High-pressure minerals and new lunar mineral changesite-(Y) in Chang’e-5 regolith

Forty-five years after the Apollo and Luna missions, China’s Chang’e-5 (CE-5) mission collected ∼1.73 kg of new lunar materials from one ofthe youngest basalt units on the Moon. The CE-5 lunar samples provide opportunities to address some key scientific questions related to theMoon, including the discovery of high-pressure silica polymorphs (seifertite and stishovite) and a new lunar mineral, changesite-(Y). Seifertitewas found to be coexist with stishovite in a silica fragment from CE-5 lunar regolith. This is the first confirmed seifertite in returned lunarsamples. Seifertite has two space group symmetries (Pnc2 and Pbcn) and formed from an α-cristobalite-like phase during “cold” compressionduring a shock event. The aftershock heating process changes some seifertite to stishovite. Thus, this silica fragment records different stagesof an impact process, and the peak shock pressure is estimated to be ∼11 to 40 GPa, which is much lower than the pressure condition forcoexistence of seifertite and stishovite on the phase diagram. Changesite-(Y), with ideal formula (Ca_(8)Y)◻Fe^(2+)(PO_(4))_(7) (where ◻ denotes avacancy) is the first new lunar mineral to be discovered in CE-5 regolith samples. This newly identified phosphate mineral is in the form ofcolumnar crystals and was found in CE-5 basalt fragments. It contains high concentrations of Y and rare earth elements (REE), reaching upto ∼14 wt. % (Y,REE)2O3. The occurrence of changesite-(Y) marks the late-stage fractional crystallization processes of CE-5 basalts combinedwith silicate liquid immiscibility. These new findings demonstrate the significance of studies on high-pressure minerals in lunar materials andthe special nature of lunar magmatic evolution.

Interactive effect of minerals on complex ore flotation: A brief review

Froth flotation is the most effective industrial method used to separate fine-grained minerals. The main problem of complex ore flotation is the negative effect of interactions among minerals in slurry, leading to variation in surface properties during separation. In this review,studies on the interactive effect among minerals on the flotation of iron ores, magnesite ores, and scheelite ores are summarized, and the main problems and mechanisms that diminish the separation efficiency of minerals are revealed in detail. Recent research progress on the flotation of these ores has confirmed that mineral aggregation, coating, and dissolution, as well as other factors caused by interacting behavior, explain the depressing effects of fine particles on mineral separation. Solvable methods for these effects are further discussed. Novel flotation processes and more selective reagents are critical for further investigations on various approaches to improve the beneficiation efficiency of these ores.This review aims to provide a good reference for conducting studies related to complex ore flotation.

Organic Gases in Fluid Inclusions of Ore Minerals and Their Constraints on Ore Genesis:A Case Study of the Changkeng Au-Ag Deposit,Guangdong,China

The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hostedprecious metal deposit. Most of the previous researchers believed that the deposit was formed bymeteoric water convection. By using a high vacuum quadrupole gas mass spectrometric system, ninelight hydrocarbons have been recognized in the fluid inclusions in ore minerals collected from theChangkeng deposit. The hydrocarbons are composed mainly of saturated alkanes C_(1-4) and unsaturatedalkenes C_(2-4) and aromatic hydrocarbons, in which the alkanes are predominant, while the contentsof alkenes and aromatic hydrocarbons are very low. The sum alka/sum alke ratio of most samples ishigher than 100, suggesting that those hydrocarbons are mainly generated by pyrolysis of kerogens insedimentary rocks caused by water-rock interactions at medium-low temperatures, and themetallogenic processes might have not been affected by magmatic activity. A thermodynamiccalculation shows that the light hydrocarbons have reached chemical equilibrium at temperatureshigher than 200 deg C, and they may have been generated in the deep part of sedimentary basins(e.g., the Sanzhou basin) and then be transported by ore-forming fluids to a shallow position of thebasin via a long distance. Most of the organic gases are generated by pyrolysis of the type IIkerogens (kukersite) in sedimentary host rocks, only a few by microorganism activity. Thecompositions and various parameters of light hydrocarbons in gold ores are quite similar to those insilver ores, suggesting that the gold and silver ores may have similar metallogenic processes.Based on the compositions of organic gases in fluid inclusions, the authors infer that the Changkengdeposit may be of a tectonic setting of continental rift. The results of this study support fromone aspect the authors' opinion that the Changkeng deposit is not formed by meteoric waterconvection, and that its genesis has a close relationship with the evolution of the Sanzhou basin,so it belongs to the sedimentary hot brine transformed deposit.

