【作者】 张世欣；

【导师】 郑怀礼；

【作者基本信息】 重庆大学 ， 市政工程， 2020， 博士

【摘要】 常规水处理流程通常包括絮凝、沉淀、过滤和消毒四步,絮凝是其中重要一环。絮凝处理效果很大程度影响后续的处理工艺和出水水质。近年来,随着对水质要求的不断提高,水处理领域对高性能、高效率和多功能的絮凝剂的需求日益增长。絮凝剂的杀菌作用引起了众多研究者的关注,但絮凝剂的杀菌过程、杀菌机理、杀菌效果和杀菌广谱性有待深入探究。此外,絮凝后对水体中细菌种类的高效、准确识别也是论文研究的重点。论文首先研究无机混凝剂和有机絮凝剂联用在除菌过程中的协同作用。深入研究了无机、有机两种絮（混）凝剂在去除细菌过程中伴随的杀菌作用、杀菌过程和杀菌机理。并在此基础上,将超声波引发聚合体系、自组装技术用于新型具有杀菌功能絮凝剂的合成,以提高絮凝剂除菌、杀菌性能。将杀菌增强型絮凝剂和表面增强拉曼（SERS）探针相结合,创新研究出一种集多种细菌絮凝、识别和杀菌功能为一体的水处理技术。论文研究了1)传统的聚合氯化铝（PAC）无机混凝剂和聚二甲基二烯丙基氯化铵（PDMDAAC）有机絮凝剂联用对细菌去除效果;2)进一步研究了PAC和PDMDAAC两种絮（混）凝剂在杀菌过程中各自的作用及其杀菌过程、杀菌机理;3)通过引入杆菌肽分子,借助模板聚合、超声波引发条件,提升了絮凝剂的絮凝和杀菌效果。所合成的带阳离子微嵌段结构和增强杀菌功能的新型絮凝剂B-g-PAMDAC对四种细菌（大肠杆菌、铜绿假单胞菌、芽孢蜡样杆菌和粪肠球菌）都有较好的絮凝和杀菌作用;4)通过对巯基化氧化石墨-银包金纳米复合物（GO-Au@Ag NPs）进行改性和制备优化,合成标记型SERS探针;5)通过SERS探针与B-g-PAMDAC联用,得到不同细菌在拉曼光谱中的“指纹图谱”,实现对多种细菌的絮凝、杀菌和识别作用。论文开展的主要工作和所得结论如下:（1）传统PAC和PDMDAAC联用,可对水体中高岭土及大肠杆菌有良好的絮（混）凝去除效果。在分批次投加两种絮（混）凝剂且总投加量为90 mg/L（其中PAC=20 mg/L,PDMDAAC=70 mg/L）时,可达到最大为93.2%的浊度去除率和96.1%的除菌率。水体为弱酸性（p H=6～7）时,除菌效果最好。碱性条件导致PAC过度水解,形成氢氧化铝凝胶或沉淀,降低了处理效率。论文采用等高线法计算得Z^*_add（联合使用两种絮（混）凝剂达到50%除菌率的有效投加量）和Z^*_mix（两种絮（混）凝剂纯加和作用时,所需混合絮（混）凝剂投加量的理论值）的95%置信区间分别为（19.0515,20.1511）和（17.1426,17.9774）,两区间没有重叠,说明PAC和PDMDAAC联合使用对细菌的去除效率大于分别单独投加可达到的去除效果的加和。两种絮（混）凝剂在除菌过程中为协同作用。（2）通过XPS表征分析、絮凝剂杀菌动力学、β-半乳糖苷酶的测定和细菌胞外多糖分泌实验研究了PAC和PDMDAAC絮（混）凝剂在除菌和杀菌方面所起的不同作用,进而阐释了絮（混）凝剂的杀菌过程和杀菌机理。PAC主要发挥混凝细菌的作用,细菌的聚集有助于PDMDAAC杀菌;同时PDMDAAC中的季铵基团发挥杀菌作用,且该阳离子基团具有电中和与电荷吸引能力,使小絮体聚集成大絮体,弥补PAC在架桥作用中的不足。PDMDAAC通过改变细胞膜通透性,引起细胞质泄露,干扰细菌新陈代谢从而杀死细菌。杀菌作用可分为快速吸附和缓慢杀死两个过程:快速吸附沉降只需要半小时,而彻底杀死细菌需要4 h。（3）研究清絮凝剂的杀菌官能团、杀菌过程和杀菌机理后,通过超声波引发丙烯酰胺、丙烯酰氧乙基三甲基氯化铵和杆菌肽发生共聚反应,得到杀菌功能强化的新型B-g-PAMDAC絮凝剂。并通过自组装技术,使B-g-PAMDAC中阳离子基团以微嵌段结构分布,以提升其电中和、架桥性能。核磁共振¹H谱、差热-热重和扫描电镜的表征结果证明了B-g-PAMDAC絮凝剂的成功合成和微嵌段结构的存在。B-g-PAMDAC对四种细菌均有良好的絮凝和杀菌效果,其浊度去除率为96.2%以上,杀菌率为99.64%以上。微嵌段结构的引入使相同絮凝剂投加量条件下出水浊度降低了31 NTU,絮体沉降时间缩短了19 min。杆菌肽分子的引入使絮凝剂杀菌率增加了48%。B-g-PAMDAC与细菌接触3 h可将细菌彻底杀死。（4）通过对GO-Au@Ag NPs改性和制备优化,得到标记型SERS探针。论文采用10^-9 mol/L罗丹明6G（R6G）来检测SERS探针的信号放大能力。结果表明,GO的引入可延长SERS探针的储存时间,防止SERS探针被氧化,提高SERS探针的灵敏度和稳定性。SERS探针在GO:Au@Ag NPs=30:1（m L:mg）且Au@Ag NPs壳核厚度为5 nm时得到最高的灵敏度和信号放大水平。（5）借助SERS探针中4-MPBA对细菌的捕获作用,将SERS探针投加到细菌废水中,絮凝后形成了絮凝剂/细菌/标记型SERS探针的复合结构絮体。将絮体进行拉曼光谱测试,在四种细菌浓度低至1×10³ CFU/m L下均能检测到其明显不同的SERS光谱。大肠杆菌在545 cm^-1、688 cm^-1、757 cm^-1、1186 cm^-1和1283 cm^-1处出现五个特征峰;铜绿假单胞菌的特征峰出现在1283 cm^-1处;芽孢蜡样杆菌在622cm^-1、1249 cm^-1和1284 cm^-1处出现三个特征峰;粪肠球菌在439 cm^-1、622 cm^-1、699 cm^-1和1368 cm^-1处出现四个特征峰。通过计算四种细菌特征峰的相对标准差,验证了指纹图谱的稳定性和可重复性。SERS探针与絮凝剂联用可作为水体中细菌高效去除和识别的有效方法。更多还原

【Abstract】 Conventional water treatment process adopts flocculation,sedimentation,filtration and disinfection.Flocculation is one of the most important steps,which has a significant impact on the following treatment processes and effluent quality.High-efficient,high performance and multifunctional flocculants are in great demand with the increasing standards of water treatment over the years.The sterilization of flocculant has attracted the wide attention by many researchers.But the sterilization process,sterilization mechanism,and the broad-spectrum sterilization of flocculant remain to be further explored.In addition,this paper also focus on the efficient and accurate discrimination of bacterial species in water after flocculation.Herein,the synergistic effect of inorganic and organic flocculants in the bacterial removal was studied.The sterilization