Investigating the effects of heat activated persulfate on the degradation of furfural, a component of hydraulic fracturing fluid chemical additives

Improper well casings and produced water handling can lead to hydraulic fracturing fluid migration and groundwater pollution. Interactions among the chemical components can cause compositional changes in hydraulic fracturing fluids. This study focuses on degradation or transformations of 3furfuraldehyde (or furfural) by activated-persulfate oxidation, two chemicals reported in hydraulic fracturing additives. As hydraulic fracturing conditions may be conducive to persulfate activation, the degradation of furfural was examined using elevated temperatures, varying persulfate dosing and Fe (III) concentration, initial pH, and the presence of other chemical additives (e.g., a gelling agent and an enzyme breaking agent). Experiments showed furfural degradation using activated persulfate followed pseudo-first order kinetics with respect to the furfural concentration. Impacts of pH and ferric sulfate concentrations were investigated at different temperatures and the results were fit to the Arrhenius model to establish the activation energy. Decreasing the pH to 2.54 caused an increase in the furfural removal. The addition of ferric sulfate to solutions with pH 5.4 had no impact on the activation energy of furfural oxidation, which was 107 kJ mol(-1), while decreasing the pH to 2.54 allowed for the activation energy to decrease to 75 kJ mol(-1). Quenching with methanol and tert-butyl alcohol indicated significant hydroxyl radical contributions to furfural degradation compared to sulfate radicals during thermal persulfate activation in the presence of iron and acidic conditions. Furthermore, furfural degradation was monitored in the presence of other hydraulic fracturing chemical additives establishing furfural degradation does not occur as rapidly. However, furfural does still degrade in this matrix and this indicates that persulfate may break down other chemicals in hydraulic fracturing fluids more preferentially than the target gelling agent. (C) 2017 Elsevier B.V. All rights reserved.