Abstract
The present work shows a methodology for the preparation of membranes with a high affinity for nitrates. For this purpose, a polymeric mixture containing an anion exchange resin was extended on a recycled pressure filtration membrane used as mechanical support. Different ion exchange resins were tested. The influence in ion fractionation of (i) the type of ion exchange resin, (ii) the use of a recycled membrane as support and (iii) the operating current density during the separation process were studied. Results revealed that the employed anion exchange resin could tune up the transport numbers of the anions in the membrane and enhance the transport of nitrates over sulfates. The use of the recycled filtration membrane as support further increased the transport of nitrates in detriment of sulfates in nitrate-selective membranes. Moreover, it considerably improved the mechanical stability of the membranes. Lowering the operational current density also boosted ion fractionation. In addition, the use of recycled membranes as support in membrane preparation is presented as an alternative management route of discarded reverse osmosis membranes, coupling with the challenging management of waste generated by the desalination industry. These membranes could be used for nitrate recovery from wastewater or for nitrate separation from groundwater.
Highlights
Nitrate pollution in natural waters has become a worldwide issue, mainly caused by the abusive use of chemical fertilizers and insufficient wastewater treatment [1]
The recycled membrane support has been thoroughly characterized in previous works [39,40]
The end-of-life reverse osmosis (RO) membranes were subjected to 800,000 ppm·h NaClO. This exposition dose ensures the complete elimination of the fouling and the active polyamide layer the achievement of UF-like properties in terms of rejection and the achievement of UF-like properties in terms of rejection
Summary
Nitrate pollution in natural waters has become a worldwide issue, mainly caused by the abusive use of chemical fertilizers and insufficient wastewater treatment [1]. The excessive concentration of nitrates in surface and groundwater causes the eutrophication of rivers and lakes and the pollution of drinking water. The European Commission limits nitrate concentration in drinking water to a maximum level of 50 ppm but recommends to keep it below. 25 ppm [3,4] This situation has motivated increasing research in the development of effective technologies for nitrate removal [5]. Used technologies for nitrate removal include ion exchange resins, membrane technology reverse osmosis (RO), ion exchange membranes (IEMs) or biological and chemical treatments. Membrane technology could be more appropriate to avoid secondary
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