新型磁性复合絮凝剂的合成及应用研究

发布时间：2018-02-09 01:45

本文关键词： 絮凝剂复合材料磁性絮凝机理分形模型　出处：《中国矿业大学》2017年博士论文　论文类型：学位论文

【摘要】：絮凝剂是水处理过程中最常使用的药剂之一,其种类繁多、应用广泛。絮凝剂去除水中悬浮颗粒的作用机理主要包括吸附电中和作用、静电簇作用、吸附架桥作用以及网捕卷扫作用等。水中的悬浮颗粒物在絮凝剂的作用下首先逐步形成较大的絮团,所形成的絮团在后续的气浮或沉淀工艺中从水中分离出来,达到净化水质的目的。净化的效率与絮凝剂的絮凝性能紧密相关,在实际使用过程中为了提高净化效果,往往将两种不同类型的絮凝剂配合投加。随着材料科学技术的发展,有机-无机复合材料不断地推陈出新,在追求稳定絮凝性能的同时可以将一些特殊功能材料与传统絮凝剂复合在一起形成具有特殊功能的复合絮凝剂。本研究采用纳米Fe_3O_4颗粒作为磁性材料制备合成了环境友好的PAM基复合磁性絮凝剂,并表征了其结构与性质;通过混凝实验,探讨各型磁性复合絮凝剂的絮凝效果及絮凝机理;利用分形理论,研究使用各型絮凝剂形成絮体的分形维数,揭示絮体分形特征与混凝效果之间的关系,建立了数学模型。本研究基于Fe_3O_4所具有稳定的晶体结构和很强的铁磁性,利用油酸将其纳米颗粒表面进行化学修饰,然后与丙烯酰胺(AM)单体和二甲基二烯丙基氯化铵(DMDAAC)单体、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)单体等在有机-无机双引发体系下进行水溶液聚合反应,合成制备了一系列磁性复合絮凝剂,即阳离子型磁性复合絮凝剂CMF1、CMF2和CMF3,阴离子型磁性复合絮凝剂AMF1、AMF2和AMF3,以及两性型磁性复合絮凝剂ACMF1、ACMF2和ACMF3。通过FTIR、TG、XRD、SEM、EDX、粒度、磁化率、特性粘度和zeta电位等分析方法,对磁性复合絮凝剂的结构和性质进行了全面地表征,结果表明:Fe_3O_4被成功引入到复合絮凝剂的分子链上,使复合絮凝剂带有磁性,在外磁场的作用下这一特性有利于缩短絮凝后续工艺泥水分离所需要的时间,从而能够减小絮凝后续气浮池或沉淀池的容积、减少占地面积、降低投资和运行成本。随着共聚单体种类的变化,磁性复合絮凝剂具有明显的带电性质,通过对单体比例的调节,制备得到一种分子链上带有正负电荷数相当的两性型磁性复合絮凝剂ACMF2。制备的系列磁性复合絮凝剂具有较好的热稳定性、水溶性,且粒度较小、分散均匀、分子量较高。通过对热重曲线的分析,判断CMF系列磁性复合絮凝剂及ACMF1、ACMF3为接枝共聚物,分子链上存在有杂环,需与其他絮凝剂配合使用,AMF系列磁性复合絮凝剂及ACMF2为嵌段共聚物,分子链呈长直线性,可单独使用。将CMF系列磁性复合絮凝剂、AMF系列磁性复合絮凝剂和ACMF2分别在高岭土模拟废水、Fe(OH)_3胶体溶液模拟废水和皂土模拟废水中进行系统地混凝实验研究。考察了加药量、pH、搅拌转速和搅拌时间等因素对絮凝性能的影响,并结合混凝反应后废水上清液中的zeta电位和形成絮体的形貌特征分析判断絮凝剂的作用机理。结果表明:除CMF3外,该类絮凝剂均具有良好的絮凝性能,絮体团块状特征明显,尺寸较大,易于快速分离,在最佳混凝实验条件下对浊度或总铁含量的去除率均大于90%,有些甚至达到了99%以上。其中AMF3在混凝过程中随着GT值的增加经历了絮体形成—破碎—再凝聚—再破碎的复杂过程。CMF1、AMF2和ACMF2的混凝作用机理主要是静电簇作用和磁凝聚作用,伴随着吸附架桥作用和网捕卷扫作用;CMF2、AMF1和AMF3的混凝作用机理主要是吸附电中和作用和磁凝聚作用,伴随着吸附架桥作用和网捕卷扫作用;CMF3的混凝作用机理主要是吸附电中和作用和磁凝聚作用,存在一定程度的吸附架桥作用,无网捕卷扫作用。其中,磁凝聚作用是该类絮凝剂所特有的机理,是对复杂的混凝作用机理的补充。利用平面图形分析技术对混凝实验形成的絮体的分形特征进行了统计计算,得出混凝实验条件下絮体的二维分形维数。在最佳混凝实验条件下形成的絮体的二维分形维数都高度接近于2,说明在静电引力、磁耦合力及范德华引力等结合力的综合作用下该类絮凝剂形成的絮体结构紧密,具有自相似性和标度不变性分形特征。实验针对在各种条件下得到的去除率和絮体的二维分形维数之间的相关性,建立了数学模型(?),并统计分析出各因素对数学模型中的α值和β值的影响变化情况,为衡量絮凝剂的性能及混凝效果提供了新的研究方法。
[Abstract]:Is one of the most commonly used chemical flocculants in water treatment, its variety, a wide range of applications. The mechanism of flocculant to remove suspended particles including neutralization, electrostatic adsorption bridging and cluster effect, sweep function. Suspended particles in the water under the action of flocculant first and gradually form a large the floc, the floc flotation or sedimentation process in the separated from the water, achieve the purpose of purifying water quality. The purification efficiency and flocculant flocculation performance are closely related, in the actual use of the process in order to improve the purification effect, often will be two kinds of different types of complex flocculant dosage. With the development of technology materials science, organic inorganic composite materials constantly at the same time, the pursuit of stable flocculation performance can be some special functional materials with traditional flocculants The composite flocculant has special function together to form. This study is the preparation of magnetic material synthesized PAM composite magnetic flocculant using environmental friendly nano Fe_3O_4 particles, and characterized its structure and properties; through coagulation experiments, investigate the flocculation effect and flocculation mechanism of the magnetic composite flocculant; the use of fractal theory, research the formation of flocculant floc fractal dimension, reveal the relationship between fractal characteristics of flocs and the coagulation effect, a mathematical model is established. Based on the Fe_3O_4 has a stable crystal structure and strong ferromagnetism, the chemical modified by oleic acid to the surface of nano particles, and acrylamide (AM) monomers and two dimethyl diallyl ammonium chloride (DMDAAC) monomer, 2- acrylamido -2- methylpropanesulfonic acid (AMPS) monomer in organic - inorganic dual initiator system of aqueous solution polymerization, A series of magnetic composite flocculants were synthesized, the cationic magnetic composite flocculant CMF1, CMF2 and CMF3, anionic magnetic composite flocculant AMF1, AMF2 and AMF3, as well