Aluminous Minerals Research Articles

Synthesis and characterization of nickel and molybdenum catalysts supported on alumina derived from bauxite

In this study, a natural ore (bauxite), which is characterized by its high content of various aluminum minerals, such as gypsite, , bohmite, and diaspore, AlO(OH), was used to obtain alumina ( ), which was used as a support for the catalyst. The components of the ore were studied using multiple techniques, such as The X-ray energy dispersion (EDX) technique, X-ray diffraction (XRD) and X-ray fluorescence (XRF) technology. Then, undesirable components that negatively affect the behavior of the prepared catalyst were removed, such as carbonates, iron, and amorphous silica, and then aluminum oxide (alumina) was prepared from the ore using a series of chemical treatments. Then the mixed catalyst consisting of (nickel/molybdenum) carried on alumina was prepared, its properties were studied, and its components were identified by measuring energy dispersion with X-rays (EDX) and ensuring the extent of its thermal stability by conducting a thermal analysis measurement. Gravimetric analysis (TGA), differential thermal analysis (DTA), measurement of the surface area of ​​the prepared catalyst (BET), scanning electron microscope (SEM) measurement, as well as X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements to identify the percentages of metals, and then estimating the percentage of these elements in their oxide form. KEY WORDS: Catalyst, Bauxite, Nickel, Molybdenum Bull. Chem. Soc. Ethiop. 2024, 38(6), 1715-1724. DOI: https://dx.doi.org/10.4314/bcse.v38i6.17

Critical roles of low-molecular-weight organic acid in enhancing hydroxyl radical production by ferrous oxidation on γ-Al2O3 mineral surface

Recognizing the pervasive presence of alumina minerals and low-molecular-weight organic acids (LMWOAs) in the environment, this study addressed the gap in the interaction mechanisms within the ternary system involving these two components and Fe(II). Specifically, the impacts of LMWOAs on hydroxyl radicals (•OH) production and iron species transformation during Fe(II) oxidation on γ-Al2O3 mineral surface were examined. Results demonstrated that adding 0.5 mM oxalate (OA) or citrate (CA) to the γ-Al2O3/Fe(II) system (28.1 μM) significantly enhanced •OH production by 1.9-fold (51.9 μM) and 1.3-fold (36.2 μM), respectively, whereas succinate (SA) exhibited limited effect (30.7 μM). Raising OA concentration to 5 mM further promoted •OH yield to 125.0 μM after 24 h. Deeper analysis revealed that CA facilitated the dissolution of adsorbed Fe(II) and its subsequent oxygenation by O2 through both one- and two-electron transfer mechanisms, whereas OA enhanced the adsorption of dissolved Fe(II) and more efficient two-electron transfer for H2O2 production. Additionally, LMWOAs presence favored the formation of iron minerals with poor crystallinity like ferrihydrite and lepidocrocite rather than well-crystallized forms such as goethite. The distinct impacts of various LMWOAs on Fe(II) oxidation and •OH generation underscore their unique roles in the redox processes at mineral surface, consequently modulating the environmental fate of prototypical pollutants like phenol.

The permeability evolution mechanism of ore-bearing strata during acid in-situ leaching of uranium: A case study of Bayanwula uranium mine in Inner Mongolia of China

Uranium mainly comes from ISL of sandstone-type uranium deposits in China. The change of porosity and permeability caused by blockage of ore-bearing strata is one of the most serious problems in acid ISL of uranium. In this paper, the groundwater tracer test was carried out before and 1 year after ISL to explore the pore and permeability evolution characteristics of the ore-bearing layer during ISL. The test results showed that the leaching solution migrated along two seepage channels and the water-bearing medium was isotropic. After 1 year of ISL, the flow rate of the leaching solution decreased obviously. However, the flow rate of the leaching solution in slower channel decreased more than that in the faster channel in all directions, which was caused by the more adequate chemical reactions between the leaching solution and the minerals of the ore-bearing layer and the more corresponding precipitation in the slower channel. In addition, the flow rate along the direction of groundwater flow decreased less than that in the direction of vertical groundwater flow. This was closely related to the transformation of aquifer medium by hydrodynamic field. Initial stage of ISL, the occurrence of plugging is closely related to the precipitation-dissolution process of iron and aluminum minerals under the change of pH, which is accompanied by the continuous precipitation of gypsum.

