Síntese de perovskitas LaCoO3 e LaFeO3 para aplicação na remoção de corantes têxteis via adsorção em fase líquida

Abstract

The environmental impacts caused by the emission of textile effluents in water bodies have attracted attention due to the toxicity and difficulty of treatment to remove these compounds present in dyeing wastewater, in particular, dyes. Among the techniques employed in the treatment of dyeing wastewater, the adsorption technology is one of the most efficient in to remove dyes from aqueous media. Several materials have been used as adsorbents and recent studies have shown the promising use of materials with perovskite structure in the removal of textile dyes. Perovskites are highly versatile mixed oxides exhibiting magnetic, electrical, optical, catalytic and adsorptive properties. In the present work, the materials LaCoO3 and LaFeO3 were synthesized, characterized and studied as adsorbents in order to remove a textile dye in aqueous medium, with the proposal of regenerating the adsorbents, in which makes the use of perovskites a promising alternative to classic adsorbents. The materials were synthesized using a modified protein method and the precursor powders of the perovskite phase were analyzed via thermogravimetric analysis (TG/DTG) and infrared spectroscopy (FTIR). The formation of the perovskite structure was proven by X-ray diffraction, obtaining the crystalline phase of the mixed oxides LaCoO3 and LaFeO3. The LCO-C material obtained a greater specific surface area compared to the LFO-C. The images obtained by scanning electron microscopy indicated that the materials LCO-C and LFO-C present a uniform particle structure. The zero charge point (pHPZC) was estimated at 6.6. The perovskite samples studied were applied to remove Congo red dye at concentrations of 10, 30 and 50 ppm. The best removal efficiency occurred at a concentration of 10 ppm, showing an efficiency of 82% for LCO-C and 71% for the LFO-C adsorbent. Among the kinetic models studied, the pseudo-second order was the one that best fit when applied using both materials. The application of the Freundlich and Langmuir adsorption equilibrium models for the adsorption data using the LCO-C and LFO-C samples was satisfactory due to the good fit with the experimental data. The adsorbents after the adsorption stage were recovered and used in new adsorption cycles maintaining similar efficiencies. The results obtained suggest the adsorbents developed are promising in the removal of dyes discarded by the textile industry, indicating potential applicability for the treatment of these effluents.