基于造紙白水特性的超濾膜污染及控制研究
發(fā)布時間：2018-08-02 09:05
【摘要】：超濾技術(shù)作為一種高效、安全的物理分離方式在造紙白水封閉循環(huán)系統(tǒng)有機污染物的去除領(lǐng)域具有廣闊的應(yīng)用前景。然而白水復(fù)雜的水體環(huán)境及其中各類有機物所引起的超濾膜污染降低了白水中有機組分的去除效率,制約了膜技術(shù)在造紙白水處理領(lǐng)域的進一步推廣。因此,深入研究造紙白水中有機物特性及白水環(huán)境對膜污染的影響,針對造紙工藝特點選擇合理的預(yù)處理方式對于超濾技術(shù)處理造紙白水過程中產(chǎn)生的膜污染程度的緩解具有十分重要的作用。本論文以造紙白水中溶解性、膠體性有機物為研究對象,考察了白水中有機物特性以及白水環(huán)境對超濾膜污染的影響,同時采用陰離子垃圾固著劑去除白水中引起膜通量下降的主要有機污染物,以此緩解膜系統(tǒng)運行負荷,減輕膜污染。溶解性有機物是造紙白水中的主要有機成分之一。論文采用大孔樹脂吸附及超濾膜分子量分級法對白水中溶解性有機物的親疏水特性及分子量分布進行了表征,并研究了溶解性有機物特性對超濾膜污染的影響。結(jié)果表明,溶解性有機物以親水性組分含量最高,占溶解性有機物總量的67.83%,而疏水性組分含量相對較少。溶解性有機物中親水性組分、疏水性組分分子量分布與試驗原水相似,均以分子量小于5KDa的小分子有機物為主。在溶解性有機物進行超濾過程中,親水性有機物是造成膜通量下降的主要組分。這一類有機物能夠在超濾初期便迅速到達膜表面,其中小分子量的親水性組分引起膜孔堵塞,大分子的親水性組分易造成濃差極化污染,從而引起嚴重的膜通量下降;疏水性有機物與聚醚砜超濾膜表面存在疏水作用,吸附在膜表面形成濾餅污染,膜通量下降較為緩慢。此外,研究通過掃描電鏡及Hermia線性方程擬合分析了溶解性有機物分子量分布對超濾膜污染的影響機理。結(jié)果表明,大分子有機物更多地被機械截留于膜表面形成濾餅層污染,而堵塞污染則是小分子有機物引起膜通量下降的主要機理。白水環(huán)境是影響超濾膜污染的重要因素。本論文采用聚丙烯酸鈉、硬脂酸鈉作為造紙白水中溶解性及膠體性有機物的模擬物,分別研究了不同白水環(huán)境對有機物造成膜污染的影響。研究結(jié)果表明,較低的p H值能夠減弱溶解性有機物與超濾膜表面的靜電斥力,加速有機物在膜表面的吸附沉積,造成嚴重的膜通量下降。離子強度的增加同樣會屏蔽有機物與膜表面的靜電斥力,同時Na+的存在還能夠通過壓縮雙電層的作用使得有機物更易接近膜表面,造成膜污染加劇。多價金屬離子的存在不僅通過“主體架橋作用”造成白水中有機物分子之間相互連接形成復(fù)雜的空間網(wǎng)絡(luò)狀大分子,同時還能夠在有機物與超濾膜之間形成“表面架橋作用”,增加有機物在超濾膜表面的吸附沉積,進而造成嚴重的膜通量下降。相同濃度條件下,Fe~(3+)比Ca~(2+)對膜通量下降的危害更大。白水環(huán)境對膠體性有機物引起的膜通量下降與溶解性有機物具有一定的相似性。酸性條件以及較高的離子強度能夠加重膠體性有機物對膜污染的影響。多價金屬離子的存在造成了膠體性組分粒徑的增加,加重有機物在膜表面的吸附沉積,造成嚴重的濾餅層污染。由于白水中溶解性與膠體性有機物的存在對超濾系統(tǒng)具有明顯的污染作用。論文針對造紙工藝特點及白水中有機物負電性較強的特點,采用高陽電荷密度的聚乙烯亞胺捕集白水中的有機污染物,同時利用聚乙烯亞胺與紙漿纖維之間的靜電作用、氫鍵作用,最終將白水中有機污染物固著于紙漿纖維,帶出白水系統(tǒng),減輕超濾膜系統(tǒng)負荷。結(jié)果表明,隨著聚乙烯亞胺用量的增加,白水中有機物發(fā)生聚集,并固著于紙漿纖維,經(jīng)過動態(tài)濾水儀過濾之后,濾液中有機物引起的陽離子需求量明顯降低,濾液濁度下降。當聚乙烯亞胺用量達到1%(相對于絕干纖維質(zhì)量)時,濾液陽離子需求量、濁度分別下降了56.42%,63.16%,說明聚乙烯亞胺能夠較好的捕集白水中的陰離子有機物并固著于紙漿纖維,明顯改善進入超濾系統(tǒng)的白水水質(zhì)。從聚乙烯亞胺(PEI)預(yù)處理前后的白水模擬溶液進行超濾的膜通量測定及膜表面掃描電鏡可以看出,白水PEI預(yù)處理可以通過減少到達膜系統(tǒng)的有機物濃度,改變膜表面濾餅層結(jié)構(gòu)提高膜通量,緩解膜污染程度。本論文完成了造紙白水中溶解性有機物親疏水性和分子量分布特性的表征,研究了白水中主要有機物特性及白水環(huán)境包括p H值、Na+濃度、多價金屬離子的存在對超濾膜污染的影響,同時提出了適合于造紙白水超濾處理的預(yù)處理方案,為白水封閉循環(huán)中的超濾膜系統(tǒng)穩(wěn)定運行提供技術(shù)支持。
[Abstract]:Ultrafiltration technology has a wide application prospect in the field of organic pollutants removal in papermaking white water closed circulation system as a high efficient and safe physical separation method. However, the complex water environment of white water and the ultrafiltration membrane pollution caused by various kinds of organic compounds reduce the removal efficiency of organic components in white water, and restrict the membrane technology. It is further popularized in the field of papermaking white water treatment. Therefore, the characteristics of organic matter in papermaking white water and the effect of white water environment on the membrane fouling are deeply studied. The selection of reasonable pretreatment methods for the characteristics of papermaking process is very important for the mitigation of the degree of membrane pollution produced during the process of white water in papermaking. The characteristics of organic matter in white water and the effect of white water environment on the pollution of ultrafiltration membrane were investigated in white water and the effect of white water environment on the pollution of ultrafiltration membrane was investigated. At the same time, the main organic pollutants that caused the decrease of membrane flux caused by the anion solid solid agent were used to relieve the operating load of the membrane system and reduce the membrane pollution. The organic compounds are one of the main organic components in the white water of paper making. The macroporous resin adsorption and ultrafiltration molecular weight classification are used to characterize the hydrophobicity and molecular weight distribution of dissolved organic compounds in white water, and the effects of the properties of dissolved organic matter on the ultrafiltration contamination are studied. The results show that dissolved organic matter is used as a result. The hydrophilic component content is the highest, accounting for 67.83% of the total dissolved organic matter, but the hydrophobic component content is relatively small. The hydrophilic component in the dissolved organic matter, the molecular weight distribution of the hydrophobic component is similar to the test raw water, all with the small molecular weight less than 5KDa, and the hydrophilic property in the ultrafiltration process of dissolved organic matter. The main components of the membrane flux decrease. This kind of