Hydrocarbon-degrading Shewanella algae shows oxidative deterioration corrosion at the aluminium alloy & coating interface

In this investigation, microbial adhesion expedites formation and alteration of aluminous minerals within aviation fuel tank systems. The corrosion mechanisms of two uncoated aluminium alloys and three types of coating-pretreated aluminium alloys by hydrocarbon-degrading Shewanella algae are examined. NO3- reduction of microorganisms induces corrosion acceleration of LY12 aluminium alloy (1.48 g*m−2*h−1) and corrosion inhibition of 7B04 aluminium alloy. CLSM and SEM observation of coating morphology highlight the microbial deterioration behaviors of coatings (pitting, swelling, and peeling). It inspires material selection and surface coating of microbial corrosion protection of aluminium alloy in marine and aerial environments.

PENGARUH SERBUK BATU PARAS BELAYU SEBAGAI SUBSTITUSI SEMEN TERHADAP KUAT TEKAN BETON

Cement is the most important building material in making concrete, cement is formed from the oxidation process or heating of limestone using coal at high temperatures. The heating process produces excess CO? which has a negative impact on the environment. So in this research, the researchers conducted research on the effect of sandstone powder (SBP) as a substitute for Portland cement (SPI) in concrete mixtures because sandstone contains silica and alumina minerals which are suitable for use. as pozzolan. The test object used in this study was a cube measuring (150 x 150 x 150) mm, with the ratio: (0% SBP: 100 SPI), (2.5% SBP: 97.5% SPI), (5%SBP: 95% SPI) and (10% SBP: 90% SPI) which were tested at 28 days of age. Concrete mix planning (mix design) is carried out based on SNI 7656-2012 with concrete design quality 20.75 MPa, classified as concrete quality for building structures. From the test results, it was found that the effect of sandstone powder as a cement substitute in the concrete mixture increased the compressive strength of the concrete at a percentage of 2.5% -5%, and at a percentage of 10% the compressive strength of the concrete decreased.

Mechanistic study on the promotion of Ca2+ leaching in steel slag through high-temperature solid waste modification.

Indirect carbonation of steel slag is an effective method for CO2 storage, reducing emissions, and promoting cleaner production in the steel industry. However, challenges remain, such as low Ca2+ leaching rates and slag management complexities arising from variations in mineral compositions. To address this, a high-temperature modification process is proposed to alter the mineral composition and facilitate the synergistic utilization of calcium and iron. This study delves into the effects of various solid waste modifications on the leaching of Ca2+ and the total iron content within steel slag. Results show that high-basicity modified slag forms Ca2(Al, Fe)2O5, reducing calcium leaching. Low-alkalinity modified slag produces calcium-rich aluminum minerals and also reduces the leaching of Ca2+ ions. At a basicity of 2.5, coal gangue, fly ash, and blast slag achieve maximum Ca2+ leaching rates of 88.93%, 89.46%, and 90.17%, respectively, with corresponding total iron contents of 41.46%, 37.72%, and 35.29%. Upgraded coal gangue exhibits a 50.02% increase in calcium leaching and a 15.58% increase in total iron content compared to the original slag. This enhances CO2 fixation and iron resource utilization. Overall, the proposed indirect carbonation and iron enrichment modification offer a novel approach for the resource utilization and environmental stability of steel slag.

