Influencing factors and controlled release kinetics of H2O2 from PVP-coated calcium peroxide NPs for groundwater remediation

Abstract

Calcium peroxide nanoparticles (nCP) as a versatile and safe solid source of hydrogen peroxide (H₂O₂) receive substantial attention from researchers as a potential groundwater remediation reagent. In this study, we synthesized polyvinylpyrrolidone-coated calcium peroxide nanoparticles (PVP@nCP-PVP) to control the release rate of H₂O₂ and modulate pH fluctuation simultaneously. The PVP@nCP-PVP is fully characterized and the H₂O₂ releasing kinetics and mechanisms are investigated. The H₂O₂ release longevity of nCP increased with the concentration of controlled release material (CRM) encapsulated shell, while the production of H₂O₂ decreased inversely. The acidic condition is favorable for increasing H₂O₂ production by promoting the complex decomposition of nCP. The low temperature prolonged the longevity of nCP and suppressed the competitive side reaction for producing O₂. The release of H₂O₂ is consistent with zero-order reaction kinetics and the release of O₂ is consistent with first-order reaction kinetics. At last, different nCP composites were employed to construct a Fenton-like system for the degradation of nitrobenzene (NB). The degradation rate was raised from 57.6% by Fe (II)/nCP to 70.0% and 93.7% by Fe (II)/nCP-PVP and Fe (II)/PVP@nCP-PVP systems, respectively. These findings demonstrate that PVP@nCP-PVP has significant advantages in repairing organically contaminated groundwater.

Environmental implication

Groundwater contamination poses a great threat to human health and ecosystems. In-situ chemical oxidation (ISCO) is a widely used groundwater remediation technology. Calcium peroxide (CP) as solid hydrogen peroxide showed merits of low cost and high stability, but the further application was limited due to its violent chemical reaction and short longivity in groundwater . In this work, we prepared polyvinylpyrrolidone-coated controlled release nCP (PVP@nCP-PVP) for modulating the release of H₂O₂. The investigation of H₂O₂ release kinetics under various environmental conditions enhances the understanding of the inherent relationship between the H₂O₂ release performance of controlled-release materials and contamination remediation. The feasibility using macromolecules preparing controlled-release oxidizing agents was confirmed, providing a novel solution for groundwater contamination remediation.