as the amphoteric magnetic composite flocculant ACMF1, ACMF2 and ACMF3. by FTIR, TG, XRD, SEM, EDX, particle size, magnetic susceptibility, intrinsic viscosity and Zeta potential analysis method, structure and properties of magnetic composite flocculant were comprehensively characterized, the results showed that Fe_3O_4 was successfully introduced into the molecular chain of composite flocculant, the composite flocculant with magnetic, the external magnetic field under the action of this characteristic is beneficial to shorten the follow-up process Xu Ning separation time required to volume Xu Ning can reduce the subsequent flotation tank or tank, reduce the area, reducing the investment and running cost. With the change of comonomer type, magnetic composite agent has obvious nature of the charged Xu Ning, By adjusting the monomer ratio, was prepared by a molecular chain with a series of magnetic amphoteric magnetic composite flocculant ACMF2. prepared composite flocculant charge very good thermal stability, water solubility, and smaller particle size, uniform dispersion, high molecular weight. Through the analysis of the thermogravimetric curves. CMF series of magnetic composite flocculant and ACMF1 ACMF3 graft copolymer, the molecular chain there are heterocyclic compounds, to be used in conjunction with other flocculants, AMF series magnetic composite flocculant and ACMF2 block copolymer molecular chain is linear, can be used alone. The CMF series of magnetic composite flocculant, magnetic composite flocculant and AMF series ACMF2 wastewater in kaolin respectively, Fe (OH) _3 colloidal solution of simulated wastewater and bentonite simulated systematically experimental study on coagulation in wastewater was studied. The dosage, pH, stirring speed and stirring time The influence factors on the flocculation performance, and with the zeta potential wastewater in the supernatant and floc morphology analysis of the coagulation reaction after the judgment mechanism of flocculant. The results showed that except CMF3, the flocculant has good flocculation, floc mass characteristics, large size, easy fast separation and in the best coagulation conditions on the turbidity and total iron content removal rate was more than 90%, some even reached more than 99%. The AMF3 in the coagulation process with the increase of GT value after floc formation - crushing - condensed -.CMF1 complex process of crushing, coagulation mechanism and AMF2 ACMF2 is the main function of electrostatic and magnetic cluster agglomeration, along with the network and bridging sweep function; CMF2, coagulation mechanism of AMF1 and AMF3 are mainly the neutralization and magnetic coagulation, adsorption with frame The role of bridge and sweep coagulation; coagulation mechanism of CMF3 is mainly neutralization and magnetic flocculation, adsorption bridging action to a certain extent, no sweep. The magnetic coagulation mechanism is peculiar to the flocculant, is a supplement to the coagulation mechanism of complex. Analysis of fractal characteristics of flocs formed by coagulation technology are calculated using plane graphics, draw mixed fractal dimension of floc coagulation under the experimental conditions. The fractal dimension of flocs formed in the optimum coagulation experimental conditions are highly close to 2, in the electrostatic attraction of flocs the structure of the formation of this type of magnetic coupling force and Fan Dehua force flocculant node force under the comprehensive action closely, with self similarity and scale invariant fractal characteristics. Experiments on two dimensional and removal rate of flocs obtained under various conditions The correlation between fractal dimensions is established, and the influence of various factors on the change of the alpha and beta values in mathematical models is statistically analyzed. It provides a new research method for measuring the performance and coagulation effect of flocculants.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

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