【作者】 谢晶晶；

【导师】 陈天虎；

【作者基本信息】 合肥工业大学 ， 矿物学矿床学岩石学， 2013， 博士

【摘要】 凹凸棒石加工和应用常常经历高温过程,热处理也是凹凸棒石粘土活化改性的常用方法之一。前人虽然认识到随着温度升高凹凸棒石脱水、结构演化,表面性质发生了很明显的变化,但是对凹凸棒石表面性质发生变化的根源尚缺少深入的认识和理解,到目前为止学术界和产业界对凹凸棒石的认识还存在很多误区,特别是凹凸棒石热活化过程中结构和物性演化规律及其变化的本质缺少深入系统地理解。为此,本文系统采取明光市官山东风矿业采矿场剖面样品,在查明矿石矿物组成的基础上,选择不同类型的典型矿石样品,利用X射线衍射、扫描电镜、高分辨率透射电镜、27A1魔角旋转核磁共振、29Si魔角旋转核磁共振对不同温度煅烧凹凸棒石结构、形貌进行研究,结合比表面积和孔径分析、热重分析、红外光谱分析,尤其是利用在线小型质谱分析仪研究凹凸棒石程序升温控制过程中水、氨、二氧化硫的吸脱附,认识凹凸棒石结构演化和物理化学性质变化之间的内在联系。本论文取得如下主要认识和成果：1、综合热处理凹凸棒石的XRD分析、热重分析、水的脱附分析结果可以得到,在低于200℃热处理凹凸棒石脱出外表面吸附水和晶体结构孔道内吸附水,晶体结构不发生任何变化；200-300℃区间热处理凹凸棒石,脱出结构中一半的结晶水,晶体结构发生调整,晶体内部孔道出现折叠；在300-500℃左右热处理凹凸棒石的另外二分之一结晶水,同时脱出晶体内部结构水和外表面结构水,晶体结构周期性基本破坏。经500-700℃煅烧凹凸棒石进一步脱出结构水成为酸酐,但是c轴方向的部分有序性仍然存在,硅氧四面链尚没有解体。2、XRD和29Si核磁共振结果都表明凹凸棒石在500-700℃温度区间热处理后处于非晶化状态,800℃开始向方石英转化。3、凹凸棒石脱出一半结晶水后,经过水化后不仅可以恢复到原来的结构状态,而且晶体的衍射峰强度得到加强,认为是凹凸棒石经过热处理-水化循环后结构有序性提高。超过350℃热处理凹凸棒石结构水完全脱出后不能通过水化作用恢复到原来的结构状态。4、安徽明光凹凸棒石结构中铝主要以AIⅥ形态存在,存在少量A1Ⅳ形态。煅烧温度在500-C以下时,铝配位没有发生明显地变化。当加热温度达到500℃时,开始出现五次配位铝(AIV)的谱峰,四配位铝明显增加,并且存在两种不同的位置,表明虽然凹凸棒石结构在向非晶化转变,但是结构有序性并没有完全破坏。当煅烧温度达到800℃时AlVI峰和A1V峰全部消失,A1Ⅳ峰强度达到最大。5、TEM、SEM图像均表明热处理温度低于800℃,凹凸棒石保持棒状形态。超过800℃热处理的凹凸棒石,形态表现出收缩、弯曲变形似蚯蚓状,出现烧结现象,因此凹凸棒石作为载体材料保持其基本形貌使用的临界温度是800℃。6、热处理温度低于700℃时凹凸棒石比表面积不发生显著地变化,温度在800℃以上时凹凸棒石比表面积急剧降低。凹凸棒石在300℃开始因失去部分结晶水结构发生折叠,在500℃脱出结构水发生结构破坏,但是比表面积直到温度700℃没有显著变化,表明BET-N2吸附法测得比表面积是凹凸棒石的外比表面积,氮气分子因动力学半径大尚不能够进入凹凸棒石的孔道中。800℃以后凹凸棒石比表面积急剧降低是凹凸棒石晶体收缩成为球型、烧结作用降低孔隙率的结果。7、在水热体系中碱性镁化合物存在导致凹凸棒石晶体结构遭到破坏,促使棒状晶体转变为片状的蒙皂石或蛇纹石。在70-200℃水热体系中凹凸棒石与中性镁盐作用可以促使晶体生长,但是凹凸棒石晶体的生长十分缓慢。中性镁盐的添加量对凹凸棒石生长的影响比较明显,而反应温度和时间的影响不大。8、白云石凹凸棒石粘土中的白云石热分解起始温度500℃、峰值温度745℃、分解完全温度780℃。普通白云石分解起始温度600℃、峰值温度797.6℃、完全分解温度825℃。白云石分解分为两个步骤,且存在中间产物方解石。白云石凹凸棒石粘土中的白云石比普通白云石分解温度低大约50℃,显示出不寻常的热化学活性。该类粘土中白云石不寻常的热化学活性归结为两个原因：第一是白云石凹凸棒石粘土中矿物都属于纳米矿物,具有纳米结构,其异乎寻常的热化学活性是纳米效应的体现；第二是凹凸棒石作为纳米粘土矿物与白云石共存,在纳米尺度上形成相嵌微结构,具有较高热化学活性的凹凸棒石在高温下与白云石的化合反应促进了白云石的分解,降低了其分解温度。活性硅质组分在促进碳酸盐热分解方面对方解石的作用比对白云石的作用大,归因于具有较高热化学活性的硅质组分与碳酸盐中的钙化合作用促进了碳酸盐的热分解。9、不同类型的凹凸棒石粘土矿石在未煅烧前对磷的吸附去除率都不高,不同类型的矿石高温煅烧改性后对磷的吸附性能有很大差异,只有白云石凹凸棒石粘土煅烧活化后才具有较好的吸附除磷效果,从而证明并非所有类型的凹凸棒石粘土矿石都可以热活化制备除磷吸附剂。白云石凹凸棒石粘土煅烧活化超过500℃才体现出明显的改性效果,最佳活化温度是600℃左右。不同温度煅烧产物除磷作用机制有很大的不同,500℃、600℃热处理样品除磷机制归因于热活化后白云石表面对磷的吸附作用：700℃、800℃热处理样品除磷机制归因于白云石热分解形成方镁石、石灰以及白云石与凹凸棒石发生热化学反应形成低结晶度的斜硅钙石、灰硅钙石水解促进了磷酸镁、磷酸钙沉淀。更多还原

【Abstract】 Usually the application of palygorskite needs pyroprocessing, so the heat-treatment is one of the most common modifications used for industrial and scientific purposes. Some concomitant changes in properties like dehydration, structure changes, surface properties changes occurred apparently with the increase of temperature, but the origin of these changes is still unclear in both scientific and industrial world. The sample is from Dongfeng mineral cooperation stope Mingguang City, Anhui Province, China. The present work investigated the structure and morphology changes of different typical types samples during calcinations using X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope,27Al and29Si magic angle spinning nuclear magnetic resonance, and also investigate the effect of heat treatment on the relationship between structure and surface, textural properties of palygorskite. The present work investigated the effect of heat treatment on the relationship between structure and