Reaproveitamento de resíduo cervejeiro para utilização na síntese de materiais zeolíticos e aplicação no tratamento de efluentes têxteis

Abstract

This work aimed to reuse diatomite from the brewing process, investigating its use in the synthesis of zeolite materials that were used as an adsorbent in the removal of methylene blue in batch and fluidized bed systems. Initially, the material was characterized by thermogravimetry, whose analysis identified thermal degradation in three stages. Then, the diatomaceous earth (DE) was thermally treated for 6 hours at 600°C. From X-ray diffraction (XRD), a phase corresponding to silica in cristobalite form was identified, while morphological analysis (SEM-EDS) confirmed the presence of carapaces. The physical adsorption of nitrogen revealed the diatomite surface area as 3.04 m²/g, the pore volume and size as 0.01 cm³/g and 16.17 nm, respectively. The pHzcp found was 4.8. Then, diatomite as a source of silica in the synthesis of zeolitic mixtures in sodium (ZMNa) and acid (ZMH) forms. The crystalline phases identified in the adsorbents by XRD were muscovite, merlinoite, quartz and illite, the SEM-EDS confirmed the formation of a structure with pseudohexagonal morphology and the presence of the main elements of the zeolite structure, silicon, aluminum and oxygen. The crystallization time favored the increase in peak intensity and elevation of textural parameters. For ZMNa crystallized for 24 and 48 h, the external surface area was 26.34 and 44.85 m²/g, micropore area 1.84 and 8.92 m²/g and pHzcp 6.2, whereas ZMH obtained surface area outdoors of 39.20 and 53.29 m²/g in 24 and 48 hours, respectively. The pHzcp was 5.2. The kinetic study showed balance in the first 5 minutes, with removal of 85.46; 60.92 and 36.32% of methylene blue (MB) at 110 mg/L using ZMNa, ZMH and DE, respectively. From the R2 and , the pseudo-first order kinetic model (PFO) and the Freundlich isotherm presented better fits to the experimental data using the three adsorbents. The thermodynamics of the process was defined as spontaneous and exothermic for the three adsorbents (∆H of -33.97; -6.03 and -19.86 KJ/mol for ZMNa, ZMH and DE, respectively). The data from the fluidized bed adsorption column were fitted to the nonlinear form of the Thomas model, but the values of the adsorption capacity (QT) and the Thomas constant (KT) differed from the experimental values since the linear form of the model presented values of QT and KT closer to the experimental ones. Thus, the potential of the zeolite mixture synthesized with diatomite for removing MB dye from aqueous environments is evident, both in batch and fluidized bed column processes.