/L、溶液流速40 mL/min、極板間距2mm可獲得吸附去除單位質量NaCl最小的電能消耗9.81kWh/kg,兩者均與模型預測值(10.60 mg/g和9.13 kWh/kg)相吻合,表明基于RSM的CDI工藝優(yōu)化是可行且有效的。綜合考慮脫鹽效果與電能消耗,采用工作電壓1.3-1.6 V、原水初始濃度800-1000 mg/L、溶液流速25-40 mL/min、極板間距2mm的運行參數,CDI脫鹽過程是最經濟高效的。以KOH為活化劑,在850℃活化溫度、1h活化時間的活化條件下,二次活化改性電極涂層材料活性炭,使涂層材料的比表面積從1770 m2/g增至1902 m2/g,改善了孔徑分布(中孔比例由35%提升到41%),以此涂層材料制備的電極活性更高,比電容量由73.62 F/g增至97.71 F/g,電極的電吸附量為12.73 mg/g,較改性前提高了20.9%。通過在CDI模塊內加入陰陽離子交換膜,采用MCDI強化脫鹽,活性炭電極的電吸附量與脫鹽率分別為13.78 mg/g與41.34%,較傳統CDI的電吸附量與脫鹽率提高了30.8%,且離子交換膜的引入并未改變其吸附機制與吸附方式。在改性電極涂層材料基礎上,通過在CDI裝置中加入離子交換膜組成MCDI,進一步強化CDI脫鹽,電吸附量與脫鹽率分別為14.75 mg/g和44.26%,較傳統CDI的電吸附量和脫鹽率提高了40%,并且在相同工藝條件下,吸附去除單位質量NaCl的能耗由CDI的12.24 kWh/kg降至11.01 kWh/kg,下降了10%。根據電極電壓與電源電壓、極板間距、溶液濃度及電流密度等因素的關系,推導了計算CDI電極電壓的公式；由該計算式所揭示的電源電壓、極板間距及電流密度等之間的規(guī)律可知：當含鹽廢水初始濃度較高時,為了既保證脫鹽效果又節(jié)省能耗,可適當選擇較低電源工作電壓或采用較大的極板間距；而處理低濃度含鹽廢水時,則需在保證不發(fā)生電極反應的前提下,盡可能增大電源電壓并縮短極板間距。通過CDI用活性炭電極的Nyquist阻抗圖譜分析了CDI系統的阻抗與近似等效電路,證實了由于濃差極化作用產生的極化電阻的存在,實際CDI研究中可通過增大溶液流速、增強電極表面活性、增大電極有效面積、縮小電極板間距等,減弱濃差極化效應,減小極化電阻,提升脫鹽效果并降低吸附去除單位質量鹽離子的能耗。另外,電極的CV曲線測試分析表明,離子的吸附去除是由于電場靜電力作用,而非發(fā)生了電化學氧化還原反應。利用準一級和準二級吸附動力學模型以及Langmuir和Freundlich吸附等溫方程,探討了CDI脫鹽的吸附機制。結果表明：NaCl在活性炭涂層電極上的電吸附符合準一級動力學模型與Langmuir吸附等溫模型,屬于單分子層吸附,且以物理吸附為主；工作電壓和溶液初始濃度的升高會加快離子遷移速率,提升脫鹽效率,使吸附平衡時電極的電吸附容量增大。綜上,通過CDI工藝運行參數的合理調控優(yōu)化、電極材料的改性、MCDI強化脫鹽可以有效提升脫鹽效率并降低能耗；關于強化CDI脫鹽的機理分析,對CDI技術的進一步開發(fā)利用有所裨益。
[Abstract]:Capacitive deionization (CDI) desalination is a new and environmentally friendly water treatment technology. Compared with the traditional desalting technology such as distillation and reverse osmosis, CDI is directly separated from the water ion under the action of the electric field force, instead of separating water from the original water without high temperature and high pressure, thus having low energy. The technical advantages of consumption, low pollution, low cost and so on are getting more and more attention at home and abroad. In view of the lack of high desalination efficiency of CDI technology and the imperfect mechanism of improving the desalination performance of CDI, a circulation type electric adsorption desalting experiment device is first constructed, and the traditional desalting performance of CDI and the optimization of process conditions are carried out with this device. On this basis, the strengthening and improvement of traditional CDI desalting technology, as well as the experimental research and Mechanism Analysis on improving the desalting efficiency and reducing energy consumption of CDI are carried out. The results are beneficial to improving the CDI desalting technology system, improving the efficiency of CDI desalting and the large-scale development and utilization of CDI. The carbon powder, the binder PVDF and the composition of the conductive graphite powder were prepared on the graphite plate (the collector plate) by the mass ratio of 85:10:5. After testing the specific surface area and pore size distribution of the BET and DFT materials, the test results showed that the specific surface area of the activated carbon of the electrode coating material was 1770m2/g, and the distribution of the mesopore was about the total. The pore size distribution is 35%. The SEM image and EDX analysis of the prepared electrodes show that the binder PVDF and the activated carbon powder are fully bonded on the collector plate and the electrode performance is stable. Through the Box-Behnken experimental design, the electro adsorption quantity and energy consumption are evaluated respectively, and the response surface (RSM) theory is constructed for the two response surface optimization model. The analysis shows that the model is significant, accurate and reliable. According to the RSM method, the power supply voltage is 1.57 V, the initial concentration of the solution is 1000 mg/L, the solution velocity is 25 mL/min and the plate spacing is 2 mm. Under this condition, the maximum electric adsorption capacity is 10.53 mg/g, and the power supply voltage is 1.38 V, and the initial concentration is 900 mg/L, The solution flow rate of 40 mL/min and the plate spacing 2mm can obtain the minimum energy consumption 9.81kWh/kg for the adsorption removal unit mass NaCl, both of which are in agreement with the model prediction value (10.60 mg/g and 9.13 kWh/kg). It shows that the optimization of CDI process based on RSM is feasible and effective. The operation voltage 1.3-1.6 V, raw water is used to consider the desalting effect and the electrical energy consumption. The initial concentration of 800-1000 mg/L, the flow