organic matter can quickly reach the membrane surface at the early stage of ultrafiltration, in which the hydrophilic components of small molecular weight cause the plugging of the membrane pores, and the hydrophilic components of the macromolecules are easily caused by the concentration polarization pollution, thus causing a serious decline in the membrane flux, and the hydrophobic organic matter and the Polyethersulfone ultrafiltration membrane table. There is a hydrophobic effect on the surface, which is adsorbed on the surface of the membrane to form a filter cake pollution, and the membrane flux decreases slowly. In addition, the influence mechanism of the molecular weight distribution of dissolved organic matter to the ultrafiltration membrane fouling is analyzed by scanning electron microscopy and Hermia linear equation. The results show that the macromolecules are more mechanically trapped on the surface of the membrane to form the filter. The main mechanism of the decrease of membrane flux caused by small molecule organic matter is the pollution of cake layer. The white water environment is an important factor affecting the ultrafiltration membrane fouling. This paper uses sodium polyacrylate and sodium stearate as the analogue of soluble and colloidal organic compounds in white water of paper making, and studies the effects of different white water environment on the organic matter. The results show that the lower P H value can weaken the electrostatic repulsion of dissolved organic matter and ultrafiltration surface, accelerate the adsorption and deposition of organic matter on the surface of the membrane, and cause a serious decrease of membrane flux. The increase of ionic strength will also shield the electrostatic repulsion of organic and membrane surfaces, while the existence of Na+ can also pass through The effect of the compression of the double layer makes the organic matter more accessible to the surface of the membrane, resulting in the aggravation of the membrane fouling. The existence of the polyvalent metal ions not only causes the interconnections among the organic molecules in white water to form complex space network macromolecules, but also can form a "surface frame" between the organic matter and the ultrafiltration membrane by the "main bridge action". "Bridge action" increases the adsorption and deposition of organic matter on the surface of the ultrafiltration membrane, resulting in a serious decrease in membrane flux. Under the same concentration, Fe~ (3+) is more harmful to the decrease of membrane flux than Ca~ (2+). The decrease of membrane flux caused by colloidal organic matter in white water environment is similar to that of dissolved organic matter. Acid conditions and higher levels are also higher. The ionic strength can aggravate the effect of colloidal organics on membrane fouling. The presence of polyvalent metal ions increases the particle size of colloidal components, aggravates the adsorption and deposition of organic compounds on the surface of the membrane, and causes serious contamination of the filter cake layer. The presence of dissolved and colloidal organic compounds in white water has obvious pollution to the ultrafiltration system. In view of the characteristics of papermaking process and the strong negative power of organic matter in white water, this paper uses polyethyleneimine with high positive charge density to capture organic pollutants in white water. At the same time, using the electrostatic interaction between polyethyleneimine and pulp fiber and hydrogen bond, the organic pollutants in white water are finally fixed to the pulp fiber and are taken out. The white water system reduces the load of the ultrafiltration system. The results show that with the increase of the polyethylenimide, the organic matter in the white water is aggregated and fixed on the pulp fiber. After the filtration of the dynamic filter, the demand for the organic matter in the filtrate is obviously reduced and the turbidity of the filtrate drops. When the amount of polyethyleneimine is 1% (relative) In the dry fiber quality, the demand of the filtrate cation, the turbidity decreased by 56.42%, 63.16% respectively, indicating that polyethyleneimine can better capture anionic organic compounds in white water and be fixed on the pulp fiber, obviously improving the white water quality into the ultrafiltration system. The white water simulated solution before and after the pretreatment of polyethyleneimine (PEI) is over. The