Use of Crushed Limestone to Neutralize Acid Wastes

by Frank H. Pearson, (A.M.ASCE), Research Asst.; Land and Water Research Inst., Pennsylvania State Univ., University Park, Pa.,
Archie J. McDonnell, (A.M.ASCE), Professor of Civil Engineer and Dir. of Water Center; Land and Water Research Inst., Pennsylvania State Univ., University Park, Pa.,

Serial Information: Journal of the Environmental Engineering Division, 1975, Vol. 101, Issue 1, Pg. 139-158

Document Type: Journal Paper


To provide for the rational design of limestone neutralization processes, the kinetics of the chemical reactions involved were evaluated by experiment, and an analysis made of the chemical and physical boundary conditions that control the extent to which the reactions are completed. The rate limiting reactions are the attack of limestone by hydrogen ions, and the exsolution of carbon dioxide which is thereby generated; the latter reaction has an increasing effect on process effciency above pH 5. Rate constants for the limiting reactions were evaluated each as a function of temperature, ionic strength, water turbulence, and for the first reaction bicarbonate ion concentration, which catalyzes the attack of limestone by hydrogen ions. A mathematical model of limestone neutralization processes was simplified to obtain a graphical procedure for the process design for neutralization. These graphs indicate the quantity of crushed limestone of given size that is required to neutralize a specified flow of acid waste from the initial pH to the required final pH.

Subject Headings: Chemical processes | pH | Limestone | Acids | Recycling | Hydrogen | Kinetics | Boundary conditions

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