發(fā)布時間：2018-04-14 21:41

  本文選題：電容去離子 + 共離子排斥��； 參考：《東華大學(xué)》2017年碩士論文

【摘要】：電容去離子(Capacitive deionization,CDI)技術(shù)通過控制充電/放電循環(huán)過程來實現(xiàn)離子的去除。在充電的過程中,流經(jīng)電極的溶液中的離子在靜電場作用下被吸附到帶相反電荷的電極上形成雙電層而從水溶液中去除,獲得淡水。充電過程結(jié)束后,通過電池短路或者反向充電的方式使吸附在電極上的離子脫附,完成電極再生。電容去離子技術(shù)與傳統(tǒng)脫鹽技術(shù)相比,具有能耗低、電極再生簡單和無二次污染等特點(diǎn)。碳材料具有較高的比表面積和豐富的孔隙結(jié)構(gòu),常常作為電極材料用于電容去離子。然而在研究過程中,發(fā)現(xiàn)電極充電時候在吸附極性相反離子的同時會排斥極性相同的離子,這一過程同樣會產(chǎn)生額外能耗,減少離子吸附總量,這一過程叫做“共離子排斥效應(yīng)”。“共離子排斥效應(yīng)”的產(chǎn)生會降低脫鹽過程中的電流效率和脫鹽性能。而活性炭本身導(dǎo)電性較差等因素制約著電容去離子技術(shù)的發(fā)展。因此,低成本高性能的新型電極材料電極的開發(fā)對電容去離子技術(shù)的推廣和應(yīng)用具有指導(dǎo)意義。本論文圍繞電容脫鹽中“共離子排斥效應(yīng)”影響脫鹽性能這一問題展開討論。首先通過對比不同電容器池(對稱活性炭電極,表面活性劑修飾活性炭電極組裝的不對稱電容脫鹽裝置以及膜電容脫鹽裝置)來分析恒流充電過程中的共離子排斥效應(yīng)產(chǎn)生的現(xiàn)象、原因及解決方法。并通過Nafion材料對活性炭電極進(jìn)行表面電荷修飾制備復(fù)合活性炭電極,組裝成非對稱電容脫鹽裝置來改善共離子排斥效應(yīng),提高電流效率,優(yōu)化脫鹽性能。主要結(jié)論如下:1、設(shè)計三種電容器,對比分析共離子排斥效應(yīng):通過制備對稱的活性炭電容器、經(jīng)過表面活性劑修飾活性炭電極組裝的不對稱電容器以及膜電容器三種電容脫鹽裝置來分析在恒流充電過程中的共離子排斥效應(yīng)。利用純活性炭電極制備的對稱活性炭電容脫鹽裝置(AC|AC)三種不同電流密度充分充電情況下,溶液電導(dǎo)率先上升后下降且吸脫附平衡點(diǎn)所對應(yīng)的充電電量保持在4.4 m Ah左右,說明對稱的活性炭電極具有特定的吸附“平衡電量點(diǎn)”。可以通過控制操作過程中的充電電量值來提高電流效率,保證脫鹽性能。利用表面活性劑修飾的活性炭電極來組裝制備得到不對稱電容脫鹽裝置(CTAB-AC||LAS-AC),發(fā)現(xiàn)其經(jīng)荷電物質(zhì)修飾后,電極的吸附“平衡電量點(diǎn)”比活性炭電極明顯增加。說明經(jīng)過表面活性劑修飾的電極有效改善共離子排斥。膜電容脫鹽裝置(MCDI)由于電荷選擇性,在充電過程中能夠有效的抑制共離子排斥,從而電流效率可達(dá)95%。然而在充電第二階段(4.7mh A),電極極化或水電解嚴(yán)重消耗電量,電流效率急劇下降,脫鹽量增加變緩。2、Nafion既可作為離子交換劑,也是廣泛采用的電極粘合劑,實驗采用Nafion為添加劑與活性炭共混,利用Nafion可以部分替代疏水性的PTFE粘合劑,制備低PTFE含量的Nafion-AC復(fù)合電極。場發(fā)射電子掃描顯微鏡和能譜儀(SEM-EDS)表征結(jié)果顯示Nafion能夠均勻的分布在活性炭電極表面,氮吸脫附測試結(jié)果表明經(jīng)過Nafion摻雜改性后的復(fù)合電極,比表面積略微增大,微孔體積增加,說明Nafion分子能夠有效的填補(bǔ)活性炭電極間的大孔結(jié)構(gòu),為離子在電極內(nèi)部的傳輸提供媒介,較少阻礙,提高離子的傳輸速率;接觸角表征結(jié)果表明由于Nafion的存在,降低了超疏水的PTFE含量,從而有效改善電極的親水性;同時Nafion表面含有豐富的磺酸基團(tuán),能夠有效的改善電極的離子導(dǎo)電性;拉伸測試證明了Nafion-AC復(fù)合活性炭電極比AC電極具有更好的機(jī)械拉伸性能。以Nafion-AC復(fù)合電極組裝成不對稱電容脫鹽裝置用于電容去離子的研究,同時探究Nafion摻雜量對電極的電化學(xué)性能和脫鹽性能的影響。結(jié)果表明,當(dāng)Nafion摻雜量為7.5%時,復(fù)合電極比電容值最高達(dá)到148 F/g。通過對Nafion-AC復(fù)合電極零電勢的研究,當(dāng)Nafion-AC復(fù)合電極用作負(fù)極時,能夠有效的減少共離子排斥效應(yīng),提高電流效率,其脫鹽值能夠達(dá)到10.8 mg/g是純活性炭電極的1.6倍,電流效率是純活性炭的2.0倍。
[Abstract]:Capacitive deionization (Capacitive deionization CDI) technology by controlling the charging / discharging process to achieve ion removal. In the process of charging, ion solution flowing through the electrode in electrostatic field is adsorbed to the electric double layer and removal from aqueous solutions, obtaining fresh water formed oppositely charged electrodes on the charge. After the end of the process, the adsorption of ions on the electrode desorption by battery short-circuit or reverse charging mode, complete regeneration of electrodes. Compared with the traditional capacitive deionization desalination technology, has the advantages of low energy consumption, simple and no regeneration electrode two times pollution. Carbon materials with high specific surface area and pore structure. Often used as electrode material for capacitive deionization. But in the course of the study, found that the electrode charging time will reject the same polarity of ions in the simultaneous adsorption of opposite polarity ions, this process The same will generate additional energy consumption, reduce the amount of ion adsorption, this process is called "total ion exclusion effect." "ion exclusion effect" will reduce the current efficiency and performance of desalination desalination process. The activated carbon itself poor conductivity and other factors to restrict the development of capacitor ion technology. Therefore, with the guidance of the significance of the promotion and application of new electrode electrode with low cost and high performance of capacitive deionization technology. This thesis focuses on the capacitive desalination ion exclusion effect desalination performance of a discussion of this issue. Firstly, through the comparison of different capacitor pool (asymmetric capacitance desalting device symmetry activated carbon electrode, surfactant modified activated carbon electrode assembly and membrane capacitance) desalination device analysis of the constant current charging process of the total ion