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The effects of high silicon-aluminum coal ashes (Shajuzi coal ash (SJZA) and Pingshuo coal ash (PSA)) on the sintering and fusion behaviors of a potassium-rich biomass ash (cotton stalk ash (CSA)) were investigated by a horizontal tube furnace and an ash fusion temperature (AFT) analyzer. X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC) techniques were applied to analyze the mineral transformations and thermal behaviors of the ash samples. As the coal ash mass ratio varied from 0 to 50%, the sintering degree of CSA/SJZA and CSA/PSA mixtures gradually mitigated. The AFTs of the two groups of mixtures all presented parabolic with respect to coal ash ratio. The potassium content in CSA was very high (K2O, 39.55%), and K-containing minerals mainly existed as low melting point (MP) matters, i.e., sylvite (KCl), arcanite (K2SO4), potassium carbonate (K2CO3), and fairchildite (K2Ca(CO3)2). The mitigation of sintering degree was ascribed to a decrease in KCl content with increasing coal ash ratio. When the coal ash ratio was less than 20%, the decrease in AFT was due to the consumption of alkaline earth metal oxide and the formation of K silicate. The conversions of low MP K salts to high MP K–Al silicates (kalsite (KAlSiO4) and nepheline (KNa3Al4Si4O16)) and the formations of other high MP minerals increased the AFTs after adding 20% coal ash. The thermogravimetric analysis showed that the endothermic peak of KCl evaporation weakened to disappear and the exothermic peaks of some reactions enhanced with rising coal ash ratio.

Hydrodynamic and thermodynamic modeling of fluid evolution in shallow magmatic hydrothermal systems based on phase equilibria for the system H2O-NaCl predicts that the fluid becomes halite saturated at some point in its evolution. A review of the published fluid inclusion data also supports halite saturation in these systems. In this study, we synthesized fluid inclusions at known pressure-temperature-composition (PTX) conditions in the H2O-NaCl and H2O-NaCl-KCl systems such that vapor + halite or liquid + vapor + halite existed at the time of trapping. Our results show that fluid inclusions trapped in the liquid + vapor + halite field in experiments along an evolving temperature path best match the phase ratios and thermometric behavior of fluid inclusions commonly reported in magmatic-hydrothermal systems (particularly in porphyry-style deposits). These results are consistent with the hypothesis that magmatic-hydrothermal fluids in porphyry settings are commonly trapped under conditions of liquid + vapor + halite equilibrium, which in turn has consequences for fluid flow and mineralization. Our results also show that the presence of KCl in the system significantly improves the agreement between microthermometric behaviors reported in natural systems and experimental results. The major effect of adding KCl is to increase the thermodynamic variance (degrees of freedom) of coexistence of liquid + vapor + halite from univariant in the system H2O-NaCl to divariant (occupying an area, rather than a line, in pressure–temperature space). Simulations based on the system H2O-NaCl predict that halite saturation occurs predominantly in the vapor + halite field with localized halite precipitation during the transition from the liquid + vapor to the vapor + halite field. By rendering the liquid + vapor + halite coexistence space as divariant, the addition of KCl also prevents an abrupt termination of liquid stability upon intersecting the liquid + vapor + halite boundary. Simulations using the system H2O-NaCl commonly predict pressure–temperature pathways constrained to the univariant liquid + vapor + halite curve, owing to volumetric and latent heat constraints. In contrast, the presence of KCl relaxes these constraints and expands the ranges of pressure and temperature over which liquid, vapor and halite can coexist. This phenomenon has major implications for the chemical and hydrological evolution in magmatic-hydrothermal systems as related to the ability of fluids to transport metals (ore deposition) and the potential loss of porosity/permeability as a result of salt and quartz precipitation.

This study aims to determine the major factors controlling the qualitative characteristics of groundwater and examine the drinking and irrigation suitability in the Marathon basin, NE Attica, Greece. In this frame, a total of 25 groundwater samples were collected from irrigation wells during October 2014. The dominant ions are Cl− for anions and Ca2+ for cations in the study area. Elevated concentrations of Cl− and Na+ were observed near the coastline indicating a zone of seawater intrusion (SWI). The groundwater quality in the coastal alluvial aquifer system of the Marathon basin is affected by several factors such as water-rock/soil interaction, SWI, reverse ion exchange, and intense agricultural activities. Saturation index (SI) of carbonate (calcite, aragonite, dolomite), sulfate (gypsum, anhydrite), and halide (halite, sylvite) mineral phases were calculated using PHREEQC geochemical software. Carbonate minerals are present in the unsaturated zone (UZ), possibly increasing Ca2+, Mg2+ and HCO3– concentrations when they are dissolved, whereas sulfate and halide minerals are minor or absent in the host rock. The water suitability assessment showed that the groundwater resources are chemical or qualitatively unsuitable for drinking purposes due to the SWI regime and the NO3− pollution, whereas they are suitable for agricultural uses according to various indices (SAR, %Na, RSC, and PI). Keywords: Seawater intrusion, Reverse ion exchange, Coastal aquifer, Multivariate statistical analysis, Groundwater quality

As the main resource of potash fertilizer, high grade of sylvite (KCl) is mainly separated from halite (NaCl) in soluble potash ores using flotation. An effective flotation collector determines the separation efficiency of sylvite. However, the collector adsorption mechanism is still the subject of much debate due to high ions concentration in the flotation pulp. This paper studies the hydration status of KCl, the flotation behavior of KCl and NaCl with lauric acid and the interfacial water structure of the soluble salts to provide further insights into the fundamental mechanisms at play. The contact angle measurements and laboratory micro-flotation experiments have shown that both the hydration status of KCl and the flotation soluble salts with lauric acid were dependent on the solution composition. Specifically, it was determined that the addition of Na-ions had an adverse effect on the hydrophobicity of KCl crystals. Both KCl and NaCl can be floated with lauric acid. However, flotation of NaCl is greatly enhanced with the addition of K-ions whereas the flotation of KCl is suppressed with the addition of Na-ions. Sum frequency generation (SFG) measurements have found, most strikingly, more disordered water molecules dominating the "structure maker" salt surfaces in a saturated NaCl solution. "Collins Concept" is employed to explain the specific ion binding behaviors in the flotation pulp.

The present communication describes a novel application of lime mud, a waste material generated in paper/pulp industries, for the recovery of potash values from mica scraps. Characterization studies of the mica scraps using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) indicate the major minerals to be muscovite and quartz while the chemical analysis confirms the presence of K2O to the tune of 7.5%. Lime mud is found to be mostly consisting of calcite and quartz as the major phases. The roast-leach studies using lime mud and NaCl as the additives have been carried out using response surface methodology to optimize the factors for maximizing the potash recovery. Under optimum conditions such as a temperature of 950 °C, a roasting period of 30 min and a ratio of mica: lime mud: NaCl – 1:0.7:0.7, around 99% of the potash value could be recovered. The results, under similar roasting conditions, are found to be comparable to the ones using CaCl2 as the additive. The formation of different phases as analysed using the characterization studies suggests that the mechanism of potash extraction may follow two routes. One of them is the direct reaction of muscovite with CaCl2 (formed due to the reaction of lime mud and NaCl) to form sylvite, anorthite, and kyanite. The other one may be an indirect route in which muscovite at high temperature along with SiO2, forms K-feldspar that further reacts with CaCl2 to give the sylvite phases. It is also noticed that a further increase in roasting temperature to 1100 °C leads to a decrease in potash recovery with the possible reasons being the formation of water-insoluble K-phases like leucite as confirmed in the SEM studies.

