Synthesis and characterization of transition metal bearing Smectite clays

Abstract

The synthesis of transition metal bearing Smectites was attempted by high and low pressure hydrothermal treatment of mixtures containing HiSi04, NaOH and metal chlorides. For the high pressure samples, hydrothermal conditions consisted of heating to 250°C under 500 psi argon. Low pressure samples were heated to 150°C under argon atmosphere. Two trioctahedral cobalt Smectites were successfully synthesized using both high and low pressure conditions. Synthesis was verified with X-ray diffraction producing a doo1 basal spacing of 15.56 Å, corresponding to a Smectite with two waters of hydration in the interlayer space. Both SEM and TEM analyses were performed, determining the cell formula to be {(Si1.91)(Cos.26)020(0H)4}•Nao.12•2H20. Cation exchange capacities, determined by the UV- visible spectrophotometric analysis of adsorbed [Ru(bipy)3}2+, estimated the amount of interlayer cations as being 0.72 meq/mol. Synthesis of dioctahedral Smectites containing V3+ and Al3+ were unsuccessful at both high and low pressure conditions. This may be due to phase separations and incomplete dissolution of metal chlorides. In addition to the synthetic clays, analyses wereperformed on a suite of natural clay minerals. Electroactive synthetic clay minerals have potential in electroanalytical chemistry and in catalysis. The use of the high pressure cobalt Smectite in the development of a clay modified electrode as an ion sensor was studied.