A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD ...gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.
The explosion of African literatures in 2021 is not a coincidence, but is dictated by the continent's decolonial, diasporic and hybrid cultural manifestations, its more than a hundred years of ...struggle for cross-regional integration, its spirit of vigorous and persistent action, and the unique attraction of an Africanness that upholds its selfhood, bridges the gaps, and remembers its history but looks to the future. The diasporic characteristic of attending to, absorbing and squarely facing the tension of heterogeneous cultures means that indigenous African literatures contain a distinctive world consciousness and rational philosophy. They have given rise to diverse civilizations marked by dialogue, inclusiveness and the contemporary spirit of African nations, enabling African literatures to participate effectively in the dialogue of world literature and in new patterns of civilization, displaying as they do a strong vitality, creativity and influence in the positive-sum game with Western culture. This will provide positive encouragement to the mutual learning, integration, harmony, symbiosis and coexistence of civilizations.
The production of polyvinyl chloride (PVC) via the calcium carbide process utilizes a catalyst containing large amounts of mercury (Hg) and is therefore one of the most important sources of ...anthropogenic Hg in China. To measure the emission of Hg from PVC production, we established a flowchart for the calcium carbide process, for which we quantified the Hg content of the material/product at each step. Results indicated that 71.5% of the total Hg (HgT) was lost from the catalyst, most of which was recovered by the Hg remover, accounting for 46.0% of the total Hg (HgT). We determined that 3.7% of the HgT was released into the environment, mostly in solid wastes and byproducts such as hydrochloric acid. Furthermore, no Hg has been detected in the PVC end product. However, we were only able to account for 78.1% of the Hg across the whole system, leaving 21.7% unaccounted for in the mass balance. A rough estimation indicates that most of the “missing” Hg had accumulated in deposits on the inner surface of converters and downstream pipelines; however, the emission to the atmosphere was ≤1% of the HgT. For a PVC production line equipped with a Hg remover, emissions of Hg to the atmosphere have been estimated to be 4.9 g per tonne PVC. Currently, almost all calcium carbide facilities have been equipped with a Hg remover, which may reduce the release of Hg in China by ∼500 t/year.
The preparation of activated carbon sorbent for Hg removal was simplified by combining activation and functionalization processes into one step. Jujube-based carbon material was first mixed with CuCl
...2
solution and then activated for the preparation of Cu-impregnated activated carbon. Physical and chemical properties of prepared activated carbon were investigated by means of N
2
adsorption, SEM-EDS, XRD. A fixed-bed reactor with CEMS (Continuous emission monitoring system) was used to test the Hg adsorption ability of prepared activated carbon. DFT (Density functional theory) method of computational chemistry calculation was applied to identify the Hg adsorption mechanisms on sorbent surface.
Since the Chinese translation of The Da Vinci Code was released in China in 2004, the "Dan Brown Craze" has swept across the country. All of Brown's novels have subsequently been translated into ...Chinese and sold millions of copies. No living foreign writer has generated so much media coverage and scholarship in China within such a short period of time; not even Toni Morrison or J.K. Rowling. Brown's rendering of dichotomies, such as science and religion, humanity and divinity, good and evil, and liberty and privacy, resonates well with his Chinese readers because they feel that these issues are no longer irrelevant to them. They see an urgent need for a revision, if not an entire redefinition, of their existing beliefs and values. This book examines the plot, characterization, themes, setting, codes, knowledge, institutions, and techniques in his novels, and delivers a careful textual analysis, a selective dissemination of relevant information on different subjects, and a perceptive comparison between Brown and other Chinese and Western writers. As such, it shows how his thrillers have been appreciated and studied in China, and what kinds of discoveries, challenges, controversies, and insights have surfaced in the Chinese appreciation of Brown's novels. Furthermore, the book explores why the "Dan Brown Craze" has lasted this long and exerted a broad and far-reaching impact upon the reading, writing, studying, translating, publishing, and marketing of fiction in China.
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•Adsorption mechanisms of SeO2 on CaO surface under O2 were firstly studied by DFT.•The adsorption energies, bond length and electron density maps were calculated.•The electronic ...structure changes upon adsorption were studied.
Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO2 in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO2 due to its low cost. In this paper, the adsorption mechanisms of single SeO2 on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO2 on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O2 atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO2 and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.
