Kinetics and stoichiometry of oxygen release from solid peroxides

Abstract

The increased interest in in situ bioremediation has fostered a commensurate increase in interest in soil chemical amendments. These amendments increase the level of one or more limiting nutrients in the natural environment. Along with the conventional constituents such as nitrogen and phosphorus, oxygen (O2) is an important, often limiting, compound in both flooded and subsurface soils. Chemical formulations have been developed to provide oxygen to these anoxic environments. We evaluated, in distilled water, the release rates of four chemical compounds formulated for the slow release of oxygen that may be used to enhance bioremediation. The release rates were determined by polarographic measurement of the O2 concentration over time in sealed batch reactors. The acquired analog data were converted to digital and logged to a computer. This research addressed the questions of release rates and oxygen-to-solid ratios. Probability of migration into the soil is evaluated on the basis of particle size. We developed a predictive model for the release of oxygen from these solid additives. The four oxidants were sodium percarbonate (Na2Co3·1.5H2O2)-encapsulated in polyvinylidene chloride (PVDC); free sodium percarbonate crystals; calcium peroxide (CaO2); and magnesium peroxide (MgO2). The highest calculated release rate was generated by the unencapsulated Na2CO3·1.5H2O2 (132 mgl-1h-1). MgO2 had the lowest release rate (1.57×10-3 mgl-1h-1). The data indicated that MgO2, or a mix of MgO2 and CaO2, hold the highest promise for use in saturated surface soil applications.