The Effect of Using Sustainable Copper Fiber on Some Mechanical Properties of High Strength Green Concrete

Finding an alternative to materials that pollute during manufacturing, most notably cement, is vital to executing the idea of sustainability in the building sector. It was vital to develop concrete that assists in the reduction of CO2 (Carbon dioxide) in the atmosphere because industrial wastes contain calcium, silica, and aluminous minerals, such as silica fume, that are employed in the production of high-strength concrete and have parameters that are identical to those of regular concrete. As a substitute for Portland cement, lime cement was utilized, and 15% of the cement's weight was substituted with silica fume. Environmentally friendly fibers (Copper Fiber) created from old electrical and electronic equipment were also employed. The purpose of the study is to produce High Strength Green Fiber Concrete (HSGFC) by incorporating silica fume as a replacement and study the effect of adding fiber on some mechanical attributes. The task needed the creation of a high strength concrete mixture of cement with a compressive strength of 65 MPa in accordance with ACI 211.4R, as well as the development of numerous experimental mixtures that relied on the findings of earlier researchers. The mechanical properties (compressive strength, flexural strength and split tensile strength) of samples are tested at 7, 28 and 60 days with standard curing. The results show that adding sustainable fiber to concrete mix enhances the mechanical properties such as compressive strength by 16% at 28 days, flexural strength by 35% and spilt tensile strength by 44% at 28 days Compared with concrete mix with no fiber. Also, the outcomes showed that it is feasible to develop High Strength Concrete (HSC) using sustainable copper fiber possessing exceptional stress resistance, tensile strength, and flexural strength.

Structural and Morphological Analysis of Untapped Clay Deposits in Itu Local Government Area Akwa Ibom State, Nigeria and its Potentials as Raw Material for Petroleum Refining

This work describes scanning electron microscope and XRD characterization of untapped clay deposits in Itu Local Government Area Akwa Ibom State and its potentials as raw material for petroleum refining. The structure and morphology of the raw kaolin clay and metakaolin were analyzed using XRD and SEM. The XRD data indicates 48.0 % quartz, 30.0% kaolinite, 3.0 % chlorite, 16.0 % illite and 2.0% albite in the raw kaolin and 68.3 % quartz, 17.3 % orthoclase, 5.9 % muscovite, 1.8 % illite , 6.68 %, albite in the metakaolin from Ikot Uso Akpan and 16.2 % kaolinite, 67.0% quartz, 2.5 % muscovite, 5.5 % orthoclase, 1.4 % chlorite, and 7.0 % albite were revealed in Ekim Itam raw kaolin. 66.0 % quartz, 10.0 % muscovite, 15.0 % orthoclase, 5.0 % illite, 5.0 % albite were recorded in the metakaolin. The XRD results confirmed the presence of quartz and alumina mineral phases from both kaolin deposits. Calcination at 1000oC increased the crystalline structure of the metakaolin and did not significantly modify surface morphology of the kaolin indicating stability of kaolin structure, one the desired property of a good zeolite. The SEM results indicated heterogeneous size and spongy like porous shape. There was no significant change in the surface morphology of the heterogeneous size calcined kaolin compared with untreated kaolin. The SEM results of the metakaolin kaolin also indicated cubic crystalline structure with well-defined edges. With adequate modification the studied kaolin could be a promising raw material for synthesis of zeolite suitable for bio and fossil fuel processing.

Thermal decomposition mechanism and characterization of phosphogypsum in suspension under multifactor coupling effect

Phosphogypsum (PG) is solid waste generated by the phosphate fertilizer industry. However, by high-temperature thermal treatment, it can be effectively decomposed into byproducts like SO2 and CaO, which are valuable raw materials for the production of sulfuric acid and construction materials, respectively. In this study, we investigated the thermal decomposition properties of suspended PG, as well as the factors governing the PG decomposition procedure. The results show that the PG decomposition rate was influenced by several parameters, with temperature being the most significant, followed by time, atmosphere, and charcoal powder dosing. Similarly, the desulfurization rate was primarily influenced by time, followed by temperature, atmosphere, and charcoal powder dosing. The PG exhibited maximum decomposition and desulfurization rates of 97.73% and 97.2%, respectively, at a calcination temperature of 1180 °C, a calcination period of 15 min, a carbon powder dosage of 4%, and a CO concentration of 6%. Kinetic studies revealed that the activation energy of the PG decomposition reaction decreased from 303.45 to 254.28 kJ/mol as the CO concentration increased from 4% to 6% upon addition of charcoal powder as a reducing agent. Furthermore, higher CO concentrations had a more pronounced effect on lowering the activation energy of PG pyrolysis. When the contents of SiO2 and Al2O3 impurities in the PG content were higher, they reacted with CaO in the decomposition products to produce silicate and aluminate minerals, respectively, decreasing both the CaO content in the product and the PG decomposition rate.

