本文關(guān)鍵詞：碳納米管和納米纖維素晶體對(duì)超濾膜性能的提升研究　出處：《哈爾濱工業(yè)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 碳納米管 納米纖維素晶體 表面涂覆改性 共混改性 膜污染 超濾膜機(jī)械強(qiáng)度

【摘要】：超濾技術(shù)能夠有效保障飲用水生物安全性。超濾工藝占地面積小、易于實(shí)現(xiàn)模塊化、自動(dòng)化程度高。超濾過(guò)程不發(fā)生化學(xué)反應(yīng)、不產(chǎn)生二次污染、環(huán)境友好。超濾技術(shù)現(xiàn)已大規(guī)模應(yīng)用在水處理中。限制超濾技術(shù)發(fā)展的瓶頸問(wèn)題主要包括膜污染現(xiàn)象、膜材料親水性弱、超濾膜機(jī)械強(qiáng)度不足。這些問(wèn)題均直接與超濾膜本身性質(zhì)相關(guān)。為了解決以上問(wèn)題,提升超濾膜性能,本論文從膜改性角度出發(fā),采用表面涂覆改性和共混改性兩種方法,選取碳納米管(CNTs)和納米纖維素晶體(CNCs)兩種納米材料作為改性材料,對(duì)聚醚砜(PES)超濾膜進(jìn)行改性。系統(tǒng)考察CNTs表面涂覆改性對(duì)膜污染控制及膜阻力分布的影響并探討其機(jī)理;研究并比較CNTs和CNCs共混改性對(duì)納米復(fù)合膜形貌、親疏水性和機(jī)械強(qiáng)度的影響及其機(jī)理。本論文以實(shí)際水體作為水源,首先考察運(yùn)行工況優(yōu)化對(duì)膜污染的控制效果。膜池內(nèi)污染物分析結(jié)果表明,超濾過(guò)程中非溶解性顆粒物質(zhì)、溶解性有機(jī)物和天然有機(jī)物在膜池內(nèi)發(fā)生污染累積。為了減緩污染物累積產(chǎn)生的膜污染,考察了過(guò)濾模式、水力反洗、排空反洗液等條件對(duì)超濾膜跨膜壓力的影響并得到最優(yōu)工況參數(shù);考察排泥周期對(duì)膜污染控制效果及對(duì)超濾工藝產(chǎn)水率的影響。結(jié)果表明,優(yōu)化運(yùn)行工況能夠通過(guò)降低濃差極化污染和濾餅層污染,從而起到控制可逆污染的效果。縮短排泥周期能夠減緩松散濾餅層向壓實(shí)濾餅層的轉(zhuǎn)化,間接降低弱吸附污染,從而緩解部分不可逆污染。縮短排泥周期導(dǎo)致超濾凈產(chǎn)水量下降,排泥周期為24、12和6 h條件下,超濾工藝產(chǎn)水量分別為96.31%、92.61%和85.23%。運(yùn)行工況優(yōu)化對(duì)可逆污染有較好控制效果,但對(duì)不可逆污染控制效果微弱。從根本上解決膜污染問(wèn)題,尤其是不可逆膜污染問(wèn)題,僅憑優(yōu)化運(yùn)行工況的角度是不夠的。控制超濾膜膜污染方面,采用多壁碳納米管(MWCNTs)表面涂覆改性方法。制備功能化碳納米管并根據(jù)官能團(tuán)種類命名為Raw-MWCNTs、COOH-MWCNTs和PEG-MWCNTs。材料表征結(jié)果顯示,功能化碳納米管表面含有大量親水基團(tuán);相同pH條件下,表面電負(fù)性關(guān)系為COOH-MWCNTsPEG-MWCNTsRaw-MWCNTs;水溶液中粒徑分布大小規(guī)律為:Raw-MWCNTsCOOH-MWCNTsPEG-MWCNTs。表面涂覆改性后,根據(jù)涂覆材料將超濾膜依次命名為Control-M、Raw-M、COOH-M和PEG-M。相比于對(duì)照膜,改性膜的純水通量略有下降。四種超濾膜表面粗糙度關(guān)系為:Raw-MCOOH-MPEG-MControl-M。以模型污染物作為天然水體有機(jī)污染物代表物,考察原始及功能化碳納米管表面改性對(duì)膜污染的控制效果并分析其機(jī)理。腐殖酸過(guò)濾試驗(yàn)顯示,Raw-M、COOH-M和PEG-M分別降低不可逆污染68.8%、75.0%和93.8%。表面負(fù)電性增強(qiáng)和表面親水性增加是主要控制因素;牛血清蛋白過(guò)濾試驗(yàn)顯示,Raw-M、COOH-M和PEG-M分別降低不可逆污染81.0%、90.5%和66.7%。表面電負(fù)性和表面粗糙度是主要控制因素;海藻酸鈉過(guò)濾試驗(yàn)顯示,Raw-M、COOH-M和PEG-M分別降低了不可逆污染69.4%、93.1%和98.3%。表面負(fù)電性增強(qiáng)和表面親水性增加是主要控制因素。在超純水反洗和污染物濾過(guò)液反洗條件下,三種改性膜中碳納米管脫附含量關(guān)系為:PEG-MCOOH-MRaw-M。提升超濾膜親水性和機(jī)械強(qiáng)度方面,采用CNTs和CNCs作為添加材料的共混改性方法。材料表征結(jié)果顯示,CNTs和CNCs表面均含羥基,均為親水材料。分別以0.5 wt%、1.0 wt%和2.0 wt%共混含量,制備0.5 CNTs-M、0.5 CNCs-M、1.0 CNTs-M、1.0 CNCs-M、2.0 CNTs-M和2.0 CNCs-M。未添加納米材料的對(duì)照膜命名為Control-M。分別考察CNTs和CNCs對(duì)超濾膜形貌、結(jié)構(gòu)及孔隙率的影響。結(jié)果顯示,Control-M活性層中聚合物排列密實(shí),孔隙結(jié)構(gòu)很少;CNTs-M和CNTs-M活性層聚合物排列松散,有明顯的孔隙結(jié)構(gòu)后;CNTs-M和CNCs-M的平均孔隙率、表面孔隙率、平均孔徑顯著增加;表面粗糙度輕微增加。Control-M表面成疏水性;CNTs-M和CNTs-M表面呈親水性,相同共混含量下,CNCs-M親水性強(qiáng)于CNTs-M。改性納米復(fù)合膜過(guò)水通量隨納米材料共混含量增加而提升,原因是改性膜親水性增強(qiáng)和孔隙率提升。相同共混含量下,CNCs-M過(guò)水通量高于CNTs-M。改性膜機(jī)械強(qiáng)度研究結(jié)果顯示,CNTs和CNCs均能提升納米復(fù)合膜剛性性質(zhì),原因是納米復(fù)合膜繼承了共混材料自身機(jī)械性質(zhì)。相同共混含量下,CNTs-M的楊氏模量和最大拉伸應(yīng)力均高于CNCs-M。提高CNCs共混含量1倍,可以使CNCs-M達(dá)到或高于CNTs-M的剛度強(qiáng)度。結(jié)合環(huán)境影響和經(jīng)濟(jì)成本方面的考慮,在增加超濾膜親水性和機(jī)械強(qiáng)度方面,CNCs有取代CNTs的可行性。
