Highly energy-efficient degradation of antibiotics in soil: Extensive cold plasma discharges generation in soil pores driven by high voltage nanopulses

Abstract

Cold atmospheric plasma (CAP) is a green and promising soil remediation approach with significant advantages in terms of energy consumption, removal efficiency and treatment time. The most critical factor for exploiting CAP is the accomplishment of very low remediation cost, while in parallel, the limited penetration of plasma species at soil layers holds back its wider implementation. In this study, we developed a novel dielectric barrier discharge plasma reactor driven by high voltage nanosecond pulses (NSP) able to generate micro-discharges within the interconnected soil pores facilitating the effective transport of reactive species within soil layers. Key-role parameters were investigated such as pulse voltage and pulse frequency, soil thickness and air flow rate. The effectiveness of the method was identified against different types of soil (sandy soil and loam soil), both under high and low ciprofloxacin concentration in soil, while soil moisture impact on degradation efficiency was also explored. An energy efficiency of 21.2 mg of pollutant/kJ was accomplished, which is the highest ever reported for CAP-based soil remediation. The most stable intermediate degradants of ciprofloxacin, and the associated degradation pathways were identified in a kinetic point of view, while the elimination of the toxic intermediates after treatment was ensured. The present effort provides a new highly energy efficient perspective for future development of a CAP-based soil remediation technology as it maximizes the transfer and penetration of plasma species in soil layers under very low estimated remediation cost (~0.4-1.2 €/tn of soil).