Imaging the Architecture of Mineral Systems and the Pathways of Ore-forming Fluids across Mongolia with Magnetotellurics

In the framework of a mineral system approach,a combination of components is required to develop a mineral system.This includes the whole-lithosphere architecture,which controls the transport of ore-forming fluids,and favorable tectonic and geodynamic processes,occurring at various spatial and temporal scales,that influence the genesis and evolution of ore-forming fluids(Huston et al.,2016;Groves et al.,2018;Davies et al.,2020).Knowledge of the deep structural framework can advance the understanding of the development of a mineral system and the emplacement of mineral deposits.Deep geophysical exploration carried out with this aim is increasingly important for targeting new ore deposits in unexplored and underexplored regions(Dentith et al.,2018;Dentith,2019).

Fluid Inclusion Studies of Ore and Gangue Minerals from the Piaotang Tungsten Deposit, Southern Jiangxi Province, China

The Piaotang deposit is one of the largest vein-type W-polymetallic deposits in southern Jiangxi Province,South China.The coexistence of wolframite and cassiterite is an important feature of the deposit.Based on detailed petrographic observations,microthermometry of fluid inclusions in wolframite,cassiterite and intergrown quartz was undertaken.The inclusions in wolframite were observed by infrared microscope,while those in cassiterite and quartz were observed in visible light.The fluid inclusions in wolframite can be divided into two types:aqueous inclusions with a large vapor-phase proportion and aqueous inclusions with a small vapor-phase ratio.The homogenization temperature(Th)of inclusions in wolframite with large vapor-phase ratios ranged from 280℃ to 390℃,with salinity ranging from 3.1 to 7.2 wt%NaCl eq.In contrast,the Th values of inclusions with small vapor-phase ratios ranged from 216℃ to 264℃,with salinity values ranging from 3.5 to 9.3 wt%NaCl eq.T_(h) values of primary inclusions in cassiterite ranged from 316℃ to 380℃,with salinity ranging from 5.4 to 9.3 wt%NaCl eq.T_(h) values for primary fluid inclusions in quartz ranged from 162℃ to 309℃,with salinity values ranging from 1.2 to 6.7 wt%NaCl eq.The results show that the formation conditions of wolframite,cassiterite and intergrown quartz are not uniform.The evolutionary processes of fluids related to these three kinds of minerals are also significantly different.Intergrown quartz cannot provide the depositional conditions of wolframite and cassiterite.The fluids related to tungsten mineralization for the NaCl-H_(2)O system had a medium-to-high temperature and low salinity,while the fluids related to tin mineralization for the NaCl-H_(2)O system had a high temperature and medium-to-low salinity.The results of this study suggest that fluid cooling is the main mechanism for the precipitation of tungsten and tin.

Effect of temperature on leaching behavior of copper minerals with different occurrence states in complex copper oxide ores

The effect of temperature on leaching behavior of copper minerals with different occurrence states in complex copper oxide ores was carried out by phase analysis means of XRD, optical microscopy and SEM-EDS. The results indicated that at ambient temperature, the easily leached copper oxide minerals were completely dissolved, while the bonded copper minerals were insoluble. At lukewarm temperature of 40℃, it was mainly the dissolution of copper in isomorphism state. With increasing temperature to 60℃, the copper leaching rate in the adsorbed state was significantly accelerated. In addition, when the temperature increased to 80℃, the isomorphic copper was completely leached, leaving 11.2% adsorbed copper un-leached. However, the copper in feldspar-quartz-copper-iron colloid state was not dissolved throughout the leaching process. Overall, the leaching rates of copper in different copper minerals decreased in the order: malachite, pseudo-malachite > chrysocolla > copper-bearing chlorite > copper-bearing muscovite > copper-bearing biotite > copper-bearing limonite > feldspar-quartz-copper-iron colloid.

