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1、粘土矿物在水中的聚集特征和方式第1页，本讲稿共14页1.1 Origin of Clay Minerals“The contact of rocks and water produces clays,either at or near the surface of the earth”(from Velde,1995).Rock+Water ClayFor example,The CO2 gas can dissolve in water and form carbonic acid,which will become hydrogen ions H+and bicarbonate ions,
2、and make water slightly acidic.CO2+H2O H2CO3 H+HCO3-The acidic water will react with the rock surfaces and tend to dissolve the K ion and silica from the feldspar（长石）.Finally,the feldspar is transformed into kaolinite.Feldspar+hydrogen ions+water clay(kaolinite)+cations,dissolved silica2KAlSi3O8+2H+
3、H2O Al2Si2O5(OH)4+2K+4SiO2Note that the hydrogen ion displaces the cations.第2页，本讲稿共14页1.2 Basic Unit-Silica Tetrahedra 1 Si4 OHexagonal hole(Si2O10)-4Replace four Oxygen with hydroxyls or combine with positive unionTetrahedronPlural:Tetrahedra第3页，本讲稿共14页Different cationsGibbsite sheet:Al3+Al2(OH)6,2
4、/3 cationic spaces are filledOne OH is surrounded by 2 Al:Dioctahedral sheet1 Cation6 O or OHBrucite sheet:Mg2+Mg3(OH)6,all cationic spaces are filledOne OH is surrounded by 3 Mg:Trioctahedral sheet第4页，本讲稿共14页第5页，本讲稿共14页第6页，本讲稿共14页Minerals-KaoliniteBasal spacing is 7.2 Si4Al4O10(OH)8.Platy shapeThe
5、bonding between layers are van der Waals forces and hydrogen bonds(strong bonding).There is no interlayer swellingWidth:0.1 4m,Thickness:0.052 m 17 mTrovey,1971(from Mitchell,1993)第7页，本讲稿共14页MontmorilloniteSi8Al4O20(OH)4nH2O(Theoretical unsubstituted).Film-like shape.There is extensive isomorphous s
6、ubstitution for silicon and aluminum by other cations,which results in charge deficiencies of clay particles.nH2O and cations exist between unit layers,and the basal spacing is from 9.6 to (after swelling).The interlayer bonding is by van der Waals forces and by cations which balance charge deficien
7、cies(weak bonding).There exists interlayer swelling,which is very important to engineering practice(expansive clay).Width:1 or 2 m,Thickness:10 1/100 width(Holtz and Kovacs,1981)第8页，本讲稿共14页Minerals-Illite(mica-like minerals)potassiumSi8(Al,Mg,Fe)46O20(OH)4(K,H2O)2.Flaky shape.The basic structure is
8、very similar to the mica,so it is sometimes referred to as hydrous mica.Illite is the chief constituent in many shales.Some of the Si4+in the tetrahedral sheet are replaced by the Al3+,and some of the Al3+in the octahedral sheet are substituted by the Mg2+or Fe3+.Those are the origins of charge defi
9、ciencies.The charge deficiency is balanced by the potassium ion between layers.Note that the potassium atom can exactly fit into the hexagonal hole in the tetrahedral sheet and form a strong interlayer bonding.The basal spacing is fixed at 10 in the presence of polar liquids(no interlayer swelling).
10、Width:0.1 several m,Thickness:30 第9页，本讲稿共14页Minerals-Vermiculite(micalike minerals)The octahedral sheet is brucite.The basal spacing is from 10 to 14.It contains exchangeable cations such as Ca2+and Mg2+and two layers of water within interlayers.It can be an excellent insulation material after dehyd
11、rated.VermiculiteIllite第10页，本讲稿共14页溶液中粘土表面的双电层溶液中粘土表面的双电层 定定义义粘粘土土颗颗粒粒在在水水中中表表面面带带负负电电荷荷，通通过过静静电电作作用用可可把把交交换换性性阳阳离离子子(称称为为反反离离子子)吸吸引引在在它它的的周周围围。这这些些反反离离子子一一方方面面受受负负电电荷荷的的吸吸引引靠靠近近粘粘土土表表面面，另另一一方方面面由由于于反反离离子子的的热热运运动动及及反反离离子子之之间间的的斥斥力力，会会脱脱离离粘粘土土颗颗粒粒向向溶溶液液中中扩扩散散，其其结结果果构构成成了了扩扩散散双双电电层层。粘粘土土颗颗粒粒周周围围的的阳阳离离
12、子子只只有有一一部部分分同同粘粘土土颗颗粒粒一一起起运运动动，这这部部分分同同粘粘土土吸吸引引得得比比较较牢牢固固的的阳阳离离子子层层，称称为为吸吸附附层层。另另一一部部分分阳阳离离子子距距离离粘粘土土颗颗粒粒稍稍远远，不不随随粘粘土土一一起起运运动动，这这一一部部分分称称为为扩扩散散层层。吸吸附附层层和和扩扩散散层层的的交交界面称为滑动面。界面称为滑动面。第11页，本讲稿共14页电解质压缩双电层作用电解质压缩双电层作用粘土颗粒运动中因丢掉扩散层中的反离子粘土颗粒运动中因丢掉扩散层中的反离子而显示出一定的电势而显示出一定的电势,称为电动电势称为电动电势(电电位位),其数值取决于吸附层内反离子总
13、电荷。其数值取决于吸附层内反离子总电荷。电解质对电动电势影响较大，溶液中阳离电解质对电动电势影响较大，溶液中阳离子浓度越高，进入吸附层的阳离子数量多，子浓度越高，进入吸附层的阳离子数量多，电位降低，当反离子全部进入吸附层时，电位降低，当反离子全部进入吸附层时，这种现象称为电解质压缩双电层。这种现象称为电解质压缩双电层。第12页，本讲稿共14页聚集方式粘土矿物一般呈片状。它们之间的接触方式主要有面-面、边-边、边-面三种基本类型。面对面的片状堆积结构称为分散结构或片堆结构（叠聚体）。以边-面、边-边联结的结构称为凝聚结构或片架结构（絮凝体）。第13页，本讲稿共14页8.2 Particle As
14、sociationsDispersed and deflocculatedAggregated but deflocculatedEdge-to-face flocculated and aggregatedEdge-to-edge flocculated and aggregatedEdge-to-face and edge to edge flocculated and aggregatedEdge-to-edge flocculated but dispersedEdge-to-face flocculated but dispersedvan Olphen,1991第14页，本讲稿共14页