Hydroxy Sodalite Research Articles

Lithium leach residue synthesis process of high crystallinity hydroxysodalite, NaX, NaA zeolites and solidification and migration of potentially toxic elements

Converting lithium leach residue (LLR) into zeolite can reduce environmental impacts while also producing high value-added products. However, the synthesis of zeolites by LLR under alkali fusion may result in the solidification and migration of potentially toxic elements with secondary environmental impacts. Systematic research into this subject is rare in the open literature and the mobility of toxic elements from LLR derived zeolites is yet to be understood. In this paper, we have investigated the highly crystalline synthesis of hydroxy sodalite, X-type zeolite (NaX), and A-type zeolite (NaA) without stencil agent and crystal species, which can be achieved by modulating the alkali fusion temperature, all three zeolites have greater than 90 % conversion of the major elements aluminum and silicon. Meanwhile, the leachability of thallium (Tl), beryllium (Be), and potentially toxic elements (lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), arsenic (As), barium (Ba), copper (Cu), nickel (Ni), cobalt (Co), zinc (Zn)) was monitored by pH-dependent leaching test for LLR and three kinds of synthesized zeolites according to the Chinese standard and the emission of toxic elements during the synthesis process was analyzed, to investigate the migration and quantify the distribution of the toxic elements in the LLR to the product zeolites and the cleaning wastewater. The migration efficiency of potentially toxic elements from LLR to the product zeolite and cleaning wastewater was explored. It was found that most of the toxic elements Tl, Be and potentially toxic elements were solidified in the structure of the zeolites by ion exchange (solidification rate > 90 %), and a small portion flowed into the cleaning wastewater. Although there are toxic elements solidified in the structure, there is no significant leaching under various pH conditions, which is in line with the Chinese standard (GB/T 5085.3–2007). Therefore, it is considered that LLR realizes environmentally friendly zeolite production and does not cause secondary pollution to the environment. This work demonstrates great potential for green recycling of LLR from the lithium extraction process and introduces an environmentally friendly slag treatment technology.

Solidification/stabilization of lead-contaminated soil using alkali-activated volcanic ash

The bioaccumulation of lead in soil poses a significant human health risk. The solidification/stabilization (S/S) technique, employing binders like Portland cement or lime, is a common method for remediating lead-contaminated soil. However, cement production has adverse environmental impacts, prompting the exploration of eco-friendly alternatives like alkali-activated materials (AAMs). This study assesses AAM efficacy in the S/S of lead-contaminated soil. The effects of several factors, including varying amounts of volcanic ash (VA), lead concentration, curing temperatures, and curing times are investigated. Unconfined compressive strength (UCS), toxicity characteristic leaching procedure test (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscope-energy-dispersive spectroscopy-mapping analyses (FESEM/EDS/mapping) analyses are used to study the specimens. The findings indicated a substantial increase in the UCS of lead-contaminated soil treated with 15% VA (under oven curing (OC) conditions), and 10% VA (under ambient curing (AC) conditions) exhibited remarkable increases of up to 600% and 458%, respectively. Moreover, the leaching of Pb2+ ions from samples contaminated with 10,000 mg/kg (under OC conditions) and 2500 mg/kg (under AC conditions) experienced significant reductions of 87% (from 135.14 to 13.36 ppm) and 91% (from 26.32 to 2.21 ppm), respectively. The S/S process in these samples operated through three primary mechanisms of chemical bonding, physical encapsulation, and the formation of insoluble silicate. The formation of N-A-S–H and hydroxy sodalite structures played a vital role in facilitating these mechanisms. Therefore, alkali-activated VA demonstrated excellent performance in the remediation of lead-contaminated soil.Graphical

Analysis of Alkali in Bayer Red Mud: Content and Occurrence State in Different Structures

