Abstract
This study focuses on the development of porous ceramer and SiOC composites which are suitable for microfiltration applications, using a mixture of polysiloxanes as the preceramic precursor. The properties of the membranes—such as their pore size, hydrophilicity, specific surface area, and mechanical resistance—were tailored in a one-step process, according to the choice of pyrolysis temperatures (600–1000 °C) and the incorporation of micro- (SiC) and nanofillers (TiO2). Lower pyrolysis temperatures (<700 °C) allowed the incorporation of TiO2 in its photocatalytically active anatase phase, enabling the study of its photocatalytic decomposition. The produced materials showed low photocatalytic activity; however, a high adsorption capacity for methylene blue was observed, which could be suitable for dye-removal applications. The membrane performance was evaluated in terms of its maximum flexural strength, water permeation, and separation of an oil-in-water emulsion. The mechanical resistance increased with an increase of the pyrolysis temperature, as the preceramic precursor underwent the ceramization process. Water fluxes varying from 2.5 to 370 L/m2·h (2 bar) were obtained according to the membrane pore sizes and surface characteristics. Oil-rejection ratios of 81–98% were obtained at an initial oil concentration of 1000 mg/L, indicating a potential application of the produced PDC membranes in the treatment of oily wastewater.
Highlights
The rapid growth of the petrochemical, pharmaceutical, food and fertilizer industries has inevitably led to the intensive production of oily wastewater, which is one of the main sources of groundwater and surface water pollution [1]
Complementary amounts of SiC (6.5 μm) and TiO2 (21 nm) were used as fillers in order to prevent the characteristic shrinkage of polysiloxanes-based material during the pyrolysis process, to increase mechanical stability, and to evaluate the effect of these micro- and nanofillers on the morphology, pore size, and surface characteristics of polymer-derived ceramics (PDC) membranes
Symmetric porous ceramer and ceramic microfiltration membranes with narrow pore size distributions were produced via the tape-casting technique, using polysiloxanes as preceramic precursors
Summary
The rapid growth of the petrochemical, pharmaceutical, food and fertilizer industries has inevitably led to the intensive production of oily wastewater, which is one of the main sources of groundwater and surface water pollution [1]. With growing environmental awareness worldwide, regulations, and the ever-increasing demand for clean water, the development of innovative and cost-effective technologies for water treatment has become a global concern [3,4] In this scenario, membrane technology has emerged as a promising separation process for oily wastewater, as it offers a high separation efficiency and lower energy consumption, and is easy to scale-up [5,6]. Ceramic membranes have attracted more and more attention due to their outstanding properties, such as their high mechanical strength, their superior chemical/thermal resistance, the easy cleaning of membrane, and, their extended operating life [7]. Their high manufacturing costs—especially that of the energy-intensive powder-sintering process—have limited their wider application [8,9]. As a suitable alternative to the conventional powder process, ceramic structures with compositions such as Si-O-C, Si-C and Si-(B)-N-C can be synthesized through the cross-linking and pyrolysis of a suitable polymeric precursor at lower processing temperatures than the ones required for the sintering process [10]
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