surface, textural properties of palygorskite by using BET surface area and pore width analysis, thermogravimetric analysis, Fourier transform infrared spectroscopic analysis, especially the in-situ mass spectrometry for detecting the surface acid-alkali properties of palygorskite through the adsorption-desorption of water, NH3and SO2, The main conclusions of the present work are showed as follow:1. Compared the XRD, TGA analysis with the desorption analysis of water, it can be concluded that:the adsorbed water on the surface of palygorskite and in the channel of the crystal is eliminated,even the structure remained unchanged when the heat-treatment temperature is lower than200℃; half crystal water expelled from the crystal structure adjusted and channels in the crystal folded at the heat-treatment temperature range of200-300℃; the other half crystal water expelled, the structure water in the crystal and at out-surface began to be expelled, also the periodicity of the structure was destroyed at the heat-treatment temperature range of300-500℃; the sample after further dehydration formed anhydride, but the partly order in C axis and the chain of Si-O tetrahedral were still exist after heated at temperature range of500-700℃.2. XRD and29Si MAS-NMR results showed that the palygorskite had became amorphous state after heated at temperature range of500-700℃, and then transformed into cristobalite at800℃3. After half crystal water expelled from the crystal structure, the original structure state could be not only recover to after rehydration, but also the diffraction peak intensity was strengthened, it can be concluded that the heat-treatment and rehydration cycle can improve the order of structure. But when the heat-treatment temperature is above350℃, the structure couldn’t be recovered after rehydration 4. The Al-coordination of sample from Mingguang Anhui is mainly AlⅥ, and a minor amount of Al IV can be found. No significant change appears when treated at the heat-treatment temperature lower than500℃. The peak of Al(Ⅳ) is strengthened and a signal of Al(Ⅴ) is detected when treatment temperature higher than500℃. There are two lattice positions existed at the same time, showing that the. orderly structure is not destroyed compeletly. The peak of Al(Ⅵ) decreases and Al appears as Al(IV) after treatment temperature higher than600℃, At800℃, Al(Ⅵ) and Al(V) disappear completely, and the peaks of Al(Ⅳ) turn to form one peak, indicating that all the Al(Ⅳ) exists in one chemical environment.5. TEM and SEM images showed that the fiber morphology when the heat-treatment temperature is lower than800℃, and it would become shrinked, bended like earthworm shape, even sintered when the heat-treatment temperature is higher than800℃, so that to palygorkit, the critical temperature for the use of carrier material is800℃.6. The specific surface area did not changed apparently when the the heat-treatment temperature is lower than800℃, but it decreased sharply when the heat-treatment temperature is higher than800℃. The structure of palygorskite was folded when partly crystal water expelled at300℃, and it was destroyed when structure water expelled at500℃, but the SSA was stable until700℃, we can concluded that the SSA