Gold Nanoparticles on 3D-Printed Filters: From Waste to Catalysts

Abstract

Three-dimensionally printed solid but highly porous polyamide-12 (PA12) plate-like filters were used as selective adsorbents for capturing tetrachloroaurate from acidic solutions and leachates to prepare PA12–Au composite catalysts. The polyamide-adsorbed tetrachloroaurate can be readily reduced to gold nanoparticles by using sodium borohydride, ascorbic acid, hydrogen peroxide, UV light, or by heating. All reduction methods led to polyamide-anchored nanoparticles with an even size distribution and high dispersion. The particle sizes were somewhat dependent on the reduction method, but the average diameters were typically about 20 nm. Particle sizes were determined by using a combination of single-particle inductively coupled plasma mass spectrometry, helium ion microscopy, and powder X-ray diffraction. Dispersion of the particles was analyzed by scanning electron microscopy with energy-dispersive spectroscopy. Due to the high adsorption selectivity of polyamide-12 toward tetrachloroaurate, the three-dimensional-printed filters were first used as selective gold scavengers for the acidic leachate of electronicwaste (WEEE). The supported nanoparticles were then generated directly on the filter via a simple reduction step. These objects were used as catalysts for the reduction of 4-nitrophenol to 4-aminophenol. The described method provides a direct route from waste to catalysts. The selective laser sintering method can be used to customize the flow properties of the catalytically active filter object, which allows the optimization of the porous catalytic object to meet the requirements of catalytic processes.

3D Printed Palladium Catalyst for Suzuki‐Miyaura Cross‐coupling Reactions

“…Based on this and our previously published work, we believe that SLS 3d printing may become a valuable and versatile preparation method in the field of heterogeneous catalysis. However, as is apparent from the recent literature, the search for truly heterogeneous catalysts for Suzuki‐Miyaura and other cross‐coupling reactions remains a demanding and challenging task, and (at least partially) pseudo‐homogeneous mode of catalysis by leached palladium is commonly observed for various supported palladium NP catalysts.…”

“…In order to study the possible changes in physical structure of the catalytic objects, SEM images of outer surfaces and internal structures of the catalyst before and after the reactions were obtained. Analysis of the images revealed – typical for SLS 3d printed objects – a highly porous structure both on the surface and in the bulk of the objects, which remained principally intact after 10 reaction cycles. The only observed changes were associated with the loss of loosely attached larger particles of sizes≥100 μm, which did not undergo sintering during the 3d printing process due to their size (Figure ).…”

“…In order to demonstrate the potential of the SLS 3d printing technology to create functional objects of various shapes, 3d printed sleeves for magnetic stirring bars were fabricated (Figure ). Impregnation of Teflon coated magnetic stirrers with transition metals has been suggested as an attractive approach to fabrication of reusable catalysts, and our group has advanced this idea by implementing removable 3d printed sleeves for stirring bars . Such design provides the advantages of constant renewal of the liquid layer around the catalyst during the reaction due to stirring, and easy removal of the catalyst from the reaction mixture by using a magnetic rod.…”

“…Therefore, SLS 3d printing allows fabrication of solid but highly porous objects, in which fluid can flow through the voids between the partially fused particles, making catalysts within the bulk of the object accessible for contact with the reaction medium. We have previously demonstrated the applicability of SLS 3d printing for the production of porous filters with various absorption properties, flexible carbonous electrodes, and heterogeneous hydrogenation catalysts, and in this work we further develop catalytically active 3d printed materials with implementation in Suzuki‐Miyaura cross‐coupling reaction.…”

“…Selective laser sintering (SLS) 3d printing is a suitable method for manufacturing objects with inherent flow‐through porosity, and catalytically active additives can be added without pre‐ or post‐processing . In an SLS process, a powder is sintered by a moving infrared laser, forming 3d objects in a layer‐by‐layer fashion.…”