Degradation of phenol and Bisphenol-A using discharged water generating system

There is a growing interest in the use of AOPs to develop efficient water treatment systems. Chlorination forms different DBPs. Ozonation has been considered to be a less attractive alternative in some applications due to expensive costs and short life-time. To cope with the disadvantages of chlorination and ozonation, a novel oxidants-generating system, named Discharged Water Generating (DWG) System has been invented. The DWG system is an innovative technique to oxidize pollutants. It is based on the principle of lightning discharge in air. This technique uses plasma discharge in 2-phase (Air-Water). Plasma produces NO, NO₂, O_3(g). Produced oxidants dissolve in water directly by high pressure of plasma and change to O_3(aq), HNO₂ and HNO₃. Moreover plasma discharge can produce many other radicals. These are helpful in degradation of contaminants. The oxidation of phenol and Bisphenol-A (BPA) in aqueous solution has been studied in detail. Phenol degradation was about 50% while BPA was degraded about 80–90% after one hour of oxidation in the DWG system. Higher phenol degradation (more than 80%) was achieved at basic pH confirming the contribution of ozone, OH radical and other oxidants present in the DWG system towards the phenol degradation. Best results for BPA degradation were achieved at pH = 3. Higher initial phenol concentration has an effect on lowering the degradation efficiency of the DWG system. The phenol oxidation product mixture has a complex composition. 2-Nitrophenol has been identified mainly among the oxidation products of phenol which confirms NO²₋ attack on the phenoxide ring and there is no involvement, whatsoever, of any reactive free radicals, such as, NO₂, NO, OH or O⁻² or any NO⁺₂ ion as an active intermediate in the reaction.