Developing novel persulfate pellets to remediate BTEXs-contaminated groundwater

Abstract

Organic-contaminated groundwater poses a growing threat to environmental sustainability and human health. As a passive plume control technology, permeable reactive barriers (PRBs)have become a popular method for groundwater pollutants degradation due to their cost-effective and sustainable merits. However, active materials adopted in conventional PRBs have the shortcomings of easy deactivation and speedy consumption. As an alternative, slow-release materials can be used as PRBs fillers to treat contaminated groundwater because of their long chemical release time. In this study, novel slow-release persulfate pellets were prepared and tested for their release capabilities and effectiveness in the remediation of groundwater organic pollution. Results show that each pellet's release efficiency and average release rate within 14 days were 87.36 % and 46.80 mg-persulfate/d, respectively, when the mass ratio of sodium persulfate to paraffin was 3/1. Dissolution and diffusion via pores are the main mechanisms of the persulfate delivery from slow-release pellets in water. Moreover, solution pH, ionic species and addition of quartz sand into release pellets play dissimilar effects on the release kinetics. Results from column experiments indicate that the pellets could expand the PS influence range in the barrier and continuously remediate BTEXs-contaminated groundwater (initial concentration of each compound = 50 mg/L) and reach 64.2–85.1 % removal efficiency. The results of electron spin resonance (ESR) spectroscopy show that both SO4− and OH contribute to the removal of BTEXs. This study demonstrates the potential feasibility of slow-release persulfate materials for groundwater pollution treatments by PRBs, which inspires for future field applications.