process and sterilization mechanism of inorganic and organic flocculants in the process of bacterial removal were emphasized.And then,ultrasonic initiated polymerization and self-assembly technology were used to synthesize the novel flocculant with the sterilization function.The removal and sterilization efficiency of flocculant were improved.Floccualnt combining with surfacing enhanced Raman（SERS）labels developed a water treatment technology integrating flocculation,discrimination and sterilization of multiple bacteria.The key research contents were described as follows.1)The removal efficiencies of bacteria were investigated by traditional polyaluminum chloride（PAC）combining with polydimethyl diallyl ammonium chloride（PDMDAAC）.2)Sterilization process,sterilization mechanism and tthe different roles of PAC with PDMDAAC were further studied.3)Flocculation and sterlization performance of flocculant were improved through introducing bacitracin,template polymerization and ultrasonic initiation in its preparation.The novel flocculant,B-g-PAMDAC,with cationic microblock structure and enhanced sterilization performed well in flocculation and sterilization of four kinds of bacteria,Escherichia coli,Pseudomonas aeruginosa,Bacillus cerevisiae and Enterococcus faecalis.4)A new SERS labels were prepared via modifying and optimizing sulfhydrylation graphite oxide and silver coated gold nanocomposite（GO-Au@Ag NPS）.5)Flocculation,discrimination and sterilization of multiple bacteria in water treatment were achieved by combination of B-g-PAMDAC flocculant and SERS labels.And the fingerprints of four bacteria were obtained in Raman spectra.Main work and conclusions of this paper were summaried as follows:（1）Kaolin and Escherichia coli were well removed from water by traditional PAC flocculant with PDMDAAC flocculant.The optimal removal rates of turbidity and bacteria,93.2%and 96.1%,were achieved after respectively dosing two flocculants with the total dosage of 90 mg/L（the dosage of PAC was 20 mg/L,and the dosage of PDMDAAC was 70 mg/L）.The weakly acidic water（p H=6-7）conduced to the best removal rate of bacteria.PAC excessively hydrolyzed at the alkaline condition and transformed to aluminum hydroxide gels and precipitation.It decreased the treatment efficiency of PAC.The 95%confidence intervals of Z^*_add and Z^*_mix calculated by contour method are（19.0515,20.1511）and（17.1426,17.9774）,respectively.There is no overlap between the two intervals.The results showed that the removal efficiency of combination PAC and PDMDAAC was greater than that of the sum of the removal effects that can be achieved by adding separately.The two flocculants have synergistic effect in the sterilization process.（2）The different roles of PAC and PDMDAAC in removal bacteria and sterilization were studied via XPS analysis,disinfection kinetics,detection ofβ-galactosidase and detection of bacterial exopolysaccharides.Sterilization process and mechanisms of flocculants were further discussed.PAC played a key role of flocculation of bacteria,which contributed to sterilization of PDMDAAC.PDMDAAC played an essential role of sterilization due to its quaternary amine groups.And charge neutralization and attraction of these cationic groups caused the aggregation of flocs.They also made up for the deficiency of PAC in bridging.PDMDAAC sterilized bacteria via changing membrane permeability of bacteria,causing the release of cytoplasm and disturbing metabolism of bacteria.The process of sterilization mainly divided into two steps,fast adsorption and slow killing.The former only cost half hour,but the latter cost 4 h for complete sterilization.