Clays may catalyze chemical reactions by acting as Brönsted acids, Lewis acids, and/or Lewis bases. The changes occurring when limonene (p-menthadiene) is heated in the presence of montmorillonite illustrate how Brönsted and Lewis acidity may operate competitively, the nature of the interlayer cations determining which reaction dominates. The rate at which the starting material disappears increases with the acidity of the clay, which depends upon the interlayer cations (Na < Mg < Al < H). The concentration of disproportionation and isomerization products reaches a maximum after reaction times which decrease with increasing surface acidity of the clay, p-cymene is produced by oxidation in concentrations inversely related to the surface acidity of the clay. The course of the chemical reaction can thus be steered in the preferred direction by an appropriate choice of interlayer cations.

Zeolites and other open framework materials provide a powerful tool for remediation and solidification of a range of cationic wastes (e.g.${\text{NH}}_4^{+}$${\rm{NH}}_4^ + $, Pb2+) due to the combined properties of large surface area and cation exchange capacity. However, practical barriers exist to the continued expansion of their use, including handling issues related to the fine particle size, and continued ion exchange following waste adsorption. This study examines the synthesis and characterization of zeolites adhered to a muscovite mica wafer, in order to assess if practical benefit can be derived from the preparation of layered composite materials. The paper demonstrates that increased metal adsorption, as demonstrated by surface chemical composition, can be induced in regions by growth of zeolite on and within the lamellar structure of the matrix. X-ray diffraction studies suggest that a site-specific crystallization mechanism controls the zeolite type and extent of growth, thereby reducing control over the zeolites prepared. However, although increased adsorption has been introduced to the mica, the amount of zeolite added is small (<50 mg per gram of muscovite), and thus any adsorption is very limited.

Greenhouse and laboratory studies were conducted to determine the physiological basis for selectivity of nicosulfuron and primisulfuron in 5 plant species. Differential sensitivity of the species was quantified by determining GR50 values (herbicide rate required to reduce plant growth 50%) for each species/herbicide combination. GR50 data indicated the following levels of sensitivity: corn—tolerant to both herbicides; seedling johnsongrass—sensitive to both herbicides; barnyardgrass—sensitive to nicosulfuron and tolerant to primisulfuron; giant foxtail—sensitive to nicosulfuron and tolerant to primisulfuron; and eastern black nightshade—tolerant to nicosulfuron and sensitive to primisulfuron. Studies using 14C-radiolabeled herbicides were conducted to determine whether differential herbicide absorption, translocation, or metabolism contributed to whole plant responses. Nicosulfuron and primisulfuron selectivity in corn, johnsongrass, barnyardgrass, and giant foxtail was primarily due to differential herbicide metabolism rate. Tolerant species metabolized the herbicide more rapidly and extensively than sensitive species. Differential herbicide absorption, translocation, or metabolism did not explain differential sensitivity of eastern black nightshade to the herbicides. Further studies indicated that the tolerance of eastern black nightshade to nicosulfuron and its sensitivity to primisulfuron was directly related to lower sensitivity of the acetolactate synthase (ALS) to nicosulfuron than to primisulfuron. Eastern black nightshade translocated very little (3%) of the nicosulfuron applied. The ALS sensitivity of johnsongrass and eastern black nightshade was similar in the presence of nicosulfuron. A combination of a higher ALS level and less herbicide translocation contributes to tolerance of eastern black nightshade and to sensitivity of johnsongrass to nicosulfuron.