Removal of tetracycline antibiotics from wastewater by pulsed corona discharge plasma coupled with natural soil particles

In this study, pulsed corona discharge plasma coupled with natural soil particles (PCDP/SPs) were used to remove tetracycline hydrochloride (TCH) from wastewater. The differences among three typical and natural soil particles (SPs, black soil (BS) of Jilin, loess soil (LS) of Shaanxi, and red soil (RS) of Hunan in China) for TCH removal were compared by the PCDP/SPs system. The energy yields upon TCH removal and synergistic effects between the pulsed corona discharge plasma (PCDP) and SPs were analyzed. The effects of various factors on removal efficiency of TCH were investigated. The results indicated that the removal efficiency of TCH and the energy yield of PCDP were obviously improved in the PCDP/SPs system. Different SPs types had significant effects on the TCH removal. The removal efficiencies of TCH in the PCDP/SPs system with LS and BS were higher than that in the PCDP/SPs system with RS. The removal efficiency of TCH increased with an increase in the pulsed peak voltage, pulsed frequency, and SPs weight and a decrease in the SPs size. The removal efficiency of TCH decreased upon increasing the initial concentration of TCH and solution conductivity. The recycling experiment showed that the removal efficiency of TCH still maintained a high level after four cycles in the PCDP/LS system; however, a decrease in the removal efficiency of TCH was also observed. The consumption of active species in solution demonstrated that center dot OH and O-3 play key roles in TCH degradation. Intermediates in the process of TCH degradation for the PCDP/SPs system with LS were identified by GC-MS, and a possible degradation pathway was also proposed.