The application of large amounts of red mud in the field of building materials is one of the main ways to reuse this material, but the high alkali content of red mud limits its application. In this paper, the washable alkali, removable alkali, and lattice alkali contents of Bayer red mud were studied, and the occurrence states of potassium and sodium in red mud were studied using XRD, IR, XPS, and NMR. On this basis, the removal mechanism for potassium and sodium in red mud was analyzed. The results showed that the Na in the red mud was mainly deposited in the shelf silicon voids of hydroxy sodalite (Na8(AlSiO4)6(OH)2(H2O)2) in the form of Si-O-Na or Al-O-Na. K is deposited in the shelf silico-oxygen void of potassium feldspar (KAlSi3O8) in the form of Si-O-K or Al-O-K. The washable Na and K contents of the mud were 13.7% and 4.47%; the alkali removal agent CaO removed 83.1% and 50.8% of Na and K in the red mud; and the lattice alkali Na and K contents were 3.20% and 44.8%, respectively. In the process of red mud dealkalization, Ca2+ ions can enter the internal voids of the hydroxyl sodalite and potassium feldspar silica skeleton and then replace Al3+ in the Si-O skeleton and Na+ and K+ in the skeleton voids. The replacement reaction changes the silica tetrahedron network structure, resulting in the disintegration of the frame-like silica tetrahedron in the hydroxyl sodalite and potassium feldspar, forming an isolated, island-like silica tetrahedron in hydrated garnet.

Preparation and application of foamed ceramic panels in interior design

Abstract A new type of foam ceramics was prepared with fly ash (CFA). Before sintering, the CFA underwent alkali activation, resulting in an even layer of hydroxy sodalite crystals covering the CFA particles. The pre-treatment of the CFA-alkali-activated material caused it to exhibit a reaction in sintering. The foamed ceramics had the best qualities when sintered at 1,300°C; the leaching toxicity studies of a material used in interior design revealed that during sintering.

A novel technique for fabrication of rod-like shape zeolite LTA and hydroxysodalite by extrusion of bentonite powder: Effects of technical factors on structural characteristics

The current investigation proposes a novel method for the fabrication of zeolite-based packed beds by extrusion of a paste, containing Ca-bentonite, boehmite, and sodium hydroxide, as rod-like shape. The formed precursor was heated at 800 °C to reinforce the extrudates, aged at different times, 3–24 h, and converted to the zeolite structure by recrystallization in the hydrothermal condition, 3–9 h. The obtained results showed that aging, and recrystallization times affect the crystalline phase structure, morphology of particles, textural properties, and cation exchange capacity (CEC) as characterized by X-ray diffractometry, field emission electron microscopy, and N2 adsorption–desorption isotherms. The thermally treated extrudates could be converted to zeolite LTA, and or hydroxysodalite (HS), depending on aging, and recrystallization times. It is necessary to age the treated extrudates in 9 h, and control the recrystallization time within 3 h to achieve zeolite LTA with a proper CEC, 232 mg g−1. Contrarily, the choice of inverse conditions, leads to create a mesoporous HS with a broad pore size distribution, 2–50 nm.

Fusion-Assisted Hydrothermal Synthesis and Post-Synthesis Modification of Mesoporous Hydroxy Sodalite Zeolite Prepared from Waste Coal Fly Ash for Biodiesel Production

Increases in biodiesel prices remains a challenge, mainly due to the high cost of conventional oil feedstocks used during biodiesel production and the challenges associated with using homogeneous catalysts in the process. This study investigated the conversion of waste-derived black soldier fly (BSF) maggot oil feedstock over hydroxy sodalite (HS) zeolite synthesized from waste coal fly ash (CFA) in biodiesel production. The zeolite product prepared after fusion of CFA followed by hydrothermal synthesis (F-HS) resulted in a highly crystalline, mesoporous F-HS zeolite with a considerable surface area of 45 m2/g. The impact of post-synthesis modification of the parent HS catalyst (F-HS) by ion exchange with an alkali source (KOH) on its performance in biodiesel production was investigated. The parent F-HS zeolite catalyst resulted in a high biodiesel yield of 84.10%, with a good quality of 65% fatty acid methyl ester (FAME) content and fuel characteristics compliant with standard biodiesel specifications. After ion exchange, the modified HS zeolite catalyst (K/F-HS) decreased in crystallinity, mesoporosity and total surface area. The K/F-HS catalyst resulted in sub-standard biodiesel of 51.50% FAME content. Hence, contrary to various studies, the ion exchange modified zeolite was unfavorable as a catalyst for biodiesel production. Interestingly, the F-HS zeolite derived from waste CFA showed a favorable performance as a heterogeneous catalyst compared to the conventional sodium hydroxide (NaOH) homogeneous catalyst. The zeolite catalyst resulted in a more profitable process using BSF maggot oil and was economically comparable with NaOH for every kilogram of biodiesel produced. Furthermore, this study showed the potential to address the overall biodiesel production cost challenge via the development of waste-derived catalysts and BSF maggot oil as low-cost feedstock alternatives.