velocity of 25-40 mL/min, the operating parameters of the plate spacing 2mm, the CDI desalination process is the most economical and efficient. With KOH as activator, at the activation temperature of 850 C and the activation time of 1H activation, the activated carbon of the modified electrode coating material is activated to increase the specific surface area of the coating material from 1770 m2/g to 1902 m2/g. The pore size distribution (the ratio of the mesopore from 35% to 41%) was improved, and the electrode activity was higher, the specific capacitance increased from 73.62 F/g to 97.71 F/g, and the electroadsorption capacity of the electrode was 12.73 mg/g. The 20.9%. was enhanced by adding the Yin and Yang exchange membrane in the CDI module and using MCDI to enhance the desalination and the electric absorption of the activated carbon electrode. The rate of desorption and desalination is 13.78 mg/g and 41.34% respectively. The adsorption capacity and desalination rate of the traditional CDI are increased by 30.8%, and the introduction of the ion exchange membrane does not change its adsorption mechanism and adsorption mode. On the basis of the modified electrode coating material, the ion exchange membrane is added to the CDI device to make up the MCDI, further strengthening the desalination of CDI and the electrical adsorption capacity. The rate of desalination and desalination are 14.75 mg/g and 44.26% respectively. The electric adsorption and desalting rate of the traditional CDI is increased by 40%. Under the same process conditions, the energy consumption of the adsorbed unit mass NaCl is reduced from 12.24 kWh/kg to 11.01 kWh/kg, and the 10%. is reduced by the 10%. electrode voltage and the power supply voltage, the plate spacing, the solution concentration and current density. The formula for calculating the voltage of CDI electrode is derived. The rule of power supply voltage, plate spacing and current density revealed by this formula shows that when the initial concentration of salt water is high, in order to ensure the effect of desalting and save energy, the lower power supply voltage or the larger plate spacing can be selected properly. When the low concentration of salt water is treated, the voltage of the power supply and the distance of the plate are shortened as much as possible without the electrode reaction. The impedance and the approximate equivalent circuit of the CDI system are analyzed by the Nyquist impedance Atlas of the activated carbon electrode by CDI. The existence of the polarization resistance caused by the concentration polarization polarization is confirmed. In the study of CDI, it is possible to increase the surface activity of the solution, increase the surface activity of the electrode, increase the effective area of the electrode, reduce the spacing of the electrode plate and so on, weaken the concentration polarization effect, reduce the polarization resistance, improve the effect of desalting and reduce the energy consumption of removing unit mass salt ions by adsorption. In addition, the CV curve test and analysis of the electrode show that the removal of ions is removed. The electrochemical oxidation reduction reaction was not occurred due to the electrostatic force of the electric field. The adsorption mechanism of CDI desalination was discussed by using the quasi first and quasi two stage adsorption kinetic models and the adsorption isotherm equation of Langmuir and Freundlich. The results showed that the electroadsorption of NaCl on the activated carbon coated electrode accorded with the quasi first order kinetic model and Langmuir The adsorption isotherm model belongs to the single molecular layer adsorption and mainly by physical adsorption. The increase of the working voltage and the initial concentration of the solution will accelerate the ion migration rate, improve the desalination efficiency and increase the electric adsorption capacity of the electrode when the adsorption equilibrium is balanced. In a sum, the optimization of the operation parameters of the CDI process, the modification of the electrode materials, and the strengthening of the MCDI Desalination can effectively improve desalination efficiency and reduce energy consumption. The mechanism analysis of strengthening CDI desalination is beneficial to further development and utilization of CDI technology.
【學位授予單位】：東北大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：P747

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