Transformation behavior of potassium-containing minerals during co-gasification of petroleum coke and biomass

Interactions between alkali metals in biomass and silicon and aluminum minerals in petroleum coke (PC) are closely related to the gasification reactivity and the deactivation of active K-catalyst during co-gasification. This study comprehensively investigated the evolution of K-containing minerals and their impact on the gasification reactivity and ash fusion characteristics during the co-gasification of PC and wheat straw (WS). The results showed that the addition of WS improved the gasification reactivity of PC, but only up to a certain point due to the K-containing mineral evolutions at high temperatures. Adding WS below 20 wt% resulted in the deactivation of K and the formation of inert kaliophilite and nepheline. However, when WS addition exceeded 20 wt%, a substantial amount of K acted as an active K-catalyst, significantly increasing gasification reactivity. The shrinking core model was found to be more appropriate than the homogeneous model when considering gasification kinetics during co-gasification.

Research progress on the enrichment of gallium in bauxite

Due to its high economic and strategic value, gallium (Ga) has been listed as a critical metal in many countries. As most important Ga resources, the exploration of Ga enriched in bauxite has attracted extensive attention globally. In order to improve the level of Ga resource exploration and utilization, it is significant to understand the occurrence state and enrichment mechanism of Ga in bauxite. To clarify the research progress of Ga enrichment in bauxite, the content distribution of global Ga in lateritic bauxite and karstic bauxite were respectively reviewed. Ga content in lateritic bauxite was mainly concentrated at 40–80 ppm with an average value of 60 ppm, while it was at 20–80 ppm with an average value of 59 ppm in karstic bauxite. In addition to Ga in global lateritic bauxite and karstic bauxite, contents of some major elements of Al, Si, Fe, and Ti were also collected to study the function on the enrichment of Ga in bauxite. In lateritic bauxite, Ga almost existed in the form of ion adsorption. In karstic bauxite, Ga predominantly existed in the form of isomorphism in aluminum minerals with small proportion of ion adsorption form on major minerals. This review intends to provide general knowledge for the research progress on the occurrence state and enrichment mechanism of Ga in bauxite, and to induce a prospection for future work.

Effects of Al3+ on the microbial community, metabolic pathways, and morphological analysis of activated sludge

Al3+ generated during aluminum mining, electrolytic industry, and aluminum-based coagulant production enters sewage treatment plants and interacts with activated sludge, interfering with microbial growth and community succession. An anaerobic-anoxic-oxic (A2O) process was used to investigate the effect of Al3+ on biological denitrification, the metal form, and the microbial community structure. The results showed that a low concentration of Al3+ improved removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) as well as biological activity. However, a high concentration of Al3+ reduced the COD and TN removal efficiencies. The removal efficiencies of COD, TN, and NH4+-N were the highest, and the INT-ETS values in the anaerobic, anoxic, and oxic zones were 93.21, 91.36, and 94.44 mg·INTF/(g·TSS·h) in the 10 mg/L Al3+ concentration treatment. Regardless of the change in Al3+ concentration, aluminum in the sludge mainly existed in the form of stable organic aluminum. Microbial richness and diversity decreased under the high concentration of Al3+. However, the relative abundance of Bacteroidetes and Chitinophagales increased, which was coincident with the change in microbial aluminum tolerance capacity. The dominant flora included Proteobacteria, Gammaproteobacteria, Betaproteobacteriales, Rhodocyclaceae, and Thauera. Amino acid and carbohydrate metabolism, as well as membrane transport and replication and repair, were the main metabolic pathways. K03088, K03406, and K02014 exhibited good adaptability under the high Al3+ concentration, which ensured effective removal of COD and TN.

