O2, CH4 and CO2 gas retentions by acid smectites before and after thermal treatment

Acid smectites in natural condition and after thermal treatment up to 900 °C were studied for their O2, CH4 and CO2 gas retentions at 25 °C and 1 kg/cm2. Two smectites, one dioctahedral and one trioctahedral, were treated with 5.0 N sulphuric acid solution for 15 and 60 min. The gas adsorptions by the smectites increased after acid treatments. The O2 (0.014–0.030 mmol/g) and CH4 (0.045–0.063 mmol/g) gas retention values were small whereas the values corresponding to CO2 (0.206–0.357 mmol/g) retentions were high for acid smectites. The acid trioctahedral smectite showed higher gas adsorption values than acid dioctahedral smectite. The CO2 gas adsorption values by acid smectites heated up to around 600 °C, decreased around 10% and 20% for acid trioctahedral and dioctahedral smectites, respectively. After that drastically decreased and at 900 °C both acid smectites showed very small adsorption values. The chemical composition, the structure and the texture of the smectites influenced the gas retention.