[Abstract]:Ultrafiltration can effectively protect drinking water biological safety. Ultrafiltration technology, small footprint, easy to realize modular, high degree of automation. The ultrafiltration process does not react, does not have two pollution, environmental friendly. Ultrafiltration technology has been widely applied in water treatment. The bottleneck of development of ultrafiltration technology including membrane fouling the phenomenon of weak hydrophilic membrane material, membrane, insufficient mechanical strength. These problems are directly related with the membrane itself properties. In order to solve the above problem, this paper improve the properties of UF membrane, membrane modification from the point of view of the surface coating modification and blending modification of two kinds of methods, selection of carbon nanotubes (CNTs) and nano crystalline cellulose (CNCs) of two kinds of nano materials as the modified material of polyethersulfone (PES) ultrafiltration membrane was modified. The system of CNTs surface coating modification of control and membrane fouling resistance distribution Influence and to explore its mechanism; to study and compare the CNTs and CNCs blend modification on the morphology of nano composite film, effects of hydrophobicity and mechanical strength and mechanism. In this paper, the actual water as water source, first examine the operation optimization of membrane pollution control effect. The analysis results of pollutants in the membrane pool showed that insoluble in the process of ultrafiltration of particulate matter, dissolved organic matter and natural organic matter in the membrane pool. In order to reduce pollution accumulation of membrane pollution accumulation of pollutants generated, investigated the filtration mode, hydraulic backwash effect, anti emptying lotion and other conditions on the membrane of the transmembrane pressure and the optimal working parameters of mud cycle on membrane; the pollution control effect and influence on ultrafiltration water production rate. The results show that the optimal operating conditions can reduce the concentration polarization and the pollution of the cake layer pollution so as to control the pollution effect. Shorten the mud cycle can be transformed into the slow loose cake layer to the compaction of the cake layer, indirectly reduce the weak adsorption of pollution, so as to alleviate some of the irreversible fouling. Shorten the mud cycle leads to ultrafiltration water production decreased, mud cycle is 24,12 and 6 h under the condition of ultrafiltration water yield were 96.31%, 92.61% and 85.23%. operation optimization has better control effect on pollution, but the irreversible pollution control effect is weak. To solve the problem of membrane fouling fundamentally, especially the irreversible membrane fouling problem, only by optimization of the operating condition of the angle is not enough. The control of membrane fouling, multi walled carbon nanotubes (MWCNTs) by surface coating the modified method. The preparation of functionalized carbon nanotubes and according to the type of functional groups named Raw-MWCNTs, COOH-MWCNTs and PEG-MWCNTs. characterization results show that functionalized carbon nanotube surface contains a large number of hydrophilic groups; the same Under the condition of pH, the surface electronegativity of COOH-MWCNTsPEG-MWCNTsRaw-MWCNTs in aqueous solution; size distribution rule: Raw-MWCNTsCOOH-MWCNTsPEG-MWCNTs. surface coating modification, coating material according to the ultrafiltration membrane are named Control-M, Raw-M, COOH-M and PEG-M. compared to control membrane, pure water