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The anomalous enrichment of the rare earth elements and yttrium (REY), U, Mo, As, Se, and V in the coal-bearing intervals intercalated within the carbonate successions in South China has attracted much attention due to the highly promising recovery potential for these elements. This study investigates the mineralogical and geochemical characteristics of the late Permian coal-bearing intervals (layers A–F) intercalated in marine carbonate strata in the Xian'an Coalfield in Guangxi Province to elucidate the mode of occurrence and enrichment process of highly elevated elements. There are two mineralogical assemblages, including quartz-albite-kaolinite-carbonates assemblage in layers D–F and quartz-illite-kaolinite-carbonates assemblage in layers A–C. Compared to the upper continental crust composition (UCC), the REY, U, Mo, As, Se, and V are predominantly enriched in layers A and B, of which layer A displays the REY–V–Se–As assemblage while layer B shows the Mo–U–V assemblage. The elevated REY contents in layer B are primarily hosted by clay minerals, zircon, and monazite; Mo, U, and V show organic association; and As and Se primarily display Fe-sulfide association. Three geological factors are most likely responsible for geochemical anomaly: (1) the more intensive seawater invasion gives rise to higher sulfur, Co, Ni, As, and Se contents, as well as higher Sr/Ba ratio in layers A–C than in layers D–F; (2) both the input of alkaline pyroclastic materials and the solution/rock interaction jointly govern the anomalous enrichment of REY; and (3) the influx of syngenetic or early diagenetic hydrothermal fluids is the predominant source of U, Mo, V, Se, and As. [ABSTRACT FROM AUTHOR]

Shaanxi is among the provinces with abundant coal resources in North China. These enormous coal resources (approx. 4143 Gt) are widely distributed in the Ordos Basin and its marginal fold belts. The main coal-bearing strata consist of the late Carboniferous Taiyuan Formation, the early Permain Shanxi Formation, the late Triassic Wayaobao Formation, and the middle Jurassic Yan'an Formation, which were respectively deposited in coastal plains and a lagoon environment, a continental environment, an inland open lake and a confined lake environment. The Permo-Carboniferous coals are low volatile bituminous and characterized by relatively high vitrinite content, which decreases from south to north, and from the lower coal seams upwards. By contrast, the late Triassic and middle Jurassic coals are highly volatile bituminous, but are respectively characterized by relatively high vitrinite and high inertinite content. Minerals in the Permo-Carboniferous coals, the late Triassic coals, and the middle Jurassic coals, are respectively dominated by kaolinite and calcite, quartz and kaolinite, and quartz and calcite. Furthermore, contemporary coals deposited in different coal fields or even different mines of the same coal field present different mineral characteristics. The Permain Shanxi Formation coals from the Shanbei C-P coalfield in the north of Shaanxi Province are characterized by higher kaolinite and lower carbonate contents compared to those from the Weibei C-P coalfield in the south of Shaanxi Province. The distinctive mineralogical characteristics of coals formed in different coalfields and different geological ages were ascribed to integrated influences of different terrigenous detrital input from sediment provenance, sedimentary settings (e.g., subsidence rate, sea transgression, and regression process), and hydrothermal activities. [ABSTRACT FROM AUTHOR]

Superhigh organic sulfur(SHOS) coals have currently attracted great attention due to their typical depositional environments and formation history as well as their great negative impact on the ecosystem. This study investigated the geochemistry of the No. 11coalof the Late Carboniferous Taiyuan Formation from the Sangshuping coalmine, Hancheng miningarea, Weibei coalfield, Shaanxi, North China. The No. 11 coal is a high-sulfur coal with a large proportion of organic sulfur content (3.7 to 5.5%, avg. 4.4%) and belongs to typical SHOS coal. The high sulfur content in the Sangshuping coal mine has been mainly caused by the combined influences of seawater and hydrothermal fluids. The SHOS in No. 11 coal was formed in the Fe-poor and S-rich high-marine influenced occlusive environment. During the late coalification stage, a high proportion of pyritic sulfur was formed due to sufficient Fe supply from the Fe–S-rich epigenetic hydrothermal fluids. The No. 11 SHOS coal is enriched in Li–Ga–Zr–Hf and Se–Mo–Cr–V–As–Pb element assemblages. The sediment provenance of the Sangshuping coal mine is predominantly felsic–intermediate rocks from both the Yinshan and Qinling Oldland. However, the elevated concentrations of critical elements (Li, Ga, Zr, and Hf) in the No. 11 coal are primarily inherited from the Yinshan Oldland. The enrichment of the Se–Mo–Cr–V–As–Pb assemblage in No. 11 coal can be ascribed to the influence of both seawater and epigenetic hydrothermal activity. [ABSTRACT FROM AUTHOR]

