Hydrothermal Synthesis of Zn-Smectites

Abstract Two varieties of Zn-smectite were synthesized hydrothermally: sauconite, with an ideal composition of Na 0.4 Zn 3 (Si 3.6 Al 0.4 )O 10 (OH) 2 · n H 2 O; and a Zn equivalent of hectorite, with an ideal composition of Na 0.4 (Li 0.4 Zn 2.6 )Si 4 O 10 (OH) 2 · n H 2 O (referred to here as Zn-hectorite). For comparison, hydrothermal synthesis of the related trioctahedral smectites of hectorite, Na 0.4 (Li 0.4 Mg 2.6 )Si 4 O 10 (OH) 2 · n H 2 O and hectorites containing Cu, Co or Ni in the octahedral sheets instead of Mg were also attempted. The results showed that sauconite, Zn-hectorite and hectorite could be synthesized in the temperature range 100–125°C but hectorites containing Cu, Co or Ni in the octahedral sheet, under the same conditions or even at a temperature of 150°C, could not.