【作者】 曾玉彬；

【导师】 杨昌柱；

【作者基本信息】 华中科技大学 ， 环境工程， 2007， 博士

【摘要】 絮凝剂是重要的水处理材料。国内外主要使用铝盐和铁盐絮凝剂。由于铝盐絮凝剂效率较低且存在环境问题,铁盐存在严重的腐蚀性。因此,目前世界上絮凝剂的研究主要向着高效低耗、安全无害、无二次污染的方向发展,而复合絮凝剂被认为是未来絮凝剂的发展方向之一。本研究利用硫酸锌等为原料,研究了絮凝效果好、能部分取代有机高分子絮凝剂、无毒及安全无害化的锌基复合絮凝剂的制备与絮凝作用机理,为应用锌基絮凝剂作了有益的探索和努力。主要研究内容有:无机高分子复合絮凝剂聚硅酸锌（PZSS）的研究;无机/有机复合絮凝剂锌基淀粉改性物（Zn-CSM）的研究;无机-有机杂化絮凝剂锌基聚丙烯酰胺（H-ZnPAM）的研究。这些均包括了制备、絮凝机理、絮凝效果的研究及水处理应用试验等。主要研究成果如下:（1）制备了聚硅酸锌（PZSS）。研究结果表明:SiO₂含量为1.3%～2.2%,Zn/Si摩尔比为1.0～2.0,PZSS的pH值为1.5～2.0,硅酸活化时间在l～2h,可获得絮凝性能优良且稳定性较好的絮凝剂。在絮凝作用机理的研究方面,利用微电泳等技术探索了PZSS的絮凝作用机理,揭示了絮凝作用的优势形态,为絮凝剂的研制开发提供了依据。通过研究聚合硅酸（PSA）及PZSS的pH变化等规律发现:在制备初期,PZSS并未达到化学平衡状态,而是存在一个相互作用、自行调整聚合的过程,表现在其pH值存在一个变化过程。IR、X-射线衍射以及TEM等研究表明:PZSS不是Zn²⁺、PSA的混合,而是复合。PZSS的聚合形态结构取决于SiO₂含量、Zn/Si摩尔比、聚合时间、pH值等的大小。PZSS体系中的硅酸、聚硅酸、锌羟基、硅羟基等各成分间存在着相互作用。Zn²⁺与共存的PSA起螯合（络合）反应生成锌硅聚合物。锌与硅酸的络合作用,以及高分子量的PSA有较强的吸附架桥功能,有利于增强絮凝剂的絮凝性能。对PZSS中硅的形态分布与转化规律,通过Si-Mo逐时络合比色法研究表明:pH值（0.8）较低时,陈化一定时间后,在PZSS中的PSA主要是高聚体或凝胶态（Sic）;pH值（1.5, 2.0）较高时,陈化一定时间后,PZSS中的PSA中聚体（Si_b）含量比低pH值（0.8）时要高。通过絮凝性能研究得出:PZSS在pH值为1.5和2.0时絮凝效果比低pH值（0.8）时更好,由此证明,PZSS中PSA的优势絮凝形态为中聚体（Si_b）。ζ电位研究表明:PZSS的电荷特性受pH值、SiO₂含量及Zn/Si摩尔比等因素影响。PZSS的电中和作用不太显著,其絮凝作用机理,表现出较明显的吸附架桥和网捕卷扫特征。（2）采用ZnSO₄·7H₂O与有机阳离子改性淀粉合成了锌基淀粉改性絮凝剂（Zn-CSM）。通过正交对比实验等,获得了制备Zn-CSM的最佳工艺条件:①环氧氯丙烷与二甲胺摩尔比为1.5:1,反应温度选择为65～70℃,反应时间3h,交联剂为乙二胺,合成阳离子聚环氧氯丙烷-二甲胺（CF）;②用NaOH预胶化淀粉,再利用CF对预胶化淀粉淀粉进行改性,制得阳离子改性淀粉（CSM）:NaOH加量为淀粉干基的4%,预胶化温度为65℃,预胶化时间为2h,CF与改性淀粉有效质量比为1.8:1,接枝温度50℃,反应时间为2h;③利用硫酸锌与CSM合成了Zn-CSM:调整CSM的pH值为5.0左右,硫酸锌与CSM的质量比为1:1,反应温度45℃,聚合反应时间3h。由絮凝试验及TEM可知:Zn-CSM的最佳絮凝pH范围为6.0～9.0,最佳絮凝形态是产生Zn（OH）₄^2-后在此基础上进一步聚合成带正电的锌基高聚物。综合分析表明,其优异的絮凝性能是由其特殊的分子结构决定的,是电性中和与吸附架桥、网捕卷扫协同作用的结果。（3）基于对无机/有机复合絮凝剂的系统研究,本课题采用原位聚合法合成了无机-有机杂化絮凝剂:氢氧化锌-聚丙烯酰胺离子键型杂化絮凝剂（H-ZnPAM）。通过IR、粘度、电导、TEM和TGA等手段对H-ZnPAM进行了表征,表明得到的H-ZnPAM是离子键结合的杂化PAM。并系统考察了氢氧化锌的粒径、用量等因素对原位聚合的影响:在原位聚合的过程中,随着氢氧化锌颗粒粒径和用量的增大,H-ZnPAM的特性粘数均呈现先升高而后下降的趋势。采用粘度法对H-ZnPAM的稀溶液性质进行了系统研究。实验表明在稀溶液状态下,与纯PAM不同,H-ZnPAM的粘度行为偏离Huggins方程。即H-ZnPAM的η_sp/C～C曲线呈向下转折。并研究了H-ZnPAM的特性粘数（分子量）、无机物粒径和无机物用量等因素对稀溶液粘度偏离行为的影响,结果表明η_sp/C～C曲线开始下折时的浓度C_η,随H-ZnPAM中无机物粒径和用量增加而增大,随H-ZnPAM特性粘数（分子量）的升高而降低。采用电导法研究了H-ZnPAM在稀溶液中的电离行为。研究结果表明H-ZnPAM的K～C关系曲线呈非线性行为,存在转折似平台现象。定义K～C曲线开始呈平台下折时的浓度为C_K,则H-ZnPAM的特性粘数（分子量）、无机物粒径和用量等因素对C_K的影响规律类同于对C_η值的影响规律。应用高分子溶液的团簇理论研究了杂化絮凝剂的絮凝机理,稀溶液中高分子链团簇的形成是产生最佳絮凝的必要条件。絮凝剂H-ZnPAM的杂化结构既有利于发挥无机絮凝剂的电中和、吸附及有机絮凝剂的架桥作用,又有利于聚合物链团簇的形成。研究表明,高分子絮凝剂最佳加量(C_od)与高分子稀溶液动态接触浓度（CS）和硅藻土悬浮液浓度(C_SS)之间存在线性依赖关系,即C_od=5.8×10^-2·(CS·C_SS)^0.5-4.1,揭示了高分子稀溶液分子链的聚集状态与絮凝效果之间的内在联系。（4）将锌基絮凝剂应用于实际稠油废水和含油污泥。锌基絮凝剂对实际稠油废水比传统絮凝剂PAC、PFS等具有较好的絮凝效果,其中以杂化絮凝剂具有最低加量和较好的絮凝效果,杂化絮凝剂形成的絮体密实且具有较高的抗剪切性能。将锌基絮凝剂用于稠油废水的絮凝处理,与过滤等结合后,出水水质可以达到回用于热采注汽锅炉的要求。对含油污泥絮凝脱水实验中,经絮凝脱水后,H-ZnPAM及PZSS絮凝的污泥比阻抗最低,热值提高为原来的40倍,污泥密实,成型容易,剥离性能好,能够更有效焚烧,节省了处理成本。可以预见,锌基絮凝剂在废水处理中具有良好的应用前景。更多还原

【Abstract】 Flocculants are the important materials in water treatment. At present, flocculants based on aluminum and ferric salts are chiefly used abroad and in China. Because of low efficiency and environment problems by the aluminum salt, and the corrosion by ferric salt, in the world, the research and application of flocculants are required to develop to high efficiency, low consumption, safety, harmlessness and non-second pollution. The composite flocculants are one of important development trends in future. In this paper, ZnSO₄·7H₂O has been used as the materials to study the preparation and flocculation theory of composite flocculant based on zinc with higher flocculation efficiency, partly replacing the organic synthesis polymer flocculants, non-toxicity and environment-friendly. The main researches of this paper are: the study of inorganic polymer composite flocculant - poly silicate zinc sulfate （PZSS）, inorganic-organic composite flocculant （Zn-CSM） based on zinc sulfate and cationic starch-modified, inorganic-organic hybrid flocculant （H-ZnPAM） on the basis of zinc hydroxide [Zn（OH）₂] in nanometer size and polyacrylamide （PAM）. They all include the investigations of preparation, flocculation mechanism, flocculation effect, wastewater treatment application and so on.（1）The studies of PZSS are summarized as following:The researches about PZSS showed that the percentge of SiO₂ was between 1.3～2.2 %, the molar ratio of zinc to silicon was between 1.0～2.0, the pH value of PZSS was 1.5～2.0, the polymerization time of silicic acid was between 1² hours, the flocculant had excellent flocculation and better stability.The flocculation theory of PZSS was probed with micro-electrophoresis technology which revealed the advantageous configuration and provided the science basis for researching the flocculants. By studying the pH value change rules of PSA and PZSS, it was found that in the initial stages of preparation, their reaction was not in equilibrium but was in the process of interaction and adjust to aggregate by self, which was exhibited that there existed a changing process of pH value. The results of IR, XRD and TEM proved that the reaction was not the simplex physical blend, but the chemical reaction forming the inorganic polymer with special structure. The structure of PZSS are lied on the concentration of SiO₂, molar ratio of Zn/Si, polymerization time, pH value and so on. There are some interactions between silicic acid, PSA, zinc hydroxide radicle and silicic hydroxide radicle. Zn²⁺ and hydrolyzed ion are chelated with polysilicic acid to produce the polymer of zinc-silicon. The chelation of Zn²⁺ with PSA, and the macromolecule PSA with stronger adsorption and bridge function can help to boost up the flocculation performance of flocculants.The researches about the species distribution and transformation of PZSS by Si-Mo timed complexation for colorimetric method displayed that the high aggregate species （Sic） was in PZSS at low pH value （0.8） after depositing for some days; the content of Si_b in PZSS with higher pH value （1.5 and 2.0） was more than that in PZSS with lower pH value. It was proved from the flocculation experiments that the optimum species in PZSS for flocculation was Si_b, and PZSS at pH 1.5 and 2.0 had better flocculation efficiency than at lower pH value of 0.8.Zeta （ζ） potential investigations showed that the charge characteristics of PZSS changed with pH value, concentration of SiO₂, Zn/Si molar ratio of f1occulants, and so on. The flocculation mechanism of PZSS does not display the prominent charge neutralization ability, but reveals the obvious effects of absorption-bridging and net-sweeping.（2）The new type of inorganic-organic composite flocculant named cationic starch-modified with zinc radicel was prepared with ZnSO₄·7H₂O and cationic starch-modified.The optimal procedure was determined by orthogonal experiments and so on. The reaction conditions are as following:①The cationic polymer （CF） was prepared with ethylene diamine as the cross-linking agent at the molar ratio n（epichlorohydyin）/n（organic amine） 1.5:1 and 65～70℃for 3 h;②Starch was preliminary gelled with 4 % NaOH at 65℃for 2 h; the cationic starch-modified （CSM） was inarched at 50℃and the weight ratio （CF/starch） 1.8:1 for 2 h;③The inorganic-organic composite flocculant of cationic starch-modified with zinc radicel （Zn-CSM） was synthesized with ZnSO₄·7H₂O and CSM at the optimum conditions: pH value of CSM was adjusted to 5.0 with the weight ration of ZnSO₄·7H₂O/ CSM 1:1 at 45℃for polymerizing 3 h.It was known by flocculation experiments, microphotometric method and TEM for Zn-CSM that the optimum range of flocculation pH value was between 6.0～9.0 and the optimal flocculation species was the complex zinc hydrolysis polymer with positive charge after forming [Zn（OH）₄]^2-. The analysis results indicated that the excellent flocculation capabilities were determined by its special structure of molecule, which was the results of charge neutralization in cooperation with adsorption bridge and net-sweeping. （3）Based on the research of inorganic-organic composite flocculants, the inorganic-organic hybrid flocculant: ionic hybrid of Zn（OH）₂–polyacrilamide （H-ZnPAM） was synthesized by in-situ polymerization.The hybrid flocculant was characterized with IR spectrum, viscosity, conductivity, TEM and TGA. The results showed that the flocculant H-ZnPAM could be the hybrid with ion bond between inorganic particles and polyacrylamide, i.e., PAM with negative chain end (-SO₄^2-) bonding to the positive particle of Zn（OH）₂ in H-ZnPAM. The influences of particle radius and dosage of Zn（OH）₂, etc., were investigated systematically and it was found that dilute solution viscosity of H-ZnPAM increased at first and then declined with the increase of Zn（OH）₂ particle radius and Zn（OH）₂ dosage.Dilute solution viscosity behaviors of the hybrid flocculant were studied by viscosity