measured by BET-N2adsorption-desorption method is the external SSA, the radius of N2molecule is too large to enter the channel of palygorskite. The reason of sharply decrease of SSA at800℃is that the palylygorskite fiber structure was shrink into a ball, and the sintering made the decrease of porosity.7. Under hydrothermal conditions, the existence of alkaline magnesium compound can destroyed the crystal structure of palygorskite, and promote the transformation of palygorskite into smectite or serpentine. Under hydrothermal conditions of70-200℃, the adding of neutral magnesium compound will benefit the growth of palygorskite crystal but the growth is slow. The adding amount of MgCl2affects the crystal growth apparently, while the acting temperature and time was slightly.8. The thermal decomposition temperature of dolomite-palygorskite started at500℃, the peak temperature is745℃, and completely decomposition temperature is780℃. While for ordinary dolomite the thermal decomposition temperaturest started at600℃, the peak temperature is797.6℃, and completely decomposition temperature is825℃. The decomposition of dolomite has two steps, and has calcite as intermediate products. The dolomite decomposition temperature in dolomint-palygorskite clay is50℃lower than ordinary dolomite, and exhibited an unusual thermal chemically active. There are two reasons of this unusual thermal chemically active:Firstly, the minerals in dolomite-palygorskite clay are nano scale with nanostructure, the nanometer effect causes the unusual thermal chemically active; secondly, palygorskite as a kind of nano mineral coexist with dolomite, and formed interdigitations microstructural in nano scale, while palygorskite as a kind of higher thermal chemically active reacted with dolomite which promote the decomposition of dolomite, and lower its decomposition temperature. Activated silica plays a greater part in carbonate thermal decomposition of calcite than dolomite, and this can be attributed to the siliceous component which has higher thermal chemically active reacted with the Ca ions in carbonate, and this will promote the thermal decomposition of carbonate.9. All types of palygorskite had no effect on the removal of phosphate before calcination, and there is a very different adsorptive property after calcinations, only calcined dolomite-palygorskite clay has good effect for phosphate adsorption, and it can be concluded that not all types of palygorskite can be made into phosphate adsorbent. The modification effect can be found only when the thermal modification temperature is higher than500℃, the best activation temperature is nearly600℃. Dolomite-palygorskite clay has an unique adsorptive property for phosphate, The phosphate removal mechanisms are so different by the samples calcined at different temperature, the phosphate removal mechanism of samples calcined at500℃and600℃can be attributed to the adsorption at the surface of modified dolomite, while the phosphate removal mechanism of samples calcined at700℃and800℃can be attributed to the precipitation of magnesium phosphate and calcium phosphate which caused by the low crystalline larnite and spurrite formed from thermal reaction of the dolomite and palygorskie.更多还原