Síntese de espumas de poliestireno sulfonadas suportando nanopartículas de ouro para descoloração do azul de metileno e redução do P-nitrofenol

Abstract

Conventional methods of treatment of industrial effluents such as flocculation, filtration and adsorption do not degrade organic compounds with toxic and carcinogenic characteristics, but only promote their simple transfer to other phases. Thus, Advanced Oxidative Processes (POAs) have gained space, as they allow the degradation and discoloration of organic compounds, including stains with stable structures. In the present work, the traditional Fenton System catalyst, the Fe^2+ ion, was replaced by gold nanoparticles obtained by the microemulsions method, supported on polystyrene foams produced by the Thermally Induced Phase Separation (TIPS) process, used for the catalysis of color removal of the methylene blue dye and reduction of p-nitrophenol to p-aminophenol. In the process of dye discoloration, 20 mL of 5 x 10^-5 mol/L methylene blue was added along with 20 mL of 30% hydrogen peroxide in a 50 mL Becker containing a magnetic bar, to which a polystyrene foam doped with nanoparticles attached to a nylon mesh was immersed and magnetic stirring was promoted for 60 minutes. In the reduction, 20 ml of solution of p-nitrophenol solution 1 x 10^-4 mol/L was added in a 25 ml Becker containing a magnetic bar, then a 300 μl aliquot of the sodium borohydride reductant, 0,66 mol/L, ending with the introduction into the system of doped polystyrene foam of gold nanoparticles. The dye discoloration and the reduction process were monitored by UV-vis spectrophotometry. The solutions of gold nanoparticles were characterized by UV-vis spectrophotometry due to their Surface Plasmon Resonance (SPR), with wavelengths of 516 nm and 522 nm. The foams were characterized by X-ray diffraction (XRD) in which the characteristic peak of polystyrene was observed at 19.2º and the peaks of planes 111 and 200 respectively at 38.2º and 44.3º of the and FTIR, which presented the symmetric (1164 to 1016 cm^-1) and asymmetric deformation (1474 to 1333 cm^-1) bands of -SO3, which evidenced the occurrence of polystyrene sulphonation. In the methylene blue discoloration test foam 1 presented the best color removal result with 16.8% and for the reduction of p-nitrophenol was foam 10 with color removal percentage of 98.52%.