【作者】 王莹；

【导师】 白朗明；

【作者基本信息】 哈尔滨工业大学 ， 土木水利（专业学位）， 2022， 硕士

【摘要】 纺织印染废水是我国排放总量最大、污染性最高、较难处理的工业废水之一。纺织印染废水的安全排放对于我国水环境安全至关重要。纳滤处理技术因其以选择透过性为工作的核心,是单纯的物理作用,在分离污染的同时,能够使废水中的物质不被破坏,便于进一步回收利用而被广泛应用。基于传统的纳滤膜分离层较为致密,难以实现高价盐和染料的高效分离的困境,疏松纳滤膜成为最有希望的解决办法之一。二维材料堆叠形成的二维层状膜因其可调节的层间距吸引了研究者的注意。利用HCl和LiF混合溶液刻蚀MAX相（Ti₃Al C₂）中的Al,合成Ti₃C₂T_x纳米片,借助XRD光谱并计算得到Ti₃C₂T_x纳米片的层间距为9.7?。通过超声剥离、高速离心和冷冻干燥获得了单/少层Ti₃C₂T_x纳米片。Ti₃C₂T_x纳米片是具有～20μm的平面和～4.6nm的厚度的薄片;Ti₃C₂T_x纳米片约为4000的纵横比确保了共沉积获得层状结构层间距的均匀性,有利于层状结构的稳定性。Ti₃C₂T_x纳米片分散液的Zeta电位证实了其具有强的负电位性质（-30～-40 m V）,是相对比较稳定的分散体系。通过共沉积Ti₃C₂T_x纳米片与海藻酸钠（Sodium alginate,SA）,并依靠Ca²⁺实现双交联制得了Ti₃C₂T_x/CaAlg水凝胶疏松纳滤膜。充分混合Ti₃C₂T_x纳米片分散液与海藻酸钠溶液,并通过共沉积制备Ti₃C₂T_x/Na Alg水凝胶膜;Ti₃C₂T_x纳米片表面丰富的含氧官能团与SA表面富含羟基（-OH）和羧基（-COOH）均可与Ca²⁺发生快速离子交换,利用Ca²⁺实现双交联形成三维互联水凝胶网络。Ti₃C₂T_x/CaAlg水凝胶膜的SEM表征显示其表面高低起伏的“水波纹”形貌,横截面呈现“珍珠层”结构,Ti₃C₂T_x/CaAlg水凝胶层厚度为～190nm,并且与MXene负载量成线性相关关系。SA与Ti₃C₂T_x纳米片的混合比例不会显著影响Ti₃C₂T_x/CaAlg水凝胶膜的表面形貌,但将膜表面的相对粗糙度降低至67.3nm,且会增加膜表面的亲水性,水接触角降低至42°。Ti₃C₂T_x/CaAlg水凝胶膜的XPS分析未检测到对应于Ti O₂的Ti⁴⁺,表明其极低的氧化度。MXene膜在p H 3-10范围的Zeta电位稳定于～-5m V,SA的加入增强Ti₃C₂T_x/CaAlg水凝胶膜表面的电负性至-20m V,并且赋予其p H敏感性。并且,Ti₃C₂T_x/CaAlg水凝胶膜具有长时运行稳定性和抗大肠杆菌的性能。SA的均匀插层扩大Ti₃C₂T_x纳米片间的层间距至16.2?,提高Ti₃C₂T_x/CaAlg水凝胶膜的纯水渗透至～160 LMH/bar、降低了盐截留率（Na Cl<5%,Na₂SO₄<20%）,对刚果红（Congo Red,CR）和孔雀石绿（Malachite Green,MG）染料截留率稳定在～99%。Ti₃C₂T_x/CaAlg水凝胶膜具有优异的盐与染料分离性能。M/S10%-Ca膜对Na Cl和CR的分离比为46.0,约为商品传统纳滤膜NF270的7倍,商品传统纳滤膜NF270的分离比仅为6.7;M/S10%-Ca膜对Na₂SO₄和CR的分离比为8.0,NF270膜的仅为1.0,约为NF270膜的8倍。Ti₃C₂T_x/CaAlg水凝胶疏松纳滤膜分别在盐、染料混合体系与盐、染料和有机物综合体系下的分离性能显示,无机盐的存在增强染料在液体中的分散性,降低染料截留率;而有机物的存在降低截盐率,进而有效提高盐和染料的分离性能。Ti₃C₂T_x/CaAlg水凝胶疏松纳滤膜的可溶性有机物（Soluble Organic Matter,DOM）去除能力介于商品超滤膜和纳滤膜之间,对其过滤污水处理厂二级出水的渗透液的EEM图谱进行区域积分,定量地表明其对芳香蛋白质类DOM具有高效的去除能力。更多还原

