Mathematical modelling of radionuclides removal from the water by the method of coprecipitation

A coprecipitation process in an apparatus under conditions of continuous water purification is analysed. Process is described by the set of balance equations defining a change of radionuclides and carrier mass in the volume of liquid and solid phase within the system. The productivity of the apparatus, concentrations degree and coefficient of distribution are defined as parameters to be optimized. The mathematical model was applied to the case of radioactive 85Sr removal from the water by the coprecipitation with BaCO3. Laboratory water treatment process consisted of three basic operations: precipitation, flocculation and separation. For the mixing of reagents pipe mixer with injection nozzles was used. Flocculation and separation process occured in the fluidized sludge blanket clarifier. Experimental results showed that mass transfer of carrier and radionuclide was completed very fast (t = < 1 min) and radioactivity removal of about 99% was achieved. Parameters of the mathematical model were experimentally determined and basic outlet characteristics of the process were calculated. Outlet characteristics of the progress were represented graphically as a functions of the inlet suspension flow. The results enabled optimal choice of working regime in the apparatus. (Author)