【作者】 刘令云；

【导师】 张明旭； 宋少先；

【作者基本信息】 安徽理工大学 ， 环境工程， 2013， 博士

【摘要】 高泥化煤泥水中含有大量的微细粘土矿物颗粒是其难以沉降澄清处理的一个重要原因。由于这些粘土矿物颗粒表面具有大量的亲水基团,在水溶液中其表面会产生一层水化膜从而增加了颗粒间的水化斥力,传统的以DLVO理论为基础的凝聚技术无法有效地实现这些微细颗粒间的聚团沉降,因此研究粘土矿物颗粒表面的水化作用机理,探索破解颗粒表面水化膜的方法是实现高泥化煤泥水高效沉降澄清处理的一项重要内容。高岭石是煤泥水中的主要矿物成分之一,本文采用试验分析、理论计算和计算机模拟的研究方法,模拟煤泥水的溶液特性,以pH值、煤泥水中常见离子、离子浓度等溶液性质作为影响因素,研究了煤系高岭石颗粒表面理化特性及与煤泥水的相互作用、颗粒表面的荷电机理及溶液性质对水化作用的影响规律,测定了颗粒表面水化参数,分析了高岭石颗粒在不同性质溶液中与水分子相互耦合的作用机理,并通过分子动力学模型软件建立了高岭石颗粒表面水化作用模型,为破解煤泥水中高岭石表面水化膜,实现高泥化煤泥水的高效沉降澄清处理提供理论支持。高岭石颗粒表面理化特性及与煤泥水的相互作用研究表明,高岭石颗粒表面含有大量的硅醇基(>SiOH)和铝醇基(>A1OH)等含羟基组,这些羟基组在低的pH溶液中会产生质子化作用,从而使溶液pH升高,同时增加了颗粒表面羟基数量,而在高pH溶液中会产生去质子化作用,从而使溶液pH降低,硅氧基(>SiO)和铝氧基(>A10)基团数量增多；对于偏碱性的煤泥水,高岭石主要有降低煤泥水pH值的作用,同时高岭石颗粒结构中及其表面吸附其它元素会溶解到煤泥水中,从而增加煤泥水中金属阳离子浓度；煤泥水中的阳离子对高岭石颗粒表面的质子化有抑制作用,对去质子化有促进作用。高岭石颗粒表面的荷电机理研究表明,煤系高岭石颗粒的IEP在3.00左右,PZNPC为5.65,煤泥水中高岭石颗粒各面均荷负电荷,整个颗粒的ξ电位在-60mV左右；煤泥水中K+、Na+离子主要通过压缩溶液中颗粒表面双电层及抑制质子化作用或促进去质子化作用来影响颗粒表面电动特性的；Mg2+、Ca2+离子则主要是通过压缩双电层和在颗粒表面产生特性吸附的方法来降低颗粒表面ξ电位,当离子浓度达到0.1mol/L时,颗粒表面ξ电位接近零值,并在较宽的pH值范围内保持稳定；无机盐类的Al化合物则通过A13+的水解降低溶液pH,减少颗粒表面的去质子化作用来降低煤泥水中微细颗粒表面ξ电位,同时利用粘土类矿物颗粒IEP点较低,Al(OH)3(s)颗粒IEP较高的特点,将Al(OH)3(s)沉淀物覆盖到粘土矿物颗粒表面,从而提高高岭石颗粒IEP值,使IEP值接近煤泥水pH值来降低颗粒表面ξ电位；高岭石颗粒粒度越小,颗粒表面酸碱响应系数α值越大,颗粒表面羟基越多,在溶液中的质子化去质子化能力越强。水化作用机理研究表明,高岭石颗粒表面的水化能力要远强于溶液中离子的水化能力；Na+、K+等离子主要是通过改变颗粒表面扩散双电层内游离水的含量以及影响颗粒表面与水分子的直接水化作用能力来使双电层中剪切面产生移动,从而改变颗粒表面水化膜的厚度；Ca2+、Mg2+等高价离子在高岭石颗粒表面的特性吸附,影响了颗粒表面与水分子的直接水化作用能力,而使双电层中剪切面向颗粒表面移动从而减小了表面水化膜的厚度；Al3+离子溶液中高岭石颗粒表面会覆盖一层厚厚的Al(OH)3(s)沉淀物,从而极大地增加了高岭石颗粒的粒度。分子动力学模拟研究表明,水分子主要通过类似于“洞水”分子的A型和类似于“连接水”分子的B型两种形式吸附在高岭石颗粒表面,从而形成一层紧密、稳固的水化膜,其中A型是水分子在颗粒表面的主要吸附形式。更多还原