exclusion effect of the phenomenon, causes and solutions. The Nafion material for surface charge modification of activated carbon electrode composite activated carbon electrode assembly, asymmetric capacitor desalination device to improve the total ion exclusion effect, improve current efficiency, optimize the desalination performance. The main conclusions are as follows: 1. The design of three kinds of capacitors, comparative analysis of total ion exclusion effect: activated carbon capacitor by symmetry, after surfactant modified activated carbon electrode assembly of asymmetric capacitor and three capacitor film capacitor desalination device to analysis in the constant current charging process of the total ion exclusion effect. Symmetric active carbon capacitor active carbon electrode pure desalting device prepared by using (AC|AC) three different current density full charge, charging electricity conductivity increased first and then decreased and the adsorption desorption equilibrium point corresponding to the 4.4 m on the Ah, that the activated carbon electrode with symmetric specific absorption With "power balance." can increase the current efficiency by charging power control in the process of operation, ensure the desalination performance. Activated carbon electrode modified by surfactant assembly prepared by asymmetric capacitance desalting device (CTAB-AC||LAS-AC), found the charged material modified electrode, the adsorption equilibrium power point "obviously increased than that of activated carbon electrode. The electrode with surfactant modified to effectively improve the total ion exclusion. The membrane capacitance desalting device (MCDI) due to the charge selectivity, can effectively inhibit the total ion exclusion in the charging process, and the current efficiency was up to 95%. but in the second stage charging (4.7mh A), or the electrode polarization water electrolysis serious energy consumption, current efficiency decreased sharply, desalination increased slow.2, Nafion can be used as ion exchange agent, electrode adhesives are also widely used, using Nafion As the additive and activated carbon blended by Nafion can partially replace the hydrophobic adhesive PTFE, Nafion-AC composite electrodes were prepared with low PTFE content. Field emission scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) results show that Nafion can be uniformly distributed on the surface of activated carbon electrode, nitrogen adsorption desorption test results show that the composite electrode after Nafion doping, the specific surface area increased slightly, the micropore volume increased, indicating that Nafion molecules can fill the pore structure of activated carbon electrode effectively, provide the media, for ion transport within the electrode less obstacles, improve the transmission rate of ions; contact angle. The results showed that due to the presence of Nafion, reduce the the content of PTFE super hydrophobic, which can effectively improve the hydrophilic electrode; at the same time, the surface of Nafion containing sulfonic groups rich, can improve the ionic conductivity of the electrode effectively; tensile test It is shown that the tensile mechanical properties of Nafion-AC composite activated carbon electrode is better than that of AC electrode. The Nafion-AC composite electrode assembly asymmetric capacitance desalting device for capacitive deionization, and explore the Nafion doping on the electrochemical performance of the electrodes and the desalination performance was studied. Results show that when the Nafion content was 7.5%, the composite electrode the specific capacitance is up to 148 F/g. through the research on the Nafion-AC composite electrode potential zero, when the Nafion-AC composite electrode used as anode, which can effectively reduce the total ion exclusion effect, improve the current efficiency, the desalination value can reach 10.8 mg/g is 1.6 times higher than that of pure activated carbon electrodes, current efficiency is 2 times higher than that of pure activated carbon.

【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P747

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