Synthesis of Hydroxy-Sodalite from Rice Husk Silica and Food-Grade Aluminum Foil as A Catalyst for Biomass Pyrolysis

In this research, food-grade aluminum foil (FGAF), rice husk silica (RHS), and sodium hydroxide were needed to synthesize hydroxy-sodalite (HS) using hydrothermal method. The raw materials were exposed to crystallization at 100 °C for 72, 96 and 120 h, and followed by calcination for 6 h at 550 °C. The products obtained were identified using X-ray diffraction (XRD) and scanning electron microscope (SEM) technique, and it applied as catalysts for pyrolysis of biomass. The bio-crude oils (BCO) produced were investigated adopting gas chromatography-mass spectrometry (GC-MS). The XRD results reveal that the products obtained with the crystallization time of 72 and 96 h are a mixture of zeolite A and HS and practically pure HS with a crystallization time of 120 h. The shapes of particles as displayed by SEM are in good agreement with the results of others. The main components of the BCO produced are hydrocarbons, with the biogasoline contents in the range of 81.67 - 96.24 % was resulted from the mixture of water hyacinth and palm oil, and 72.92 - 92.58 % from the mixture of cassava solid waste and palm oil. In this respect, it can be concluded HS is a prospective catalyst for the pyrolysis of biomass.
 HIGHLIGHTS
 
 Hydroxy sodalite zeolites were synthesized from rice husk silica and food-grade aluminum foil using hydrothermal method at different temperatures
 Formation of hydroxy sodalite was confirmed by characterizations using XRD and SEM techniques
 Hydroxy sodalite zeolites produced were applied as catalyst for pyrolysis of a mixture of cassava solid waste with palm oil and a mixture of water hyacinth with palm oil
 The bio crude oils produced from the pyrolysis experiments were characterized using GC-MS technique to identify their chemical components
 
 GRAPHICAL ABSTRACT

Direct single-step synthesis of phase pure zeolite Na–P1, hydroxy sodalite and analcime from coal fly ash and assessment of their Cs+ and Sr2+ removal efficiencies

Combustion by-products of coal from thermal power plants cause environmental pollution; efforts are made to develop techniques and green processes that could reduce the waste volume and convert the waste to useful materials. Synthesis of phase pure zeolites from coal fly ash and its use as adsorbent and ion exchangers to remove Cs+ and Sr2+ from simulated nuclear waste solutions is the focus of the current study. Zeolite Na–P1, hydroxy sodalite and analcime were synthesized from fly ash obtained from an Indian thermal power plant by using hydrothermal method. Zeolite synthesis conditions were optimized by studying the effect of concentration of NaOH solution, homogenization time, hydrothermal temperature and time. The zeolite phase formation, surface morphology, thermal stability studies were carried out by XRD, SEM, TG-DTA techniques; specific surface area was determined by BET analysis. Crystalline pristine zeolite Na–P1 was prepared from fly ash on reaction with 1 M NaOH at 150 °C. Similarly, hydroxy sodalite and analcime were also synthesized from the fly ash by hydrothermal reaction with 3 M NaOH at 150 °C and 5 M NaOH at 200 °C respectively. The removal efficiencies of synthesized zeolites were investigated with aqueous simulated nuclear waste solutions containing Cs+ and Sr2+. The adsorption capacities and cation exchange capacity (CEC) of zeolite Na–P1, hydroxy sodalite and analcime for Cs+ and Sr2+ ions were demonstrated. The results show the adsorption capacity of Na–P1 for Cs+ is 39.3 mg/g and for Sr2+ is 92.48 mg/g respectively and is a better adsorbent than analcime and hydroxy sodalite.

