Atomic force microscopy (AFM) makes it possible to directly detect morphological changes on the surface of a zeolite that are due to dissolution when the crystal is immersed in either an alkaline (0.1 N NaOH) or acidic (0.2 N H2SO4) aqueous solution at room temperature. The AFM images revealed for the first time that for heulandite (a natural zeolite crystal) (i) NaOH attacked the uppermost layer of aluminosilicate of the (100) surface, leaving isolated or agglomerated islands, (ii) similarly, H2SO4 attacked the (010) surface, forming pits, and (iii) step retreat did not occur for either solution. This unique dissolution pattern, in which the aluminosilicate layers of heulandite dissolve from terraces layer-by-layer, results from the characteristic pore structure of heulandite. This microscopic-level analysis should prove vital in the further development of new zeolite structures, which are critical to the activity of this important class of materials.

<p>Polar organic chemical integrative samplers (POCIS) are promising devices for measuring time-weighted average concentrations of hydrophilic compounds in aquatic environments. However, the mechanism of POCIS uptake remains unclear. This study characterizes the permeation properties of polyethersulfone and polytetrafluoroethylene and the sorption properties of Oasis HLB (Waters), Envi-Carb (Supelco), and Oasis WAX (Waters) under identical conditions via calibration experiments of the POCIS. Plant protection products, neonicotinoid herbicides, and linear alkyl benzene sulfonates (LAS) were tested. The permeation experimental results suggested that the penetration rate constants (<i>k</i>_m) with high <i>K</i>_ow values (<i>K</i>_ow: octanol–water partition coefficient) were low, which indicated that the sorption of chemicals on the membrane may constitute a limiting factor for the permeation. The sorption experiments indicated that the sorption rate constants (<i>k</i>_s) depended on the type of sorbent instead of the <i>K</i>_ow values. Low <i>k</i>_s/<i>k</i>_m ratios were obtained for chemicals with low <i>K</i>_ow values, which implied that the POCIS uptake for highly hydrophilic compounds was controlled by both membrane and sorbent kinetics. The <i>k</i>_m and <i>k</i>_s values corresponded to the model and predicted the values of the sampling rates<i> </i>(<i>R</i>_s) for the LAS. These findings revealed the possibility of using <i>k</i>_s and <i>k</i>_m values to predict <i>R</i>_s values.</p>