Characteristics and provenance implication of detrital minerals since Marine Isotope Stage 3 in Core SYS-0701 in the western South Huanghai Sea

The previous studies of the sedimentology and chronology of sediment core SYS-0701, which was recovered from the western South Huanghai Sea （Yellow Sea）, have revealed the changes in the sea-level and sedimen- tary evolution during the late Quaternary in the region. The present study used mineralogical data from the section of the core deposited since Marine Isotope Stage （MIS） 3, to decipher the provenance of sediments of the paleo-delta deposited during MIS 3 and MIS 1. Based on the lithologic features and the variations with depth of the concentrations of carbonates and both heavy and light minerals in bulk samples, the up- per part of Core SYS-0701 can be divided into three units designated DU1, DU4, and DU5, in accord with previouslyused terminology. Sub-units of units DU1 （DU1-1 and DU1-2） and DU4 （DU4-1 and DU4-2） have also been identified. DU1 was deposited during MIS 1, and DIJ4 and DU 5 were formed during MIS 3. All data pertaining to dominant heavy mineral assemblages, diagnostic minerals, ratios of diagnostic minerals, light mineral associations, textural maturities, and carbonate contents, indicate that the sediments of Core SYS-0701 are comparable with Huanghe River （Yellow River） sediments. Moreover, the mineralogy of the sediment evidenced its dependence on supply rates and hydrodynamic conditions. Weak hydrodynamics （DU5 and DU4-2） and/or low sediment supply （DU1-2） led to sediment containing less hornblende and epidote, with a large specific gravity and high content of flaky minerals, and vice versa in cases of strong hydrodynamics （DIJ4-1） and very large sediment supply （DUI-1）.

Geochemistry, mineral paragenesis and geothermal conditions of oreforming fluids from the Ain El Bey Cu–Fe deposit: potential occurrence of native gold and precious metal traces (North African orogenic belt, Northern Tunisia)

The Ain El Bey abandoned mine, in North-West Tunisia, fits into the geodynamic context of the European and African plate boundary. Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization related to various hydrothermal fluid circulations. Petromineralogical studies indicate a rich mineral paragenesis with a minimum of seven mineralization phases and, at least, six pyrite generations. As is also the case for galena and native silver, native gold is observed for the first time as inclusion in quartz which opens up, thus, new perspectives for prospecting and evaluating the potential for noble metals associated with the mineralization. Scanning Electron Microscope--Energy Dispersive Spectroscopy and Transmission electron microscopy analyses show, in addition, a large incorporation of trace elements, including Ag and Au, in mineral structures such as fahlores(tetrahedrite-tennantite) and chalcopyrite ones. The mineral/mineral associations, used as geothermometers, gave estimated temperatures for the mineralizing fluids varying from 254 to 330 ℃ for phase Ⅲ, from 254 to 350 ℃ for phase Ⅳ, and from 200 to 300 ℃ for phases Ⅴ and Ⅵ. The seventh and last identified mineralization phase, marked by a deposit of native gold, reflects a drop in the mineralizing fluid’s temperature(< 200 ℃) compatible with boiling conditions. Such results open up perspectives for the development of precious metal research and the revaluation of the Cu–Fe ore deposit at the Ain El Bey abandoned mine, as well as at the surrounding areas fitting in the geodynamic framework of the Africa-Europe plate boundary.

Rare Earths, Niobium and Tantalum Minerals in Bayan Obo Ore Deposit and Discussion on Their Genesis

Bayan Obo ore deposit is endowed with and lie hidden in the Proterozoic strata. The localities and occurrences of the minerals in the ore deposit were described. It is obviously that some minerals are strata minerals and some are post strata minerals. The rare earths, niobium and tantalum minerals are exactly the post strata minerals. In these minerals the hydrothermal metasomatic phenomena distinctly reveal their metallogenic characteristics. According to tectonic movement, magma activity, mineral paragenesis, hydrothermal metasomatism, geological age and lasting time scale of metallogenesis, and some other factors, it is supposed that genesis of rare earths, niobium and tantalum minerals in Bayan Obo ore deposit are closely related with hydrothermal metallogenic solution which is differentiated from silica acid and carbonic acid magma and derived from deep seated source, and then intruded into Proterozoic strata and metasomatized. It is recognized that the metallogenesis of Bayan Obo ore deposit is undergoing a long geological period and many episodes.

Comprehensive recovery of gold and base-metal sulfide minerals from a low-grade refractory ore

The comprehensive recovery of small amounts of valuable minerals such as gold and base-metal sulfide minerals from a low-grade refractory ore was investigated. The following treatment strategy was applied to a sample of this ore： gold flotation-gold concen- trate leaching-lead and zinc flotation from the gold concentrate leaching residue. Closed-circuit trials of gold flotation yielded a gold concen- trate that assayed at 40.23 g·t-1 Au with a recovery of 86.25%. The gold concentrate leaching rate was 98.76%. Two variants of lead-zinc flotation from the residue--preferential flotation of lead and zinc and bulk flotation of lead and zinc--were tested using the middling processing method. Foam from the reflotation was returned to the lead rougher flotation or lead-zinc bulk flotation, whereas middlings from reflotation were discarded. Sulfur concentrate was a byproduct. The combined strategy of flotation, leaching, and flotation is recommended for the treatment of this kind of ore.

