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Mathematical Modeling of Leaching of Heavy Metals from Biofilm Coated Cement Based Waste Forms

Norman W. Loney, Mojdeh Tabatabaie, and Rachna Jaiswal. Department of Chemical Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ 07102

Solidification/stabilization processes have been used to immobilize heavy toxic metals in contaminated wastes for decades. These processes are designed to protect the environment from the harmful impacts of disposed hazardous wastes. Cement based solidification/stabilization of wastes containing heavy metals has been widely practiced. The stability of the captured heavy metals in cement based forms has been investigated under different physical, chemical and biological conditions. Experimenters have observed that under certain acidic conditions, a significant number of heavy metals in substantial amounts can be leached from refined biofilm-coated cement based waste forms. In order to explain the controlling mechanism in this leaching process, a mathematical model is proposed. The proposed model is developed for cylindrical geometry with the Michaelis-Menten kinetics as the primary mechanism controlling the leaching process. The primary species concentration profile will be derived analytically by first using a regular boundary perturbation followed by separation of variables or Laplace transforms as appropriate.