Abatement and biotoxicity assessment of chlorpyrifos residue from green coffee beans: Effect of non-thermal plasma generated ozone and nitric oxide species

Abstract

Chlorpyrifos (CP) is an organophosphate pesticide (OPP) that is widely used in coffee plantations to mitigate the impacts of insects and maximize productivity. However, the environmental persistence of CP has become an issue. Non-thermal plasma (NTP) generated ozone and nitric oxide (NO) species have demonstrated the ability to remediate organic contaminants and promote plant growth. In this study, the washing of CP-contaminated green coffee beans (GCBs) by using plasma activated water (PAW) via ozone and NO dominated species was investigated, respectively. The results revealed degradation efficiencies of 89 and 87 % for ozone and NO dominated treatment, respectively. The concentration of hydroxyl radicals in ozone plasma-activated water (PAW), crucial for initiating and sustaining CP degradation, decreased from 25 μM after 30 min of treatment to 5 μM after 150 min. The concentration of H2O2 remained steady at 1.6 μM while NO2- concentration increased gradually from 0.37 to 3.06 mM during the treatment. Nevertheless, NO dominated NTP treatment resulted in the darkening of the GCBs, whereas ozone NTP treatment brought no physical changes. Therefore, ozone NTP treatment is recommended for large-scale treatments. Moreover, three degradation mechanisms were proposed based on the identified intermediate products (IPs) from liquid chromatography-mass spectrometry (LC-MS) analysis. The cytotoxic effects of these residual IPs after ozone dominated NTP washing were examined using human colon cancer-derived HT29 cells. The results showed cell viability increased to 90 and 95 % when exposed to ozone NTP-treated GCBs for 90 and 120 min, respectively.