1Defence Research and Development Establishment 2Defence Research and Development Establishment 3Defence Research and Development Establishment 4Defence Research and Development Establishment 5Defence Research and Development Establishment
Samples of active carbon of 1150 m2/g surface area were impregnated with ammoniacal salts of copper, chromium and silver,with and without triethylenediamine. The samples of impregnated carbon were aged at 50oC, with and without 90% RH(relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium(VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. Thesevalues were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retardwas significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsiblefor the reduction of chromium (VI) and coper (II) species in impregnated carbons. The prolonged ageing of the samples withand without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction ofchromium (VI) was very low, i.e. 5-10% and of coper (II) was 2-25%. Silver is not reduced due to carbon, as it remainedunchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were agedconcentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).