(519b) Lignocellulosic Materials for Nanofiltration Membrane Synthesis

Authors: 
Colburn, A., University of Kentucky
Bhattacharyya, D., University of Kentucky
Lignocellulosic materials are readily available from renewable sources, and possess many interesting properties for membrane development, such as solvent resistance any hydrophilic functional groups. This work looks at two approaches for integrating cellulose and lignin materials into high performance membranes.

In the first approach, cellulose nanocomposite membranes capable of selectively separating small organic molecules were created using 1-ethyl-3-methylimidazolium acetate as a solvent. Membrane morphology has been thoroughly studied using dual beam FIB/STEM and confocal microscopy. Cellulose nanocomposite membranes have been shown to reject up to 80% methylene blue (MW 319.8 Da) while maintaining a water permeability of 10 LMH/bar. Cellulose composite membranes exhibited no swelling or deformation during permeation of isoproponal solvent, which suggests strong solvent resistance. Recovery of lignin trimers and tetramers was studied using an isopropanol solvent. High-throughput concentration of these plant derived molecules can significantly increase the value of processing lignin for chemicals.

The second approach involves functionalizing lignin sulfonate, a common byproduct of paper production, onto the surface of the DOW-Filmtec NF-270. Lignin sulfonate is baked onto the NF-270 surface for 30 minutes at 90°C. . The pure water permeability of the functionalized membrane was 14.8 LMH/bar, only slightly below the 16.3 LMH/bar measured for the commercial membrane. The LiS functionalized membrane rejected 97.1% of 1000 mg/L Na2SO4 solution compared to 98% for the unmodified NF270 membrane. After fouling with 100 mg/L BSA, 5 minutes of tangential water washing (12.2 cm/s) of LiS membranes lead to flux recovery of 100% (of the initial flux) after the first fouling cycle and 90% after the second fouling cycle. The un-functionalized commercial NF-270 membrane flux declined below 40% of the initial flux after BSA fouling and never recovered after the same water washing.