Recondicionamento de membranas de osmose inversa: aplicação na osmose direta para rejeição de desreguladores endócrinos

Abstract

The increasing water demand has driven the expansion of reverse osmosis (RO) desalination technologies on a global scale, which is associated with increased membrane disposal at the end of their useful life. At the same time, conventional wastewater treatment has limitations in the removal of endocrine disruptors (ED), which expose environmental and human health risks, and the forward osmosis process (FO) appears as a promising and low-cost technology to face these challenges. In this context, this research aimed to evaluate the reconditioning conditions of OI membranes for FO in the rejection of DE. The reconditioning took place via cleaning and chemical oxidation, and the membranes were evaluated in FO as to permeate flow (J) and solute inverse flow (Js), and physical-chemical characterization was performed by tests of hydraulic permeability, rejection, scanning electron microscopy, Infrared spectroscopy by Fourier transform, and zeta potential. The membrane determined as an optimal process was analyzed in the rejection of 17β-estradiol (E2) by estrogenic activity (RAE). In the preliminary tests, the desalination membrane with the best performance was exposed to KMnO4 at 250 ppm h, which reached J greater than 3,8 kg m⁻² h⁻¹, while the membranes from deionization systems presented more satisfactory results, with J greater than 7 kg m⁻² h⁻¹. In the definitive tests, the membrane reconditioned with NaClO at 10.000 ppm h showed better performance in FO with Js/J of 0,34 g kg-1, the lowest among those evaluated. Although the results of hydraulic permeability and rejection indicated better balance for the protocols with NaClO 5.000 ppm h and KMnO4 250 ppm h, the global analysis by means of membrane reconditioning index pointed to treatment with NaClO 10.000 ppm h as the most efficient, with a value of 0.96. This result indicates that the protocol removed incrustations and partially degraded the polyamide layer without compromising selectivity, being therefore selected as an optimal condition for the RAE analysis. The characterization suggests that the desalination membranes have severe and irreversible incrustations due to the cleaning and oxidation processes to which they were submitted, which was predicted in all FO tests. The membrane reconditioned with the optimal protocol was evaluated for E2 rejection, presenting a RAE greater than 99%, with a final concentration of 19,3 E2-Eq. ng L-1 in the osmotic solution. The membrane treated with KMnO4 250 ppm h also showed similar performance, with 19,75 E2-Eq. ng L-1 and 99,13% rejection. It is concluded that the reconditioning of OI membranes by chemical oxidation was effective for conversion and application in FO, with satisfactory performances and selectivity like new membranes.