RESUMO
Oil emulsified in water is one of the most difficult mixtures to treat due to the good stability of emulsions, so there is a growing demand for more efficient methods for separating immiscible oil/water mixtures. In this context, the focus of this study was to obtain an adsorbent for the selective treatment of a simulated oily wastewater. To this aim, a modified hydrotalcite sample with hydrophobic and magnetic characteristics was prepared and characterized. Initially, the effect of sodium dodecyl sulfate (SDS) amount on the adsorbent characteristics was evaluated (266-800 mgSDS g-1LDH). The hydrophobic hydrotalcite (LDH-SDS) containing 533 mgSDS g-1LDH (LDH-SDS2) presented a higher interlayer space where the surfactant molecules were arranged perpendicular to the lamellae, allowing better access to the hydrotalcite pores and facilitating the selective adsorption of oil compounds. Moreover, the synergistic association of hydrophobic properties with super-wetting and effective adhesion oil to Fe3O4 favoured the selective adsorption of the simulated oily wastewater onto the hydrophobic and magnetic hydrotalcite (LDH-MSDS), facilitating the post-treatment separation. The kinetic analysis demonstrated that the adsorption equilibrium was attained in 120â min and the pseudo-second order model was the most suitable for predicting the removal of total organic carbon (TOC) from the simulated oily wastewater. The Langmuir model described very well the equilibrium experimental data, with a maximum adsorption capacity for TOC removal using LDH-MSDS of 659.9â mg g-1. Therefore, the modified hydrotalcite prepared in this study showed intrinsic characteristics that make it a promising adsorbent for the selective treatment of oily wastewaters.
Assuntos
Águas Residuárias , Poluentes Químicos da Água , Cinética , Hidróxido de Alumínio/análise , Óleos , Adsorção , Fenômenos Magnéticos , Poluentes Químicos da Água/químicaRESUMO
This work investigated the efficiency of bioremediation of heavy fuel oil (HFO) in aqueous solutions by living Eichhornia crassipes (Mart.) Solms, also known as water hyacinth. Possibility of using post-biosorption macrophytes to produce briquettes was also studied. HFO was characterized by its density, viscosity, and Fourier-transform infrared spectroscopy. Water hyacinth was characterized by scanning electron microscope, pH of zero point of charge, buoyancy, and wettability. Experiments were performed to evaluate effects of contact time and initial oil concentration on biosorption. E. crassipes presented a hydrophobic nature, ideal for the treatment of oily effluents. Hollow structures in macrophytes were also identified, which favor capillary rise and retention of oils of high density and viscosity. Biosorption efficiency of HFO reached 94.8% in tests with initial concentration of 160 mg.L-1. A calorific value of 4022 kcal.kg-1 was obtained in briquettes made of water hyacinth post-biosorption. These results reinforce the great potential of E. crassipes as a sustainable and efficient alternative for treatment of oily effluents.