Potash fertilizer ensures the necessary agricultural yields to feed an increasing world population. Over 80% of the world’s potash fertilizer is produced by the selective froth flotation of KCl (sylvite) from NaCl (halite). However, all the surfactants used in the potash froth flotation process are traditional monomeric surfactants contain a single similar hydrophobic group in the molecule, which leads to a low production efficiency. In this work, a novel Gemini surfactant, N,N'-bis (octadecyldimethyl)-1,4-butane diammonium dibromide (BOBD) was prepared, and originally recommended as a collector for froth flotation separation of sylvite from halite for potash ore. The performance of BOBD was compared with the results acquired using its traditional monomeric surfactant octadecylamine hydrochloride (OAH). The bench-scale flotation results showed that BOBD had excellent collecting power for sylvite and significant selectivity against halite at natural pH. Moreover, BOBD presented stronger desalination efficiency than OAH. The results gained with the Gemini collector were better in terms of KCl recovery and NaCl content than those gained with four times higher dosages of the conventional monomeric surfactant.

The Yanjing region of Tibet is famous for its saline springs and salt deposits. It is located between the Qiangtang and Lanping-Simao basins that also have saline springs and salt-bearing strata. The hydrochemical and stable water and C-13 isotopes of saline springs, hot springs, surface waters and rocks from Yanjing are reported and compared with data from those basins. Results indicate that 1) the saline springs are high TDS, Na-Cl type waters and brines with unusually high K contents that indicate interaction with evaporite minerals; 2) for the saline springs from Yanjing, the circulation depth is moderate, 3–4 km, and the Late-Triassic strata (T3b) are considered as the salt bearing strata and the aquifer; 3) the hot springs are of two distinct geochemical types, Na·Ca-HCO3 type waters with higher temperature, and Na·Ca-SO4 waters with somewhat higher TDS content; and 4) all waters are of meteoric origin or have a large meteoric component. Furthermore, the lithofacies' evolution of the salt-bearing belt from Lanping-Simao to Qiangtang, and the affinities of Yanjing with these two basins, are also discussed, and it is concluded that the saline water in Yanjing has a good utilization prospect with regard to sylvite.

Cu-Mo deposits are commonly associated with calc-alkaline porphyries and derived from subduction-modified lithosphere in magmatic arcs. Here we report the Wangjiazhuang Cu-Mo deposit, which is peculiarly associated with an alkaline quartz monzonite that originated from a metasomatized asthenospheric mantle within an intracontinental setting in the eastern North China Craton (NCC). The deposit was formed at ca. 128.3 ± 0.7 Ma (2σ), basically coincident with the emplacement of the host quartz monzonite (128.8 ± 1.0 Ma, 2σ). Pegmatitic vein-type and stockwork-/disseminated-type mineralizations were identified in the deposit, of which the former is shallowly situated and characterized by coarse and well-crystallized Cu- and Mo-bearing sulfides + quartz + biotite + K-feldspar assemblages, whereas the latter is deeply situated and characterized by stockworks or Cu- and Mo-bearing sulfides disseminated in the altered quartz monzonite. Separation between Cu-rich and Mo-rich ore bodies at shallow depth was also observed. The Cu-Mo mineralization is typically associated with potassic-silicic alteration. High-temperature fluid inclusions with halite/sylvite daughter minerals (having homogenization temperatures of 287–466 °C and salinities of 33.8–55.3 wt% NaCl equivalent) suggest a magmatic origin of the ore-forming fluids. Differentiation of the fluids into vapor-rich and liquid-rich phases occurred during the magmatic-hydrothermal processes, as indicated by the coexistence of vapor-rich, liquid-rich and daughter mineral-rich fluid inclusions with similar homogenization temperatures. LA-ICP-MS analysis of the fluid inclusions shows that Cu is highly partitioned into the vapor-rich fluid inclusions, whereas Mo is mainly concentrated in the daughter mineral-rich fluid inclusions. This implies that phase differentiation of the ore-forming fluids was likely responsible for the separation of Cu-rich and Mo-rich ore bodies. The presence of hematite in the fluid inclusions also suggests high oxidation state of the ore-forming fluids. Based on the variations of δ34S in sulfides and Al contents in quartz, continuous reduction of the oxidized ore-forming fluids, coupled with pH change of the fluids during water-rock interaction, led to the deposition of the ore-forming metals. The host quartz monzonite shows adakitic geochemical signatures. Fractional crystallization of low-Mg amphiboles contributed to the adakitic signatures. According to the mixing modeling using Sr-Nd isotopes, the quartz monzonite was mainly derived from asthenospheric mantle-derived magma mixed by ∼15–20% lower crust components at the base of the lower crust. Zircon saturation thermometry and Ti-in-quartz thermobarometer suggest that the rock was emplaced at the temperature of ∼746 °C and the depth of ∼4 km. High water (H2O ≥ 4 wt%) and metal (Cu is up to 840 ppm and Mo is up to 11.9 ppm) contents as well as high oxidation state (fO2 > fayalite-magnetite-quartz oxygen buffer) are featured in the quartz monzonite, indicating that the asthenospheric mantle source had been hydrated and oxidized by the water released from the stagnant Paleo-Pacific slab in the transition zone (410–610 km). Such modification by the deep stagnant oceanic slab beneath the eastern NCC thus not only triggered the remarkable thinning of the Archean lithospheric keel (loss of >120 km), but also promoted the asthenospheric mantle to become the favorable magma and metal source for the Cu-Mo deposits in the study region.

In the Tibetan Plateau, most geothermal springs show an unusual enrichment of boron and lithium and other typical resources dissolved in hot water or geothermal deposits. The evolution of the geothermal water and the distribution of elements during the phase separation of residual liquid and associated deposits remain unclear. Through a chemical analysis of the deposits and geothermal water in the Kawu area during primary discharge and later evaporation, the elemental distribution and enrichment processes between the two phases of deposits and the mother water are discussed. Basic results show that the elements Li, B and K are preferentially enriched in the geothermal water rather than distributed into the geothermal deposits of travertine during the primary phase separation of geothermal water discharge. The elements B and K, as a whole, are enriched in the late residual mother water in the later stages during evapoconcentration. However, Li shows a distinctly depleted trend in the residual mother water at the stage when the lithium carbonate precipitates in the deposits. The most important finding of the evapoconcentration experiment is that the zabuyelite, an unusual lithium carbonate mineral, is firstly detected in the mineral association of geothermal deposits. It is only precipitated within a very small interval during an intermediate stage with a very high concentration of Li while there are very low concentrations of Ca and Mg and an unusually high Li/Mg ratio in the mother geothermal water. The zabuyelite is a trademark mineral in the salt lake deposits in the Tibetan Plateau. This is the first time it has been found in the mineral association of deposits of evapoconcentrated geothermal water. This indicates that geothermal water discharge may be the main source for Li, B and K accumulation in the salt lakes. In addition, the typical elements of Li, B and K are extremely enriched during the late stage of the residual mother water or precipitate as zabuyelite or sylvite within a very concentrative stage. They are also very promising mineral resources for development and utilization.

Stone alteration in the environment is caused by various extrinsic disintegration agents, besides, their intrinsic properties "mineralogical composition, textures and internal structure". Therefore, the purpose of the current study was to evaluate the weathering state affecting the Luxor Avenue of the Sphinxes by studying its chemical, mineralogical and physio-mechanical characteristics, in addition to morphological features. Scientific techniques, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), Petrographical microscopy (PM), Cathodoluminescence (CL), Environmental Scanning Electron Microscope (ESEM) and micro energy-dispersive X-ray fluorescence (μ-EDXRF) were used. The results showed that quartz represents more than 96% of the sandstones and the main cement of the grains is quartz overgrowth. Alteration and formation of kaolinite was clearly observed. Halite, sylvite and bischofite were the main salts that affected the statues representing approx. 78.40%. The study also provided information about the different deterioration factors affected the Avenue of the Sphinxes namely; burial environment, solar effects, soil moisture and groundwater. These caused some deterioration forms such as soiling & crusting, breaking down most of the statues heads, saturation forms, salt crystallizations and stone abrasion. Cleaning, desalination and consolidation using different materials and techniques, in addition to reducing the human anthropogenic impacts are recommended for future conservation of the Luxor Avenue of the Sphinxes.