Optimizing iron separation and recycling from iron tailings: A synergistic approach combining reduction roasting and alkaline leaching

Iron tailings, a type of refractory iron ores, pose a challenge for effective iron recovery due to the complex mineral combinations and liberation modes. In this study, we proposed a new approach to improve the quality of iron concentrates by combining alkaline leaching with magnetization roasting-magnetic separation, which promoted the leaching of silica and aluminum minerals from iron tailings. We investigated the leaching process conditions, phase transitions, and microstructure evolution of joint magnetization roasted iron tailings in the presence of an alkaline solution. Our research findings showed that with optimal leaching conditions, the iron concentrate from magnetic separation was improved from 59.97 % to 65.07 % in iron grade while maintaining an iron recovery of 92.05 %. The heat and mineral phase transformation during magnetization roasting destroyed the structure of iron tailings particles, resulting in the formation of pores and microcracks that weakened inter-mineral bonding. Additionally, alkaline leaching facilitated the extraction of Si and Al from the structure-damaged iron tailings particles, eliminating 83.75 % of Si minerals and 68.73 % of Al minerals. This study offers a promising solution for iron recovery from refractory iron ores, reduces environmental pollution from tailings, and could enhance current iron recovery technology.

Strategic Marketing Approach of Indonesia Aluminium Mineral Industry: Upstream and Downstream Analysis

The research aimed to determine the causes of imports by analyzing the upstream and downstream sides of the existing aluminium industrial chain. The research applied a descriptive-exploratory approach by collecting secondary data from credible sources. Interviews and focus group discussions with appropriate experts were also conducted to obtain supporting data. Research shows that aluminium imports will continue both in the short and long term. It is due to the upstream supply, especially in aluminium smelters, which cannot keep up with the increasing demand. Even though the market opportunity, especially in the automotive, construction, and power cable segments, is enormous and continues to grow, if there is not enough supply, the deficit of aluminium metal will continue to occur. It takes encouragement from the Government's political will to provide ease of electricity sources, increase production capacity and technology, change the mindset from relying on traders solely towards the mindset of the industrialist.

Polyphosphate hydrolysis, sorption, and conversion in two different soils

AbstractPolyphosphate fertilizer is an alternative to traditional orthophosphate fertilizer, but it is unclear whether it provides greater soil phosphorus (P) mobility and availability than orthophosphate fertilizer. This study aimed to examine the chemical behaviour of polyphosphate after its application to the soil. The hydrolysis, sorption, and P transformation of two types of polyphosphate fertilizers (short‐chain and long‐chain) were examined for two types of soils (acidic Acrisol and calcareous Cambisol), with orthophosphate serving as the control treatment. 31P NMR spectroscopic analyses indicated that polyphosphate in soil was rapidly converted to pyrophosphate, which was then hydrolyzed to orthophosphate at a slower rate. In general, in the calcareous Cambisol, the addition of short‐chain polyphosphate fertilizer resulted in greater soil P mobility as measured by greater soil pore water orthophosphate concentration than the control. Thus, short‐chain polyphosphate fertilizer tended to be more effective than orthophosphate in calcareous soils. This was in contrast to the result of an aqueous incubation experiment, in which a lower pH increased the rate of polyphosphate hydrolysis. Indeed, in both soils, the sorption of total P was greater when P was added as polyphosphate than when it was added as orthophosphate. Moreover, polyphosphate sorption appeared to be mainly controlled by soil iron and aluminium minerals, because the Acrisol showed stronger polyphosphate sorption than the Cambisol due to its greater amorphous iron content. It appears that polyphosphate was first adsorbed on soil minerals before being hydrolyzed to release orthophosphate, and calcium may have played an important role in the hydrolysis of polyphosphate as evidenced by the greater P release in calcareous Cambisol. Our results suggest that soil characteristics, such as acidity, iron, aluminium, and calcium content, should be considered when evaluating the P efficiency of polyphosphate fertilizers.Highlights 31P NMR spectroscopy successfully tracked the fate of added Poly‐P in soil Poly‐P was rapidly converted to Pyro‐P, and then hydrolyzed to Ortho‐P slowly P supplied as Poly‐P had stronger sorption affinity than Ortho‐P in all soils Short‐chain Poly‐P induced greater P mobility than Ortho‐P in Cambisol but not in Acrisol

