Avaliação da remoção de bisfenol-a por adsorção em carvão ativado produzido da borra de café

• Autor(a) principal: Alves, Andreia Cristina Fonseca
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/8390
• topic: Poluentes emergentes; Disruptores endócrinos; Carvão microporoso; BPA; ENGENHARIA SANITARIA::SANEAMENTO AMBIENTAL

Bisphenol-A (BPA) is an emerging pollutant potentially capable of interfering with the endocrine system of living things. Employed mainly in the industry, in the production of resins, packaging and polycarbonate monomers, its main sources in the environment are effluent discharges. Since the conventional treatment systems used in Brazil can’t remove a series of pollutants, the use of activated carbon is one of the alternatives fairly used for this purpose. Its production from alternative materials is becoming more and more frequent, as agroindustrial wastes, object of numerous studies of the production of activated carbon. The coffee grounds are one of these residues that has been used generating good carbonaceous adsorbents. Thus, the objective of this work was to evaluate the efficiency of the activated carbon produced from the coffee grounds, in the adsorption of BPA in aqueous medium. Water vapor (CAH), KOH (CAK), K2CO3 (CAKC) and ZnCl2 (CAZn) were used as the activating agente characterized by analysis of X-ray diffraction (XRD), Fourier transform infrared (FTIR), N2 adsorption and desorption, elemental composition (CHNS-O) and determination of zero charge potential. For the selection of the best coal, a preliminary adsorption test was carried out with the adsorbents produced, with the coffee grounds and a commercial coal for comparative purposes. The effect of the initial pH of the solution was also evaluated. The kinetic adsorption studies at the concentrations of 5, 20 and 30 mg/L of BPA were adjusted to the pseudo-firstorder and pseudo-second order models. The nature of the process was studied by the Langmuir and Freundlich isotherm models. Among the developed coals, the CAK and CAKC presented low production yield and were not submitted to the adsorption tests. The CHNS-O, XRD, FTIR and N2 adsorption/desorption analyzes of CAH and CAZn generated results close to those reported in the literature. In terms of specific surface area, the CAH proved to be out of the expected. The CAZn had an area of 1,038.51 m²/g. Of the materials tested, the CAH didn’t present adsorptive capacity, while the CAZn was the one with the best performance, with little variation in efficiency when the pH of the medium changed. The use of coffee grounds as bioadsorbent wasn’t promising, being 86 percentage points below the efficiency of CAZn. Adsorption kinetics revealed a relatively slow process at the concentrations studied, reaching equilibrium after 720 minutes. The kinetic data for the three systems presented a fractional order close to 2, thus indicating a better fit for the pseudo-second order model. The equilibrium data were better adjusted to the Langmuir model, assuming that the CAZn has a homogeneous surface with adsorption occurring in monolayer. The maximum adsorption capacity of BPA according to the same model was 123.22 mg/g. The results showed that CAZn can be considered a promising promoter in the removal of BPA, indicating coffee grounds as an alternative raw material for the production of activated carbon with the potential to remove emerging pollutants such as BPA in water.