This study aims at investigating the possibility of using dust, collected in air filters during the melting of mineral wool raw materials (mineral wool cupola dust) as an additive for Portland cement. It was found that the investigated dust mainly consists of quartz, periclase, albite, dolomite, and the amorphous phase. The main impurities are halite and sylvite. The investigated additive was additionally milled and prepared as a microfiller. The results showed that the cupola dust additive increases the initial hydration of cement, yet prolongs the dormant period. It was estimated that up to 15 wt% of Portland cement can be replaced by the dust additive without impairing the strength properties of samples after 28 days of hardening. However, after 90 days of hydration, the compressive strength of all samples with the investigated additive is lower than in pure OPC samples. This phenomenon is concerned with the formation of a significant amount of Friedel's salt. The content of chlorides in the raw material was reduced from 4.901 to 0.612 wt% by washing with water, when the water-to-solid ratio was equal to 10. The results of the investigation showed that the washed and ground cupola dust had a positive effect on the compressive strength of the cement samples. When 5, 10, and 15 wt% of prepared dust additive were used, the compressive strength of samples after 28 and 90 days of hydration was greater than that of pure Portland cement sample. The findings suggest that the additionally prepared dust additive leads to the formation of a stable structure of the cement stone, accelerates the calcium silicates hydration, and promotes the formation of gismondine.

Natural sylvite samples have been studied by laser-induced time-resolved luminescence techniques. The specific combinations of luminescence and excitation spectra together with luminescence decay times enabled their interpretation as Pb2+ and O2- emission centers. Such conclusions have been supported by luminescence study of artificial KCl crystals, activated by the corresponding emission centers.

The present study examined the influence of metal ions (Cu2+, Pb2+, and Zn2+) on kinetics and morphology of struvite precipitated from aqueous solutions containing equimolar ratios of struvite components: Mg2+, NH4+, PO4−3. Kinetics of the struvite precipitation in the presence of metal ions [0,1, 10, 50 and 100 ppm] was evaluated through the change of pH of the precipitating solution. The kinetic evaluation demonstrated that the precipitation satisfactorily followed the first-order kinetic with respect to Mg2+. It was found that for the three metal ions tested, the higher the concentrations of the metal ions: 0, 1, 10, 50, 100 ppm, the less the crystals obtained and the lower the rate constants. Depending on the concentrations of the metal ions added into the solution, the rate constants varied from 4.344 to 1.056 h−1 which agree with most published values. It was postulated that the metal ions were adsorbed onto the surface of the crystals and hence retarded the growth. The crystals obtained were characterized using SEM-EDX and XRPD Rietveld. The characterization revealed that the precipitates were mainly struvite of various sizes (between 10 and 60 μm) with sylvite as impurities. It is envisaged that the present study would add to the understanding of the removal of metal ions from industrial wastewater through struvite precipitation.

The evaporites of the Aptian Loeme Formation occur along the stable structural domain of onshore Congo as horizontally well-stratified depositional halite interbedded with Mg-poor potash minerals including carnallite, bischofite, tachyhydrite and sylvite. Eleven correlative depositional recharge-to-evaporation cycles are composed of suites of organic-prone shale followed by primary halite and carnallite beds, sometimes punctuated by a bischofite-tachyhydrite end-member. A sedimentological and petrographical analysis performed on cores and thin sections allowed an interpretation of nine facies associations, named as FA1 to FA9, relying upon the occurrence of bands of fluid inclusions, grain-size, dissolution features, detrital sediments, minute inclusions and sedimentary structures. A depositional model reconciles the spatial distribution of primary textures, hydrology, brine saturation and palaeo-depth during a standard regressive evaporation cycle. Shallow burial eo-diagenesis led to compaction-driven dissolution and recrystallization into fine-grained halite and carnallite laminites but poorly affected the overall preservation of primary deposits. Measurements and profile analysis of bromine trace element concentrations reveal a palaeo-salinity increase of the parent brine for cycle II to base IX caused by a relative brine level fall and a gradual confinement of the salt basin, likely associated with an excess of saline elements inflow from hydrothermal vents. Similar depositional textures and bromine concentration variations are observed in the lower cycles of the Aptian evaporites from the counter-part Sergipe Basin in the northern part of the Brazilian margin, testifying of a progressive brine salinity rise due to a palaeogeographic confinement along the northern segment of the South Atlantic Ocean. In Congo, the sylvite displays horizontal “pseudo-stratifications” that unconformably overlay the crests of anticlines and propagate along flanks as a sharp-based caprock. The flushing and transformation of depositional carnallite – halite into secondary sylvite – halite is interpreted as having been caused by down-stepping incremental dissolutions sourced by younger pervasive connate to phreatic waters. In Sergipe, the sylvite is interpreted as secondary but further results from syndepositional dissolution of carnallite and tachyhydrite due to a regional North Atlantic Ocean ingression.

The formation of springs is vital for understanding the subsurface transport of substances and energy in groundwater circulation. The Xiannvshan hot spring in the sandstone aquiclude near the Tongluoxia anticline in northeast Sichuan Basin of China is an up-flow spring discharging thermal groundwater from the underlying carbonate aquifer of the basin-anticline controlled type. This rarely-encountered up-flow spring neither issues directly from an aquifer, nor is controlled by a fault. The spring water is a very hard (hardness of 1050.069-1835.697 mg/L) and brackish hot spring water (TDS of 1650-2802 mg/L) of SO4-Ca type and low temperature (34-38°C) issuing from a neutral and reduction subsurface environment, and is characterized by high ratios of γNa/γCl (average 1.354) and low γCa/γSO4 (average 0.779), and high concentrations of Sr (7.62-17.183 mg/L) and F (1.87-8.15 mg/L). The ΣMREE of the hot water samples are greater than ΣLREE, and positive Eu and negative Ce anomalies exist. The dissolved constituents in the hot water are derived from the dissolution of calcite, dolomite, anhydrite, gypsum, polyhalite, halite, albite and K-feldspar and small amount of sylvite, epsomite, thenardite, langbeinite, celestite, barite, strontianite, magnesite, and fluorite in the carbonate aquifer, and the dissolution of sulphates prevails in the groundwater system. Hydrochemical similarity is found among the water samples from the two springs’ vents and the flowing borehole near the vents. Faster groundwater circulation caused by the flowing hot water borehole encourages the dissolution of minerals in the carbonate aquifer and slightly increases the TDS and temperature of the hot water from the flowing borehole.

Alkali-rich Cu (Au, Mo) deposits are of increasing economic significance and are an attractive exploration target. They include some of the world's highest grade and largest porphyry related gold resources as well as some of the largest gold accumulations in epithermal settings. The Jinshajiang–Red River alkali-rich intrusive belt, with many porphyry Cu (Au, Mo) deposits, is a representative magmatic belt associated with mineralization. The Jinshajiang–Red River alkali-rich intrusive belt contains several Cu (Au, Mo) mineralized alkali-rich porphyry rocks including the Yulong quartz monzonite porphyry, the Machangqing granite porphyry, the Tongchang quartz syenite porphyry, and the Beiya quartz syenite porphyry. Additionally, there are also some barren alkali-rich porphyry rocks in the belt, such as the Yanshuiqing quartz syenite porphyry. Fluid inclusion petrography and microthermometry on those porphyry rocks are carried out in detail. The results show that the fluid inclusion assemblages in ore-bearing and barren porphyries are distinct: inclusions from barren porphyry are dominated by primary melt inclusions, and contain rare or no fluid inclusions, whereas inclusions from ore-bearing porphyries are dominated by fluid inclusions, and contain rare melt inclusions. Furthermore, halite, sylvite, calcite daughter minerals and an opaque phase in fluid inclusions from ore-bearing rocks are common, but rare in fluid inclusions from barren rocks. The results suggests that the evolution of ore forming fluids especially the halite, sylvite, calcite and opaque daughter minerals bearing fluid inclusions of quartz phenocrysts could be used to judge the degree of metasomatism and mineralization of a porphyry system.

