Espumas de poliestireno impregnadas com nanopartículas de prata para a redução catalítica de P-nitrofenol em água

Abstract

Research related to the treatment of wastewater has been growing in recent years due to the amount of harmful substances present in the water, compromising not only the survival of aquatic fauna and flora, as well as human health and when ingested in higher concentrations than recommended by World Health Organization (WHO) causes serious injuries, being more frequent in the liver and can lead to liver cancer. In this sense, the reduction in less polluting compounds has become a very urgent issue. Currently, some treatment methods for the removal and/or reduction of P-nitrophenol (PNF) are used, such as photocatalytic degradation, biodegradation, Fenton reaction, electrochemical methods and catalytic reduction. The catalyst developed in this work presents good results since, it was used a very active noble metal in catalytic reduction reactions of pollutants and somehow can contribute to the minimization of the aggressive effects to the environment caused by phenolic compounds. Silver nanoparticles (AgNP) due to the surface plasmonic resonance effect they have, are able to provide active sites when in contact with a strong reducing agent becoming able to attract compounds causing their reduction through chemical reaction processes. And for this reason, it has great possibilities of acting as a catalyst in a reduction process, since the use of the active sites formed has a certain efficiency in removing phenolic compounds with PNF, which has been proven through works reported so far in the literature. In this context, this work aimed to develop a catalyst based on silver nanoparticles impregnated in polystyrene foams, an industrial waste discarded in large quantities into the environment, using the method of obtaining thermally induced phase separation (TIPS). The silver nanoparticles were synthesized using the microemulsion method and the samples were characterized using spectrophotometry in the visible region (UV-Vis) and dynamic light scattering (DLS). Fourier transform visible infrared (FTIR), Scanning Electron Microscopy (SEM), X-Ray Diffractometry (DRX) and Thermogravimetric Analysis (TGA) and DTG. AgNP were synthesized in the size of 31.1 nm in diameter, polystyrene foams impregnated with AgNP were successfully obtained through the thermally induced phase separation method and the presence of nanoparticles on the support was proven through FTIR and XRD, it was It was also verified that several parameters such as the concentration of the reducing agent (NaBH4), concentration of the silver salt, concentration of the surfactant (CTAB) and the purification time of the nanoparticles are of great importance in the process of synthesis of AgNP since the achievement of smaller particle size resulted from the use of a higher concentration of reducing agent, higher concentration of CTAB and silver salt and a longer purification time. The polystyrene foams impregnated with the synthesized AgNP showed significant results at a PNF: NaBH4 ratio of 1:1320, the system showed results with 98% reduction for PS 5 / AgNP in 20 min in the presence of a photocatalytic reduction with Power Lamp 50 W with light emission length 400-500 nm and 96.6% for PS 7 / AgNP. Furthermore, it presented good results in catalytic reduction, resulting in greater efficiency with the increase of the % of catalyst than for PS 7/ AgNP 0.4 it was 97% reduction.