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Impact of Factors on Remediation of Miscellaneous (Fe, Cs) and Nontoxic Elements (Sc, Ti, Ga, Ge) Via Batch Adsorption Process
Published in Deepak Gusain, Faizal Bux, Batch Adsorption Process of Metals and Anions for Remediation of Contaminated Water, 2021
Deepak Gusain, Shikha Dubey, Yogesh Chandra Sharma, Faizal Bux
The percentage removal for cesium with chabazite-type zeolite increased with increase of temperature from 293 to 323 K, but on further increase of the temperature to 353 K, the percentage removal declined (Du et al. 2017). This is attributed to motion of cesium ions and expansion of the framework with change of temperature. The increase of temperature led to increase in the motion of the cesium ions, and this lead to the difficulty of cesium ions to be adsorbed. In addition, the increase of the temperature also causes the expansion of the framework of the chabazite-type zeolite. The expansion led to the increase of the exposure of the adsorption sites and led to the increase of the adsorption. The aforementioned factors in the adsorption of cesium on chabazite-type zeolite led to counter each other, and this is the reason for the increase of removal up to 323 K and the decline afterward.
x Emissions
Published in Ozcan Konur, Petrodiesel Fuels, 2021
R. J. G. Nuguid, F. Buttignol, A. Marberger, O. Kröcher
Large pore-BEA and medium pore-ZSM-5 zeolites have been the most investigated supports for Fe-based SCR catalysts. Although satisfactory NOx reduction activities are generally achieved, they deactivate quite readily at high temperatures in the presence of steam (Iwasaki et al., 2011). Because of this, small-pore chabazite-type zeolites such as SSZ-13 have received growing attention. Gao et al. (2015) synthesized a Fe-SSZ-13 catalyst with a remarkably low temperature activity that can be retained up to 550°C in the fresh state. Upon aging, the catalyst exhibited lower activity but still achieved 80% NO conversion at 450°C (GHSV = 200,000 h–1). The hydrocarbon tolerance can be improved by careful selection of the zeolite framework. Ma et al. (2012) studied the effect of propene poisoning on the activity of Fe-BEA, Fe-ZSM-5, and Fe-MOR. While Fe-BEA and Fe-ZSM-5 deactivated significantly, Fe-MOR retained high NOx conversion even after propene coking at 350°C. The exceptional stability of Fe-MOR could be traced back to the one-dimensional pore structure of the zeolite framework, which could limit hydrocarbon diffusion in the first place. Furthermore, hydrocarbon activation is hindered in MOR because it is not as acidic as BEA and ZSM-5.
NMR of Layered Materials for Heterogeneous Catalysis
Published in Alexis T. Bell, Alexander Pines, NMR Techniques in Catalysis, 2020
Grant W. Haddix, Mysore Narayana
Anderson et al. [106], using gas chromatography as well as 13C and 1H NMR, monitored the shape-selective catalytic conversion of methanol to low molecular weight olefins and aliphatics by SAPO-34. This phosphate has the framework topology of the naturally occurring zeolite chabazite. The primary limiting factor determining the length of the hydrocarbon chain appears to be the size of the eight-membered window. They claimed that the main species present in the intracrystalline space are branched C4 and C5 aliphatics, which owing to their size are trapped and impose additional constraints on the diffusion of the linear species. Furthermore, they hypothesized that by preparing the catalyst either with partial occlusion or with very large cations, formation of branched hydrocarbons could be prevented and thus the diffusional constraints on C2 and C3 hydrocarbons could be reduced. As a result, selectivity for propylene would improve.
