Aplicação de membranas de nanofiltração NF90 pré-tratadas em etanol e água na remoção de 2-MIB e geosmina

Abstract

The presence of secondary originating from cyanobacteria metabolites has been an obstacle in water treatment stations, since the conventional processes used only remove intact cells of these microorganisms, but not the produced metabolites. In this sense, the filtration membrane technology, in particular, nanofiltration, has been studied aiming at the removal of these compounds. This work aimed to evaluate the efficiency of the membrane NF90 nanofiltration pretreated with water and ethanol in the retention of secondary metabolites 2-MIB and geosmin. The evaluation was initiated with the pre-treatment of the membrane in water and 50% ethanol solution (v/v) for a period of 60 minutes. The pre-treated membranes were tested for water permeability and retention capacity of metabolites from the constant pressure of 4, 7 and 10 bar. For the pressure that showed the best permeate flow rates and retention metabolites, tests were performed with pre-treatment of the membrane in 99.9% ethanol (absolute). Characterizations of the membranes were performed membrane through scanning electron microscopy techniques (SEM), atomic force microscopy (AFM) and wettability. The retention evaluation of metabolites was performed from working solutions at starting concentrations of 100 ng L-1 or 500 ng L-1 (testing at a pressure of 7 bar) of 2-MIB and geosmin, prepared from Standard commercial. Quantification of the metabolites was performed by gas chromatography followed by mass spectrometry (GC/ES). With the pre-treatment of the membrane in ethanol solution of 50% (v/v) there was an increase in the permeate flow with the passage of 2-MIB and geosmin solution with a higher proportion occurring pressure of 7 bar (5 , 6 times) to be retained over 93% of metabolites. The treatment of the membrane in ethanol 99.9%, however, resulted in lower retention of metabolites by the membrane (average 88%) and permeate flux of approximately 4.8 times greater than that obtained with the membrane for water treatment. From the results obtained, it can be considered that pre-treatment with ethanol provided an improvement in performance of nanofiltration membrane in terms of permeate flux, especially when treated with a 50% solution, without, however, altering the ability of retention of metabolites.