【Abstract】 Textile printing and dyeing wastewater is one of the industrial wastewater with the largest total discharge,the highest pollution and the most difficult to treat in China.The safe discharge of textile dyeing wastewater is very important for the water environment safety in China.Nanofiltration membrane treatment technology is widely used because of its selective permeability as the core of its work and pure physical effect.While separating pollution,it can keep the substances in the wastewater from being destroyed,which is convenient for further recycling and is in line with the concept of sustainable development.Due to the technical defect that the separation layer of traditional nanofiltration membrane is relatively dense,it is difficult to achieve efficient separation of high-priced salts and dyes.Loose nanofiltration membrane has become one of the most promising solutions.Two-dimensional lamellar films formed by stacking of two-dimensional materials have attracted the attention of researchers because of adjustable layer spacing.Ti₃C₂T_x nanosheets were prepared by etching Al in MAX phase（Ti₃Al C₂）in mixed solution of HCl and Li F.By means of XRD spectrum,the layer spacing of Ti₃C₂T_xnanosheets was calculated to be 9.7?.Monolayer or few-layer Ti₃C₂T_x nanosheets were obtained by ultrasonic stripping,high-speed centrifugation and freeze drying.Ti₃C₂T_xnanosheets are about 20 microns flat and about 4.6nm thick.The aspect ratio of Ti₃C₂T_xnanosheets is about 4000,which ensures the uniformity of lamellar spacing obtained by co-deposition and is conducive to the stability of lamellar structures.Zeta potential of the dispersion of Ti₃C₂T_x nanosheets proves that it has strong negative potential,from about-30m V to about-40 m V,and is a relatively stable disprsion system.Ti₃C₂T_x/CaAlg hydrogel loose nanofiltration membranes were prepared by co-deposition of Ti₃C₂T_x nanosheets with Sodium alginate（SA）and double cross-linking with Ca²⁺.Ti₃C₂T_x/Na Alg hydrogel films were prepared by co-deposition mixed solution of Ti₃C₂T_x nanosheet dispersion solution and sodium alginate solution.Both the rich oxygen-containing functional groups on the surface of Ti₃C₂T_x nanosheets and the rich hydroxyl（-OH）and carboxyl（-COOH）groups on the surface of SA can undergo rapid exchange ions with Ca²⁺,and a three-dimensional interconnected hydrogel network can be formed by double cross-linking with Ca²⁺.SEM characterization of the Ti₃C₂T_x/CaAlg hydrogel membranes shows that the surface undulation is like water ripple,and the cross-section presents a nacre structure.The thickness of Ti₃C₂T_x/CaAlg hydrogel layers is about 190 nanometers,and is linearly correlated with MXene loading capacity.The mixing ratio of SA and Ti₃C₂T_x nanosheets has no significant effect on the surface morphology of Ti₃C₂T_x/CaAlg hydrogel membranes,but the relative roughness of those is reduced to 67.3 nanometers,and the hydrophilicity is increased,and the water contact Angle is reduced to 42°.XPS analysis of Ti₃C₂T_x/CaAlg hydrogel films does not detect Ti⁴⁺corresponding to Ti O₂,indicating its extremely low degree of oxidation.In addition,the zeta potential of MXene membranes is stabilized at about-5m V in the p H range of from 3 to 10,and the addition of SA enhances the electronegativity of the surface of the Ti₃C₂T_x/CaAlg hydrogel membrane to-20m V and endows it with p H sensitivity.Moreover,the Ti₃C₂T_x/CaAlg hydrogel membranes have long-term operational stability and anti-Escherichia coli performance.The uniform intercalation of SA enlarges the interlayer spacing between Ti₃C₂T_x nanosheets to 16.2?,improves the pure water penetration of the Ti₃C₂T_x/CaAlg hydrogel membranes to～160 LMH/bar,and reduces the salt rejection including rejection of Na Cl below 5 percent and rejection of Na₂SO₄ below 20 percent,with a stable rejection of about 99%for Congo Red and Malachite Green.Ti₃C₂T_x/CaAlg hydrogel membranes have excellent salt and dye separation performance.The separation ratio of M/S10%-Ca membrane to Na Cl and CR is 46.0,which is about 7 times that of commercial traditional nanofiltration membrane NF270,a which was only about 6.7.The separation ratio of Na₂SO₄ and CR was about 8.0 for M/S10%-Ca membrane,and only about 1.0 for NF270 membrane,which was about 8times of NF270 membrane.The separation performance of Ti₃C₂T_x/CaAlg hydrogel loose nanofiltration membrane in the mixed system of salt and dye and the comprehensive system of salt,dye and organic matter respectively shows that the presence of inorganic salt enhances the dispersibility of dye in liquid and reduces dye rejection rate.And the presence of organic matter reduces the salt rejection rate,thereby effectively improving the separation performance of salts and dyes.The soluble organic matter（DOM）removal capacity of Ti₃C₂T_x/CaAlg hydrogel loose nanofiltration membrane is between that of commercial ultrafiltration membrane and nanofiltration membrane.The regional integration of the EEM map of the osmotic liquid from the secondary effluent of the sewage treatment plant shows that Ti₃C₂T_x/CaAlg hydrogel loose nanofiltration membrane has an efficient removal ability of aromatic protein DOM.更多还原