Seawater-mixed alkali-activated materials: a comparative investigation of metal slag suitability
Published in Journal of Sustainable Cement-Based Materials, 2023
Yubin Jun, Seong Ho Han, Young Hwan Bae, Jae Hong Kim
Alkali-activated binders have been developed as an alternative to cement. Many studies have shown that alkali-activated binders have mechanical properties superior to Portland cement [1–3]. An alkali-activated binder is produced by a chemical reaction between an alkaline activator and a solid aluminosilicate precursor. Fly ash (from a coal-fired power plant), blast-furnace slag (from iron production blast furnaces), and metakaolin (from the clay mineral kaolinite) are good solid aluminosilicate precursors for alkali activation [1, 4, 5]. The main components of fly ash and metakaolin are the SiO2-Al2O3 system; the chemical components of blast-furnace slag (BFS) are mainly the CaO-SiO2-Al2O3 system. The main reaction products of fly ash and metakaolin are aluminosilicate gel and crystalline zeolite phases such as chabazite, hydroxysodalite, and hydroxycancrinite [6]. The major reaction products of alkali-activated BFS are calcium silicate hydrate (C-S-H) with a low Ca/Si ratio (mean ratio of 0.8) and calcium silicate hydrate I (C-S-H(I)) [7, 8].
Cycles of carbon, nitrogen and phosphorus in poultry manure management technologies – environmental aspects
Published in Critical Reviews in Environmental Science and Technology, 2023
Małgorzata Kacprzak, Krystyna Malińska, Anna Grosser, Jolanta Sobik-Szołtysek, Katarzyna Wystalska, Danuta Dróżdż, Anna Jasińska, Erik Meers
AD is often limited by low C/N ratio, high content of nitrogen, hydrogen sulfide in biogas as well as problem with foaming (Figure 1). Optimization and improvement of anaerobic digestion efficiency is achieved by feedstock pretreatment before introduction to the digestion chambers and/or co-digestion of poultry manure with other organic waste (Dróżdż et al., 2020; Khoshnevisan et al., 2021; Kreidenweis et al., 2021). Bioaugmentation and the use of additives in the form of nanoparticles or trace elements supplementation also seem to be an promising option (Aguilar-Moreno et al., 2020; Hassanein et al., 2019; Shah et al., 2021) Furthermore, to reduce the risk of failure of the process due to ammonia accumulation, the following solutions can be applied: i) stripping (Guštin & Marinšek-Logar, 2011); ii) addition of ion exchange/adsorption materials such as e.g., zeolite (Ziganshina et al., 2015), natural chabazite (Lin et al., 2016) or biochar (Ma et al., 2021; Pan et al., 2019); iii) membrane separation (Wang et al., 2018); d) dilution of the feedstock (Duan et al., 2018). Table S2 (supplementary materials) summarizes some results of AD of poultry manure within the above-mentioned solutions.
Impact of the mineralogical composition of natural pozzolan on properties of resultant geopolymers
Published in Journal of Sustainable Cement-Based Materials, 2021
Rafia Firdous, Dietmar Stephan
Considering the differences in the mineralogy of both natural pozzolans and resultant reaction products, the higher reactivity of RT is may be due to the presence of zeolites actively participating in the reaction. Previous studies have shown the pozzolanic reactivity of zeolite minerals (chabazite, phillipsite, analcime) [47,48]. For a tuff majorly composed of zeolite (mordenite) upon its reaction with sodium silicate solution, the formation of N-A-S-H gel has been observed [49]. The formation of zeolite-like geopolymer gel in RT geopolymers and participation of zeolite minerals is in good agreement with the literature. Additionally, RT also contained calcite which had also participated in the reaction (Figure 4(a)), but the formation of sodium carbonate was not observed. This can be because of two reasons (1) low content of calcite in RT, (2) the higher reaction degree of RT suppresses the negative effect of calcite. As a result, RT exhibited higher compressive strength in comparison to BT. For BT, a lower silica modulus of the alkaline solution was required to achieve useful strength. Moreover, the formation of sodium carbonate hindered the determination of the degree of reaction by selective dissolution indicating that selective dissolution cannot be accurately applied to low reactive natural pozzolan samples, which are prone to alkali carbonate formation.