（3）After the research of bactericidal functional groups,sterilization process and sterilization mechanisms,a novel flocculant,B-g-PAMDAC,was prepared via copolymerization of acrylamide,2-trimethylammonioethyl methacrylate chloride and bacitracin under the initiation of supersonic wave.The sterilization capacity of flocculant was strengthened.The microblock structure of cationic functional groups was found on B-g-PAMDAC with the aid of self-assembly in the preparation.The microblock structure improved charge neutralization and briding of B-g-PAMDAC.Characterization analysis,such as ¹H NMR,TG/DSC and SEM,confirmed that B-g-PAMDAC was successfully synthesized and there were microblocks on B-g-PAMDAC.B-g-PAMDAC performed well in coagulation-flocculation and sterilization of four bacteria.Their removal rate was above 96.2%,and their sterilization rate was above 99.64%.B-g-PAMDAC with cationic functional groups had the higher coagulation efficiency in the treatment of gram negative bacteria than in the treatment of gram positive bacteria.The microblock structure on B-g-PAMDAC contributed to low turbidity of treated water,decreasing for 31 NTU,and short settlement time of flocs,decreasing for 19 min,compared with B-g-PAMDAC without microblock at the same dosage.Bacitracin on B-g-PAMDAC enhanced sterilization rate for 48%and reduced the contact time to 3 h for completely killing bacteria.（4）SERS labels were prepared via preparation optimization and modification of GO-Au@Ag NPs.Rhodamin 6G（R6G）with the concentration of 10^-9 mol/L was used to detect the signal amplification capability of SERS lables.The results indicated that GO prolonged the storage time of SERS labels,prevented oxidation of SERS labels and improved their sensitivity and stability.The highest intensity and sensitivity of SERS labels were achieved at the ratio of GO to Au@Ag NPs of 30:1（m L/mg）and the shell thickness of Au@Ag NPs of 5 nm.（5）The modified SERS labels was applied to discriminate bacteria in wastewater containing bacteria for the strong interaction between 4-MPBA on SERS labels and bacteria.The composite flocs of flocculant/bacteria/SERS labels were generated after coagulation.The different SERS spectra of four bacteria were detected in Raman spectrum,even at low bacterial concentration of 1×10³ CFU/m L.Five characteristic peaks of Escherichia coli were discovered at 545 cm^-1,688 cm^-1,757 cm^-1,1186 cm^-1and 1283 cm^-1.The peak at 1283 cm^-1 was related to Pseudomonas aeruginosa.The peaks of 622 cm^-1,1249 cm^-1 and 1284 cm^-1were corresponding to Bacillus cerevisiae.The peaks of Enterococcus faecalis were detected at 439 cm^-1,622 cm^-1,699 cm^-1 and1368 cm^-1.The fingerprint of four bacteria were stable and repeatable according to the standard deviation of characteristic peaks of four bacteria.SERS labels combining flocculant were able to be applied in efficient removal and discrimination of bacteria in water.更多还原