Porous Scaffolds as Catalysts for New Waste-Reduction Solutions

With the word “scaffolds” a variety of research fields is addressed, ranging from chemistry to medicine, from biology to civil engineering. Scaffolds can be found at different length scales, from supporting structures in construction sites to tissue engineering and bone regeneration. Scaffolds are open porous structures that can be made active by applying a magnetic or electric field or be used as backbone structures for biological and medical purposes. They can be used also as filters, for instance for wastewaters treatment, where hydrogen is produced. Hydrogen production from wastewaters can achieve the dual environmental benefits of waste reduction along with production of high value energy fuel. Moreover, wastewaters can be considered as ideal substrates for biohydrogen production since they are rich in carbon and nitrogen. The addition of nanoparticles (NPs) can improve the biohydrogen production, can promote the bioactivity of hydrogen-producing species and increase the bacterial growth. Micro- or nanosized porous materials possess large surface areas and large pores, which are beneficial for the diffusion, adsorption, and activation of reactants, especially if pores are interconnected.<br/>Materials containing porous silicones with excellent mechanical performance, e.g., high compressibility and stretchability, and thermal stability, are in high demand in many practical applications. Recently, porous polydimethylsiloxane (PDMS) materials have been successfully synthesized for selective oil absorption from water. For example, Choi et al. fabricated PDMS sponges with fast oil absorption and excellent recyclability using sugar particles as templates [1]. Zhang et al. prepared PDMS sponges with high oil absorbency by using <i>p</i>-xylene as solvent and sugar particles as templates [2].<br/>In this contribution we show our first attempts to fabricate porous scaffolds which can host bacteria colonies and can serve as catalysts for wastewaters treatment. The samples were produced via sugar cube template and consist of PDMS and Fe₂O₃ or TiO₂ nanoparticles. The samples went through several water treatment cycles and maintained their structure without deterioration, creating a suitable environment for bacteria colonies, with consequential hydrogen production.<br/><br/>[1] S. J. Choi, T. H. Kwon, H. Im, D. I. Moon, D. J. Baek, M. L. Seol, J. P. Duarte and Y. K. Choi, ACS Appl. Mater. Interfaces, 2011, 3, 4552–4556<br/>[2] A. J. Zhang, M. J. Chen, C. Du, H. Z. Guo, H. Bai and L. Li, ACS Appl. Mater. Interfaces, 2013, 5, 10201–10206.