Optimal synthesis of nanosize seeds for secondary growth of high performance hydroxy-sodalite (H-SOD) zeolite membranes for small gas and water separations

Nanosize H-SOD particles were hydrothermally synthesized as seeds for the secondary growth of hydroxy-sodalite (H-SOD) zeolite membrane. The size and phase purity of H-SOD zeolite particles were carefully controlled by changing several hydrothermal conditions. Especially, NaOH concentration in the hydrothermal solution made a significant effect on the phase purity and particle size. The high phase purity particles with a mean diameter of 80 nm were successfully synthesized at a 3 M NaOH concentration and applied for secondary growth. Overall, uniform H-SOD zeolite membranes with various thicknesses (3, 7, and 9.5 μm) were prepared by varying secondary growth time. The 9.5 μm thick H-SOD zeolite membrane exhibited high H 2 /N 2 permselectivity of 95 at 473 K and a transmembrane pressure of 0.3 MPa. And, the pervaporation performance was evaluated for 90 wt% methanol-water mixture at 423 K, an elevated temperature. It showed a high water/methanol separation performance; its water/methanol separation factor was 2726 and the total flux, 1.02 kg/m 2 h. The high small gases and water separation performances were because interparticular voids between the nano size seeds were small and the surface of seed layer was flat. Therefore, the secondary growth remained a continuous zeolite layer with few non-zeolitic pores. In the present work, it was well proven experimentally that application of nanosize seed is an effective option to prepare high performance zeolite membrane in H-SOD zeolite system. • High purity H-SOD zeolite particles with a mean diameter of 80 nm were carefully prepared for the secondary growth of H-SOD zeolite membranes. • Synthesis temperature, time and NaOH concentrations played major roles on the particle size. • The H-SOD zeolite membranes prepared by using the nanosize seeds showed excellent performances for H 2 /CO 2 , H 2 /N 2 and water/methanol separations. • The good performance was due to smaller interparticular voids between nano size seeds and the increased surface flatness of seed coating layer.

The effect on the compressive strength of fly ash based geopolymer concrete with the generation of hydroxy sodalite

The influence factors of the high compressive strength of fly ash based geopolymer concrete (FGPC) were studied rarely mentioned the generation of hydroxy sodalite before. In this paper, FGPC was prepared by using low-calcium fly ash and NaOH acted as the main component in the base activator. By comparing the compressive strengths of FGPC under different preparation parameters, the microstructures of cross-section and hydroxy sodalite (Na4Al3Si3O12OH) in FGPC were observed by SEM. The spectra information of FGPC were characterized by XRD and FT-IR. The compressive strength of FGPC was analyzed by studying the growth of hydroxy sodalite and the microstructure of the matrix section under different conditions. The results showed that increasing the concentration of NaOH solution, changing curing temperature and curing time in a certain range can effectively enhance the activity of fly ash and promote the generation of N-A-S-H gel and hydroxy sodalite. The compressive strength of FGPC was decided by matrix structure and the generation of hydroxy sodalite. When the ratio of Na2SiO3/NaOH is 1.7, the ratio of alkali activator/fly ash is 0.58, the compressive strength of the FGPC can reach 110.2 MPa by curing at 75 ℃ for 24 h after 28 days. The results can help to understand the mechanism of promotion of hydroxy sodalite and give a novelty reference to produce a high compressive strength FGPC.

Synthesis and Evaluation of HSOD/PSF and SSOD/PSF Membranes for Removal of Phenol from Industrial Wastewater.

Phenol is regarded as a major pollutant, as the toxicity levels are in the range of 9–25 mg/L for aquatic life and humans. This study embedded silica sodalite (SSOD) and hydroxy sodalite (HSOD) nanoparticles into polysulfone (PSF) for enhancement of its physicochemical properties for treatment of phenol-containing wastewater. The pure polysulfone membranes and sodalite-infused membranes were synthesized via phase inversion. To check the surface morphology, surface hydrophilicity, surface functionality, surface roughness and measure the mechanical properties of the membranes, characterization techniques such as Scanning Electron Microscope (SEM), contact angle measurements, Fourier Transform Infrared, Atomic Force Microscopy (AFM) nanotensile tests were used, respectively. The morphology of the composite membranes showed incorporation of the sodalite crystals decreased the membrane porosity. The results obtained showed the highest contact angle of 83.81° for pure PSF as compared to that of the composite membranes. The composite membranes with 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF showed mechanical enhancement as indicated by a 20.96% and 19.69% increase in ultimate tensile strength, respectively compared to pure PSF. The performance evaluation of the membranes was done using a dead-end filtration cell at varied feed pressure. Synthetic phenol-containing wastewater was prepared by dissolving one gram of phenol crystals in 1 L of deionized water and used in this study. Results showed higher flux for sodalite infused membranes than pure PSF for both pure and phenol-containing water. However, pure PSF showed the highest phenol rejection of 93.55% as compared to 63.65% and 64.75% achieved by 10 wt.% HSOD/PSF and 10 wt.% SSOD/PSF, respectively. The two sodalite infused membranes have shown enhanced mechanical properties and permeability during treatment of phenol in synthetic wastewater.