filtration membrane flux measurement and membrane surface scanning electron microscopy (SEM) show that white water PEI pretreatment can reduce the concentration of organic matter to the membrane system and change the membrane surface filter cake layer structure to improve the membrane flux and alleviate the membrane fouling. The study has completed the characterization of the hydrophobic and molecular weight distribution characteristics of the dissolved organic matter in white water. The main characteristics of organic matter in white water and white water environment include the effect of P H, Na+ concentration and polyvalent metal ions on the ultrafiltration membrane pollution. At the same time, a pre treatment scheme suitable for ultrafiltration of white water in papermaking is proposed to provide technical support for the stable operation of the ultrafiltration system in the white water closed cycle.
【學位授予單位】：南京林業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：X793;TQ051.893
本文編號：2158937
[Abstract]:Ultrafiltration technology has a wide application prospect in the field of organic pollutants removal in papermaking white water closed circulation system as a high efficient and safe physical separation method. However, the complex water environment of white water and the ultrafiltration membrane pollution caused by various kinds of organic compounds reduce the removal efficiency of organic components in white water, and restrict the membrane technology. It is further popularized in the field of papermaking white water treatment. Therefore, the characteristics of organic matter in papermaking white water and the effect of white water environment on the membrane fouling are deeply studied. The selection of reasonable pretreatment methods for the characteristics of papermaking process is very important for the mitigation of the degree of membrane pollution produced during the process of white water in papermaking. The characteristics of organic matter in white water and the effect of white water environment on the pollution of ultrafiltration membrane were investigated in white water and the effect of white water environment on the pollution of ultrafiltration membrane was investigated. At the same time, the main organic pollutants that caused the decrease of membrane flux caused by the anion solid solid agent were used to relieve the operating load of the membrane system and reduce the membrane pollution. The organic compounds are one of the main organic components in the white water of paper making. The macroporous resin adsorption and ultrafiltration molecular weight classification are used to characterize the hydrophobicity and molecular weight distribution of dissolved organic compounds in white water, and the effects of the properties of dissolved organic matter on the ultrafiltration contamination are studied. The results show that dissolved organic matter is used as a result. The hydrophilic component content is the highest, accounting for 67.83% of the total dissolved organic matter, but the hydrophobic component content is relatively small. The hydrophilic component in the dissolved organic matter, the molecular weight distribution of the hydrophobic component is similar to the test raw water, all with the small molecular weight less than 5KDa, and the hydrophilic property in the ultrafiltration process of dissolved organic matter. The main components of the membrane flux decrease. This kind of organic matter can quickly reach the membrane surface at the early stage of ultrafiltration, in which the hydrophilic components of small molecular weight cause the plugging of the membrane pores, and the hydrophilic components of the macromolecules are easily caused by the concentration polarization pollution, thus causing a serious decline in the membrane flux, and the hydrophobic organic matter and the Polyethersulfone ultrafiltration membrane table. There is a hydrophobic effect on the surface, which is adsorbed on the surface of the membrane to form a filter cake pollution, and the membrane flux decreases slowly. In addition, the influence mechanism of the molecular weight distribution of dissolved organic matter to the ultrafiltration membrane fouling is analyzed by scanning electron microscopy and Hermia linear equation. The results show that the macromolecules are more mechanically trapped on the surface of the membrane to form the filter. The main mechanism of the decrease of membrane flux caused by small molecule organic matter is