Biomass ash management is an escalating issue in many countries because of increasing numbers of biomass power plants. Comprehensive characterization of biomass ashes with emphasis on element speciation, and solubility of nutrients (e.g., K and P) and pollutants is essential for potential utilization of these residues for soil nutrition. All the UK biomass ashes investigated, whether from combustion of poultry litter, meat and bone meal, and straw, were alkaline and contained high concentrations of P, K, and Ca. The biomass air pollution control (APC) residues were enriched in K, Cl, S and Zn, and contained less lithophile elements, such as Al, Ca, P, Mg, Si, Ti, and Ba, compared to the bottom ashes. P appeared in: 1) bottom ashes as apatite and other phosphates (potassium hydrogen phosphate and potassium iron phosphate in the bottom ashes from combustion of poultry litter); 2) APC residues from combustion of poultry litter as potassium sodium calcium phosphate. K is present mainly in sylvite, arcanite, and some phosphates. Na, K, Cl, and S were easily leached by water from the biomass APC residues. However, water leaching of P, Ca, and Mg was very low, with leaching of P possibly controlled by hydroxyapatite. Aqueous Zn, Cu and Pb appear to prevail in the form of neutral and anionic hydroxide complexes, which are toxic and easily accessible chemical forms for live organisms. Application of the poultry litter bottom ashes as a PK fertiliser in agriculture is appropriate. However, direct application of APC residues to agricultural fields is not appropriate but recovery of K and P from that material should be considered.

The difficulties of beneficiation of the potash ores by flotation is controlled by the structural similarity of the soluble salt minerals such as halite NaCl and sylvite KCl leading to the same surface properties and reactivity of those minerals when cationic reagents are used as collector. In this work, the effect of sonication on the selective flotation and separation contrast between sylvite KCl and halite NaCl in saturated salt solutions was investigated. The flotation experiments were performed on the potash ore samples from the Verkhnekamskoye deposit, Russia, using primary amine as the collector. Different particle sizes (0.5–1 mm, 0.25–0.5 mm, and 0.1–0.25 mm) with similar contents of K (26–29 %) and Na (16.5–18 %) and the same mineralogical compositions were studied. Pulp sonication was performed during the conditioning and/or flotation stages at 30 % solid content in a mechanical flotation machine using an ultrasonic generator at powers from 10 to 75 W at a resonant frequency of 20 kHz. In the absence of the sonication, the maximum recovery of sylvite was obtained for the size fraction of 0.25–0.5 mm (93.99 %) while the sylvite recovery was low for the coarse-grained fraction (0.5–1 mm). The lowest flotation selectivity was observed for the fine-grained ore sample (0.1–0.25 mm). The combined ultrasonic treatment of this sample during conditioning and flotation approximately halved the recovery of NaCl in the potash concentrate (from 17.9 % to 9.9 %) and increased the KCl recovery from 89.9 % to 95.9 %. The addition of a frother increased significantly the sylvite recovery under sonication for coarse size fraction while the effect was less prononoced for the intermediate size fraction. The enhanced flotation selectivity between KCl and NaCl under sonication was attributed to the increased detachment of weak hydrophobic NaCl particles from air bubbles according to the particle size and mode of treatment. The collector desorption from the halite surface unrevealed by the diffuse reflectance infrared spectroscopy was suggested as a factor controlling the selective detachment of low hydrophobic particles under sonication. Therefore, based on our results, a balance must be established between the particle size, collector consumption, ultrasound treatment power, and sonication method (during conditioning with reagents or/and flotation) to optimize the separation between NaCl and KCl.

In this work, the pyrolysis behavior of electric arc furnace dust (EAFD) mixed with poly(vinyl) chloride (PVC) was studied under inert conditions. Unwashed (UW) EAFD was found to contain lead hydroxychlorides which were converted to hydrocerrusite upon washing. It also contains appreciable amounts of soluble salts such as halite and sylvite; the effect of these salts on the pyrolysis behavior of EAFD-PVC mixtures was investigated. These salts delayed the dechlorination of PVC, by at least 20 ⁰C, during the pyrolysis of EAFD-PVC and altered the mineral composition of the pyrolysis residue. The later was rich in PbCl2, FeCl2. H2O for both unwashed (UW) and washed (W) EAFD samples. However, the W-EAFD-PVC residue was rich with ZnCl2. H2O, which was not detected in the UW-EAFD-PVC pyrolysis residue. Instead, it is believed that UW-EAFD-PVC pyrolysis residue is rich with the metastable Na2ZnCl4 as well as K2FeCl5. H2O and NaFeCl4. The capturing and monitoring of the released gases during the pyrolysis of UW- and W-EAFD-PVC mixture, confirmed the inhibiting effect of the halite and the sylvite on the dehydrochlorination of PVC. The released gases demonstrate a strong evidence of the solid-solid reaction between EAFD compound (mainly ZnO) and PVC without evolution of hydrochloric acid (HCl) at temperatures below 200 ⁰C. The subsequent leaching of the pyrolysis residue has resulted in the recovery of Zn (up to 100%), Fe (up to 64%) and Pb (up to 76%) in water. It is inferred that decreasing iron recovery can be achieved by oxidizing Fe+2, while increasing Pb recovery can be achieved by controlling the pH of the leachate solution.

The field of geochemical modelling has developed rapidly since the early 1960s when the first attempts were made to predict the concentrations of dissolved chemical species in the seawater. Researchers have eventually realized the significance of predicting the behavior of different chemical elements in geological environments in order to understand the complexities of the chemical reactions. Henceforth, the construction of geochemical models based on numerical simulations with a set of empirical data, aims to predict the behavior of species. The constructed model is thereafter correlated with the existing geological evidence of the study area. Hereby, this work aims to generate a geochemical model capable of predicting the quality of hydrocarbon reservoirs by analyzing the diagenetic reactions between marine connate water and salt domes in a petroleum system. In order to achieve this goal, the software like PHREEQC™, GWB™ and TOUGHREACT™ (batch mode); GWB™ and TOUGHREACT™ in 1D have been used. The study area for this particular research was selected to be Gulf of Mexico where water-rock interactions occur within the turbidite reservoir of the petroleum system. Simulation results in "batch" mode at 25°C reveals the increasing saturation index of halite and sylvite. Dependening on the variable software, the steady-state has been achieved at different time interval. In low temperatures (25°C–100°C), there has been a convergence of results, while at higher temperatures (120°C–160°C), however, each software generates unique curve profiles. The 1D simulations of different geochemical modelling software display reproducibility of the results. Users must be cautious while selecting a specific geochemical modelling software with a simulator, which has a compatibale temperature range for the analyses.

Magnesium phosphate cement (MPC) composited by dead burned magnesia (MgO) and potassium dihydrogen phosphate (KH2PO4, KDP) is a type of excellent repairing material, and its volume stability has great influence on its applications. This paper studied the effects of different types of mineral admixtures on the volume stability of MPC mortar by testing its volume deformation at different curing ages. The main mechanisms to explain how the mineral admixtures affect the volume stability were studied by XRD and ESEM analyses. The experimental results indicate that the influence of ultra-fine fly ash on the volume deformation is different from that of fly ash and silica fume. The volume expansion increases as the content of fly ash in mortar increases while the volume expansion decreases as the content of ultra-fine fly ash increases. For MPC-fly ash system, the use of ultra-fine fly ash can decrease the volume expansion significantly. Moreover, the addition of dipotassium hydrogen phosphate also has significant influence on the volume stability of MPC mortar. The XRD analysis indicates that the amount of sylvite in MPC mortar is the reason for the changes in the volume stability after adding mineral admixtures. The ESEM imaging confirms that the use of ultra-fine fly ash can decrease the quantity of micro cracks in the MPC mortar.

Salts and brines have very low rare earth element (REE, La-Lu) concentrations. Thus, there is less knowledge of possible transfer of REE patterns during salt dissolution in water-rock interaction. REE levels in both media are close to or rather below limit of detection of commonly used methods. By dissolving salt samples in water followed by REE pre-concentration, REE contents of about 6.2 to 322 ng g−1 were measured for four samples from the Merkers salt mine, Germany. These salts previously were identified to consist mainly of carnallite, halite and/or sylvite. Assuming congruent dissolution, REE patterns of brines and salts differ. Thus, a more complex interaction with (secondary) phases and complexation of REE should be taken into account to explain REE patterns in brines.

Alkali halides are wide band gap dielectric materials, which are very important for luminescence dosimetry. Nevertheless, only some of them were studied comprehensively. Potassium chloride (KCl) is alkali halide material, which shows pronounced thermoluminescence (TL) and optically stimulated luminescence (OSL). The material occurs also in natural mineral form as sylvite (or sylvine). This paper presents results of spectrally resolved thermoluminescence (SR-TL) measurements of pure KCl crystals in temperature range 300–550 K for various doses of beta irradiation. Four emission bands were found relating to different recombination centers in this material. TL curves relating to these centers have different shape. It indicates that recombination centers are not filled concurrently.

Potash basins similar to those in the geological past no longer exist at present. There are only hypersaline lakes such as those in the Tibetan Plateau where carnallite [KCl·MgCl2·6H2O] precipitates. Given that the purpose of common saltworks is to obtain NaCl, the halitic stage is not exceeded. By contrast, saltworks extracting lithium by solar evaporation reach more advanced stages of brine evolution and saline precipitation. In the Salar de Atacama saltworks, with a relative humidity commonly below 30% (monthly average), salts precipitate following a sequence of halite [NaCl], sylvite [KCl], carnallite and bischofite [MgCl2·6H2O] and display a useful model of evolution similar to that which gave rise to MgSO4-free potash deposits in the past. Prismatic-acicular gypsum [CaSO4·2H2O], the main accessory mineral, is transformed into a less hydrated calcium sulfate, probably anhydrite [CaSO4], during carnallite precipitation. Mineral crystal size and annual sedimentary thickness of each paragenesis are compared with those in ancient potash deposits. The behavior of sylvite and carnallite as cements is observed at the onset of their precipitation in ponds where both minerals coexist with previous halite. Millimeter cyclicity due to day-night thermal variations is observed in these saltworks, whereas cm- and mm-cyclicities have been interpreted in ancient sites as annual (regular) and intra-annual (irregular), respectively. Conditions similar to those existing at the Salar de Atacama were necessary to preserve carnallite, which is commonly the most evolved mineral in the ancient deposits. The development of potash deposits in the South Pyrenean Foreland Basin and the Rhine Graben, near the Eocene-Oligocene boundary, is attributed to global aridity and cooling and to the basin restriction associated with a decrease in the ocean level caused by the spread of the Antarctic ice cap.

Geothermal energy is a renewable energy source by which heat is extracted from the subsurface. Due to changes in pressure and temperature and chemical reactions when the geothermal fluid is pumped through the wells and surface installations, scales can be formed. These scales can accumulate in different locations of the geothermal system and/or parts of the surface installation and cause clogging of the wells, pumps, pipes, heat exchangers and/or filter units. Consequently, the efficiency of the geothermal system can decrease. To obtain insight into the formation of scales in the surface installation of the Balmatt geothermal site, heat exchanger and filters scaling material was sampled after a circulation time of 240 h and 46 h respectively. This material was chemically, mineralogically and radiologically characterized. The scaling material found in the heat exchanger consists mainly of galena (PbS). Minor amounts of challacolloite (KPb2Cl5) and laurionite (PbClOH) were also observed. Additionally, in the filter scaling material carbonates such as witherite (BaCO3), siderite (FeCO3) and possibly rhodocrosite (MnCO3) are present as well, together with an amorphous phase and elemental copper. Salt minerals such as sylvite (KCl), halite (NaCl) and challacolloite (KPb2Cl5) and iron oxides such as hematite (Fe2O3) were also observed in the scaling material. However, these minerals are thought to be formed during drying of the scalings after sampling. Together with these minerals, radionuclides such as 226Ra, 210Pb and 210Po are observed. 226Ra seems to predominantly co-precipitated with and/or sorb on witherite and hematite, while 210Pb and 210Po are rather accumulated in galena and laurionite. Equilibrium calculations, using the PhreeqC software were performed to gain insight into the geochemical processes. The calculations indicate that galena is one of the main oversaturated minerals. Precipitation of native copper and carbonates are also observed and supported by the equilibrium calculations. The formation of these precipitates is probably a result of electrochemical corrosion of carbon steel and/or corrosion by dissolved CO2.

Thermal behavior of municipal solid waste incineration (MSWI) fly ash is extremely complicated due to the simultaneously occurred reactive processes and the products with different chemical compositions, therefore, the investigation of chemical compounds transition behavior and mechanism during the integrated thermal process is of great significance. In this study, the macro-thermal treatment of fly ash and thermo-gravimetric analysis via non-isothermal methods were carried out and Malek method was firstly introduced to explore the mechanism of multi-step reaction for fly ash. The mineral transition results suggested that the halite, sylvite in the raw fly ash transformed to more complex crystals in treated samples, such as chlorellestadite, polyhalite and enstatite during the thermal process. And the heavy metals leaching concentration decreased with the temperature increased from 300 °C to 1200 °C, and the leaching values were lower than the standard limitation after thermal treatment. In addition, three major steps of fly ash reactions (300–380 °C, 650–750 °C and 890–1130 °C) during the thermal process were observed and expressed by first order reaction for the first step, three-dimensional diffusion for the second step and three dimensions of limiting surface reaction between both phases for the third step, respectively. The kinetic study revealed that the mineral transition process was in well accordance with the simulated reaction mechanism during the thermal treatment. The obtained results are expected to provide the research basis for studying detailed thermal characteristics and reaction mechanism during the thermal treatment of MSWI fly ash.

The Middle Devonian-age Saskatchewan potash deposit represents approximately half of the proven global potash reserve. Salts of the Saskatchewan Basin were laid down in a basin of deposition referred to as the Elk Point Basin that consists of multiple marine transgression-regression cycles and multi-stage marine basins sitting in northwest-southeast direction. In south Saskatchewan, there are three evaporite cycles thinly deposited within the Saskatchewan Basin during the Middle Devonian age. The lowermost evaporite termed as “the Prairie Evaporite” is characterized by four potash members representing the largest potash deposit all over the world. The Prairie Evaporite accumulated of carbonate, anhydrite, halite and sylvite was deposited due to the combined effect of repeated transgressions, intensive evaporation and sea level lowering. Some iconic markers are used for prospecting, such as “the second red bed” and the Dawson Bay Group. Researching in the geological structure and the subsurface stratigarphy has great support to the exploration and development of local potash.

The relationship between sylvinite (KCl + NaCl) and carnallite (KCl·MgCl 2 ·6H 2 O) is important in potash mines containing carnallite, and especially where sylvinite overlies carnallite. It is generally believed that this reversal of the normal depositional sequence may be caused by dissolution of carnallite. To obtain sylvite (KCl) from carnallite ore in the present study, first carnallite ore dissolution was performed in an aqueous solution at 25 °C, and then the sylvite was separated from halite (NaCl) in the sylvinite by a flotation method. The Br and Rb concentrations in the sylvite derived from the carnallite ore were determined. The results showed that more than 4/5th of the Br and Rb in the carnallite ore transferred to the mother liquor, while the remainder of the Br and Rb was in the sylvinite. The sylvite separated from this sylvinite had purity of 94–96%. In the sylvite derived from carnallite, the Br concentration was obviously lower (by an order of magnitude) than the concentration in primary sylvite from evaporation of MgSO 4 -deficient sea water, and the Rb concentration was twice that in primary sylvite from evaporation of MgSO 4 -deficient sea water. Compared to the Br and Rb concentrations in secondary sylvite from Khorat Plateau, Sergipe, and Prairie evaporites, the concentrations in the sylvite derived from carnallite ore were similar. The redistribution of Br and Rb in the form of secondary sylvite was in a relative stable proportion according to the comparison of Br and Rb. The lower Br and higher Rb concentrations in sylvite derived from carnallite ore could be caused by KCl re-crystallization and redistribution of Br and Rb between the solid and liquid phases. The driving force behind changes in the partition coefficients of Br and Rb is that the dissolution of carnallite is much slower than the nucleation of KCl.

Nepheline syenite is an igneous rock, which contains around 5.4% of potassium oxide (K 2 O), but finely dispersed and, locked in the host matrix. The characterization studies reveal the presence of orthoclase, nepheline and biotite as the major potassium bearing mineral phases. The present study aims at the extraction of potash values through microwave heating for its possible application as fertilizer. The microwave assisted roasting studies of nepheline syenite have been carried out and optimized using a statistical approach based on Taguchi design. It is possible to extract around 88% K 2 O values at 900 W microwave power and 6 min of roasting time using 20% charcoal and 50% calcium chloride. Charcoal is used as a microwave absorbing material that raises its temperature in a much lesser time, while calcium chloride for the favorable formation of KCl. The transformation of different mineral phases of nepheline syenite is characterized using XRD, and SEM showing the formation of a soluble potassium bearing phase (Sylvite) along with calcium aluminum silicate.

The Hongshan skarn Cu–Mo deposit is located in the southern Yidun terrane, SE Tibet Plateau, with more than 78.7 Mt resources (Cu: 0.64 Mt @ 1.23%, Mo: 5769 t @ 0.03%). The ore deposit was spatially and temporally associated with post-subduction Late Cretaceous monzogranite porphyries. Detailed geological mapping and deep drill-hole loggings reveal the vertical skarn zonation patterns of pyroxene skarn – garnet skarn – magnetite skarn – pyrrhotite-chalcopyrite skarn – garnet skarn – pyroxene skarn away from the marble, which is similar with typical skarn Cu deposit worldwide. Three hydrothermal stages have been recognized at Hongshan. They are characterized by assemblages of prograde skarn (stage 1), retrograde skarn and Cu–Fe–Mo sulfides (stage 2), and Pb–Zn sulfides associated with calcite and quartz (stage 3). Prograde skarns contain mainly andraditic garnet (two series: And37–82Gro17–61Spe+Alm+Pyr0–4 and andradite) and pyroxene (Di64–88Hd12–35) resulted from the interaction between magmatic-hydrothermal fluids and carbonate wall-rocks. Retrograde skarn mineralogy is controlled by hydrous Mg–Fe-rich silicate minerals, such as tremolites, actinolites, and epidotes. Petrographical and microthermomertic studies on fluid inclusions (FIs) in garnet, epidote, quartz and calcite from the three stages reveal four types of fluid inclusions: vapor CO2–Liquid CO2–H2O (C-type), vapor-rich two-phase inclusions (V-type), liquid-rich inclusions (L-type) and halite (sylvite)-bearing hypersaline inclusions (H-type). The C-type, l -type and V-type FIs within the garnet of stage 1 have homogenization temperatures between 400 and 550 °C, and salinities of 3.9–11.5 wt% NaCl eqv. A boiling fluid inclusion assemblage with coexisting l -type and V-type FIs was defined within the epidote and quartz of stage 2. The fluids of stage 3 are characterized by lower homogenization temperatures of 100–300 °C, developing a fluid inclusion assemblage defined solely by l -type FIs. The wide range of calculated δ18OH2O values in garnet (2.0 to 13.1 ‰), magnetite (10.9 to 26.3 ‰), tremolite (15.9 to 16.4 ‰) and sericite (10.5 ‰) further indicate the mixing of δ18O-enriched components with magmatic fluids. Sulfur isotope compositions of sulfides have a narrow range of δ34S values, ranging from 3.5 to 5.4 ‰, consistent with a magmatic origin and reducing conditions throughout the process of sulfide precipitation. The increased pH caused by water-rock interaction and CO2 degassing, decreasing temperatures and decompression boiling could be crucial for the extensive ore deposition.

The flotation separation of sylvite (KCl) and halite (NaCl) had drawn much attention, but the mechanism is still controversial. In this work, the atomic insights into the flotation separation of KCl and NaCl was conducted using molecular dynamics simulation (MDs). A novel concept that the hydration layer on minerals surface has been introduced. The molecular dynamic calculation shows that the adsorption energy between the octadecylamine (ODA, the most common collector for KCl flotation) and NaCl is smaller than the cohesive energy in the hydration layers on NaCl surface. However, the adsorption energy of ODA/KCl is much larger than the cohesive energy of the hydration layers on KCl surface. Hence, the collector ODA can pass through the hydration layers and then be adsorbed onto the KCl surface, but that cannot do occur on the NaCl surface, which perfectly explains the mechanism of the separation of KCl and NaCl by ODA. Notably, the new viewpoint of hydration layer may open up a new path to explain the behavior of flotation separation. The flotation experiment results also show the KCl is easily floated while the NaCl hardly floated by ODA, which agrees well with the calculation results.

Ash residues produced from biomass gasification could agglomerate and cause severe ash-related problems. The objectives of this study were to determine the impacts of different operating parameters (including equivalent ratio (ER), residence time (RT), and gasification temperature (GT)) on ash deposits during corncob gasification and to further elucidate ash agglomeration mechanisms. The results indicated that the major difference between the ashes in gasifier and the cyclone fly ash (CFA) in mineralogy was that the CFA had a higher content of potassium-bearing compounds, particularly sylvite and potassium silicates, the contents of which could be as high as 47.33 wt% and 12.61 wt%, respectively. Compared with the gasifier fine ash (GFA), the microstructure of gasifier slagging block (GSB) seemed to be much denser and could be divided into three types, skeleton structure, porous texture, and dense structure. However, the melting of CFA was more severe than that of the gasifier ashes. During gasification, a higher ER and a higher GT favored the capture of more volatile species such as K, Ca, S and Cl in the cyclone while a lower GT and an increased RT favored the retention of Si, Al and Fe in the bottom residues. Moreover, when the ER was increased, less silicate minerals could be concentrated on the CFA. With regards to the operations performed at different times, no obvious variation in the ash mineralogy was observed. The ER had little influence on fly ash morphology while the slagging degree of fly ash could be enhanced with the increasing of RT.

Pyrolysis of waste materials aiming to produce biochar has been considered as an effective strategy to add value and to recycle such materials. The properties of the produced biochars depends on pyrolysis temperature and feedstock type, for example. Some waste materials have been still poorly studied. The objective of this study was to evaluate the changes in physicochemical characteristics, mineral composition, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) of biochars derived from agricultural and industrial wastes produced by different pyrolysis temperatures and feedstocks. Two agricultural solid wastes (poultry litter - PL and swine manure - SM) and three industrial wastes (construction wood - CW, tire - TR and PVC plastic - PVC) were pyrolyzed at five temperatures (300, 400, 500, 600 and 700 °C) in an oxygen-limited environment at a heating rate of 10 °C min−1 for one hour. Increased pyrolysis temperature reduced the yield of solids and volatile compounds and increased pH in water and Ksoluble in all studied biochars. Nevertheless, the temperature caused no significant changes in electrical conductivity, water-soluble nutrients and total elements, and CEC, in the industrial wastes (CW, TR and PVC). The XRD patterns revealed similarities in mineral formation among the studied biochars, including quartz, sylvite, calcite and dolomite. Data of FTIR spectra evidenced the presence of aromatic and aliphatic functional groups. The results obtained enable the design of biochars for a desired purpose, which might be solutions for agronomic and environmental issues, taking into account the effects of pyrolysis temperature and the type of waste to be processed.

In this work, the ions hydration insights into the effects of Mg2+ on KCl flotation were investigated. The flotation tests show that the recovery of KCl was sharply decreased with addition of Mg2+. The radial distribution function of water molecules indicates that Mg2+ has strong hydration ability. Molecular Dynamic simulation results show that the hydration of Mg2+ will significantly strengthen the cohesive energy of hydration layers on KCl surface. As a result, it is difficult for the collector molecule to pass the hydration layers in MgCl2 solution. The experimental results are well consistent with the simulation results.

In order to guide the separation of valuable lithium and potassium pentaborate productions, the phase equilibria for the two reciprocal quaternary systems (Na+, K+//Cl−, B5O8− - H2O) and (Li+, K+//Cl−, B5O8− - H2O) at 298.15 K and atmospheric pressure were studied using the isothermal dissolution method. Based on experimental data, the phase diagrams as well as the diagrams between physicochemical properties including densities and refractive indices against J(K+) in the two systems were established for the first time. For the former system, there are four crystallization zones corresponding to halite (NaCl, Ha), sylvite (KCl, Sy), sodium pentaborate pentahydrate (NaB5O8·5H2O, Sp5) and potassium pentaborate tetrahydrate (KB5O8·4H2O, Pp4), two invariant points of three solid phases existed (Ha + Sy + Pp4) and (Ha + Sp5 + Pp4), and five univariant curves, but for the later system, there are also four crystallization zones corresponding to Sy, Pp4, lithium chloride monohydrate (LiCl·H2O, Lc1) and lithium pentaborate pentahydrate (LiB5O8·5H2O, Lp5), two invariant points of three solid phases existed (Sy + Lc1 + Pp4) and (Lc1 + Pp4 + Lp5), and five univariant curves, respectively. The diagrams for the physicochemical properties including density and refractive index against J(K+) in the solution of two systems were also established.

Soluble and insoluble radioactive cesium in municipal solid waste incineration fly ash were analyzed by X-ray diffraction and gamma-ray spectrometry. A total of 60% of soluble radioactive cesium was determined using the Tessier extraction method, and it was almost same extraction rate with Japanese leaching test No.13. In addition, chloride compounds such as halite (NaCl) and sylvite (KCl) showed same behavior with soluble radioactive cesium, therefore, soluble radioactive cesium existed as a chloride (CsCl) with water solubility characteristics. Almost insoluble radioactive cesium trapped into silicate of crystalline phase or amorphous phase was eluted by hydrogen fluoride treatment. Radioactive 137Cs was released in three stages by heating treatment (untreated - 400 °C, 600 °C–800 °C, and 800 °C–1000 °C) according to decreasing amorphous content. The relationship between the concentrations of radioactive 137Cs and amorphous phase exhibited good linearity (R = 0.9278). Insoluble radioactive 137Cs was contained in inner part of the amorphous phase, and free radioactive cesium was determined from the concentration of the amorphous phase.

The physicochemical and slagging characteristics of inorganic constituents in ash residues from biomass gasification in a 25 kg/h lab-scale fixed-bed gasifier were experimentally investigated. The results indicated that among the studied ashes, the wheat straw ash (WSA) had the highest alkali and alkaline earth contents, followed by corn straw ash (CSA) and rice straw ash (RSA). Whilst, the chlorine content in the CSA (5.38 wt%) was higher than that of WSA (3.67 wt%) or RSA (3.26 wt%). Besides, the CSA presented the highest specific surface area of 86.98 m2/g, with the average pore size of 9.29 A and pore volume of 0.162 cm3/g. But the WSA showed the lowest deformation temperature (938 °C) and could be completely melted at 1256 °C. These results indicated that ash melting and slagging behaviours were determined by alkali/alkaline earth content. The coexistence of arcanite and sylvite played important roles in promoting slag formation. The RSA particles were agglomerated with no obvious melting while an evident molten appearance with smooth surfaces on large aggregates of WSA was observed, coating with sylvite and potassium silicates. The formation and transformation of potassium containing minerals was regarded as the dominant reason for the slagging of herbaceous biomass ash.

We present a profitable pathway from desalination waste brines to negative CO2 emissions. The method, termed ‘brine to bricks’ (BtB), mineralizes CO2 as nesquehonite (MgCO3･3H2O) using the Mg content of brines. Fresh water, gypsum (CaSO4･2H2O), halite (NaCl), mirabilite (Na2SO4･10H2O), sylvite (KCl), and hydrochloric acid are concurrently produced. To prevent ‘carbon leakage’, BtB does not rely on external chemicals, fossil fuel-derived heat and power, or captured CO2. BtB selectively precipitates CaSO4･2H2O, NaCl, and Na2SO4･10H2O by evaporative concentration and temperature-control. The remaining Na+ and K+ ions are separated as NaCl and KCl from the magnesium chloride slurry by hydrochloric acid-based precipitation. Super-azeotropic hydrochloric acid is regenerated from the slurry using a novel method: low hydration magnesium chloride addition. Purified magnesium chloride is decomposed to amorphous MgO prior to reaction with ambient CO2. The current NET potential of BtB, including the CO2 emissions from desalination, is 136 MtCO2/y. In the current market, BtB can operate at a profitability up to $266/t-CO2, dependent primarily on the availability of waste heat and the local performance of renewable energy. Based on current desalination adoption projections, BtB could remove 0.350-1.784 GtCO2/y by 2050 while providing substantial increases in fresh water, construction materials, and chemicals that are of use to other negative emission technologies.

Qarhan Salt Lake contains approximately 296 million tonnes of low-grade solid potash ores. The exploitation and utilization of this low-grade solid potash ore represents the fundamental framework for the sustainable development of Qarhan Salt Lake's potash fertilizer industry. It also alleviates the shortage of potash resources of China. In this paper, we studied species and characteristics of the low-grade solid potash minerals from the Bieletan area in Qarhan Salt Lake and analyzed the solvent that affected the dissolution extraction of low-grade solid potash ore. The major potash minerals in the Bieletan Subbasin are polyhalite, carnallite and sylvite. An effective solvent for dissolving these potash minerals is prepared with old bittern and water from Senie Lake, which contains average Mg2+, Cl−, K+ and Na+ values as 3.69%, 15.23%, 0.23% and 1.60%, respectively. Theoretically calculating by PHREEQC shows that the chemical composition of the solvent is nearly in equilibrium with halite and far away from equilibrium with polyhalite, carnallite and sylvite. This solvent does not significantly cause dissolution and precipitation of halite. Thus its influence on the porosity and permeability of the salt bed in the strata is minimum, which enables the solvent to flow to deeper and farther areas and dissolve more low-grade solid potash ores, showing excellent ability to selectively dissolve K+-bearing saline minerals. After dissolution extraction experiments, the concentration of K+ in the solvent increased from 0.23% to 0.68%, showing the higher-dissolution effect of the solvent for the low-solid potash ores. Hence, the solvent plays an important role in developing of the low-grade potash ores.

The low flotation recovery of sylvite from salt lakes at low temperatures has dogged the cryogenic producer for many years. Interfacial water structure at sylvite crystal surfaces has been considered as one noticeable aspect on interpreting the selected KCl collection during flotation, and so the microscopic structure of the water membrane over KCl crystal surfaces at low temperatures was modeled through the use of molecular dynamics methods. In our simulation, the properties of the water membrane adjacent to KCl crystal surface, such as molecular mobility, water structure and preferred molecular orientation, were compared to the results for an otherwise identical system at higher temperatures or in saturated KCl solutions in the absence of a KCl crystal. In our simulation, hydrogen atoms approached the KCl crystal surface more closely, and the mobility of water molecules was more restricted compared to results for saturated KCl solutions. When the temperature decreased, the mobility of water molecules decreased, the number of hydrogen bonds made by the water molecules in the membranes was reduced and the molecules exhibited greater order than in other systems we studied. It was proposed that the property of KCl salt may change from water ‘structure breaker’ to ‘structure maker’ when temperature decreases. These results may provide complementary information which cannot be obtained from experiments on the research of flotation at low temperature directly.

