Avaliação da casca da vagem de Libidibia Ferrea (Fabaceae) como adsorvente de cromo aplicado a um efluente de curtume sintético

• Autor(a) principal: Oliveira Júnior, José Augusto
• Data de Publicação: 2023
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/jspui/handle/riufs/18487
• topic: Meio ambiente; Adsorção; Cromo; Biomassa; Desenvolvimento sustentável; Biomassa vegetal; Cromo; Curtume; Libidibia ferrea; Adsorção; Biomass; Chrome; Tannery; Libidibia ferrea; Adsorption; OUTROS

Industrial effluents can present adverse effects on the natural environment. Among them, those from the tanning industry are harmful due to the presence of Cr(VI) ions. Commercial removal techniques are costly, so biosorption may be an economically viable solution. Recent works show that biomass, such as the pod of Libidibia ferrea (PLF), exhibits excellent biosorption properties for Cr(VI). Thus, the present work studied the role of PLF biomass to treat tannery effluents. The PLF were collected in the rural region of Nossa Senhora Aparecida, SergipeBrazil. The material underwent processing in various granulometries and modifications. After carrying out preliminary adsorption assays, unmodified (UM) and modified alkaline (AM) samples with an average diameter of 920 µm were chosen. Then, optimization tests were conducted using these biosorbents, which revealed that only the adsorbent dosage and Cr(VI) concentration were significant factors. The following characterizations were also carried out before and after adsorption: FTIR spectroscopy, revealing that the alkaline treatment in AM hydrolyzed the lignocellulosic compounds and that Cr(VI) ions could be linked to the -OH and C–O groups; SEM, which shown that the UM presents irregular particles and that the AM surface reduced roughness after the alkaline treatment; Energy-dispersive X-ray fluorescence spectrometry, which identified the highest percentage of chromium adsorption for UM (0.7%); surface area (volume and pore diameter analysis), classifying the samples as microporous and revealing that the surface area and pore volume were decreased with the alkaline modification (445.4 to 160.9 m2.g-1 and 0.3797 to 0.1470 cm3.g-1, respectively); and finally, Raman spectroscopy, corroborating the infrared results, as it showed delignification in AM sample and the presence of chromium in the loaded material, with greater notoriety for UM. Also, a study of the adsorption capacity as a function of pH was carried out, which shown that be pH does not account to adsorption. The analysis of the zero charge point revealed that, for UM, the result was undefined, and for AM, the ideal surface for Cr(VI) adsorption would be below pH 7.24 (protonated surface). The adsorption equilibrium study revealed a fit to the Sips isotherm in UM, suggesting a heterogeneous surface, and in AM the Redlich-Peterson isotherm tending to Langmuir, revealing a monolayer adsorption. For the kinetic study, the UM sample fitted to the pseudo-first and pseudo-second order models, with physisorption and chemisorption acting simultaneously; on the other hand, for AM, the adjustment was made to the Elovich model, with chemisorption as the mechanism. The adsorption test with the synthetic tannery effluent showed a possible application to a real effluent, where the best adsorption capacity was attributed to UM (above 90% removal in Cr (VI)). Thus, this research demonstrated that unmodified PLF (UM) biomass can be used as a Cr(VI) biosorbent, with the possibility of being applied to an effluent from a real tannery.