Synthesis and Characterization of NaA Zeolite Using Natural Kaolinite Clays from Nigeria by Low Temperature Hydrothermal Method

Zeolites NaA is one of the most valuable synthetic zeolites widely used as ion-exchange material, catalysts, and adsorbents in industry. There is therefore need to adopt a more energy-efficient route for its synthesis from low-cost and sustainable raw materials. In this present work, zeolites Na-A was synthesized from natural kaolinite clays obtained from three selected regions (Ikere, Okpella and Kankara) in Nigeria. The as-received kaolinite clays (IKclay, OKclay and KAclay) were initially beneficiated thoroughly to obtain pure powders (˂75 μm). The processed kaolinite clay powders were then subjected to heating in a muffle furnace at 850oC for 3 h at a heating rate of 10oC/min to convert the kaolinite clays to their respective metakaolins. The obtained metakaolins were then reacted with NaOH solutions at varying concentrations of 3.0 and 4.0M respectively using a low temperature hydrothermal transformation to obtained Zeolites Na-A powders. The obtained zeolites were then analyzed by scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FT-IR). The results showed that zeolite NaA is produced with mixture of hydroxysodalite (HS) while the EDS revealed the presence of Si, Al, O and Na indicating chemical constituents of typical zeolite NaA. All the tested kaolinite clays are therefore suitable for preparation of zeolite NaA as cheaper source of silica and aluminum.

Ultrasonic Powered Hydrothermal Modification of Coal Fly Ash to Cost-Effective Zeolites

Coal fly ash (CFA) waste is one of the anthropogenic materials having detrimental impact as particulate and leachate contaminant. Dumping of such solid waste into landfills and other improper waste management conduct can be lethal for environment. In this work CFA waste was attempted to modify into zeolites using ultrasonic assisted hydrothermal and conventional heating approaches. The conventional and ultrasonic assisted synthesized zeolites showed entirely different cation exchange capacity (CEC) and morphology. However, FTIR and XRD patterns of zeolites synthesized by both of techniques were almost similar. However, a better crystalline structure, functionality and morphology of Na-X, NaP1 and hydroxy sodalite (SOD) classes of zeolites synthesized in ultrasonic (USZ-8) and hydrothermal (HT-48) curing modes were observed. Hydrothermally treated (HT-8) material was found with a lower porosity and low CEC (109 meq/100g) in contrast to USZ-8 with high porosity and CEC (390 meq/100g) for the same reaction time. ICP-OES analysis demonstrated that ultrasonic cavitation was more appropriate way to convert coal fly ash based aluminosilicates into active zeolites, economically. It can be concluded reasonably that ultrasonic modification of coal fly ash into valuable zeolites is a constructive approach and a step to gear up greener innovation.

Ultrasonic Powered Hydrothermal Modification of Coal Fly Ash to Cost-Effective Zeolites

