Studies on the dissolution characteristics of airborne particulates generated during the separation and powdering of monazite, using simulated lung serum

Dissolution half-life of the airborne particulates generated during separation and powdering of monazite, has been studied. The particulates were collected on Glass fibre filter paper using air sampling pumps of suction rate of 60 lpm, for a period of 30 to 60 minutes. The samples were preserved for a period of one month to allow for the decay of the short lived components. The long lived alpha activity was determined using an alpha counter. The air filter samples were mounted in Perspex coupling and immersed in simulated lung serum. The samples were taken out at regular intervals and the retained activity was determined. The observed activity at different time intervals were fitted in an equation of the form At= Ao e-λt, after refining the data by least square fitting. From known values of At, Ao and λ, the dissolution half-life was calculated. It was found that airborne particulates for the mineral separation plant has dissolution half-life of 693±68 days and that from monazite powdering area the dissolution half-life 97 ± 8 days. The study is useful in modifying the ALI and DAC values applicable for these plants. (author)