Release mechanism of sustained-release persulfate materials based on stearic acid

Polycyclic aromatic hydrocarbons (PAHs) in groundwater demonstrate poor degradability and wide contamination plumes. The widely utilized in-situ chemical oxidation technology can effectively oxidize and degrade PAHs in groundwater. However, conventional in-situ chemical oxidation for PAHs in groundwater faces challenges including rapid reaction of oxidants and potential rebound of pollutant concentrations. Therefore, there is a current need to develop novel sustained-release oxidants. This study developed persulfate release materials (PDS@SA) by blending sodium persulfate (PDS) with stearic acid (SA) at different mass ratios. Batch and column experiments were conducted to investigate the influence of mass ratio and particle size on the PDS release process. The results revealed that the mass ratio of PDS in PDS@SA was positively correlated with the cumulative release percentage of PDS, as well as the intermediate release rate and the final decomposition rate of PDS. The particle size of PDS@SA was directly proportional to the release lifespan of PDS, while inversely proportional to the total release amount of PDS. The release mechanisms was examined by Bhaskar and Rigter-Peppas models. The results were further validated by fitting with a dual boundary dissolution-diffusion model, which predicted the release lifespan of PDS@SA with different particle sizes with a PDS:SA ratio of 1:3. The prediction indicated that PDS@SA with particle sizes of 30 and 40 mm exhibited good sustained-release performance and significantly mitigated burst release effect. Compared to traditional methods of directly oxidizing organic matter in groundwater using activated persulfate, this study achieves enhanced controlled release and prolonged lifespan.