Evaluación técnica de la elaboración de membranas revalorizadas desde membranas desechadas de osmosis inversa para el tratamiento del agua gris.
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Date
2025
Journal Title
Journal ISSN
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Publisher
Universidad de Concepción
Abstract
Ante la creciente crisis hídrica, intensificada por el cambio climático y el crecimiento urbano, se propone una solución sostenible que revaloriza membranas de osmosis inversas (RO) descartadas para tratar aguas grises, provenientes de usos domésticos no sanitarios. Con ello se reduce la presión sobre fuentes hídricas convencionales y promueve la economía circular.
El proceso de revalorización de las membranas considera una etapa de hidratación y limpieza, seguida de una transformación mediante oxidación química con hipoclorito de sodio (NaOCl), que degradó la capa activa de poliamida (PA) y permitió su conversión a membranas revalorizadas de nanofiltración/ultrafiltración (NF/UF). Se realizaron caracterizaciones operacionales y superficiales para evaluar los efectos del tratamiento. La hidratación con etanol y la limpieza química con hidróxido de sodio (NaOH) y ácido etilendiaminotetraacético (EDTA) restauran parcialmente la permeabilidad sin comprometer el rechazo de sales. La oxidación aumentó significativamente la permeabilidad (entre 400% y 3000%), siendo el tiempo de exposición más significativo que la concentración de NaOCl. El rechazo de iones monovalentes y divalentes respalda la conversión efectiva a membranas Re NF/UF. Las pruebas de caracterización superficial SEM, evidenciaron la remoción de contaminantes orgánicos en la membrana limpia y un aumento de porosidad en la membrana oxidada. La espectroscopía infrarroja con transformada de fourier acoplada a reflectancia atenuada (FTIR) muestra la eliminación de las bandas 1543, 1609, 1663 cm-1, características de PA, confirmando la degradación de la capa activa. Asimismo, un aumento en el ángulo de contacto sugiere una mayor exposición a la capa polisulfona, ubicada debajo de la capa PA.
El agua gris tratada con estas membranas modificadas fue evaluada para determinar su calidad y seguridad. En particular, las membranas oxidadas con soluciones de NaClO al 4% y 5% durante 120 minutos lograron una reducción significativa de la demanda biológica de oxígeno (DBO), la turbidez y la dureza (CaCO3), así como la eliminación de microorganismos contaminantes. Además, se observó un rechazo efectivo de contaminantes específicos como el manganeso (Mn2+) y los tensioactivos aniónicos, con eficiencias del 88% y 35%, respectivamente. El agua tratada con la membrana oxidada al 4% durante 120 minutos cumplió con los requisitos establecidos por la Ley 21.075 para su reutilización en riego. Finalmente, ensayos de riego en cultivos de trigo con esta agua tratada demostraron que no existen efectos adversos en el crecimiento, validando su uso.
In the face of a growing water crisis, intensified by climate change and urban growth, a sustainable solution is proposed by repurposing discarded reverse osmosis (RO) membranes to treat greywater from non-sanitary domestic uses. This approach reduces pressure on conventional water sources and promotes the circular economy. he membrane repurposing process involves a hydration and cleaning stage, fallowed by a transfarmation through chemical oxidation with sodium hypochlorite (NaOCl), which degrades the active polyamide (PA) layer and allows their conversion into repurposed nanofiltration/ultrafiltration (NF /UF) membranes. Operational and surface characterizations were carried out to assess the effects of the treatment. Hydration with ethanol, combined with chemical cleaning using sodium hydroxide (NaOH) and ethylenediaminetetraacetic acid (EDTA), partially restares permeability without compromising salt rejection. Oxidation significantly increased permeability (between 400% and 3000%), with exposure time being more significant than NaOCl concentration. The rejection of monovalent and divalent ions supports the effective transfarmation of RO membranes into repurposed NF/UF ones. SEM surface characterization tests showed the removal of organic contaminants in the cleaned membrane and increased porosity in the oxidized membrane. Fourier-transfarm infrared spectroscopy with attenuated total reflectance (FTIR-ATR) showed the elimination ofbands at 1543, 1609, and 1663 cm-1, characteristic of PA, confirming degradation ofthe active layer. Likewise, an increase in contact angle suggests greater exposure of the polysulfane layer, located beneath the P A layer. The greywater treated with these modified membranes was evaluated to determine its quality and safety. In particular, membranes oxidized with 4% and 5% NaClO solutions far 120 minutes achieved a significant reduction in biochemical oxygen demand (BOD), turbidity, and hardness (as CaCO3), as well as the removal of microbial contaminants. Additionally, effective rejection was observed far specific pollutants such as manganese (Mn2+) and anionic surfactants, with efficiencies of88% and 35%, respectively. The water treated with the membrane oxidized at 4% far 120 minutes met the requirements established by Law 21.075 far greywater reuse in irrigation. Finally, irrigation trials on wheat crops with this treated water showed no adverse effects on growth, validating its use.
In the face of a growing water crisis, intensified by climate change and urban growth, a sustainable solution is proposed by repurposing discarded reverse osmosis (RO) membranes to treat greywater from non-sanitary domestic uses. This approach reduces pressure on conventional water sources and promotes the circular economy. he membrane repurposing process involves a hydration and cleaning stage, fallowed by a transfarmation through chemical oxidation with sodium hypochlorite (NaOCl), which degrades the active polyamide (PA) layer and allows their conversion into repurposed nanofiltration/ultrafiltration (NF /UF) membranes. Operational and surface characterizations were carried out to assess the effects of the treatment. Hydration with ethanol, combined with chemical cleaning using sodium hydroxide (NaOH) and ethylenediaminetetraacetic acid (EDTA), partially restares permeability without compromising salt rejection. Oxidation significantly increased permeability (between 400% and 3000%), with exposure time being more significant than NaOCl concentration. The rejection of monovalent and divalent ions supports the effective transfarmation of RO membranes into repurposed NF/UF ones. SEM surface characterization tests showed the removal of organic contaminants in the cleaned membrane and increased porosity in the oxidized membrane. Fourier-transfarm infrared spectroscopy with attenuated total reflectance (FTIR-ATR) showed the elimination ofbands at 1543, 1609, and 1663 cm-1, characteristic of PA, confirming degradation ofthe active layer. Likewise, an increase in contact angle suggests greater exposure of the polysulfane layer, located beneath the P A layer. The greywater treated with these modified membranes was evaluated to determine its quality and safety. In particular, membranes oxidized with 4% and 5% NaClO solutions far 120 minutes achieved a significant reduction in biochemical oxygen demand (BOD), turbidity, and hardness (as CaCO3), as well as the removal of microbial contaminants. Additionally, effective rejection was observed far specific pollutants such as manganese (Mn2+) and anionic surfactants, with efficiencies of88% and 35%, respectively. The water treated with the membrane oxidized at 4% far 120 minutes met the requirements established by Law 21.075 far greywater reuse in irrigation. Finally, irrigation trials on wheat crops with this treated water showed no adverse effects on growth, validating its use.
Description
Tesis presentada para optar al título de Ingeniera Civil Química
Keywords
Aguas servidas Purificación, Osmosis inversa, Membranas