Properties of calcium peroxide for release of hydrogen peroxide and oxygen: A kinetics study

• CaO2 can react with water to form O2 directly without the intermediate of H2O2.
• The release kinetic pattern for H2O2 was pseudo-zero-order.
• The release kinetic pattern for O2 was pseudo-first order.
• Increasing temperature and decreasing pH accelerate both O2 and H2O2 release rates.
• Increasing temperature and pH decrease the H2O2 yield and increase the O2 yield.

Calcium peroxide (CaO2), as one of the solid peroxides, has been increasingly used in contaminated site remediation due to its ability to release oxygen (O2) and hydrogen peroxide (H2O2). Biodegradation can be enhanced by the existence of O2. Hydrogen peroxide can be used to for in situ chemical oxidation via the modified Fenton. Previous studies show inconsistent results about O2 and H2O2 release during CaO2 decomposition. Additionally, the release characteristics of O2 and H2O2 are not evaluated in detail.A series of batch experiments was conducted to investigate the properties of CaO2 decomposition and the release kinetics of O2 and H2O2. O2 and H2O2 were released directly from CaO2 dissolution and H2O2 was not an essential intermediate in the conversion of CaO2 to O2. The two release paths formed a parallel reaction system, with a competitive relationship between the two paths. The release of H2O2 and O2 followed a pseudo-zero-order kinetics pattern and a pseudo-first-order kinetics pattern, respectively. Increasing temperature and decreasing pH could accelerate both O2 and H2O2 release rate. However, increasing temperature could decrease the H2O2 yield and increase the O2 yield, which were similar to the impact of increasing pH.