Zerovalent Se (Se atom and small Se2 molecule) adsorption mechanisms on a CaO surface were studied by both density functional theory (DFT) calculations and adsorption experiments. Nonvalent Se ...adsorption on the CaO(001) surface was simulated using a slab model. The adsorption energy, adsorption structure, electron density clouds, and electron properties were calculated. Different Se surface coverages were investigated to elucidate the adsorption process. In the experiments, the Se adsorption products were prepared in a U-shaped quartz reactor at 300 °C. The properties were investigated by X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), and X-ray diffraction (XRD), respectively. The experimental results match up with the DFT results, which reveal fundamental monochemisorption mechanisms of zerovalent Se on the CaO surface.
The activity and hydrothermal stability of Cu/SAPO and
x
Mn-2Cu/SAPO for low-temperature selective catalytic reduction of NO
x
with ammonia were investigated. An ion-exchanged method was employed to ...synthesize
x
Mn-2Cu/SAPO, which was characterized by N
2
adsorption, ICP-AES, X-ray diffraction (XRD), NH
3
-temperature programmed desorption (NH
3
-TPD), NO oxidation, X-ray photoelectron spectrum (XPS), UV-vis, H
2
-temperature programmed reduction (H
2
-TPR) and diffuse reflectance infrared Fourier transform spectra (DRIFTS). 2Mn-2Cu/SAPO and 4Mn-2Cu/SAPO showed the best SCR activity, in that at 150 °C NO conversion reached 76% and N
2
selectivity was above 95% for the samples. NO oxidation results showed that the 2Mn-2Cu/SAPO had the best NO oxidation activity and the BET surface area decreased as manganese loading increased. XRD results showed that the metal species was well dispersed. NH
3
-TPD showed that the acid sites have no significant influence on the SCR activity of
x
Mn-2Cu/SAPO. H
2
-TPR patterns showed good redox capacity for
x
Mn-2Cu/SAPO. UV-vis and H
2
-TPR showed that the ratio of Mn
4+
to Mn
3+
increased as manganese loading increased. XPS spectra showed a significant amount of Mn
3+
and Mn
4+
species on the surface and addition of manganese increased the ratio of Cu
2+
. The promotion effect of manganese to 2Cu/SAPO comes from the generation of Mn
3+
and Mn
4+
species. Deduced from the DRIFTS spectra, the Elay-Rideal mechanism was effective on 4Mn-2Cu/SAPO.
The activity and N
2
selectivity of Cu/SAPO and
x
Mn-2Cu/SAPO for low-temperature selective catalytic reduction of NO
x
with NH
3
were investigated.
The activity and hydrothermal stability of Cu/SAPO and
Mn-2Cu/SAPO for low-temperature selective catalytic reduction of NO
with ammonia were investigated. An ion-exchanged method was employed to ...synthesize
Mn-2Cu/SAPO, which was characterized by N
adsorption, ICP-AES, X-ray diffraction (XRD), NH
-temperature programmed desorption (NH
-TPD), NO oxidation, X-ray photoelectron spectrum (XPS), UV-vis, H
-temperature programmed reduction (H
-TPR) and diffuse reflectance infrared Fourier transform spectra (DRIFTS). 2Mn-2Cu/SAPO and 4Mn-2Cu/SAPO showed the best SCR activity, in that at 150 °C NO conversion reached 76% and N
selectivity was above 95% for the samples. NO oxidation results showed that the 2Mn-2Cu/SAPO had the best NO oxidation activity and the BET surface area decreased as manganese loading increased. XRD results showed that the metal species was well dispersed. NH
-TPD showed that the acid sites have no significant influence on the SCR activity of
Mn-2Cu/SAPO. H
-TPR patterns showed good redox capacity for
Mn-2Cu/SAPO. UV-vis and H
-TPR showed that the ratio of Mn
to Mn
increased as manganese loading increased. XPS spectra showed a significant amount of Mn
and Mn
species on the surface and addition of manganese increased the ratio of Cu
. The promotion effect of manganese to 2Cu/SAPO comes from the generation of Mn
and Mn
species. Deduced from the DRIFTS spectra, the Elay-Rideal mechanism was effective on 4Mn-2Cu/SAPO.
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