中文摘要：
埃洛石作为自然界普遍存在的一类粘土矿物材料,有着卓异的管状形貌,是许多科学研究方向的重点,近年来其在环境领域的研究与应用势头攀升。天然的埃洛石应用前景有限,通过各种手段对埃洛石表面性能进行提升或活化改性,可有效拓展其应用领域。但是,现有科研成果通常着眼于埃洛石经过改性后整体性能的检验,对其在矿物学方面的探索较为缺乏,较少深入探究埃洛石的活化及改性机理,也就缺乏对埃洛石改性的定向调控研究成果。因此,本文选用湖北产埃洛石,针对酸活化埃洛石的效果及机理进行探究,并在不同溶剂体系下将γ-氨丙基三乙氧基硅烷(APTES)负载到埃洛石的原样和酸活化样上,从而探究不同溶剂体系对负载效果和机理的影响,通过X射线衍射(XRD)、透射电镜(TEM)、电感耦合等离子体质谱(ICP)、傅里叶变换红外光谱(FTIR)、热分析(TG)、氮气等温吸附脱附测试、核磁共振(NMR)等多种表征手段,创新性地将酸活化与有机硅烷改性方法相结合,开展了埃洛石经强酸活化预处理后在不同反应溶剂体系下进行有机改性的效果及机理探索,进而得到针对埃洛石有效且可控的定向调节有机改性手段,从而为埃洛石的改性研究、应用以及后续实验积累科学经验。本文得出以下主要结论:(1)埃洛石在强酸(4 mol/dm~3盐酸溶液)活化过程中,由管内腔首先受到侵蚀,管内径逐步增大,管壁变薄,管腔内逐渐出现石英颗粒,样品中逐渐出现埃洛石脱落片层。溶液中的C_(Al(Ⅲ))呈现稳定上升态势,而C_(Si(IV))经过6天的快速增长后达到动态平衡平台。在活化时间为10天以内,样品仍能大量且良好地保持管状形貌。(2)在无水甲苯溶剂体系下,对埃洛石原样和管状形貌维持较好的酸活化样品开展有机硅烷(APTES)嫁接,得到其改性反应原理包含直接嫁接反应和低聚反应。酸活化处理通过改变埃洛石形貌和表面羟基的分布来达到对有机硅烷改性的定向调控。经计算,酸活化6天的埃洛石(HNTs-6)有着最高的有机硅烷负载量(4.16 mass%),改性效果最佳。(3)在无水乙醇和不同比例乙醇/水溶剂体系下,对埃洛石原样和HNTs-6进行APTES改性,通过对比探究发现,埃洛石的有机硅烷负载量受到溶剂的极性以及含水量的强烈影响。经过与非极性溶剂体系对比发现,极性溶剂体系下由低聚而负载到埃洛石上的有机硅烷占比较低,有机硅烷负载量也较少;而酸活化样在极性溶剂中仍比原样有更多的有机硅烷负载量;溶剂中含水量的增大可促进有机硅烷的水解和缩合反应,使有机硅烷负载量增多(在乙醇/水的比例为8/2时,改性效果最佳),但仍低于极性溶剂条件的负载量。溶剂含水量过多会使埃洛石出现团聚现象,且加剧有机硅烷之间的水解和缩合反应,降低体系中的硅醇含量,导致有机硅烷负载量降低。
英文摘要：
As a kind of common clay mineral material in nature,halloysite has sepcial tubular morphology and great application potential in multiple domains.However,a variety of phenomenon,such as surface electron and hydrogen bond,often exist in the nutural halloysite nanotubes,which affect their properties and application range.The surface modification to halloysite has been proposed as an efficient strategy to avoid such phenomena as well as additional performance improvements.Up to now,most research achievements concentrated on the test of the entire performance of modification but less exploration focused on the directional regulation of hallosite modification from perspective of mineralogy.Hence,this study focused on the research of the surface modification of acid-treated Hubei halloysite(by APTES),combined with TEM,XRD,ICP,FTIR,TG,NMR,nitrogen adsorption and other characterization methods,investigating the effects of acid pretreatment and the influence of diverse reaction solvents on the modification of halloysite.The valid parameters for the motivated regulation of halloysite modification were acquired and the basic data for the practical application of modified halloysite in the correlative territory was gathered in this study.This paper has got several conclusions below:(1)During the acid(4 mol/dm~3 HCl solution)activation of halloysite,the inner(concave)surface of halloysite composed by AlO_6 octahedra is firstly attacked by the acid resulting in the release of Al(III)to the solution.Further dissolution predominantly continues on the concave surface leading to the release of Si(IV),which rapidly reaches a saturated concentration in 6 days and precipitates in the form of amorphous SiO_2 nanoparticles inside the nanotubes.Over a long period of time,the inner diameter of nanotubes and the diameter of SiO_2 nanoparticles increase.Within 10 days of activation,the samples were still maintained in tubular morphology well.(2)In the polar reaction solvents(anhydrous toluene),the acid-treated halloysite with good tubular structure and the raw sample were modified by APTES.The results proved that the modification mechanism included not only direct grafting but also oligomerization.The acid activation principally regulated the modification by influencing the tubular morphology and the distribution of hydroxyl groups.The6-days acid-treated sample(HNTs-6)was the optimal sample for silanization,which has the highest silane loading of 4.16 mass%.(3)In the nonpolar reaction solvent(anhydrous ethanol)and the diverse proportions of ethanol/water,HNTs-6 was modified by APTES.Through comparative study,it was found that the organosilane load of HNTs-6 was strongly affected by the polarity of solvent and water content in the system from the point of the modification mechanism and the modification extent.Silanized HNTs-6 modified in the nonpolar reaction solvent had higher silane load and oligomerization extent in comparison with the samples modified in the polar solvent.And it has higher silane load and oligomerization extent than silanized raw halloysite in the polarity of the solvent.Besides,a certain percentage of water in the solvent was capable of promoting the hydrolysis and condensation reaction of the organosilane,increasing the loading capacity of organosilane.When the ethanol/water ratio was 8/2,the modification effect was best,but still lower than the loading capacity in hte polar reaction solvent.Nonetheless,excessive water in the solvent would cause the aggregation of HNTs-6,and aggravated the hydrolysis and condensation reaction between organosilane,reducing the content of silanol in the system,resulting in the reduction of the degree of oligomerization and organosilane load.
