Environmental risk assessment of mechanically strengthened cellulose-based electrospun nanocomposite fibrous membranes

Abstract

Membrane technology has been employed for water purification, wastewater treatment, and reprocessing of polluted water in recent years. Membrane-based filtration technologies can be used in water purification in primary metallurgy, metal processing, petroleum sectors, etc. An innovative sustainable method to selectively separate molecules and ions has been developed using polymer nanocomposite membranes that consist of a continuous polymer bulk phase and a nanofiller phase. This technology has been recognized for its potential to contribute to both sustainability and efficiency in filtration applications. The balance between sustainability and efficiency is of utmost importance in membrane technologies to ensure optimal performance while minimizing environmental impact. To address the challenges associated with the membrane technology, firstly, we have optimized the material parameters, i.e., cellulose acetate (CA) concentration and N, N-dimethylformamide (DMF)/ acetone mixture solvent composition and electrospinning membrane fabrication process parameters, i.e., feed flow rate, voltage, tip-to-collector distance, and processing time. Secondly, we developed, and compared the nanofibrous cellulose acetate (CA)-based membranes reinforced with cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). Several properties including the morphologies, chemical interactions, and mechanical strength of the membranes were investigated after they were synthesized using the electrospinning technique and after they were heat treated. The polymer solutions were composed of various weight percentages of CNCs, 2,2,6,6-tetramethyl- 1-piperidinyloxyl (TEMPO)-mediated oxidized CNFs( i.e., 0 wt% to 1 wt%), and 15 wt% of CA solved in an equal (1/1) volume fraction of DMF/ acetone mixture solvent. Based on our study, the reinforcing properties of TOCNF nanofillers were superior to CNC nanofillers. Heat-treated 0.25TOCNF/CA composite nanofibrous membrane achieved maximum ultimate tensile strength and elongation at the break-point of 33.31 MPa and 1.8%, respectively. The process-structureproperty relationships outlined in this study can facilitate the fabrication and improve the efficiency of the application of electrospun nanocomposite membranes for the purification of water. On the other hand, sustainability is a fundamental consideration when developing and implementing membrane technologies. These technologies offer several advantages that contribute to a more sustainable approach. This study evaluates the environmental impact of the conventional wet spinning method (NIPS) and the innovative dry spinning technique (electrospinning) for cellulose-based nanocomposite electrospun nanofibrous membranes. Life cycle assessment (LCA) of the 0.25TOCNF/CA nanocomposite membrane was conducted to understand the environmental impacts of the fabrication process and to evaluate the potential for use in industrial and other applications that require an assessment of the environmental footprint. The findings will be valuable for researchers, engineers, and policymakers working in the field of water treatment and membrane technology. Several impact assessment methods were used in this analysis, including the Cumulative Energy Demand (CED) and IMPACT2002+ methods. In order to consider the variations in results and tackle the associated uncertainties, we employed Monte Carlo simulation and conducted sensitivity analysis. We also delved into uncertainties linked to the Life Cycle Impact Assessment (LCIA) method and the parameters and data sources. The results suggest that employing the electrospinning technique for membrane fabrication is a more environmentally sustainable choice compared to the NIPS method, particularly concerning climate change and fossil depletion impact categories. However, the uncertainty analysis revealed that definitive conclusions couldn’t be reached regarding the impact categories of eutrophication and toxicity. The total energy that the NIPS method uses for one batch spinning of 50 gr of 0.25TOCNF/CA polymeric solution was 1030 MJ while for the electrospinning process was 768 MJ. The nonrenewable fossil fuel energy consumption by the NIPS method is more than the electrospinning method. So, the electrospinning method is more efficient than the NIPS method in terms of energy consumption. The NIPS method has a greater impact on the environment due to its higher water consumption and solvent-contaminated wastewater release, and a higher contribution to human carcinogenic, non-carcinogenic toxicity, mainly due to more electricity demand.

Date	9 May 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Robert Hausler (Supervisor)