3D printing has emerged as an attractive way of formulating structured adsorbents, as it imparts lower manufacturing costs compared to hydraulic extrusion while also allowing for unprecedented geometric control. However, binderless structures have not been fabricated by 3D printing, as ink formulation has previously required clay binders which cannot be easily removed. In this study, we report the development of a facile approach to shape engineer binderless zeolites. 3D-printed inks comprised of 13X, 5A, ZSM-5, and experimental South African zeolites were prepared using gelatin and pectin as binding agents along with dropwise addition of various solvents. After printing, the dried monoliths were calcined to remove the biopolymers and form 100% pure zeolite structures. From N 2 physisorption and CO 2 adsorption measurements at 0 • C, all monoliths showed narrowing below 1 nm from their powders, which was attributed to pore malformation caused by intraparticle bridging during calcination. The various adsorption isotherms indicated that this narrowing led to varying degrees of enhanced adsorption capacities for all three gases, as the slightly smaller pores increased electrostatic binding between the sorbent walls and captured species. Analysis of CO 2 adsorption performance revealed comparable diffusivities and adsorption capacities to the commercial bead analogues, implying that biopolymer/ zeolite printing can produce contactors which are competitive to commercial benchmarks. The binderless monoliths also exhibited faster diffusivities compared to zeolite monoliths produced by conventional direct ink writingon account of an enhancement in macroporosityhighlighting that this new method enhances the kinetic properties of 3D-printed scaffolds. As such, the sacrificial biopolymer technique is an effective and versatile approach for 3D printing binderless zeolite structures.

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Zeolite-NaA membranes were synthesized from an extract of fused South African fly ash on a porous titanium support by a secondary growth method. The influence of the synthesis molar regime on the formation of zeolite NaA membrane layer was investigated. Two synthesis mixtures were generated by adding either aluminium hydroxide or sodium aluminate to the fused fly ash extract. The feedstock material and the synthesized membranes were characterized by X-diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). It was found by XRD and SEM that the cubic crystals of a typical zeolite NaA with a dense intergrown layer was formed on the porous Ti support. The study shows that the source of Al used had an effect on the membrane integrity as sodium aluminate provided the appropriate amount of Na(+) to form a coherent membrane of zeolite NaA, whereas aluminium hydroxide did not. Morphological, the single hydrothermal stage seeded support formed an interlocked array of zeolite NaA particles with neighbouring crystals. Also, a robust, continuous and well-intergrown zeolite NaA membrane was formed with neighbouring crystals of zeolite fused to each other after the multiple stage synthesis. The synthesized membrane was permeable to He (6.0 × 10(6) L m(-2)h(-1) atm(-1)) and CO2 (5.6 × 10(6) L m(-2)h(-1) atm(-1)), which indicate that the layer of the membrane was firmly attached to the porous Ti support. Membrane selectivity was maintained showing membrane integrity with permselectivity of 1.1, showing that a waste feedstock, fly ash, could be utilized for preparing robust zeolite NaA membranes on Ti support.

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