Green Synthesis of Mesoporous Sodalite and Graphene Oxide Hybrid Sodalite Using Lithium Silica Fume Waste

Abstract

Mesoporous zeolite and hybrid zeolite are indispensable materials for the chemical industry; however, their fabrication always involved high production cost, long times, and adverse environmental impact. Here, we report a vacuum− ultraviolet (VUV)-initiated reactive oxygen species (ROS) route for the green and fast synthesis of mesoporous sodalite (SOD) zeolite and a hybrid SOD zeolite directly from lithium silica fume (LSF) waste without template. The fast synthesis is based on in situ generation of ROS (e.g., • OH, O 2•− , and 1 O 2 ) in amorphous precursor using VUV irradiation, which significantly shortens the crystallization process to produce SOD with high crystallinity and abundant mesopores at low temperature. Further addition of graphene oxide (GO) during SOD preparation could not only inhibit the zeolite aggregation but also initiate electron transfer to further induce generation of superoxide ion radicals (O 2•− ), and yield a stable hybrid SOD zeolite with narrower band gap within 2 h. The physicochemical properties of the produced SOD and hybrid SOD were carefully studied, whereby electron paramagnetic resonance (EPR) was used to probe the existence of ROS which promote crystallization process. The metal ion adsorptive experiments revealed zeolites produced own superior ion-exchange capacity toward copper ion. This study opens up a new avenue to enable green and ultrafast synthesis of zeolites and hybrid zeolites with improved time efficiency.

Economical and Sustainable Synthesis of Small-Pore Chabazite Catalysts for NOx Abatement by Recycling Organic Structure-Directing Agents

“…Zeolites, a class of crystalline solid materials with regular microporous frameworks, are widely used in various environmental processes ranging from the adsorptive removal of heavy metal ions and organic pollutants in aqueous media, the catalytic abatement of gaseous emissions in automotive exhausts, to the capture and conversion of greenhouse gases (e.g., CO 2 and CH 4 ). − The synthesis of zeolites, however, often needs tedious hydrothermal crystallization processes using expensive organic structure-directing agents (OSDAs), most commonly organic amines, as templates, − which are normally added in an excess amount to ensure a high zeolite yield. − As a typical example, the small-pore chabazite (CHA) zeolite SSZ-13, which is being utilized as the state-of-the-art catalyst (after introducing Cu ions into the zeolite framework) in diesel exhaust after-treatment systems to eliminate the harmful nitrogen oxides (NO x ) and in the selective methane-to-methanol oxidation, ,, is synthesized using the high-cost N , N , N -trimethyl-1-ammonium adamantine hydroxide (TMAdaOH) as OSDA. After collection and separation of zeolite products, the unreacted OSDAs are discharged as organic pollutants in the wastewater, which not only leads to a waste of the high-value OSDA materials but also requires additional costs for wastewater treatment.…”

Insights into the Crucial Role of Electron and Spin Structures in Heteroatom-Doped Covalent Triazine Frameworks for Removing Organic Micropollutants

“…The increased k f value indicated that external mass transfer of BPs in S-CTF-1 was enhanced by S-doping originating from formation of slight compaction and wrinkling. HSDM described the diffusion process of adsorbates from external surfaces to final internal adsorption sites along the pore surface of CTFs . The D s for BPs adsorption onto CTFs can be determined using Excel Solver through the error minimization method.…”

Future Perspectives on Zeolite/Graphene Oxide Composite Synthesis and Applications

“…It has been reported that different pore structures can be created to adjust the growth of a range of materials, such as zeolites. Silicalite zeolite, having slit-like mesopores (size of 2.0 to 2.5 nm), has also been developed by the addition of graphene oxide nanosheets throughout the synthesis and subsequent calcination of synthesized samples. − Cationic polyelectrolyte functionalized GO was synthesized by the hard template method via incorporation of poly­(diallyl dimethylammonium chloride) (PDDA) into GO, which leads to the formation of slit-like mesopores throughout both sides of the GO surface. The synthesized nanoporous zeolite-Y and zeolite-Y/GO nanocomposites were then examined for their water adsorption capacity. − …”