Lignocellulose Fiber- and Welded Fiber- Supports for Palladium-Based Catalytic Hydrogenation: A Natural Fiber Welding Application for Water Treatment

Abstract

In our study, lignocellulose yarns were fabricated via natural fiber welding (NFW) into a robust, free-standing, sustainable catalyst for water treatment. First, a series of powder catalysts were created by loading monometallic palladium (Pd) and bimetallic palladium−copper (Pd−Cu) nanoparticles onto ball-milled yarn powders via incipient wetness (IW) followed by a gentle reduction method in hydrogen gas that preserved the natural fiber while reducing the metal ions to their zerovalent state. Material characterization revealed Pd preferentially reduced near the surface whereas Cu distributed more uniformly throughout the supports. Although no chemical bonding interactions were observed between the metals and their supports, small (5−10 nm), near-spherical crystalline nanoparticles were produced, and a Pd−Cu alloy formed on the surface of the supports. Catalytic performance was evaluated for each Pd-only and Pd−Cu powder catalyst via nitrite and nitrate reduction tests, respectively. Next, the optimized Pd−Cu linen powder catalyst was fiber-welded onto a macroporous linen yarn scaffold via NFW and its catalyst performance and reusability were evaluated. This fiber-welded catalyst reduced nitrate as effectively as the corresponding powder, and remained stable during five consecutive cycles of nitrate reduction tests. Although catalytic activity declined after the fiber-welded catalyst was left in air for several months, its reactivity could easily be regenerated by thermal treatment. Our research highlights how lignocellulose supported metal-based catalysts can be used for water purification, demonstrating a novel application of NFW for water treatment while presenting a sustainable approach to fabricate functional materials from natural fibers.

Engineering Lignocellulose Fibers with Higher Thermal Stability through Natural Fiber Welding

“…NFW not only packs the microfibrils closer together, but as discussed, also leaves a very thin film of dissolved and subsequently reconstituted cellulose on the surface of the yarn (Figure b, top profile) where the void spaces between microfibrils on the surface have been filled. These phenomena are something we had observed in each our previous NFW studies, although we had yet to correlate it with enhanced thermal stability. Our current set of data suggests that the structural reorganization (caused by NFW) improved the yarns thermal stability by collapsing and covering the void spaces between the microfibrils, slowing heat transfer in and out of the fiber bundle, causing a temporal delay in decomposition of the lignocellulose yarn.…”

“…Previous work in our lab demonstrated how careful control of NFW process variables (i.e., time, temperature, solvent) can significantly improve the tensile strength (in‐line and 45°) of nonwoven cotton cloth . We have also shown how NFW can improve the bulk mechanical strength of biopolymer yarns (i.e., cotton, linen, and bamboo) by more than 30% while incorporating activated carbons to fabricate high performance supercapacitor yarns for knittable textiles, or while integrating Pd‐based nanoparticle catalysts for wastewater treatment . Rather than focusing again on mechanical properties, this present study explores a new question—how can NFW be used to improve the thermal stability of textile yarns.…”

“…Micro‐ and nano‐ forms (i.e., nanocellulose) are finding applications in diverse areas such as packaging, polymer reinforcements, and biomedical devices . Biopolymers have also been modified for energy storage, and are promising catalyst supports because their surface chemistry promotes nanoparticle deposition …”

“…Both approaches yielded yarns with improved thermal stability over the untreated lignocellulose yarn, and studying these methods together provided insight on how the NFW process rendered the fibers more thermally stable. While unmodified cellulose binders have been used in previous NFW applications, this is a novel application of chemically modified cellulose coatings in NFW, and the first to specifically target improved thermal stability metrics.…”

Solvent Welding and Imprinting Cellulose Nanofiber Films Using Ionic Liquids

“…The welding procedure is applied to aim the mechanical properties enhance and promote nanocellulose surface patterning. Even though some previous works report the welding surface treatment for natural and cellulose-based fibers and films 18, [22][23][24]26 and more recently the use of ILs for improving transparency and mechanical performance in microfibers and papers based materials 34,28 , the present work presents the treatment of nanofibrillated surfaces using distillable ILs; these ILs in contrast to the traditional ILs can be recyclable by distillation with recoveries and purities over 99% 29,36 . Distillable ionic liquids are ILs that can be recovered by distillation.…”