Kinetics of Permanganate Consumption by Natural Oxidant Demand in Aquifer Solids

Effectiveness of permanganate (...) injection for in situ chemical oxidation is often controlled by the natural oxidant demand (NOD) of the aquifer solids. In this work, a simple procedure was developed and applied to generate a database of NOD kinetic parameters for six different models for 50 different aquifer materials. Representing oxidant consumption as an initial instantaneous reaction with a portion of the total NOD and as a second order reaction between ... and the remainder of the NOD provided a good match with experimental results from batch studies, without imposing an unnecessary computational burden. Wide variations in NOD parameters were observed including total NOD, fraction fast/instantaneous, and second order rate coefficients. Approximately 80% of the samples had a total NOD between 0.002 and 0.158 mmol/g with a median value of 0.028 mmol/g. Most of the NOD present was slow reacting, so ... could persist for weeks to months once the fast reacting fraction is depleted. Total NOD was not correlated with fraction fast/instantaneous or the reaction rate coefficients, thus indicating that NOD reactivity is independent of the total amount of NOD. Results from 48-h NOD measurements were also shown to be poor predictors of total NOD and should not be used to estimate long-term ... consumption.