Coal fly ash (CFA) waste is one of the anthropogenic materials having detrimental impact as particulate and leachate contaminant. Dumping of such solid waste into landfills and other improper waste management conduct can be lethal for environment. In this work CFA waste was attempted to modify into zeolites using ultrasonic assisted hydrothermal and conventional heating approaches. The conventional and ultrasonic assisted synthesized zeolites showed entirely different cation exchange capacity (CEC) and morphology. However, FTIR and XRD patterns of zeolites synthesized by both of techniques were almost similar. However, a better crystalline structure, functionality and morphology of Na-X, NaP1 and hydroxy sodalite (SOD) classes of zeolites synthesized in ultrasonic (USZ-8) and hydrothermal (HT-48) curing modes were observed. Hydrothermally treated (HT-8) material was found with a lower porosity and low CEC (109 meq/100g) in contrast to USZ-8 with high porosity and CEC (390 meq/100g) for the same reaction time. ICP-OES analysis demonstrated that ultrasonic cavitation was more appropriate way to convert coal fly ash based aluminosilicates into active zeolites, economically. It can be concluded reasonably that ultrasonic modification of coal fly ash into valuable zeolites is a constructive approach and a step to gear up greener innovation.

Modeling and Simulation of a Steam-Selective Membrane Reactor for Enhanced CO2 Methanation

A modelling and simulation study of a hydroxy sodalite (H-SOD) membrane reactor for in-situ water removal during CO2 methanation reaction is presented. A non-isothermal, steady-state, pseudo-homoge...

Synthesis of high purity hydroxy sodalite nanoparticles via pore-plugging hydrothermal method for inorganic membrane development: Effect of synthesis variables on crystallinity, crystal size and morphology

The effect of synthesis parameters on crystallinity, crystal size and morphology of hydroxy sodalite particles developed via the pore-plugging hydrothermal (PPH) synthesis method is reported in this study. The PPH method is promising in developing nanocomposite membrane materials with superior performance to those prepared from other methods. Towards developing high-quality nanocomposite sodalite/ceramic membrane for CO2 capture via the PPH method, obtaining high-purity sodalite (SOD) nanoparticles via PPH is essential. Thus effect of synthesis variables (e.g. ageing, interruption time, and synthesis temperature) on purity of as-prepared SOD crystals was investigated. A precursor solution with molar concentration of 5SiO2:0.5Al2O3:50Na2O:1005H2O was used in the synthesis. During the synthesis, 45 mL of the vigorously mixed precursor solution (with or without ageing) was poured into a Teflon-lined stainless-steel autoclave and subjected to PPH synthesis. Physico-chemical properties of the as-synthesized crystals were characterized with x-ray diffraction (XRD) for crystallinity and purity, scanning electron microscope (SEM) coupled with energy-dispersive x-ray spectrometer (EDS) for morphology and elemental composition, and Fourier transform infrared spectroscopy (FT-IR) for surface chemistry. In this study, the sizes of SOD crystals obtained was in the range of 227–493 nm and a percentage crystallinity of SOD crystals as high as 75% was obtained. When two interruptions of one hour each was introduced in the synthesis protocol (total synthesis time of 3.5 h), pure SOD crystals were obtained. The SEM images of this protocol revealed SOD crystals of typical thread ball aggregate similar to those reported in literature. Ageing the precursor prior to PPH was not instrumental to forming high-purity SOD crystals, and this could result in developing low-quality nanocomposite SOD/ceramic membranes via the PPH synthesis method. Furthermore, adjusting the synthesis temperature and interruption time of the PPH do have effect on the purity and crystallinity of the as-prepared SOD crystals.

Evaluation of silica sodalite infused polysulfone mixed matrix membranes during H2/CO2 separation

Global warming and environmental degradation have stimulated the drive towards the capture of large point source carbon emissions and reducing high energy intensity of industrial processes. Mixed membranes infused with high porosity silica sodalite are potential useful for pre-combustion CO2 capture. However, development of high quality mixed matrix membranes is a challenge. In this study, silica sodalite (SSOD) infused polysulfone (PSF) membranes were developed and evaluated for pre-combustion CO2 capture. The SSOD was obtained via topotactic conversion of layered silicates; and the membrane was prepared using the phase inversion method. The physicochemical nature of the SSOD and the SSOD/PSF was checked using XRD, SEM, and N2 physisorption at 77 K. Single gas permeation used to check membrane quality. N2 physisorption shows that the SSOD possesses higher surface area of 56.56 m2/g and pore volume of 0.181 cm3/g, when compared to that of the hydrothermally-synthesized hydroxy sodalite (HSOD) crystals (surface area: 27.43 m2/g; pore volume: 0.084 cm3/g). The SSOD/PSF membrane is asymmetric with higher mechanical strength than the ordinary PSF. Loading the PSF with SSOD enhanced its H2 permeance from 4.9 × 10−7 mol/m2·s·Pa but with a decrease in H2/CO2 separation factor from 2.2 to 0.6. While the enhanced H2 permeance is attributed to the enhanced porosity of the SSOD, the ideal selectivity is low but still within the values reported in literature. Increasing the SSOD loading up to 10 wt% enhanced the quality and performance of the PSF membrane, displaying H2 permeance of 6.5 × 10−7 mol/m2·s·Pa and a separation factor of 1.1. Though results reported in this study are promising, a robust synthesis protocol that will further enhance both the H2 selectivity and H2 permeance of the membrane is required. Furthermore, more studies are required on the process optimization and techno-economic feasibility for pre-combustion CO2 capture.