the pollution of cake layer. The white water environment is an important factor affecting the ultrafiltration membrane fouling. This paper uses sodium polyacrylate and sodium stearate as the analogue of soluble and colloidal organic compounds in white water of paper making, and studies the effects of different white water environment on the organic matter. The results show that the lower P H value can weaken the electrostatic repulsion of dissolved organic matter and ultrafiltration surface, accelerate the adsorption and deposition of organic matter on the surface of the membrane, and cause a serious decrease of membrane flux. The increase of ionic strength will also shield the electrostatic repulsion of organic and membrane surfaces, while the existence of Na+ can also pass through The effect of the compression of the double layer makes the organic matter more accessible to the surface of the membrane, resulting in the aggravation of the membrane fouling. The existence of the polyvalent metal ions not only causes the interconnections among the organic molecules in white water to form complex space network macromolecules, but also can form a "surface frame" between the organic matter and the ultrafiltration membrane by the "main bridge action". "Bridge action" increases the adsorption and deposition of organic matter on the surface of the ultrafiltration membrane, resulting in a serious decrease in membrane flux. Under the same concentration, Fe~ (3+) is more harmful to the decrease of membrane flux than Ca~ (2+). The decrease of membrane flux caused by colloidal organic matter in white water environment is similar to that of dissolved organic matter. Acid conditions and higher levels are also higher. The ionic strength can aggravate the effect of colloidal organics on membrane fouling. The presence of polyvalent metal ions increases the particle size of colloidal components, aggravates the adsorption and deposition of organic compounds on the surface of the membrane, and causes serious contamination of the filter cake layer. The presence of dissolved and colloidal organic compounds in white water has obvious pollution to the ultrafiltration system. In view of the characteristics of papermaking process and the strong negative power of organic matter in white water, this paper uses polyethyleneimine with high positive charge density to capture organic pollutants in white water. At the same time, using the electrostatic interaction between polyethyleneimine and pulp fiber and hydrogen bond, the organic pollutants in white water are finally fixed to the pulp fiber and are taken out. The white water system reduces the load of the ultrafiltration system. The results show that with the increase of the polyethylenimide, the organic matter in the white water is aggregated and fixed on the pulp fiber. After the filtration of the dynamic filter, the demand for the organic matter in the filtrate is obviously reduced and the turbidity of the filtrate drops. When the amount of polyethyleneimine is 1% (relative) In the dry fiber quality, the demand of the filtrate cation, the turbidity decreased by 56.42%, 63.16% respectively, indicating that polyethyleneimine can better capture anionic organic compounds in white water and be fixed on the pulp fiber, obviously improving the white water quality into the ultrafiltration system. The white water simulated solution before and after the pretreatment of polyethyleneimine (PEI) is over. The filtration membrane flux measurement and membrane surface scanning electron microscopy (SEM) show that white water PEI pretreatment can reduce the concentration of organic matter to the membrane system and change the membrane surface filter cake layer structure to improve the membrane flux and alleviate the membrane fouling. The study has completed the characterization of the hydrophobic and molecular weight distribution characteristics of the dissolved organic matter in white water. The main characteristics of organic matter in white water and white water environment include the effect of P H, Na+ concentration and polyvalent metal ions on the ultrafiltration membrane pollution. At the same time, a pre treatment scheme suitable for ultrafiltration of white water in papermaking is proposed to provide technical support for the stable operation of the ultrafiltration system in the white water closed cycle.
【學位授予單位】：南京林業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：X793;TQ051.893
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