Aluminum interlayers in layer silicates: Effect of OH/AI ratio of A1 solution, time of reaction, and type of structure: Clays

Abstract--Aluminum intertayers were synthesized under the same experimental conditions in a number of vermiculites and montmorillonites from different sources to determine the effects of the degree of neutralization fAI solutions, the time of reaction, and the ' type of structure. Vermiculite fixed AI as well as hydroxy-Al ions in its interlayers, producing astable 14, ~ spacing and decreasing its cation exchange capacity considerably. Heating the Al-interlayered vermiculite at 300 ~ produced an interstratified mixture, indicating that some interlayers collapsed while others did not. The different collapse was attributed to different charge on vermiculite layers. Neither the aging of vermiculite in AI solutions nor their OH/AI ratios changed the stability of the interlayers appreciably. Montmorillonites, on the other hand, did not fix AI ions but fixed appreciable amounts ofhydroxy-AI ions. In addition, the stability of the interlayers in montmorillonite increased on aging in hydroxy-A1 solutions and exceeded the stability of the interlayers produced in vermiculite. To explain the greater stability of montmorillonite interlayers, it was postulated that the more expanded interlayer space in montmorillonite provides a favorable locale for the organization of hydroxy-A1 ions into gibbsite structure while the restricted expansion i vermiculite prevents it