Porous polymer derived ceramic membranes for bioelectricity generation and wastewater treatment

Abstract

The pollution caused by the use of conventional energy sources represents a serious threat to the existing global ecological system, which stimulates the ongoing search for alternative environmentally safe biochemical energy sources that are able to fulfill the future energy demand. The microbial fuel cell (MFC) technology is one of such alternative energy resources conceptualizing the waste-to-energy principle, which can be used for wastewater treatment with simultaneous recovery of bio-energy using microorganisms as biocatalysts. The Membrane bioreactor (MBR) is another promising technology for wastewater treatment, it is combination of activated sludge process and membrane filtration. The integration of these two technologies will be an efficient one for wastewater treatment and bioelectricity generation. The selection of proton conducting and water permeable membrane are currently the key factors that decide the performance of microbial fuel cell (MFC) and Membrane bioreactor (MBR), respectively. Porous Polymer derived ceramics (PDC) membranes were prepared by a simple uni-axial hydraulic pressing technique, using polysiloxane as a precursor and proton conducting materials as fillers. The ceramic membranes produced have tailorable surface characteristics and uni-modal pore size distribution in a range between 0.1 and1 µm. These porous ceramic membranes are designed for MFC and MBR applications that involve proton ion diffusion and water permeability. The ceramic membrane properties were tailored by addition of filler materials such as cation exchange material, graphitic carbon and hygroscopic material. The cation exchange materials are montmorillonite and H3PMo12O40/SiO2 filler used in the first approach with variable pyrolysis temperature (400 -1000 oC). This results in high MFC performance using cation exchange filler functionalized ceramer membrane (pyrolysed at 400 oC). In the second approach, functionalized ceramic membranes with different weight percentage of graphene oxide and multiwall carbon nanotube pyrolyzed at 1100 oC, were prepared and showed a high MFC performance specially for functionalized ceramic membranes with 0.5 wt.% graphene oxide. Functionalized with ceramic membrane with hygroscopic fillers such as SiO2 (as particle), SiO2 (derved from TEOS) and TiO2 were pyrolysed at 1100 oC, which results in high MFC performance and water permeability for MBR application by using ceramic membrane functionalized with 15 wt% TiO2. In all the approaches, the physical characteristics, such as porosity, hydrophilicity, mechanical stability, ion exchange capacity, and oxygen mass transfer coefficient, of the membranes were measured to identify the suitability of the membrane material for further testing in MFC and MBR systems. Finally, the 20 liter capacity pilot scale integrated MFC and MBR system were studied using a ceramic membrane pyrolysed at 1000 oC and reported the bioelectricity generation and wastewater treatment efficiency.