Magnetic mining waste based-membranes for trimethoprim removal and fouling mitigation with ozone

Abstract

The use of ceramic membranes for microfiltration have increased due to their high performance and physical–chemical properties, but their production is still very expensive. For this reason, geopolymeric membranes (GPMs) have been developed with similar characteristics and reduced fabrication costs by incorporating industrial waste. In this study, GPMs were synthesized by incorporating different amounts of magnetic mining waste (MMW), characterized, and used to remove trimethoprim antibiotic from an aqueous solution. Moreover, the presence of high iron oxide content in the membrane composition, ozone could be used as the cleaning agent due to the in situ generation of reactive oxygen species. The porosity of the membranes was widely investigated with micro-CT. MMW incorporation was found to be highly beneficial for increasing the percentage of open pores’ and narrowing the distribution of pore size. The addition of a porogenic agent (H2O2) did not have the expected effects, since a significant number of both closed and very large pores (400–800 µm) were formed. The geopolymeric membranes produced by MMW incorporation up to 50% (w/w) exhibited high hydraulic permeability (6.4–7.0 L·m−2·h−1·bar−1), mechanical strength (30–38 MPa) and open porosity. Yet, rejection rates doubled with the incorporation of 50% (w/w) MMW, despite its high flux decay. Nevertheless, the flux was easily recovered by the reactions between foulant compounds and ozone, which was used as cleaning agent. The filtration performance was evaluated to remove trimethoprim dissolved in aqueous solution and the flux decay was successfully described according to the Hermia’s law, and a complete pore blocking mechanism was used. It is possible that trimethoprim molecules interact between them or with buffer reactants, forming complexes, which can be removed by ozone reactions.