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Role of Smectite Quasicrystal Dynamics in Adsorption of Dinitrophenol

^a Dep. of Crop and Soil Sciences, Michigan State Univ., East Lansing, MI 48824-1325
^b USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011
^c Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
^d Dep. of Agronomy, Lilly Hall, Purdue Univ., 915 W. State St., West Lafayette, IN 47907-2054

View larger version (6K): [in this window] [in a new window]   Fig. 1. Structural formula and ionization of 4,6-dinitro-o-cresol (DNOC) below and above the acid dissociation constant (pKa).

View larger version (17K): [in this window] [in a new window]   Fig. 2. Suspension x-ray diffraction pattern of (A) freeze-dried and (B) never-dried K-saturated Wyoming montmorillonite (K-SWy-2) with added 4,6-dinitro-o-cresol (DNOC).

View larger version (18K): [in this window] [in a new window]   Fig. 3. X-ray diffraction pattern of (A) air-dried K-saturated Wyoming montmorillonite (K-SWy-2) at 54% relative humidity (RH) and (B) oven-dried (105°C) K-SWy-2 at 0% RH with or without added 4,6-dinitro-o-cresol (DNOC).

View larger version (16K): [in this window] [in a new window]   Fig. 4. Suspension x-ray diffraction pattern of (A) freeze-dried and (B) never-dried K-saturated Arizona montmorillonite (K-SAz-1) with added 4,6-dinitro-o-cresol (DNOC).

View larger version (17K): [in this window] [in a new window]   Fig. 5. X-ray diffraction pattern of (A) air-dried K-saturated Arizona montmorillonite (K-SAz-1) at 54% relative humidity (RH) and (B) oven-dried (105°C) K-SAz-1 at 0% RH with or without added 4,6-dinitro-o-cresol (DNOC).

View larger version (15K): [in this window] [in a new window]   Fig. 6. Suspension x-ray diffraction pattern of (A) freeze-dried and (B) never-dried Ca-saturated Wyoming montmorillonite (Ca-SWy-2) with added 4,6-dinitro-o-cresol (DNOC).

View larger version (16K): [in this window] [in a new window]   Fig. 7. X-ray diffraction pattern of (A) air-dried Ca-saturated montmorillonite (Ca-SWy-2) at 54% relative humidity (RH) and (B) oven-dried (105°C) Ca-SWy-2 at 0% RH with or without added 4,6-dinitro-o-cresol (DNOC).

View larger version (15K): [in this window] [in a new window]   Fig. 8. Suspension x-ray diffraction pattern of (A) freeze-dried and (B) never-dried Ca-saturated Arizona montmorillonite (Ca-SAz-1) with added 4,6-dinitro-o-cresol (DNOC).

View larger version (16K): [in this window] [in a new window]   Fig. 9. X-ray diffraction pattern of (A) air-dried Ca-saturated Arizona montmorillonite (Ca-SAz-1) at 54% relative humidity (RH) and (B) oven-dried (105°C) Ca-SAz-1 at 0% RH with or without added 4,6-dinitro-o-cresol (DNOC).

View larger version (10K): [in this window] [in a new window]   Fig. 10. Schematic diagram showing the interaction between 4,6-dinitro-o-cresol (DNOC) and smectite quasicrystals. In suspension, DNOC is adsorbed on surfaces of individual layers and external surfaces of quasicrystals. On drying, the phenolate form of DNOC disrupts formation of large Ca-smectite quasicrystals but the neutral form of DNOC and neutral K-saturated DNOC complexes fit in the interlayers of smectite quasicrystals. The lines represent smectite lamellae, open dots represent phenolate DNOC molecules, black dots represent neutral form of DNOC, and K indicates K ions that form complexes with the phenolate form of DNOC. Not shown are exchangeable cations or water molecules. pKa is the acid dissociation constant.