Solution plasma process: An option to degrade bisphenol A in liquid-phase to non-toxic products

Abstract

Bisphenol A (BPA) is a potential endocrine disruptor. It causes hormonal imbalances and also affects aquatic organisms when discharged in untreated form into the ecosystems. Many attempts have been made to degrade BPA in the liquid phase using chemical and or biological methods, which often require multiple steps and are not effective to any great extent. In this study, solution plasma process (SPP) was adopted for the degradation of BPA in liquid phase. BPA at a constant concentration (100 mg·mL−1) was degraded using SPP at various of discharge times (0–45 min) and various pH (3–6). Physical conditions for SPP were voltage at 800 V, frequency 35 kHz with bandwidth of 2 μS and unipolar and bipolar power supplies were used. The degraded BPA was extracted and investigated for the degradation adopting Gas chromatography-Mass Spectroscopy (GC–MS). During SPP, intermediates were formed at 15 min of treatment, and degradation was achieved to a maximum of 86% at 18 min. The GC–MS results revealed that dimethyl ester (91%), hydroxyl‑bicyclooctenone (56%), imidazole (23%), pyridine (10%) and benzene (9%) fragments were formed abundantly due to plasma treatment. Plasma-treated BPA was not toxic to aquatic fern, Lemna minor as revealed in relative growth rate (RGRarea) analysis. SPP causes release of free radicals, which are actively involved in BPA degradation without any additive chemicals. The approach in this study could be projected as an effective SPP-based clean-technology for degradation of toxicants in the aquatic ecosystems and also for effective wastewater treatment.