The Effect of Heat Treatments on the Total Charge and Exchangeable Cations of Ca-, Na-, and Li-Saturated Kaolinite

Abstract

Abstract--The effect of heat treatments on the total charge and water adsorption by Ca-, Na-and Lisaturated kaolinite was studied using extraction techniques and thermal gravimetric analysis, respectively. Measurements of cation exchange capacity indicated that the total charge of Li-kaolinite was reduced by approximately 50% after heating to 110 or 130~ In contrast, the total charge of Ca-kaolinite remained essentially constant while that of Na-kaolinite decreased slightly. Water adsorption and desorption on Ca-and Li-kaolinite following heat treatments at 150~ were consistent with the total charge of the respective kaolinites. Ion extraction of Li-kaolinite using NH4C1 revealed that only 6% of the Li remained exchangeable after heating, while A1 and H were released. Thus, non-exchangeable Li ions not only reduced the total charge of the kaolinite but also displaced AI and H from the kaolinite structure. Infrared spectroscopy also indicated that Li migrated into the kaolinite structure and replaced a portion of the A1 from the octahedral sheet. The results presented here indicate that Li-kaolinite represents a surface of reduced charge rather than a surface free of cation-hydration effects. Therefore, Li-kaolinite is not recommended as a reference for the study of vapor-phase adsorption, and conclusions based on such a reference material should be reevaluated.

Silver Dissolution and Release from Ceramic Water Filters

“…Due to the high clay content of the filter material, cation exchange reactions could play an important role in Ag + transport and release. Based on a Ca 2+ / Mg 2+ batch exchange method, the CEC of the crushed ceramic filter material was determined to be 5.2 ± 0.4 mequiv/100 g, consistent with CEC values reported for representative kaolinite clay minerals (2.4−4.2 mequiv/100g) 28 and natural soils (2−50 mequiv/100 g). 32 The CEC of intact ceramic disks, determined by saturation and extraction of exchanged Ca 2+ , was 4.2 mequiv/100g (Figure 2A).…”

“…The CEC of the disk material was determined using both crushed and intact disks. CEC of crushed samples was determined by a Ca/Mg batch exchange method using the methods of Pennell et al 28 CEC of the intact disk was measured by first flushing the filter disk with 25 PV of 1 M Ca(NO 3 ) 2 to saturate exchange sites with Ca 2+ . The disk was rinsed with 10 PV of ethanol to remove excess salt, and then flushed with 60 PV of 0.5 M Mg(NO 3 ) 2 to exchange and recover Ca 2+ .…”

“…The CEC of the disk material was determined using both crushed and intact disks. CEC of crushed samples was determined by a Ca/Mg batch exchange method using the methods of Pennell et al 28 then flushed with 60 PV of 0.5 M Mg(NO 3 ) 2 to exchange and recover Ca 2+ . In addition, the capacity of an intact filter disk to exchange Ag + was determined by introducing 25 PV of 1 M AgNO 3 , followed by a DI water rinse (AgNO 3 is reduced by ethanol to produce precipitates) and 60 PV of 0.5 M Mg(NO 3 ) 2 .…”

Mullite–β‐Spodumene Composites from Aluminosilicates

“…Kaolin particles also carry exchangeable cations on the external basal surfaces. [27][28][29] The particles can become trapped in the interlamellar region or in the channels formed along the edges of layered kaolinite. Sometimes, natural kaolinite contains stacks (book of kaolin) that also can act as cation traps.…”

THE ADSORPTION OF [Au(HS)2] ON KAOLINITE SURFACES: QUANTUM CHEMISTRY CALCULATIONS

“…Interactions at solid-liquid interfaces are considered to be important in governing the transport of a number of trace and major elements in natural systems. Many investigations of cation and anion adsorption on kaolinite surfaces have been undertaken, and most of these ions are of environmental interest, such as divalent cobalt, divalent cadmium and organic acids (Pennell et al 1991, Angove et al 1998, Ward & Brady 1998. However, adsorption of Au-bearing complex ions onto claymineral surfaces has barely been studied; moreover, whether the complex ion is present in chemical combination with clay minerals or whether it occurs as a result of electrostatic interaction remains controversial.…”