Na-4-mica: simplified synthesis from kaolinite, characterization and Zn, Cd, Pb, Cu and Ba uptake kinetics

A swelling Na-4-mica of the brittle mica type (ideal chemical composition of Na4Mg6Al4Si4O20F4·xH2O) was prepared by a simplified one-step synthetic process from kaolinite at or below 800 °C. Hydrated and well-dispersed Na-4-mica particles of about 2 µm in size were prepared at 800 °C. The 27Al MAS-NMR spectrum of this mica showed that almost all Al was in tetrahedral coordination while the 29Si MAS-NMR spectrum showed that the nearest neighbor environment of Si was mainly Si(3Al), as expected based on the Si ∶ Al molar ratio of 1 ∶ 1 in the Na-4-mica. The CEC of the mica was determined to be 447 mequiv (100 g)−1. With this Na-4-mica, the Zn, Cd, Pb, Cu and Ba uptake kinetics were investigated in a 0.5 M NaCl background solution at room temperature and were found to be quite rapid.