Selective recovery of high-grade rare earth, Al, and Co-Mn from acid mine drainage treatment sludge material

Rare earth elements (REEs) and critical elements (CEs) have been in the spotlight recently due to their vital role in high-tech applications and green energy initiatives. Due to the scarcity of mineral resources for the majority of these elements, there has been significant interest in the recovery of these elements from secondary resources. Among the secondary resources, acid mine drainage (AMD) and associated sludge materials have been found to be viable sources of multiple critical elements, including REEs, Al, Co, and Mn. AMD and sludge samples from 3 AMD treatment sites in Pennsylvania were characterized for elemental content and contained value evaluation. A novel purification process based on a previously developed 3-stage AMD treatment process was designed to recover high-grade Al, REE, Co, and Mn products from the sludge materials through aqueous processing with multiple cleaner steps and precise control of the process parameters. The final products of the three stages of this purification process are boehmite and dawsonite in Stage I, adamsite-(REE) in Stage II, and cobalt oxide and ramsdellite in Stage III. Recoveries of > 99 % for the target elements were achieved with the design of a recycling load. Through the proposed purification process, 92.8 % aluminum minerals in Stage I, 88.5 % mixed-REE-carbonate in Stage II, 68 % ramsdellite, and 6.9 % cobalt oxide in Stage III were produced.

Beneficiation of low-grade limestone by flotation

Low-grade limestone samples from Northern Telangana, India were put through to beneficiation by flotation to upgrade the CaO value by minimizing the unwanted (gangue) minerals for utilizing in the various industries. Analyzation of the sample unfolds the minerals such as 50.85% CaO, 4.86% SiO2, 0.986% Al2O3, 91.31% TC, and 39.40% LOI. XRD characterization reveals that it predominantly contains calcite, quartz minerals, and minor traces of alumina mineral. Wet Sieve analysis of the sample shows 80% of the feed material was 53% microns or finer and mineral sample was found to be limestone having density of 2697.16 kg/m3 from gas pycnometer analysis. Direct flotation was espoused to improve calcium oxide grade by minimizing the gangue minerals (alumina and silica) in laboratory experiments by variations of grinding time, depressant dosage, collector dosage, and pH value. This study comes out with optimum results at pH 6, 12 min grinding time, 0.67 kg/ton of sodium oleate (collector), 1.25 kg/ton of sodium silicate (depressant) and concentrate assayed 52.03% CaO, 3.89% SiO2, and 0.77% Al2O3.

ENERGY SAVING FACTORS IN WINTER CONCRETING

This article considers energy-saving technologies for winter concreting of building structures and constructions. Various authors have studied mathematical models of the thermal regime of a three-dimensional building structure. The mathematical model of the heat balance equations in the concrete structure, the thermal conductivity coefficient, the dependences of the heat balance equations in the concrete structure and the junction, the thermal conductivity coefficient, the volumetric thermal conductivity, respectively, in the erected fragment and the previously erected part of the wall was implemented on a computer. The article considers the processes of cement and concrete strength gain during early freezing of concrete. In previous studies by various authors, it was found that with an increase in the time for gaining critical strength, the cost of electricity is reduced by 25-50%, due to the use of thermal inertia of the structure. The rate of cooling of monolithic structures at negative temperatures is revealed. The chemistry of cement hardening processes during early freezing is shown. Thermodynamic calculations set the limits of negative temperatures at which concrete strength curing stops, but under the action of repeated positive temperatures, the cement hydration process resumes and concrete continues to harden. The aluminum minerals of Portland cement clinker are usually the first to hydrate when the cement hardens with water, and in the presence of gypsum they form calcium hydrosulfoaluminate. This connection is very fragile and is destroyed by mechanical stress (repeated vibration) and over time even at normal temperatures. The article reviews the foreign experience of winter concreting and the preferred methods of work in this case.

