Effect of temperature and surface area on adsorption of chlorine on different adsorbent carbons

Abstract

Chlorine is used in several ways in industry. In such situations, where residual chlorine persists as pollutant, Activated carbons like animal charcoal, carbon black and coconut charcoal can serve as agents to remove residual pollutant “chlorine” by the process of adsorption. Five samples of Carbon black, six samples of active Carbons and two samples of charcoals were treated with a stream of chlorine @0.4 litre/hour at temperature varying from 300 to 1200 C. Chlorine is adsorbed partially physically and partially chemically. Percentage of the chemisorbed increases with rise in the temperature. Maximum percentages of chemisorptions occur at 1200 C while the maximum uptake, physical as well as chemical, takes place at 300 C, which was the lowest temperature. It is seen that activated carbon, carbon blacks and charcoal differ markedly by in their total chlorine uptake at 300 C. Activated carbons associated with high surface were seen to take up maximum chlorine. Fall in surface area is more in active carbons as compared to carbon black due to greater adsorption of chlorine. This probably shows that micro porous carbons are better adsorbent for chlorine adsorption. The unsaturated sites also play far dominant role and provide centres where the adsorption takes place predominantly. Uptake of chlorine is enhanced on evacuating the carbon samples at 6000 C and 10000 C. This is due to the creation of more unsaturated sites. Process of adsorption cum chemisorption takes place through different kinetic stages with different energetics. The activation energies keep on increasing with increasing amounts of chemisorption.