Evaluation of Modified Fly Ash Based Naa-Zeolite: Effect of Crystallinity on Co2 Adsorption Capacity

Mukaba, Muvumbu Jean-Luc; Ameh, Alechine E.; Eze, Chuks Paul; Petrik, Leslie

doi:10.30638/eemj.2020.045

Cited by 4 publications

(5 citation statements)

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“…On the one hand, this may have been caused by an incomplete ion exchange between the zeolitic Na and H-forms. Otherwise, previous studies on this material indicated that the zeolite's pores are too narrow for N 2 permeation at 77 K [26,27], meaning that definitive conclusions pertaining to differences in the monolith's and powder's textural properties could not be drawn N 2 physisorption alone. The slight enhancement in surface area and pore volume implied that its active sites were more accessible to the condensing gas, thus suggesting that there was some degree of difference between the two materials' pore structures, possibly stemming from the interparticle bridging observed in in Fig.…”

Section: S Lawson Et Almentioning

confidence: 87%

“…Zeolite 13X and Zeolite 5A were purchased from UOP while H-ZSM-5 (Al 2 O 3 /SiO 2 = 50) was purchased from Zeolyst. The South African (SA) zeolite was provided by Petrik et al and was synthesized from fly ash with their established method [26,27]. The binderless zeolite 13X beads used in the dynamic adsorption experiments were provided by Ingevity, while the zeolite 5A beads were provided by Sylobead.…”

Section: Methodsmentioning

confidence: 99%

“…In this proof-of-concept study, we manufactured binderless monoliths using four different zeoliteszeolite 13X, zeolite 5A, H-ZSM-5, and an experimental South African zeolite synthesized from fly ash and provided by Petrik's group [26,27] by implementing pectin and gelatin as sacrificial binding agents. We also manufactured zeolite 13X monoliths with small concentrations of bentonite clay (1-5 wt%), to enhance their mechanical strength, since the 100% pure zeolite monoliths were somewhat brittle.…”

Section: Introductionmentioning

confidence: 99%

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Binderless zeolite monoliths production with sacrificial biopolymers

Lawson

Newport

Al-Naddaf

et al. 2021

Chemical Engineering Journal

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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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Section: S Lawson Et Almentioning

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Binderless zeolite monoliths production with sacrificial biopolymers

Lawson

Newport

Al-Naddaf

et al. 2021

Chemical Engineering Journal

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“…Other applications include CFA utilisation for mine back-filling, as well as agricultural remediation of soil and water treatment using modified CFA [17,23]. Another major area of research in CFA valorisation is the production of value-added, porous materials such as zeolites (i.e., zeolitisation) as well as metal extraction/recovery [24][25][26][27][28][29][30][31][32][33][34][35]. As South Africa is largely reliant on coal for energy production [15], CFA research and the development of various CFA valorisation technologies remain major priorities.…”

Section: Introductionmentioning

confidence: 99%

“…It was reported that the glassy, aluminosilicate phase of CFA contained the majority of the REE content and a process involving size classification, magnetic separation and hydrothermal treatment was proposed as a method of enriching the REE content of CFA [42]. Zeolitisation is a common method utilised in the transformation of the Si and Al content in CFA into a crystalline, porous material with high industrial value [24][25][26][28][29][30][31][32][33][34]. The distributional fate of elements found in CFA during the process of zeolitisation by two different methods (a two-step process and solid fusion-assisted process) was previously reported in literature [26].…”

Section: Introductionmentioning

confidence: 99%

The Behaviour of Rare Earth Elements from South African Coal Fly Ash during Enrichment Processes: Wet, Magnetic Separation and Zeolitisation

et al. 2021

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Rare earth elements (REEs) are essential raw materials in a variety of industries including clean energy technologies such as electric vehicles and wind turbines. This places an ever-increasing demand on global rare earth element production. Coal fly ash (CFA) possesses appreciable levels of REEs. CFA, a waste by-product of coal combustion, is therefore a readily available source of REEs that does not require mining. CFA valorisation to zeolites has been achieved via various synthesis pathways. This study aimed to evaluate one such pathway by monitoring how REEs partition during CFA processing by the wet, magnetic separation process and zeolitisation. South African CFA was subjected to wet, magnetic separation and subsequent zeolitisation of the nonmagnetic fraction (NMF); solid products were characterised by XRD, SEM, XRF and LA-ICP-MS. The wet, magnetic separation process resulted in the partitioning of a specific set of transition metals (such as Fe, Mn, Cr, V, Ni, Zn, Cu, Co and Mo) into the magnetic fraction (MF) of CFA, while REEs partitioned into the NMF with a total REE content of 530.2 ppm; thus, the matrix elements of CFA were extracted with ease. Zeolitisation resulted in a solid zeolite product (hydroxysodalite) with a total REE content of 537.6 ppm. The process of zeolitisation also resulted in the selective enrichment of Ce (259.1 ppm) into the solid zeolite product (hydroxysodalite), while other REEs were largely partitioned into the liquid phase. CFA valorisation by wet, magnetic separation and zeolitisation therefore allowed for the partitioning of REEs into various extraction products while recovering the matrix elements of CFA such as Fe, Si and Al. The findings of this study highlight the geopolitical importance of REEs in terms of the development of alternative processes for REE recovery from waste and alternative sources, which may potentially give countries that employ and develop the technology a key advantage in the production of REEs for the global market.

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