【Abstract】 One of the vital reasons why it is difficult to achieve sedimentation and clarification of the high marlaceous coal slurry is that there are a lot of fine clay mineral particles in the slurry. Thick hydration layers will be formed on the surfaces of clay mineral particles in the aqueous solutions to increase the repulsive hydration force between two particles because of the large number of hydrophilic groups of surface. The conventional technology of aggregation based on the DLVO theory cannot make these fine particles agglomerate and settle effectively. Thus, to study the hydration mechanism and look for ways to crack the hydration layers on clay mineral particle surfaces are the important parts of high efficiency method of high marlaceous coal slurry treatment. In consideration of kaolinite being a kind of main mineral in high marlaceous coal slurry, in this work the surface physicochemical characteristics, and effects of solution chemical properties and surface charging characteristics on hydration of kaolinite particles have been researched based on the test analysis, theoretical calculations and computer simulations methods. In addition the hydration mechanism of kaolinite particles has been analyzed and the hydration model has been established according to molecular dynamic simulation. This work will provide a theoretical support for cracking hydration layer on the surface of kaolinite particles and high efficiency clarification treatment of high marlaceous coal slurry.The research results of the physicochemical characteristics of kaolinite surface and the interaction between particle surface and coal slurry show that kaolinite particle surface contains a lot of hydroxyl groups such as> SiOH and> A1OH. These hydroxy groups will produce protonation at low pH solutions resulting in the increasing of solution pH and the numbers of surface hydroxyl groups, on the contrary produce deprotonation at high pH solutions resulting in the reducing of solution pH and the increasing of the numbers of> SiO and> A1O groups. In alkaline slurry, kaolinite can reduce the solution pH value, and the other elements in the structure of kaolinite particles and adsorbed on surface can dissolve into the solutions, thereby increasing the concentration of the solution metal cations. The presence of metal cations in the solutions can restrain the protonation of the kaolinite particle surfaces, and promote the deprotonation of the kaolinite particle surfaces inversely. The research results of kaolinite surface charging characteristics shows that the IEP and PZNPC of kaolinite are around pH3.00and pH5.65respectively. All the surfaces of kaolinite are negatively charged and theζpotential of entire kaolinite particle is around-60mV. The K+and Na+ionsaffect the kaolinite electrokinetic properties by compressing the electrical double layer of the particles and weakening the protonation or strengthening the deprotonation of the kaolinite particle surfaces. The Mg2+and Ca2+ionsreduce the absoluteζpotential of kaolinite particles by compressing the electrical double layer of the particles and having specific adsorption on the kaolinite particle surfaces. Once the ion concentration of Mg2+and Ca2+increases to0.1mol/L, theζpotential of entire kaolinite particle becomes around zero and keeps steady in a lager range of solution pH. The aluminiumcompound inorganic salts can decrease the deprotonation of the kaolinite particles by reducing the solution pH caused by the hydrolysis of Al3+ions, resulting in theζpotential of kaolinite particles decreasing. Additionally, on account of the low IEP of clay mineral particlesand high IEP ofAl(OH)3(S)particles, once the A1(OH)3(S)precipitate onto the particle surface, the IEP of particles with A1(OH)3(S) on surfacewill increase to approach the pH of coal surry and reduce theζpotential of the entire particles. The smaller the size of kaolinite particle is, the larger the acid-base response coefficientα value is, and the more hydroxyl groups there are on the particle surface, and the stronger the protonation/deprotonation capability of particles is.The research results of the hydration mechanistic of kaolinite particle surfaces prove that the hydration capability of kaolinite particle surfaces is stronger than that of ions in solutions. The K+and Na+ions can make the shear plane in the electric double layer moves by changing the free water content in the diffuse electric double layer and affecting the hydration capacity between water molecules and kaolinite particle surfaces, resulting in the changing of the thickness of hydration layers on the particle surfaces. The Mg2+and Ca2+ionscan make the shear plane move to the particle surfaces and reduce the thickness of hydration layer by having specific adsorption on the kaolinite particle surfaces which can affect the surfaces hydration capacity. In the Al3+ions solution the A1(OH)3(S) will deposit on the kaolinite particle surfaces and increase the size of kaolinite particles greatly. The molecular dynamics simulation shows that the water molecules adsorb on the surface of kaolinite particles to form a dense, firmhydration layer in two types. The water molecules are similar to the "hole water" in type A, and the water molecules are similar to the "connect water" in type B. Type A is the major adsorption form of water molecules on the surface of kaolinite surfaces.更多还原