Treatment of waste water aiming at the removal of contaminants is an important task in order to fight the problem of water shortage, which is already a significant issue in many regions of planet earth. Pollutants are present at almost all length scales, from large particles in the mm range down to microbes on the micro and nano-scale. For the purpose of removing contaminants on the nano-scale, nanofiltration (NF) or tight ultrafiltration (UF) membranes are required. These membranes are predominantly made of synthetic polymers derived from fossil resources that require significant amounts of chemicals and energy during their manufacture. In addition, they constitute a serious waste problem after use. Therefore, utilization of membranes based on renewable resources, such as nanocellulose papers, could be an alternative. Cellulose papers have a long tradition as filter and membrane material dating back to ancient times. However, conventional filter papers, produced from cellulose microfibrils, exhibit certain limitations when pollutants in the nanometer range are to be removed. Using a conventional paper making process utilizing cellulose microfibrils fails to produce papers capable of UF or even NF operations. Recently, we demonstrated the utility of nanocellulose and bacterial cellulose papers, also often referred to as nanopapers, as tight aqueous UF membranes by application of a simple papermaking process. Unfortunately, the permeance of these membranes is limited, which is connected to a relatively high density resulting in low porosity. To target this drawback, it is assumed that producing nanopapers from dispersions of BC in organic solvents rather than water should give rise to a change in density and thus porosity of BC papers, too. This enhancement in overall porosity is proposed to significantly enhance the permeance of BC papers but without sacrificing the pore size and thus the efficiency of the membrane. We here present nanopapers made from bacterial cellulose from a set of different types of organic solvents through a simple paper making process via solvent exchange that exhibit unchanged pore size but increased permeability due to increased porosity.

Designing the porosity of bacterial cellulose nanopapers

249th National Meeting (2015)

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