Estudo da degradação fotocatílica de p-nitrofenol em reator batelada, utilizando sistema fotólise direta e UV/H2O2

Abstract

Nitrophenolic compounds are widely used in the industry for product synthesis. Among the Nitrophenolic compounds, the p-nitrophenol (PNP) has widespread industrial use in the Brazilian industry. Because it is highly toxic, carcinogenic and have bioaccumulation potential, affecting aquatic ecosystems and human health, wastewater containing pop should be treated before being released into the receiving body. This study evaluated the degradation and mineralization efficiency of the p-nitrophenol contaminant present in aqueous solution. Contaminant degradation occurred through two treatment systems: direct photolysis by means of a UV light source (36 W) and combined UV/H2O2 process, H2O2 being the primary oxidizing agent chosen in this work, using a batch photochemical reactor. For this purpose, we used experimental planning Of Rotational Central Composite Design - Two-level DCCR. The degradation kinetics was obtained through the direct photometric method, and the mineralization of p-nitrophenol was evaluated by the removal of Total Organic Carbon (TOC). The presence of residual peroxide at the end of photochemical assays was also studied. For the direct photolysis reaction, the best degradation response occurred at low pollutant concentrations (15 mg.L-1 ) and liquid blade height of 2 cm, coming to degrade 65.67% of p-nitrophenol in 7 hours of reaction. While the UV/ H2O2 process, 100% of the contaminant was degraded in several trials, and the best responses were obtained with pnitrophenol concentrations of up to 50 mg.L-1 and hydrogen peroxide concentration of 50, 100 and 150 mg.L-1 , and in the highest contaminant and oxidizing agent ratios, degradation kinetics was favored and 100% degradation was obtained in the shorter reaction times, 10 and 30 minutes. In the process of direct photolysis, toc removal was not significant. The removal of TOC for the UV/ H2O2 system obtained better results, coming to mineralize 100% of the pollutant in a trial conducted with a PNP concentration of 10 mg.L-1 and 50 mg.L-1 of H2O2 concentration. From the studies it is possible to affirm that the process of direct photolysis is not effective due to the high time of residence and smaller removals. However, UV/ H2O2 was promising for the treatment of wastewater containing PNP. The good degradability presented in low oxidizing concentrations results in a reduction in process cost when aiming at largescale application.