flux of the modified membrane decreased slightly. Four kinds of ultrafiltration membrane the relationship between surface roughness is Raw-MCOOH-MPEG-MControl-M. to model natural water pollutants as organic pollutant, and investigate the original functionalized carbon nanotube surface modification effect on membrane fouling and analyze its mechanism. Humic acid filtration test showed that Raw-M, COOH-M and PEG-M respectively to reduce the irreversible pollution 68.8%, increased 75% and 93.8%. surface electronegativity enhanced and surface hydrophilicity is the main control factor; bovine serum albumin filtration test showed that Raw-M, COOH-M and PEG-M were not reduced The inverse pollution 81%, 90.5% and 66.7%. surface electronegativity and the surface roughness is the main control factor; sodium alginate filtration test showed that Raw-M, COOH-M and PEG-M were decreased by irreversible pollution 69.4%, increased 93.1% and 98.3%. surface electronegativity enhancement and surface hydrophilicity is the main control factor. In ultrapure water backwashing and pollutant filtration backwash under the condition of three kinds of modified carbon nanotube membrane desorption content relationship: PEG-MCOOH-MRaw-M. enhance ultrafiltration membrane hydrophilicity and mechanical strength, using CNTs and CNCs as the material blending addition modification method. Characterization results show that the CNTs and CNCs surfaces are hydrophilic materials containing hydroxyl group, respectively with 0.5 wt%. 1, wt% and 2 wt% blend content, preparation of 0.5 CNTs-M, 0.5 CNCs-M, 1 CNTs-M, 1 CNCs-M, 2 CNTs-M and 2 CNCs-M. control film without adding nano material named Control-M. CNTs and CNCs were investigated respectively. The effect of ultrafiltration membrane morphology, structure and porosity. The results showed that the activity of Control-M in dense polymer layer, the pore structure of CNTs-M and less; CNTs-M active layer polymer arranged loosely, pore structure obviously after CNTs-M and CNCs-M; the average porosity, surface porosity, average pore size increased significantly; the surface roughness increased slightly a hydrophobic.Control-M surface; hydrophilic CNTs-M and CNTs-M surface, blending the same content, CNCs-M strong hydrophilicity of CNTs-M. modified nano composite membrane water flux with the increase of the content of nano materials was promoted, the reason is to change the hydrophilic membrane and enhanced porosity improvement. The same blend content, water flux CNCs-M the research results of mechanical strength higher than that of CNTs-M. film shows that CNTs and CNCs can enhance the rigidity properties of nanocomposite films, because nano composite film inherited its mechanical properties of blends. The same blend content, the young's modulus and the maximum tensile stress of CNTs-M was higher than that of CNCs-M. CNCs was increased in 1 times, the stiffness and strength of CNCs-M can be reached or higher than that of CNTs-M. Combined with the environmental impact and economic cost, the increase in membrane hydrophilicity and mechanical strength, CNCs has replaced the feasibility of CNTs.

【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU991.2
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本文編號(hào)：1404724