Self-propelled micromotors based on natural pyrolusite for dynamic remediation of organic contaminated soil

Abstract

For in situ chemical oxidation (ISCO) technologies in soil remediation, one of the key challenges is the limited diffusion range of chemical oxidants in soil without external agitation. Herein, self-propelled micromotors based on natural pyrolusite with abundant micro/nanobubble generation were developed as active heterogeneous catalysts to improve the mass transport of remediation reagents. The micromotors composed of natural pyrolusite and Fe2O3 were employed as activators of peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) for dynamic remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs). The prepared micromotors exhibited speeds of 185 ± 33.7 µm/s, 280 ± 53.9 µm/s and 312 ± 66.2 µm/s in 1 %, 3 % and 5 % H2O2, respectively. The dual effect of NPF micromotors in catalytic degradation and mass transport led to a pyrene degradation efficiency of 100 % in 5 h and a total organic content removal rate of 93.36 % in the reaction condition of 1.0 g/L of NPF, 20 mM of PMS, 20 mM of H2O2, 84.10 mg/kg of pyrene and natural pH. Meanwhile, the main reactive oxidant species (ROS) and degradation pathway of pyrene were investigated. This research demonstrates the high potential of natural-pyrolusite-based micromotors for in situ remediation of organic contaminated sites.