Trace Elements and Rare Earth Elements of Sulfide Minerals in the Tianqiao Pb-Zn Ore Deposit,Guizhou Province,China

Trace elements and rare earth elements（REE） of the sulfide minerals were determined by inductively-coupled plasma mass spectrometry.The results indicate that V,Cu,Sn,Ga,Cd,In,and Se are concentrated in sphalerite,Sb,As,Ge,and Tl are concentrated in galena,and almost all trace elements in pyrite are low.The Ga and Cd contents in the light-yellow sphalerites are higher than that in the brown and the black sphalerites.The contents of Ge,Tl,In,and Se in brown sphalerites are higher than that in light-yellow sphalerites and black sphalerites.It shows that REE concentrations are higher in pyrite than in sphalerite,and galena.In sphalerites,the REE concentration decreases from light-yellow sphalerites,brown sphalerites,to black sphalerites.The ratios of Ga/In are more than 10, and Co/Ni are less than 1 in the studied sphalerites and pyrites,respectively,indicating that the genesis of the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis associated with hydrothermal genesis.The relationship between LnGa and LnIn in sphalerite,and between LnBi and LnSb in galena,indicates that the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis.Based on the chondrite-normalized REE patterns,δEu is a negative anomaly（0.13-0.88）,andδCe does not show obvious anomaly（0.88-1.31）;all the samples have low total REE concentrations（〈3 ppm） and a wide range of light rare earth element/high rare earth element ratios（1.12-12.35）.These results indicate that the ore-forming fluids occur under a reducing environment.Comparison REE compositions and parameters of sphalerites,galenas,pyrites,ores,altered dolostone rocks,strata carbonates,and the pyrite from Lower Carboniferous Datang Formation showed that the ore-forming fluids might come from polycomponent systems,that is,different chronostratigraphic units could make an important contribution to the ore-forming fluids.Combined with the tectonic setting and previous isotopic geochemistry evidence,we conclude that the ore-deposit genesis is hydrothermal,sedimentary reformed,with multisources characteristics of ore-forming fluids.

Research progress of CO_(2) capture and mineralization based on natural minerals

Natural minerals,such as kaolinite,halloysite,montmorillonite,attapulgite,bentonite,sepiolite,forsterite,and wollastonite,have considerable potential for use in CO_(2) capture and mineralization due to their abundant reserves,low cost,excellent mechanical prop-erties,and chemical stability.Over the past decades,various methods,such as those involving heat,acid,alkali,organic amine,amino sil-ane,and ionic liquid,have been employed to enhance the CO_(2) capture performance of natural minerals to attain high specific surface area,a large number of pore structures,and rich active sites.Future research on CO_(2) capture by natural minerals will focus on the full utiliza-tion of the properties of natural minerals,adoption of suitable modification methods,and preparation of composite materials with high specific surface area and rich active sites.In addition,we provide a summary of the principle and technical route of direct and indirect mineralization of CO_(2) by natural minerals.This process uses minerals with high calcium and magnesium contents,such as forsterite(Mg_(2)SiO_(4)),serpentine[Mg_(3)Si_(2)O(OH)_(4)],and wollastonite(CaSiO_(3)).The research status of indirect mineralization of CO_(2) using hydro-chloric acid,acetic acid,molten salt,and ammonium salt as media is also introduced in detail.The recovery of additives and high-value-added products during the mineralization process to increase economic benefits is another focus of future research on CO_(2) mineralization by natural minerals.

The effects of clay minerals and organic matter on nanoscale pores in Lower Paleozoic shale gas reservoirs, Guizhou, China

