Avaliação da remoção do íon cádmio em solução aquosa utilizando processos de osmose inversa e nanofiltração

• Autor(a) principal: Figuerêdo, Elizabete Pereira de
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/15753
• topic: Cadmium; reverse osmosis; nanofiltration; concentration polarization; Cádmio; osmose inversa; nanofiltração; polarização de concentração; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA

Effluents containing cadmium may be produced by a variety of industries. The application of the reverse osmosis and nanofiltration technologies for the treatment of effluents containing cadmium, in order to reduce environmental degradation, were studied in the present work. Synthetic samples containing the cadmium ion in different concentrations were prepared and treated by reverse osmosis and nanofiltration. The removal process was divided in three steps: 1- the reverse osmosis and nanofiltration processes were analyzed concerning the rejection of the cadmium ion, correlating and evaluating the main process parameters (feeding solution concentration, permeated flow and pressure), and comparing the systems between themselves. In steps 2 and 3, the effects of salinity in the elimination of the cadmium ion in aqueous solutions, containing a combination of cadmium sulfate and zinc sulfate, or a combination of cadmium sulfate and sodium sulfate, were assessed by the use of zinc and sodium counterions. The concentrations of cadmium and zinc were measured by atomic absorption spectroscopy, and the concentrations of sulfate and sodium were measured by ion chromatography. The results obtained in the first step of the experiments show that the reverse osmosis and the nanofiltration processes are efficient in removing cadmium, with an average rejection rate of 92,4% and 96,6%, respectively. Considering the standard relative incertitude associated to the results, the values obtained are considered of the same magnitude. In both systems, the permeated flow and the rejects were not influenced by a rise in cadmium concentration in the feeding solution. In step 2, the results showed a decrease in cadmium rejection related with a rise in the zinc sulfate concentration in the feeding solution. This phenomenon is due to the similarity between the Cd2+ and Zn2+ ions, associated to their hydration ionic radius and to their hydration energies. A decrease in the permeated flow and of the rejects related to a rise in the feeding concentration was observed and was probably due to the polarization effect. In step 3, the cadmium ion rejection was not affected by a sodium sulphate concentration rise in the feeding, as well as in the permeated flow. Another aspect related to the rejection is that, due to its smaller hydration radius, sodium has a better diffusion rate through the membrane than cadmium