Clay minerals microwave irradiation

Aluminas, silicas, clays, zeolites or graphite can be selected as acidic, basic or neutral supports, depending on the type of reactions. Alumina alone can act as a base towards a acid compounds but if a strong base is necessary, KF on alumina can ionize carbon acids up to pKa = 35. On the other hand, montmorillonites (clays) such as K10 or KSF offer acidities very comparable to strong mineral acids (e.g., nitric and sulfuric acids, respectively). Reactions are simply performed by mixing reagents and a mineral support in the absence of any organic solvent followed by microwave irradiation [52]. 

The present mineral experiments were designed to look at the mineralogical changes that occur as clay components are subjected to each step in this process. The microwave irradiation step in our experiments, however, was not entirely comparable to that in the GE experiments because a smaller, 500-watt unit was used while the 2.0-kW unit was being constructed. Future experiments in our laboratory will monitor clay reactions at higher microwave power levels. 

The clay mineral or mixture was reacted with NaOH for about 20 minutes and then placed in a drying oven at 105 for 5 to 30 minutes to reduce the moisture content. The sample was then removed from the oven, filtered, water washed, and air dried. In a few experiments the caustic-treated clay mixture was filtered to remove excess moisture and then placed in the drying oven the sample was again filtered and water washed. These two sets of experiments evaluated the effect of the treatment steps prior to microwave irradiation. 

The clay mineral or mixture was reacted with the aqueous NaOH solution for about 20 minutes at room temperature and then was irradiated in a Microwave Drying/Digestion System (Model MDS-81, GEM Corporation, P. 0. Box 9, Indian Trail, N.C. 28079) at 500 watts (2.45 GHz) for 30 seconds to 3 minutes. The sample was then filtered, water washed, and air dried. 

The results of experiments in which binary and ternary mixtures of the three clay minerals were reacted with 30% NaOH and irradiated in the microwave oven are summarized in Tables IV and V, respectively. Reacting mixtures of these clay minerals did not result in the... 

---