Granite-bauxite provenance of abnormally enriched boehmite and critical elements (Nb, Ta, Zr, Hf and Ga) in coals from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, China

Critical elements in coal have attracted much attention in recent years as some coals and coal combustion products may provide an alternative source of these. This paper provides mineralogical and geochemical data on the No. 4 coal seam, the major minable coal from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, northern China. It also discusses the provenance of mineral matter, the origin of aluminum minerals (boehmite), carbonates (calcite and ankerite) and phosphates (goyazite) and the potential economic significance of critical elements (e.g., Al, Nb, Ta, Zr, Hf, and Ga). Mineralogically, the studied coal samples are characterized by high kaolinite (64.7% on average, low-temperature ash basis) and boehmite (24.1%) contents, followed by carbonates (calcite, ankerite, siderite, and dolomite), titanium oxides (anatase and rutile), goyazite, quartz, and apatite. In comparison with average values for Chinese coals, the studied coal samples are characterized by high Al2O3 contents (mean 11.82% on a whole-coal basis and mean 49.49% on an ash basis). Compared with world hard coals, the No. 4 Coal is enriched in Ga, Se, Zr, Nb, La, Ce, Hf, Ta and Pb. In addition to Al, critical elements including Nb, Ta, Zr, Hf, and Ga in this coal have an economic significance. The Al2O3/TiO2 vs. Nb/TiO2, Al2O3/TiO2 vs. Zr/TiO2, Zr vs. Nb, Hf vs. Ta, and REY distribution patterns (REY, rare earth elements plus Y), indicate that the provenance of mineral matter (e.g., boehmite and critical elements Nb, Ta, Zr, Hf and Ga) in the No. 4 Coal is a number of sediment-source regions including the Neoarchean granites of the Yinshan Oldland, and the Paleoproterozoic granites and Benxi Formation bauxites (Late Carboniferous, to the northeast of the coal basin) of the northern Trans North China Orogen. Carbonate minerals (calcite and ankerite) are of epigenetic origin while the phosphate mineral (goyazite) was syngenetically deposited in the peat swamp during a period of a low water table.

Charred plant fragment–aluminium complexes in buried humic horizons of a cumulative volcanic soil profile: Formation, accumulation and potential role

AbstractThe objective of the present study was to investigate the formation, accumulation and potential role of charred plant fragment (CPF)–aluminium (Al) complexes in several buried A (Ab) horizons of a cumulative volcanic soil profile, focusing on CPFs, active Al components and soil age. Nineteen soil samples were collected from four buried humic horizons (2A–5A, from 7.3 cal ka BP to AD 1471), and their CPF–carbon (C), soil organic C (SOC), acid oxalate‐extractable Al (Alox), pyrophosphate‐extractable Al (Alpy, Al–humus complexes) and short‐range ordered Al minerals (Alox − Alpy) were quantified. The proportion of CPF–C content (up to 15.8 g kg−1) to SOC content (up to 117 g kg−1) ranged from 2.3% to 15.1% (8.4% on average). The contents of active Al components (6.71–77.1 g kg−1) increased: Alpy < Alox − Alpy < Alox. No consistent trends with age were found for the accumulation levels of CPF–C, SOC and active Al components. However, significant positive correlations (p < 0.001) were found between the Alpy and CPF–C and SOC contents, suggesting that the accumulation and stabilisation of soil organic matter in these humic layers proceeded simultaneously with the formation of organo–Al complexes, including CPF–Al complexes. On the other hand, significant negative correlations (p < 0.01) were obtained between the Alox − Alpy and Alpy, CPF–C or SOC contents. From these correlations, it was assumed that the complexation of organic constituents, including CPFs, with Al competed with the synthesis of short‐range ordered Al minerals (including allophane and imogolite), irrespective of soil age and climatic conditions with the range of more than 6000 years. This competitive relationship in the presence of CPFs was first described in the current study.Highlights Significance of charred plant fragment–aluminium complexes in humic horizons was discussed. There were no consistent trends with age for the accumulation levels of organic constituents. The accumulation of organic matter proceeded simultaneously with the formation of the complexes. The formation of the complexes competed (>6000 years) with the synthesis of aluminium minerals.