In organic-rich gas shales, clay minerals and organic matter(OM) have significant influences on the origin, preservation, and production of shale gas. Because of the substantial role of nanoscale pores in the generation,storage, and seepage of shale gas, we examined the effects of clay minerals and OM on nanoscale pore distribution characteristics in Lower Paleozoic shale gas reservoirs.Using the Niutitang and Longmaxi shales as examples, we determined the effects of clay minerals and OM on pores through sedimentation experiments. Field emission–scanning electron microscopy combined with low-pressure N2 adsorption of the samples before and after sedimentation showed significant differences in pore location and pore size distribution between the Niutitang and Longmaxi shales. Nanoscale pores mostly existed in OM in the Longmaxi shale and in clay minerals or OM–clay composites in the Niutitang shale. The distribution differences were attributed largely to variability in thermal evolution and tectonic development and might account for the difference in gas-bearing capacity between the Niutitang and Longmaxi reservoirs. In the nanoscale range, mesopores accounted for 61–76% of total nanoscale pore volume.Considerably developed nanoscale pores in OM were distributed in a broad size range in the Longmaxi shale, which led to good pore connectivity and gas production.Numerous narrow pores(i.e., pores \ 20 nm) in OM–clay composites were found in the Niutitang shale, and might account for this shale's poor pore connectivity and low gas production efficiency. Enhancing the connectivity of the mesopores(especially pores \ 20 nm and those developed in OM–clay composites) might be the key to improving development of the Niutitang shale. The findings provide new insight into the formation and evolutionary mechanism of nanoscale pores developed in OM and clay minerals.

Assessment of Some Secondary Metabolites, Minerals and Alcohol Content of Noni Juice Obtained by Fermentation of Morinda citrifolia L. Fruit from Senegal

The fruit of Morinda citrifolia L., commonly known as noni, has an extensive history of use as a food and traditional medicine around the world. Adding value to Morinda citrifolia L. products, particularly the fruit, could be one way of building resilience in vulnerable farming households. The aim of this study was to determine the secondary metabolite and mineral composition of noni juice obtained by fermenting the fruit of Morinda citrifolia L. Fruits were collected in August 2022 from the local field in Thiès region, West of Senegal. Extraction yields were determined and the secondary metabolites were determined using conventional analytical methods. Calcium, magnesium, iron, sodium and potassium were determined by atomic absorption spectrophotometer coupled with a CCD detector. The results show that an average fruit mass (503.2 ± 110.96 g) consists of 171.44 ± 50.01 g pulp and 34.06 ± 10.35 g seeds. The traditional extraction yield of noni juice is 16.46% after three weeks of fermentation. The contents of total polyphenols, flavonoids and tannins obtained in noni are 608.97 ± 4.53 mg EAG/100mL, 7.78 ± 0.01 mg EQ/100mL and 0.191 ± 0.01 mg EC/100mL respectively. The ethanol content of noni varies from 3.57 to 5.23 mL/100mL during extraction. Noni has a high calcium content with a concentration of 383.79 ± 33.23 mg/L. This is followed by a good concentration of magnesium, potassium and sodium, at 278.47 ± 26.30, 187.43 ± 10.7 and 155.95 ± 28.66 mg/L respectively. Noni also has an iron content of 202.15 ± 0.05 mg/L.

Triboelectric properties of ilmenite and quartz minerals and investigation of triboelectric separation of ilmenite ore

Triboelectric separation, as an entirely dry technology, is a prospective method to process fine minerals.The aim of this paper is to investigate the performance of triboelectric separation of ilmenite and quartz minerals in a lab unit and to get ready for the separation of ilmenite ore. A tribocharge measurement system was used to test the triboelectric properties of ilmenite and quartz particles with tribochargers respectively made of PVC, PPR, PMMA, Teflon, copper, stainless steel and quartz glass. The results show that the ilmenite particles charged positively while quartz charged negatively when tribocharged with PVC tribocharger. The mixture of 12% ilmenite and 88% quartz was prepared for the triboelectric separation. The recovery of ilmenite increases with the increase of airflow rate, decreases with the increasing feed rate, and grows up firstly and then decreases with the increasing voltage. A maximum ilmenite recovery of 51.71% with ilmenite content 32.72% was obtained at 40 m^3/h airflow rate, 6 g/s feed rate and 20 kV voltage. According to the optimal parameters of the separation of ilmenite and quartz mixture,fine ilmenite ore with 7.55% Ti content was beneficiated using the unit and the Ti content increased to 12.32% in concentrate product.

