Oxygen consumption test to evaluate the diffusive flux into reactive tailings: interpretation and numerical assessment

Abstract

The oxygen consumption (OC) test is conducted on sulphide tailings by measuring the decline of oxygen concentration in a closed headspace, at the top of a cylinder, as a result of diffusion and oxidation reactions. For a short-duration test, the measurements may be interpreted using a simplified analytical method based on modified Fick’s laws, which provides the combined value of the effective oxygen diffusion (De) and reaction rate (Kr) coefficients of the tailings. This lump value can be used to evaluate the steady-state oxygen flux entering the exposed sulphide tailings. In this paper, a numerical parametric study is performed to investigate the effect of test duration and headspace height, h, on results obtained from OC tests. The assessment also considers tailings with different values of De and Kr. The results indicate that the simplified interpretation method usually tends to underestimate the surface oxygen flux, in proportions that depend on the testing conditions. Results from this study can be used to estimate the relative precision of the oxygen flux for specific conditions, thus helping practitioners decide how to best interpret testing measurements for a given application.