The potential utilization of boiler slag generated in large amounts from pulverized-coal-combustion (PCC) power plants has recently drawn much attention due to the serious problems caused to ecosystems. In order to make maximal use of the boiler slag and reduce the environmental risk it poses, this study focused on manufacturing acoustic materials using boiler slag from Chinese PCC power plants. Three promising acoustic materials were successfully manufactured from up to 80% boiler slag with different grain sizes, with the addition of 20% Portland cement. The density and compressive strength of the products were inversely proportional and the sound absorption coefficient was positively proportional to the grain size of the boiler slag. The best sound absorption coefficient was obtained in products made from the coarsest fraction of the boiler slag (MS-C). Nonetheless, all the boiler-slag-based acoustic products still demonstrated compressive strength and densities comparable to those of other acoustic materials made of Spanish bottom ash or other conventional/recycled materials. The acoustic products made from the coarsest fraction (MS-C) and medium fraction (MS-M) of the boiler slag presented good noise absorption characteristics, like those of the commercial coarse porous cement that is traditionally used as an acoustic product. Furthermore, the acoustic products were characterized by very low leach ability of potentially hazardous elements. Consequently, the manufacture of acoustic materials is a very promising application for boiler slag. On the one hand, it consumes huge amounts of boiler slag that is generated in large amounts in China. On the other hand, the acoustic products can be used extensively to produce road acoustic barriers with a high sound absorption efficiency, no significant physical or mechanical limitations and no environmental implication. [ABSTRACT FROM AUTHOR]

Mineralogical and geochemical characteristics of coals provide crucial information on their potential clean, efficient, and integrated utilization. In this paper, the mineralogical and geochemical behaviors of the No. 5 coals of the Taiyuan Formation in the Weibei Coalfield, North China, were investigated, and their geological controlling factors were subsequently discussed. The minerals in the Weibei coals mainly consist of kaolinite (8.3%), calcite (5.0%), and pyrite (3.1%), with minor proportions of tobelite (2.9%), dolomite (1.7%), quartz (1.8%), and traces of siderite (0.4%) and gypsum (0.6%). Several critical elements, including Nb (19.8 mg/kg), Ta (3.6 mg/kg), Zr (71.0 mg/kg) and Li (32.3 mg/kg), occur at concentrations higher than those averages for world hard coals, making the Weibei coals potential sources of these critical elements. Several factors, terrigenous material, seawater invasion, and hydrothermal fluids are responsible for these mineralogical and geochemical characteristics. The L-type rare earth elements and yttrium (REE-Y) enrichment in the roofs and partings, Al2O3-TiO2 and Zr/TiO2-Nb/Y plots, and negative Eu and weak negative Ce anomalies in the Weibei coals indicate a felsic-intermediate dominated sediment provenance primarily derived from the Qilian-Qinling Oldland on the South. Marine bioclastic limestone, negative Ce and positive Y anomalies in coals imply the influence of seawater on the Weibei coals. Last but not least, the cleat-infilling and/or fracture-infilling calcite, pyrite, barite, and tobelite as well as the positive Eu and Gd anomalies, H-type, and M-type REE-Y enrichment patterns suggest the influence of hydrothermal fluids, which lead to re-distribution of some critical elements from roof and parting to the underlying coal seam. [ABSTRACT FROM AUTHOR]