Non-thermal plasma activated peroxide and percarbonate for tetracycline and oxytetracycline degradation: Synergistic performance, degradation pathways, and toxicity evaluation.

Tetracycline (TC) and Oxytetracycline (OTC) are common antibiotics increasingly detected in the environment, posing a potential risk to human and aquatic lives. Although conventional methods such as adsorption and photocatalysis are used for the degradation of TC and OTC, they are inefficient in removal efficiency, energy yield, and toxic byproduct generation. Herein, a falling-film dielectric barrier discharge (DBD) reactor coupled with environmentally friendly oxidants (hydrogen peroxide (HPO), sodium percarbonate (SPC), and HPO + SPC) was applied, and the treatment efficiency of TC and OTC was investigated. Experimental results showed that moderate addition of the HPO and SPC exhibited a synergistic effect (SF > 2), significantly improving the antibiotic removal ratio, total organic removal ratio (TOC), and energy yield by more than 50%, 52%, and 180%, respectively. After 10 min of DBD treatment, the introduction of 0.2 mM SPC led to a 100% antibiotic removal ratio and a TOC removal of 53.4% and 61.2% for 200 mg/L TC and 200 mg/L OTC, respectively. Also, 1 mM HPO dosage led to 100% antibiotic removal ratios after 10 min of DBD treatment and a TOC removal of 62.4% and 71.9% for 200 mg/L TC and 200 mg/L OTC, respectively. However, the DBD + HPO + SPC treatment method had a detrimental effect on the performance of the DBD reactor. After 10 min of DBD plasma discharge, the removal ratios for TC and OTC were 80.8% and 84.1%, respectively, when 0.5 mM HPO + 0.5 mM SPC was added. Moreover, principal component and hierarchical cluster analysis confirmed the differences between the treatment methods. Furthermore, the concentration of oxidant-induced in-situ generated ozone and hydrogen peroxide were quantitatively determined, and their indispensable roles during the degradation process were established via radical scavenger tests. Finally, the synergetic antibiotic degradation mechanisms and pathways were proposed, and the toxicities of the intermediate byproducts were evaluated.

Advances of non-thermal plasma discharge technology in degrading recalcitrant wastewater pollutants. A comprehensive review.

With development and urbanization, the amount of wastewater generated due to human activities drastically increases yearly, causing water pollution and intensifying the already worsened water crisis. Although convenient, conventional wastewater treatment methods such as activated sludge, stabilization ponds, and adsorption techniques cannot fully eradicate the complex and recalcitrant contaminants leading to toxic byproducts generation. Recent advancements in wastewater treatment techniques, specifically non-thermal plasma technology, have been extensively investigated for the degradation of complex pollutants in wastewater. Non-thermal plasma is an effective alternative for degrading and augmenting the biodegradability of recalcitrant pollutants due to its ability to generate reactive species in situ. This article critically reviews the non-thermal plasma technology, considering the plasma discharge configuration and reactor types. Furthermore, the influence of operational parameters on the efficiency of the plasma systems and the reactive species generated by the system during discharge has gained significant interest and hence been discussed. Also, the application of non-thermal plasma technology for the degradation of pharmaceuticals, pesticides, and dyes and the inactivation of microbial activities are outlined in this review article. Additionally, optimistic applications involving the combination of non-thermal plasma and catalysts and pilot and industrial-scale projects utilizing non-thermal plasma technology have been addressed. Concluding perceptions on the challenges and future perspectives of the non-thermal technology on wastewater treatment are accentuated. Overall, this review outlines a comprehensive understanding of the non-thermal plasma technology for recalcitrant pollutant degradation from a scientific perspective providing detailed instances for reference.

Influences of nitrite on paracetamol degradation in dielectric barrier discharge reactor.

The frequent detection of paracetamol in natural water increased environmental concerns. The dielectric barrier discharge (DBD) technology is an effective paracetamol removing method, however, this research showed that the removal of paracetamol using DBD technology at 30 min dropped from 100% to 53.3% as the initial paracetamol concentration increased from 10 mg/L to 100 mg/L, due to the formation of more competitive intermediate products at higher paracetamol concentration. The removal of TOC was found to be much slower than that of paracetamol, as paracetamol was removed completely after 5 min treatment, the removal rate of TOC was 46.3% after 20 min treatment under 500 W discharge power and 50 mL/min air flow rate. The orthogonal experiment showed that the removal of TOC was significantly influenced by the treatment time, discharge power and recirculating flow rate, while less influenced by the discharge frequency. In the removal process of paracetamol, nitrite ion that generated during DBD treatment reacted with paracetamol to form an intermediate product of 3-nitro-4-acetamidophenol. The presence of nitrite ion retarded the removal of 3-nitro-4-acetamidophenol and thus the TOC, however, the nitrate ion did not. The degradation of paracetamol followed a sequence of 3-nitro-4-acetamidophenol, nitrosophenol/acetamide, N-methylacetamide, acetamide and small molecule organic acids in the DBD reactor, and these intermediates were finally oxidized to CO2, H2O and NO3-.