Leaching Behavior of Fossil Fuel Wastes: Mineralogy and Geochemistry of Calcium
- PDF / 861,724 Bytes
- 13 Pages / 420.48 x 639 pts Page_size
- 59 Downloads / 174 Views
LEACHING BEHAVIOR OF FOSSIL FUEL WASTES: MINERALOGY AND GEOCHEMISTRY OF CALCIUM DHANPAT RAI, L.E. EARY, S.V. MATTIGOD, C.C. AINSWORTH and J.M. ZACHARA Battelle, Pacific Northwest Laboratories, P. 0. Box 999, Richland, Washington 99352 Received 11 December, 1986; refereed ABSTRACT A literature review [1] of the leaching behavior of inorganic constituents contained in fossil fuel wastes indicated that most of the available information deals primarily with (1) determination of the elemental composition of different wastes, (2) examination of the physical characteristics of waste solids, and (3) empirical leaching studies involving different solutions and procedures (e.g., water, acids, extraction procedure, toxicity characteristic leaching procedure). A comprehensive mechanistic approach and data are needed to predict accurately the composition of pore waters from fossil fuel wastes. An approach that relates the aqueous concentrations in leachates to solubility-controlling or adsorption-controlling solid phases- in the wastes is described. The behavior of calcium is used as an example to show the relevance of existing data to predicting leachate composition and to identify the type of data needed. The application of this approach to pore waters from flue gas desulfurization sludge shows that Ca concentrations can be accurately predicted from the nature of the Ca solids present and the thermo-chemical data descriptive of precipitation/dissolution and complexation reactions. INTRODUCTION Fossil fuel wastes contain many chemical constituents,
some of which may
become mobile and adversely affect groundwaters and surface waters. Safe and effective disposal procedures require the ability to predict the leaching behavior of various waste constituents under different environmental and disposal conditions. A large volume of literature pertaining to fossil fuel wastes exists. However, most of this literature deals with (1) the elemental composition of different wastes, (2) the physical characteristics of waste solids, and (3) empirical leaching studies involving different solutions and procedures (e.g., water, acids, extraction procedure, toxicity characteristic leaching procedure) [1]. Seriously lacking at the present time is a compreehensive mechanistic approach and requisite thermochemical descriptors that can be used to (1) develop a generic capability for predicting the leaching behavior of elements contained in fossil fuel wastes, (2) show the relevance of the existing data to developing such a capability, and (3) identify and develop the data needed for such a capability. To develop the ability to predict pore water concentrations of inorganic elements in fossil fuel wastes, mechanistic data on precipitation/dissolution and adsorption/desorption reactions in the given system are required. For redox-sensitive elements, data on the kinetics of redox transformations are also needed to determine the distribution of redox species and their precipitation/dissolution and adsorption/desorption reactions. A schematic of the mec
Data Loading...
