Decontamination of 2-Chloroethyl ethyl sulfide on the surface by atmospheric pressure plasma jet

Highlights

• 2-Chloroethyl ethyl sulfide could be decontaminated in a very short time.

• The device had the characteristic of low power.

• The safety has been verified even used on skin surface.

• No intermediate products were detected in the gaseous, ensured the safety of personnel operating in open spaces.

Abstract

Atmospheric pressure plasma jet (APPJ) were used to decontaminate the surface’s 2-Chloroethyl ethyl sulfide (2-CEES), a kind of sulfur mustard (HD) simulant. The power of the APPJ device didn’t exceed 7.77 W. Helium APPJ was easier to generate plasma jet than argon APPJ. The treated nude mouse skin surface’s temperature slowly reached 30.4 °C and no obvious lesions in the dermis and skin appendages after 15 min treatment. Compared with argon APPJ, the helium APPJ produced more ·OH and the maximum concentration of ·OH was 3.748 × 10⁻⁹ mol/L. Attributed to the low density and more ·OH content, the helium APPJ had a better decontamination effect. With a maximum voltage of 7 kV and a helium flow rate of 4 L/min, 2-CEES (4.53 mg/cm²) can be completely decontaminated in 2.5 min, and no gaseous 2-CEES was detected. The detection of the 2-Hydroxyethyl ethyl sulfide proved the role of ·OH in the reaction system. During the reaction, 2-Chloroethyl ethyl sulfoxide and 2-Chloroethyl ethyl sulfone were also detected. The plasma jet could reduce the toxicity by destroying the parent molecule (2-CEES) in a short time, but it took more time to eliminate the intermediate products. No relevant intermediate products were detected in the gaseous, ensured the safety of personnel operating in open spaces.

Introduction

Sulfur mustard (HD) is a harmful blistering chemical warfare agents (CWAs), and has been used as a chemical weapon since World War I (Eckert, 1991). It quickly causes erythema, swelling and blistering after contact with the skin (Razavi et al., 2012). With the signing and entry into force of the Chemical Weapons Convention (CWC), the possibility of CWAs being used on the large-scale militaryoperations has been reduced, but the possibility of being used by terrorists to carry out terrorist attacks or illegal military action cannot be ruled out. Therefore, the emergency decontamination technology of CWAs has always been an important part of the public safety technology system.

Since the toxic properties of the agents, low-toxic substitutes are often used in the research to carry out experiments. 2-Chloroethyl ethyl sulfide (2-CEES) and HD have similar functional groups and similar molecular diameters, it indicates that 2-CEES has similar properties to HD in terms of degradation pathway, toxicological properties and skin penetration, so 2-CEES is a commonly used HD simulant. For the research on the decontamination of HD and simulants, the currently reported research methods include physical adsorption (Lee et al., 2019, Osovsky et al., 2014), chemical oxidation (Talmage et al., 2007, Wang et al., 2017), catalytic oxidation technology (Chen et al., 2017, Chen et al., 2015, Han et al., 2008), etc. These technical methods face the challenge of shortening the treatment time and avoiding secondary pollution.

Plasma pollution treatment technology is a green technology caught the attention of researchers. Many plasma generation technologies, such as streamer plasma, corona plasma and arc plasma, cannot be touched by the human body due to their high voltage and high temperature characteristics, and are often used to eliminate pollutants in water (Chen et al., 2015, Chen et al., 2015, Chen et al., 2014) or VOCs (Adelodun, 2020, Liu et al., 2021). Atmospheric pressure plasma jet (APPJ) is a mild and effective pollution treatment technology, which uses the active groups generated in APPJ plasma to degrade various pollutants. Under the premise of controlling the temperature, it has the potential to treat the surface of sensitive materials, even in contact with the skin. Based on the above characteristics, APPJ is often used in the field of medical sterilization (Deng et al., 2018). However, APPJ has little research on the treatment of surface contaminants, especially CWAs contaminated on the surface. For the currently reported plasma degradation of CWAs, the temperature of the treatment has not been the focus of attention (Hong et al., 2005, Moeller et al., 2002, Herrmann et al., 2002). In this study, APPJ was used to degrade the surface-contaminated HD simulant 2-CEES. On the one hand, the main focus was on the degradation time and effect. On the other hand, the APPJ in many reports belongs to the thermal plasma, and its temperature reaches thousands of K or more (Casado et al., 2020, Laux et al., 2003). The resulting problem is ablation and damage to the treated surface. Therefore, while ensuring the degradation effect, this research focuses on the temperature of APPJ to ensure that the temperature range of APPJ can be applied to the surface of various materials, even human skin.