Metallogenesis of the Baidi Au-Sb deposit, southwest Guizhou Province, China: mineralogical and geochemical evidence from sulfur-bearing minerals

The Baidi Au-Sb deposit, which contains 8 t of Au and 10,979 Mt of Sb, is a typical and rare paragenetic deposit located in southwestern Guizhou Province, China.Previous studies have focused on individual ores, but have not combined them to identify their paragenetic mechanism or metallogenic regularity. Therefore, we used field investigations, microscopic observations, and in situ analyses to identify the spatial distribution, mineral paragenesis, compositional evolution, and metallogenic material sources of the ore bodies. We also determined the Au and Sb paragenetic characteristics and the metallogenesis of the deposit. The main Au-bearing minerals in the deposit were early(Apy1–2) and late(Apy3) stage arsenopyrites, as well as pre-mineralization(Py1), mineralization(Py2–5), and late mineralization(Py6–7) stage pyrites. The main Sb-bearing minerals were stibnite(Snt), skinnerite, bournonite,and valentinite. The minerals formed in the order of Py1,Py2–3 + Apy1, Py4–5 + Apy2, Snt, and Py6–7 + Apy3.The δ34S values of the arsenopyrites and pyrites ranged from-5 to 5‰, while those of stibnite were mostly less than-5‰ in the later mineralization stages. Sulfur was provided by deep magmatic hydrothermal fluids, but sedimentary sulfur was added in the later stages. Moreover,the trace elemental contents fluctuated and eventually became similar to those of the sedimentary strata. By comprehensively considering the ores along with the geological characteristics of the deposit, we determined that deep magma provided the Au during ore formation. Later tectonic changes provided Sb from the sedimentary strata,which precipitated along fault expansion areas and produced Au and Sb paragenesis.

Enhancement of Au–Ag–Te contents in tellurium-bearing ore minerals via bioleaching

The purpose of this study was to enhance the content of valuable metals, such as Au, Ag, and Te, in tellurium-bearing minerals via bioleaching. The ore samples composed of invisible Au and Au paragenesis minerals(such as pyrite, chalcopyrite, sphalerite and galena) in combination with tellurium-bearing minerals(hessite, sylvanite and Tellurobismuthite) were studied. Indigenous microbes from mine drainage were isolated and identified as Acidithiobacillus ferrooxidans, which were used in bioleaching after adaption to copper. The effect of the microbial adaption on the bioleaching performance was then compared with the results produced by the non-adaptive process. The microbial adaption enhanced the Au–Ag–Te contents in biological leaching of tellurium-bearing ore minerals. This suggests that bioleaching with adapted microbes can be used both as a pretreatment and in the main recovery processes of valuable metals.

Minerals in edible insects:a review of content and potential for sustainable sourcing

In response to the rapid increase in world population and subsequent demands for food,edible insects represent an alternative food source for humans that is rich in proteins,amino acids and minerals.Entomophagy is a tradition in many countries including China and Thailand,and edible insects have attracted a lot of attention in Western World due to their suitable nutrient composition,high mineral content(e.g.,Fe,Zn,Ca,Mg)and potential use as a supplement in human diet.In this study,we surveyed mineral content in seven insect orders and 67 species of mass produced and wild-harvested edible insects.The total content of essential elements in edible insects was very high in Tenebrio molitor,Bombyx mori,and Zonocerus variegatus.The heavy metal content(summarized for eight species)was below the maximum limit allowed for safe consumption.Sustainable supply of minerals derived from insect biomass is complicated due to the high variations of mineral content in insects and the potential of its change due to processing.

Distribution Characteristics of Minerals and Elements in Chromite Ore Processing Residue

In this paper, environmental scanning electron microscopy （ESEM） is applied to characterizing the mineral and element distribution of chromite ore processing residue （COPR）. The test results show that Cr-bearing brownmillerite occurs in the rim of COPR particle, while hydroandradite with Cr （Ⅵ） in its structure presents inside the COPR particle. Periclase and calcite occur in the interstitial area. Element analyses show that Ca, Fe and Al are distributed throughout the COPR particle, and Mg exists mostly in the interstitial area or on the particle surface. A lower content of Cr is evenly distributed in the COPR particle, while slightly higher concentration of Cr occurs inside the particle. It is suggested that it will take a relatively longer time for Cr to migrate out of COPR, especially fbr hexavalent chromium, so the leaching time and the particle size may be two important factors to affect the release of Cr （Ⅵ）.

OSDA-free synthesis of FeZSM-22 zeolite from natural minerals for n-octane hydroisomerization

A seed-directed approach to synthesizing Fe ZSM-22 zeolite without organic structure directing agent(OSDA)was developed by using Fe-rich diatomite as all aluminum and iron sources.The Fe ZSM-22zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions.Characterizations show that Fe ZSM-22 zeolite synthesized with OSDA-free owns high crystallinity,obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio.Significantly,when used for n-octane hydroisomerization reaction,its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C_(8)isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals,respectively.This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance.