【作者】 杨斌武；

【导师】 常青；

【作者基本信息】 兰州交通大学 ， 环境工程， 2008， 博士

【摘要】 水处理滤料的表面物理化学性质对深床过滤除油效果具有重要影响,近年来已受到国内外研究者们的普遍关注。为了更深入地理解滤床中乳化油的捕集机理,便于滤料的选择和滤床的设计,本论文主要研究了核桃壳、无烟煤、磁铁矿、锰砂、石英砂和沸石等常见硬质粒状水处理滤料的表面结构、润湿性、自由能成分和Zeta电位等表面性质,同时考察了模拟含油废水的深床过滤性能。（1）采用扫描电子显微镜（SEM）、比表面积分析仪（BET）、X射线能量色散谱仪（EDS）、电子能谱仪（XPS）和红外光谱仪（FTIR）等技术对水处理滤料的表面物理形态和化学组成进行了表征。SEM结果显示,6种滤料样品的外观形状都极不规则且局部有菱角,其中核桃壳和无烟煤表面排列较有规则,呈现各向同性的特征;磁铁矿表面分布有晶粒和晶片,排列不规则,各向异性明显;锰砂、石英砂和沸石表面排列不规则,呈各向异性特征,其中沸石表面孔隙率和比表面积较大。EDS、XPS和FTIR分析结果表明,核桃壳和无烟煤表面主要是由C、H和O元素形成的有机官能团,呈现非极性特征,表面能较低;磁铁矿表面主要为Fe₃O₄物相,存在剩余键力,表面能较高,极性较强:锰砂表面主要是MnO₂和Mn₂O₃,此外有Si-O键存在,有一定的极性特征;石英砂表面主要是SiO₂,极性较强;沸石表面主要为Ca、Si和Al形成的多价态氧桥联接配合物,因此极性较强。（2）根据润湿基本理论和水处理滤料的结构特征,本论文首次提出了亲油亲水比（LHR）的概念,并与Washburn重量方程相结合,得出如下关系并用于水处理滤料表面润湿性的实验研究:实验测得20℃时0.45-0.9mm核桃壳、无烟煤、磁铁矿、锰砂、石英砂和沸石的LHR值依次为76.4、2.41、1.06、0.74、0.65和0.64,表明核桃壳和无烟煤亲油,锰砂、石英砂和沸石亲水,而磁铁矿既亲油又亲水。这与滤料表面物理形态和化学组成的表征结果一致,即:核桃壳和无烟煤表面呈现非极性特征且表面能较低,对表面张力小、非极性的油相（环己烷）润湿性好;磁铁矿表面能较高,对表面张力小的油相和表面张力大的水相均能较好润湿;锰砂、石英砂和沸石表面极性较强,为亲水性表面,故对极性水相的润湿性好于油相。从van Oss-Chaudhury-Good（VCG）理论出发,推导了表征水处理滤料润湿性的LHR参数与滤料表面自由能成分之间的关系,并将20℃时水和环己烷的物理参数代入可得:该式从理论上表明水处理滤料LHR的大小主要取决于其表面自由能酸性成分γ_s⁺和碱性成分γ_s^-。同时,本论文基于Washburn方程和VCG理论,以正己烷、1-溴奈、甲酰胺和水为探针液,用多孔介质毛细渗透技术测得核桃壳、无烟煤、锰砂、石英砂和沸石滤料的表面自由能非极性成分γ_s^LW依次为38.8mJ·m^-2、38.8mJ·m^-2、38.1mJ·m^-2、37.7mJ·m^-2和38.2mJ·m^-2,而极性成分γ_s^AB为0.37mJ·m^-2、0.73mJ·m^-2、6.79mJ·m^-2、8.66mJ·m^-2和9.42mJ·m^-2,从而验证了水处理滤料润湿性的差异主要归因于其表面自由能极性成分（γ_s⁺和γ_s^-）,而后者在本质上主要取决于其表面化学组成,与水处理滤料表征结果基本吻合。（3）以Helmholtz-Smoluchowski方程为依据,用自制装置测得核桃壳、无烟煤、磁铁矿、锰砂、石英砂、沸石滤料在蒸馏水和0.1mol·L^-1。KCl流体介质中的Zeta电位分别为-17mV、-17mV、-11mV、-34mV、-64mV、-11mV和-5.1mV、-4.2mV、-1.4mV、-0.11mV、-0.19mV、-0.15mV。在蒸馏水中测得的滤料表面Zeta电位绝对值均大于在0.1mol·L^-1KCl溶液中的测定值,说明电解质溶液的浓度较大时,对滤料表面Zeta电位的测定值影响明显。（4）通过实验室模拟的含油废水过滤系统,比较了几种水处理滤料的除油效果和反冲洗效果。在过滤10h的实验周期内,核桃壳、无烟煤、磁铁矿、锰砂、石英砂和沸石的除油效率η分别为96%、80%、72%、64%、60%和78%,反冲洗效率,η_r依次为16%、30%、37%、73%、83%和69%。将实验结果进行拟合,即可得到水处理滤料的亲油亲水比与深床过滤除油效果和反冲洗效果之间的定量关系:（5）运用XDLVO理论,求得过滤过程中核桃壳、无烟煤、锰砂、石英砂和沸石滤料颗粒与油/水所形成的体系间的界面静电作用能增量△G₁₃₂^EL≈0;Lifshitz-van derWaals作用能增量△G₁₃₂^LW依次为-7.52×10^-20J、-7.52×10^-20J、-7.25×10^-20J、-7.09×10^-20J和-7.29×10^-20J;Lewis酸碱作用增量△G₁₃₂^AB分别为-4.31×10^-18J、-3.99×10^-18J、-3.39×10^-18J、-2.93×10^-18J和-2.87×10^-18J;总界面能增量△G₁₃₂^TOT分别为-4.38×10^-18J、-4.07×10^-18J、-3.46×10^-18J、-2.99×10^-18J和-2.94×10^-18J。5种滤料介质和油/水构建的过滤体系中均有△G₁₃₂^TOT<0,说明废水中乳化油珠被滤料颗粒表面捕获均为自发行为,且这种自发趋势与其表面润湿性和过滤除油效率顺序基本吻合。此外,总界面能增量△G₁₃₂^TOT的主要贡献者为Lewis酸碱作用增量△G₁₃₂^AB,即主要归因于滤料的表面自由能极性成分γ_s^AB,从而也证明滤料表面润湿性LHR与其表面自由能极性成分γ_s^AB对过滤除油效果的影响在热力学本质上是一致的。更多还原

【Abstract】 Surface physicochemical characteristics of water and wastewater treatment filter media play an important role in oil removal during oil-bearing water treatment when using deep bed filtration process. This important role is becoming universally concerned in research field at home and abroad in recent years. Therefore, in order to get a better understanding of the mechanisms affecting oil partcle attachment which helps a lot in selecting and designing of more efficient filter meia for a wide range of industrial applications, the surface properties such as wettabilities, free energy components and Zeta potentials of several commonly-used granular filter media with hard texture, i.e. walnut shell, anthracite, magnetite, manganese sand, zeolite and quartz sand, were investigated in this thesis. At the same time, a laboratory simulated small scale deep bed filtration process was also constructed to treat oil-in-water emulsions.（1） Surface physical morphologies and chemical compositions of these filter media were characterized using Scanning Electron Microscope （SEM）, Specific Surface Area System （BET）, Energy Dispersive X-ray Spectroscopy （EDS）, X-ray Photoelectron Spectroscopy （XPS） and Fourier Transform Infra-Red Spectroscopy （FTIR）. The unaided visual inspections and SEM images indicate that all the filter media particles are irregular in shape, being angularly rectangular or rhombic. SEM micrographs at 1000 time magnification of samples show the regular morphological and homogenous characterization of the walnut shell and anthracite partical surfaces, and irregular surface micro structure and heterogenous nature of the magnetite dotted with crystal particulates and crystal plates. At the same time, the morphologies of manganese sand, zeolite and quartz sand particals are uneven, disorder and heterogenous as the magnetite, of which the zeolite presents notablely larger pore volume and specific surface area. The analysis results of EDS, XPS and FTIR spectra tell us that walnut shell and anthracite surfaces are principally organic functional groups constituted of carbon, hydrogen and oxygen elements, making them an apolar and lower energy chemical surface. Magnetite surface is mostly made up of iron and oxygen elements, which combine into Fe₃O₄ species. Magnetite possesses a higher surface energy because the chemical bonds of Fe₃O₄ on the surface are not saturated. Manganese sand has MnO₂ and Mn₂O₃ on surface, and zeolite and quartz sand contain Si-O bonds and multivalent coordination compounds, which make them a polar and hydrophilic surface characterization.（2） Considering the irregular and uneven nature of filter media and based on Washburn’s equation, a lipophilic hydrophilic ratio （LHR） concept was defined for the first time and used to compare quantitatively the wettabilities of the above-mentioned filters:The calculated LHR values of walnut shell, anthracite, magnetite, manganese sand, quartz sand and zeolite with a size range of 0.45-0.9mm at 20℃were 76.4, 2.41, 1.06, 0.74, 0.65 and 0.64 respectively, which means walnut shell and anthracite are lipophilic, magnetite is not only lipophilic but also hydrophilic, while manganese sand, zeolite and quartz sand are hydrophilic. These results of LHR values are in accordance with the differences of filter’s surface physicochemical propoties. Namely, walnut shell and anthracite surfaces are apolar and have lower energy, which makes them wetting easily only to apolar oil（cyclohexane） with lower surface tension. Magnetite possess a higher surface energy, therefore, not only apolar oil but also polar water with higher surface tension are wettable favorably. Manganese sand, zeolite and quartz sand, however, are wetted better with polar water than apolar oil because of their polar surfaces.Oginating from van Oss-Chaudhury-Good （VCG） theory and valuating the physical data of water and cyclohexane at 20℃, the relationship between LHR and surface free energy components of filter media was deduced as follows:This equation theoretically discloses that filter’s LHR value is attributed to their surface free energy acidic componentγ_s⁺ and basic oneγ_s^- Also, surface free energy components of the filters were estimated through porous capillary penetration technique, using Washburn’s equation and VCG theory with n-hexane, a-bromonaphthalene, formamide and water as probe liquids in this paper. The estimated surface free energy apolar and polar components of walnut shell, anthracite, manganese sand, quartz sand and zeolite were 38.8mJ·m^-2, 38.8mJ·m^-2, 38.1mJ·m^-2, 37.7mJ·m^-2, 38.2mJ·m^-2 and 0.37mJ·m^-2, 0.73mJ·m^-2, 6.79mJ·m^-2, 8.66mJ·m^-2, 9.42mJ·m^-2, experimentally verifying that the wettabilities of filter media are correlated to their surface free energy polar components （γ_s⁺andγ_s^-）, and the latter could be ascribed to the differences in surface physicochemistry which is consistent with the characterized results in Section 4.（3） Zeta potentials of filter particles were also measured on the basis of Helmholtz-Smoluchowskiequation. Theζvalues of walnut shell, anthracite, magnetite, manganese sand, quartz sand and zeolite in fluid media of distilled water and 0.1mol·L^-1 KC1 solution at 20℃were -17mV, -17mV, -11mV, -34mV, -64mV, -11mV and -5.1mV, -4.2mV, -1.4mV, -0.11mV, -0.19mV, -0.15mV, respectively. These results make clear that concentration of electrolyte solution will bring significant effect on the Zeta potentials on filter media surfaces.（4） During 10 hours of filtration process running in a lab simulated small scale deep media bed, the oil removal efficiencisηand backwash efficienciesη_r of walnut shell, anthracite, magnetite, manganese sand, quartz sand and zeolite packed media were 96%, 80%, 72%, 64%, 60%, 78% and 16%, 30%, 37%, 73%, 83, 69%. Compared these efficiencies with LHR values, the following relations were fitted which illustrate that the better the filter’s lipophilicity （the greater of the LHR） is, the easier the removal of oil from wastewater and the harder the backwash of it from packed media, and vice versa:（5） Calculated by XDLVO theory, the Electrostatic interaction energy changing between filter grain, oil and water were all about zero, i.e.△G₁₃₂^EL≈0; the Lifshitz-van der Waals energy changing△G₁₃₂^LW for walnut shell, anthracite, manganese sand, quartz sand and zeolite were -7.52×10^-20J, -7.52×10^-20J, -7.25×10^-20J, -7.09×10^-20J, -7.29×10^-20J; the Lewis acidic-basic energy changing△G₁₃₂^AB for them were -4.31×10^-18J, -3.99×10^-18J, -3.39×10^-18J, -2.93×10^-18J, -2.87×10^-18J; and the total interaction energy changing△G₁₃₂^TOT for them were -4.38×10^-18J, -4.07×10^-18J, -3.46×10^-18J, -2.99×10^-18J, -2.94×10^-18J, respectively. All△G₁₃₂^TOT between filter grains and oil/water were less than zero, indicating the attachment of oil particulates on media surfaces is spontaneous and these spontaneous trends of filter media are identical to their orders of LHR values and oil removal efficiencies. Furthermore,△G₁₃₂^AB ofsystem is the major donor to△G₁₃₂^TOT, once again proving that the effects of LHR andγ_s^AB of filter media on oil removal are identical in thermodynamic essence.更多还原