Cross‐Linking between Sodalite Nanoparticles and Graphene Oxide in Composite Membranes to Trigger High Gas Permeance, Selectivity, and Stability in Hydrogen Separation

AbstractThin membranes (900 nm) were prepared by direct transformation of infiltrated amorphous precursor nanoparticles, impregnated in a graphene oxide (GO) matrix, into hydroxy sodalite (SOD) nanocrystals. The amorphous precursor particles rich in silanols (Si−OH) enhanced the interactions with the GO, thus leading to the formation of highly adhesive and stable SOD/GO membranes via strong bonding. The cross‐linking of SOD nanoparticles with the GO in the membranes promoted both the high gas permeance and enhanced selectivity towards H2 from a mixture containing CO2 and H2O. The SOD/GO membranes are moisture resistance and exhibit steady separation performance (H2 permeance of about 4900 GPU and H2/CO2 selectivity of 56, with no degradation in performance during the test of 50 h) at high temperature (200 °C) under water vapor (4 mol %).

Cross‐Linking between Sodalite Nanoparticles and Graphene Oxide in Composite Membranes to Trigger High Gas Permeance, Selectivity, and Stability in Hydrogen Separation

Thin membranes (900 nm) were prepared by direct transformation of infiltrated amorphous precursor nanoparticles, impregnated in a graphene oxide (GO) matrix, into hydroxy sodalite (SOD) nanocrystals. The amorphous precursor particles rich in silanols (Si-OH) enhanced the interactions with the GO, thus leading to the formation of highly adhesive and stable SOD/GO membranes via strong bonding. The cross-linking of SOD nanoparticles with the GO in the membranes promoted both the high gas permeance and enhanced selectivity towards H2 from a mixture containing CO2 and H2O. The SOD/GO membranes are moisture resistance and exhibit steady separation performance (H2 permeance of ~4900 GPU and H2/CO2 selectivity of 56, with no degradation in performance during the test of 50 h) at high temperature (200 ºC) under water vapor (4 mol. %).

Synthesis of feldspathoids and zeolite K–F from waste amber container glass

The hydrothermal formation of mineral products from a mixture of amber container glass and aluminium waste (Al:Si = 1) in 4 M NaOH(aq) or 4 M KOH(aq) at 100 °C was monitored at 1, 3 and 10 days by X-ray diffraction analysis with Rietveld refinement, Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. In NaOH(aq), at 1, 3 and 10 days, respectively, 48%, 55% and 63% of the glass crystallised to form hydroxysodalite (HS) and hydroxycancrinite (HC) with minor proportions of katoite and tobermorite. The partial successive transformation of HS to HC was also observed with time. The initial rates of dissolution of the glass and formation of the principal zeolite K–F and secondary katoite phases were considerably slower in KOH(aq); although, the subsequent development of the products was greater than that in NaOH(aq). The zeolite K–F product achieved only 5% crystallinity within the first day which then increased markedly to 60% and 78% at 3 and 10 days, respectively. Despite the incomplete conversion of amber glass into crystalline zeolitic phases, the uptake capacities of the 10-day feldspathoid and zeolite K–F products for Pb2+ (4.3 and 4.5 meq g−1, respectively) and Zn2+ (3.9 and 4.1 meq g−1, respectively) ions compared favourably with those of many other zeolites and waste-derived inorganic sorbents reported in the literature.