method. The experiments proved that the viscosity behaviors of H-ZnPAM were deviated from Huggins equation in dilute solution, which was different from pure PAM. That is, the reduced viscosity (η_sp/C)～concentration （C） curve of the H-ZnPAM had a downturn at low concentration region. The effects of molecular weight, particle radius of inorganics and content on the deviation of dilute solution viscosity behaviours were researched. The results displayed that the concentration （C_η） correspond to the moment when the curve ofη_sp/C～C started to downturn, increased with enhancing the inorganics particle radius and content, but reduced with increasing the hybrid molecular weight. This phenomenon is accounted for assuming ionization of the ionic hybrid PAM. Studies on ionization behavior of H-ZnPAM in dilute solution by conductivity method were illuminated that the curve of K^C displayed non-linear behaviours. If C_K was defined the concentration when the curve of K^C began to downturn, the influence rules of molecular weight of H-ZnPAM, radius of inorganics particles and dosage on C_K were analogous with that on C_η.The cluster theory of polymer solution was applied to explain the mechanism of polymer flocculation. The formation of polymer chain cluster in dilute solution is the necessary condition to cause the optimal flocculation. The structure of hybrid flocculant H-ZnPAM can be not only in favour of exerting charge neutralization and adsorption for inorganic flocculants as well as bridge for organic flocculants, but also can help to produce chain cluster for polymer. The investigation showed that the optimal dosage (C_od) of polymer flocculants was linearer to the dynamic contact concentration （CS） of polymer flocculants and the suspension solid concentration (C_SS) in diatomite suspensions, i.e., C_od=5.8×10^-2·(CS·C_SS)^0.5 - 4.1. The result illuminated the interrelation between the congregation state of polymer molecular chain in dilute solution and flocculation effect. Furthermore, it is important to form the polymer clusters in dilute solutions for reaching the optimal flocculation.（4）Zinc flocculants were applied in oily wastewater and oily sludge.The new type of zinc flocculants had better flocculation efficiency than conventional flocculants such as poly-aluminum chloride （PAC） and poly-ferric sulfate （PFS）, and the hybrid flocculant showed the best flocculation performance, less shear sensitivity and more dense flocs than other flocculants. The results of oily sludge dewatering experiments indicated that the hybrid flocculant and PZSS had the best dewatering efficiency, the heat value was increased to 40 times of the primary after treated. The densed sludge was easy to mold and peel off, and could be incinerated with low cost and less pollution. Accordingly, the zinc flocculants are promising in wastewater treatment.更多还原