Rapid removal of ultra-high-concentration p-nitrophenol in aqueous solution by microwave-enhanced Fe/Cu bimetallic particle (MW-Fe/Cu) system.

Ultra-high-concentration PNP-contained wastewaters are produced sometimes due to the wide application of this nitrophenolic compound in the chemical industry. However, there is a lack of appropriate technologies to rapidly pretreat the ultra-high-concentration wastewater. Therefore, a new microwave-enhanced Fe/Cu bimetallic particles (MW-Fe/Cu) system was developed to rapidly remove ultra-high-concentration PNP. First, the priority of the determinative parameters was obtained by orthogonal experiment. Based on this result, the effects of initial pH, microwave power, Fe/Cu dosage and initial PNP concentration on PNP removal were optimized thoroughly. Under the optimal conditions (i.e. initial pH = 1.0, MW power = 385 W, Fe/Cu dosage = 30 g/L and initial PNP concentration = 4000 mg/L), four control treatment systems (i.e. MW-Fe0, heating-Fe/Cu, MW alone and Fe/Cu alone system) were set up to compare with the MW-Fe/Cu system. The results suggest that high PNP removal (more than 99% with 2.5 min, k1/k2 = 1.18/6.91 min-1) and COD removal (26.6% with 5 min treatment) could be obtained by the MW-Fe/Cu system, which were much superior to those obtained using the MW-Fe0 (k1/k2 = 0.62/2.21 min-1) and the heating-Fe/Cu system (k1/k2 = 0.53/1.52 min-1). Finally, the determination of the intermediates of PNP degradation by HPLC indicated that the MW assistance process did not change the degradation pathway of PNP. This concludes that the new MW-Fe/Cu system was the promising technology for pretreatment of wastewater containing ultra-high-concentration toxic and refractory pollutants at a fairly short treatment time.