Activated carbon is produced from coconut shell char using steam
or carbon dioxide as the
reacting gas in a 100 mm diameter fluidized bed reactor. The
effect of process parameters such
as reaction time, fluidizing velocity, particle size, static bed
height, temperature of activation,
fluidizing medium, and solid raw material on activation is studied.
The product is characterized
by determination of iodine number and BET surface area. The
product obtained in the fluidized
bed reactor is much superior in quality to the activated carbons
produced by conventional
processes. Based on the experimental observations, the optimum
values of process parameters
are identified.
A method has been developed for the removal of cesium from the aqueous radioactive waste using a composite ion-exchanger consisting of Copper-Ferrocyanide Powder (CFC) and Polyurethane (PU) Foam. Polyvinyl acetate has been used as a binder in the preparation of CFC-PU foam. The physical properties of CFC such as density, surface area, IR stretching frequency and lattice parameters have been evaluated and also its potassium and copper(lI) content have been estimated. Optimization of loading of CFC on PU foam has been studied. The CFC-PU was viewed under microscope to find out the homogeneity of distribution. Exchange capacities of the CFC-PU foam in different media have been determined and column studies have been carried out. Studies have been undertaken on extraction of cesium from CFC foam and also on digestion of spent CFC-PU foam and immobilization of digested solution in cement matrix. The cement matrices have been characterized with respect to density, bio-resistance and leaching resistance.
Sorption data analysis was carried out using the Freundlich, Langmuir, and Modified Freundlich isotherms for the uptake of sodium and potassium in an initial concentration range of 10-100 mg/L on backfill materials, viz., bentonite, vermiculite, and soil samples. The soil samples were collected from a shallow land disposal facility at Kalpakkam. The Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of K + by all the selected backfill materials. The Modified Freundlich isotherm equation is validated as a preferred mathematical tool for representing the sorption of Na + by the soil samples. Since a negative sorption was observed for the uptake of Na + by commercial clay minerals (vermiculite and bentonite clay in the laboratory experiments), sorption analysis could not be carried out using the above-mentioned isotherm equations. Hill plots of the sorption data suggest that in the region of low saturation (10-40 mg/L), sorption of K + by vermiculite is impeded by interaction among sorption sites whereas sorption by soil and bentonite clay is enhanced by interaction among sorption sites. In the region of higher saturation (60-100 mg/L), sorption of K + by all three backfill materials is enhanced by interaction among sorption sites. The Hill plot of the sorption data for Na + by soil suggests that irrespective of Na + concentration, sorption of Na + at one exchange site enhances sorption at other exchange sites.
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