Facile Postprocessing Alters the Permeability and Selectivity of Microbial Cellulose Ultrafiltration Membranes

Abstract

Water filtration membranes produced sustainably through microbial cellulose production can have filtration properties altered through facile chemical treatments. Microbial cellulose is an effective membrane filtration medium, and pristine microbial membranes can serve as ultrafiltration membranes with a permeability of 143 L m −2 h −1 bar −1 and a particle size cut off of 35 nm. As living biofilms, these membranes consist of microbial cellulose, bacteria, and extracellular polymers. Thus, additional biofilm components may reduce the intrinsic permeability of the cellulose. Here, microbial membranes were treated with hydrogen peroxide (H 2 O 2 ) and sodium hypochlorite (NaOCl, liquid bleach) to remove impurities present in microbial cellulose and increase membrane permeability. For example, permeability increased from 143 to 257 L m −2 h −1 bar −1 with treatment by 0.3% H 2 O 2 for 12 min. The membranes were also treated with sodium hydroxide (NaOH) to increase membrane selectivity, and the particle size cutoff was reduced from 35 to 10 nm post-treatment with 0.8% NaOH for 20 min. Scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, contact angle goniometry, and X-ray diffraction were used to characterize the physical and chemical properties of the membrane matrix. Facile chemical treatments provide a significant degree of flexibility to tailor microbial membranes to meet specific needs. Microbial membrane production is inherently accessible, and this study furthers that accessibility by utilizing only readily available components to treat microbial membranes and expand their potential applications.

Permeability is the Critical Factor Governing the Life Cycle Environmental Performance of Drinking Water Treatment Using Living Filtration Membranes

“…It has successfully treated deionized water at the 100 L/day scale, and achieved filtration performance comparable to that of ultrafiltration with a size cutoff of 30 nm. 11 Figure 1. Overview of LFM-based water filtration.…”

“…LFMs have created a new category of water filtration technologies, as they are a biodegradable material that may be fabricated into virtually any shape from μm to mm dimensions, 16 and be structurally and chemically modified to impregnate anti-fouling 17,18 and/or diffusion properties. 4,19 A multitude of subsequent studies can be developed upon this proof of concept, e.g., permeability modifications, 11 functional modifications through incorporation of other molecules, [20][21][22] and optimization of the engineering design and operation conditions. 23 To integrate environmental considerations into future technology development (i.e., Ecodesign), 24,25 herein we conduct a preliminary life cycle assessment of LFMs as a drinking water filtration technology.…”

“…They have successfully treated deionized water at the 100 L/day scale and achieved filtration performance comparable to that of ultrafiltration with a size cutoff of 30 nm. 11 Goal of the Life Cycle Assessment. The goal of this study is to estimate the life cycle environmental impacts of LFMs in a full-scale drinking water operation, and to the extent possible, compare them with those of conventional full-scale membrane filtration technologies to assess whether LFMs can reduce the environmental impacts associated with drinking water treatment in their current state.…”

“…Permeability is an LFM property that determines the flux of LFMs under a certain TMP. It was shown that LFMs has the capability of undergo chemical treatments to achieve different permeability and selectivity 11. This capability has direct engineering and environmental implications.…”

“…two chemical treatments and a no treatment baseline). The flux-TMP relationship for each treatment is extrapolated from lab results and shown in Table1 11. Fouling resistance is an LFM property that characterizes how the flux decreases as fouling develops.…”