The Clay Interlayer Structure And Adsorption Characteristics Of Bentonite

Bentonites show good table/interface reactivity due to its special two-dimensional nanolamellar structural and great theoretical specific surface area.Organic cation modifiedbentonites (Organobentonites) have a good sorption capacity to hydrophobic organiccontaminants (HOCs) in the environment, and which is a kind potential pollution controlmaterial of HOCs. Thereinto, sorption principle of bentonites which are modified with shortcarbon chain organic cations (such as tetramethylammonium cation TMA+) to HOCs, ismainly surface adsorption, hydrophobic siloxane surface of bentonites is the mainly sorptionsite, reducing the charge density of bentonite and interlayer dehydration are beneficial foradding siloxane surface exposure levels, and then enhancing the organic bentonite sorptioncapacity.In this dissertation, the structural stability and sorption capacity of reduced-chargeTMA-bentonite had been primarily discussed on the basis of the structural characteristics andsorptive capacity of bentonites, attempting to figure out the structure and sorption capacity ofreduced-charge TMA-bentonites; then the paper tried to synthesize the lower charge densityof K-Bt using K+saturating reduced-charge Li-Bt, and studied its structural characteristics andsorption properties for the purpose of understanding the relationship between its of theinorganic bentonite with lower charge density; simultaneously, the structural characteristicsand sorption properties of interlayer-dehydrated TMA-bentonite and K-bentonite withdetermined temperature, were also researched to further explore the structure-sorptionrelationship of bentonite. The results will be beneficial to promoting the application oforganobentonites in the controlling of environmental pollution,And the theoreticallysignificant results of this dissertation are as the follows:(1) In this work, we want to show a new method to preserve the structural stability ofreduced-charge TMA-bentonite. First the inorganic cations on bentonite were exchangedwith Li+, and then part of the Li+were further exchanged with tetramethylammonium cation(TMA+); After that the samples were heated to make sure most of the Li+were transferred tobentonites’ sheets, finally make sure that TMA+fully replace the rest Li+between the layers.Compared to the original method (i.e., first reducing the charge density and then exchangingTMA+), the layer charge of bentonite can be effectively reduced while the layers of bentonitecan be preserved by pre-exchanged TMA.(2) The potential mechanisms for the enhanced sorption of HOCs on the reduced chargeTMA-bentonite were proposed. The resulting organobentonites showed larger surface areasand better adsorption capacity than those synthesized using traditional method. the siloxane surface adsorption sites of the interlayer exposed is greatly increased and then enhance theadsorption capacity of organobentonites towards HOCs.For example, in the case oforganobentonite with20%TMA, the one synthesized using new method has almost twice thesurface areas as the one synthesized using traditional method (236m2/g vs131m2/g).(3) The results found the sorption capacity of the bentonites heated for HOCs isenhanced. In this work, TMA-bentonite and K-bentonite are heated in the condition of145℃,then interlayer water are removed, the interlayer from the hydrophilic environmentto hydrophobic environment of hydrophobic, enhancing sorption capacity for HOCs.Adsorption capacity of bentonite with heating dehydration towords to HOCs depends on thehydration ability of interlayer ions, the adsorption capacity of TMA-bentonite after heatedincreased by38.5%, K-bentonite increased by9.3%,The clay interlayer ions hydration abilityof bentonites is more weaker,the water absorption hysteresis effect of bentonites heateddehydration is more significant.