Transformation of carbon tetrachloride in the presence of sulfide, biotite, and vermiculite

Abstract

Carbon tetrachloride is transformed in aqueous solutions containing dissolved hydrogen sulfide more rapidly in the presence of the minerals biotite and vermiculite than in homogeneous systems. Approximately 80-85% of the CCl4 was transformed to CO2 via the measured intermediate, CS2. Chloroform comprised 5-15% of the products. The remaining 5% of the products were an unidentified non-volatile compound and CO. At 25C, the half-life of CCl4 with 1 mM HS was calculated to be 2600, 160, and 50 days for the homogeneous, vermiculite (114 sq m/L), and biotite (55.8 sq m/L) systems, respectively. The CCl4 transformation rate was found to be dependent on the type and quantity of the solid and the temperature, but was independent of pH and HS(-) concentration above a critical HS(-) concentration. The activation energies (+ or - 95% confidence intervals) were determined to be 122 + or - 32, 91.3 + or - 8.4, and 59.9 + or - 13.3 kJ/mol for the homogeneous, vermiculite, and biotite systems, respectively. The CCl4 transformation rate exhibited first-order behavior with respect to biotite surface area concentration SC(sub biotite) below 55.8 sq m/L. The rate of CCl4 transformation was independent of HS(-) concentration when (HS(-)) = 0.5-4 mM and SC(submore » biotite) = 55.8 sq m/L. Below (HS(-)) = 0.5-4 mM, the rate law was dependent on HS(-) concentration.« less