The Lanping–Simao Basin (LSB) is a Mesozoic–Cenozoic continental margin rift basin in Western China. It formed during the opening and closing of the Tethys Ocean. This basin is also known as a “metal belt” as it hosts several metal deposits, besides, the Mengye potash deposit. However, the exact dates of the formation either in the Paleocene or the Cretaceous, and thus the origins of the marine, continental or mixed origins of the Mengye deposits, remain disputed. Based on the basin's evolution, materials of marine origin and/or remnant seawater should be present, but instead the salt layers of the Mengye potash deposit present typically continental lithological features. This study examines and reviews evaporative minerals, Br/Cl and I/Cl molar ratios, and isotopes of S, B, and Sr·I and I/Cl data for this area has not been previously reported. The basin's evaporative minerals are dominated by halite and sylvite. The amounts of anhydrite, chlorocalcite, langbeinite, glaserite, tachyhydrite and glauberite are small. All of these form in both marine and continental environments. The values of I and the I/Cl molar ratios of halite and sylvite are from 0.07 to 0.27 ppm, and from 0.03 to 0.11 × 10 − 6 , respectively, dependent on organic substances. Br and molar Br/Cl values are from 89.08 to 555.45 ppm and from 0.06 × 10 − 3 to 0.38 × 10 − 3 , respectively. All of the Br/Cl molar ratios are lower than those of seawater, and most of them are 34 S, δ 11 B and 87 Sr/ 86 Sr values for evaporative minerals indicate a continental origin for the Mengye potash deposit. However, materials of hydrothermal origin are widely distributed in the basin and may have played an active role for the formation of the potash deposit. Thus the Mengye potash deposit could be of continental origin, with a remnant seawater trace.

Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78 BHD samples collected from 13 different SAP facilities across the U.S. were investigated. The XRD semi-quantitative analysis of BHD samples suggests the presence of metallic aluminum, aluminum oxide, aluminum nitride and its oxides, spinel, elpasolite as well as diaspora. BHD also contains halite, sylvite and fluorite, which are used as fluxes in SAP activities. Total aluminum (Al) in the BHD samples averaged 18% by weight. Elevated concentrations of trace metals (>100 μg L−1 As; >1000 μg L−1 Cu, Mn, Se, Pb, Mn and Zn) were also detected in the leachate. The U.S. toxicity characteristic leaching procedure (TCLP) results showed that some samples leached above the toxicity limit for Cd, Pb and Se. Exceeding the TCLP limits in all sample is independent of facilities generating the BHD. From the metal content perspective only, it appears that BHD has a higher potential to exhibit toxicity characteristics than salt cake (the largest waste stream generated by SAP facilities).

Orbital measurements obtained by the MESSENGER Gamma-Ray Spectrometer have been analyzed to determine the surface abundance of chlorine in Mercury’s northern hemisphere. The derived Cl/Si mass ratio is 0.0057 ± 0.001, which for an assumed Si abundance of 24.6 wt% corresponds to 0.14 ± 0.03 wt% Cl. The abundance of Cl is a factor of 2.9 ± 1.3 higher in the north polar region (>80°N) than at latitudes 0−60°N, a latitudinal variation similar to that observed for Na. Our reported Cl abundances are consistent with measured bulk concentrations of neutron-absorbing elements on Mercury, particularly those observed at high northern latitudes. The Cl/K ratio on Mercury is chondritic, indicating a limited impact history akin to that of Mars, which accreted rapidly. Hypotheses for the origin of Mercury’s high metal-to-silicate ratio must be able to reproduce Mercury’s observed elemental abundances, including Cl. Chlorine is also an important magmatic volatile, and its elevated abundance in the northern polar region of Mercury indicates that it could have played a role in the production, ascent, and eruption of flood volcanic material in this region. We have identified several candidate primary mineralogical hosts for Cl on Mercury, including the halide minerals lawrencite (FeCl 2 ), sylvite (KCl), and halite (NaCl), as well as Cl-bearing alkali sulfides. Amphiboles, micas, apatite, and aqueously deposited halides, in contrast, may be ruled out as mineralogical hosts of Cl on Mercury.

Nepheline syenite is a complex rock consisting of different mineral phases such as nepheline, alkali feldspar, and biotite. It is a promising source for the recovery of potassium and alumina values. India is importing most of its potassium demand from the global market. An attempt is therefore made to extract potassium values from nepheline syenite available in the state of Odisha. It contains 2.8% Fe 2 O 3 , 19.9% Al 2 O 3 , 55.5% SiO 2 and 5.4% K 2 O as its prime constituents. Magnetic separation and flotation techniques are found unsuitable to recover appreciable amounts of potassium values. Chemical leaching with dilute sulphuric acid could recover only ~ 40% of the potassium values. The potassium values present in nepheline syenite are unlocked through roasting with calcium chloride followed by water leaching. In this approach, it is possible to recover ~ 99.6% K 2 O value at 900 °C temperature and 30 min of roasting time. The results indicate that the use of planetary mill grinding prior to roasting is favorable for potassium extraction due to mechanical activation of the potassium bearing phases. The different mineral phases present in the feed and the leach residue have been characterized by using optical microscope, XRD and SEM-EDX which shows a phase conversion of locked potassium into sylvite which is soluble in water.

The Tongkuangyu porphyry copper deposit is located in the Zhongtiaoshan region, southern margin of the North China Craton. More than 2.8 million tons of Cu (Average Cu grade: 0.68%) is hosted in the Paleoproterozoic quartz-monzonite porphyry (2122 ± 10 Ma). The ore-forming processes of the Tongkuangyu porphyry Cu deposit are divided into three mineralization stages, namely the early-, main- and late mineralization stages. The majority of Cu ores were formed in the main stage, which is characterized by veinlets and disseminated chalcopyrite and minor molybdenite, pyrite, magnetite and hematite. Quartz is the major gangue mineral, which occurs as veinlets and associates with metallic minerals. Through systematic petrographic observation, the ore-bearing quartz veins (A-type quartz) and the quartz hosted in chalcopyrite (B-type quartz) were studied in detail to investigate the fluid evolution of the Tongkuangyu porphyry Cu deposit. Four types of fluid inclusions were recognized in the A-type quartz, which include (1) pure vapor or vapor-rich (V-type) inclusions, (2) CO 2 –H 2 O (C-type) inclusions, (3) liquid-rich (L-type) inclusions, and (4) daughter mineral-bearing (S-type) inclusions. S-type inclusions in the main stage A-type quartz contain mainly halite and minor sylvite, calcite, hematite, chalcopyrite and anhydrite, with homogenization temperatures of 233–450 °C. V-type inclusions (coexisting with the S-type inclusions) homogenize to vapor phase at 282–375 °C, suggesting that the ore-forming fluids may have experienced boiling in the main mineralization stage. The late stage S-type inclusions have homogenization temperatures of 186–245 °C and contain largely halite with minor sylvite. Fluid inclusions in the B-type quartz (intergrown with chalcopyrite) are closely associated with the ore-forming processes. The main stage B-type quartz contains predominantly S-type inclusions with homogenization temperatures of 250–412 °C and minor V-type inclusions. On the other hand, the late stage B-type quartz contains abundant S-type inclusions with homogenization temperatures of 195–230 °C and less L-type inclusions. Our results show that the S-type inclusions in both the A- and B-type quartz (of the same ore stage) have very similar homogenization temperatures. Therefore, fluid boiling may have promoted the Cu enrichment in the high salinity fluids and the brine phase is the main metal transport medium in the Tongkuangyu porphyry Cu deposit. The common occurrence of hematite and anhydrite daughter minerals in the S-type inclusions further suggests that ferrous ion oxidization may have caused sulfate reduction. This process may have played an important role during the Cu precipitation event. The progressive cooling of fluids and the incorporation of meteoric water in the late mineralization stage possibly resulted in the small-scale vein-type mineralization.

During the Cretaceous–Tertiary transition in eastern China, abundant halites formed in non-marine areas. Many continental salt deposits from inland salt lakes were formed in eastern China in faulted basins as a result of the northward movement and collision of the Indo-China Plate with the Eurasian Plate, including the Bohai Gulf Basin. However, a marine transgression versus a non-marine origin of these evaporites remains to be determined. Primary fluid inclusions trapped in halite deposits can directly record the composition of evaporated seawater or salt lake water, such as those in the Cretaceous halite in the Khorat Plateau (Laos and Thailand) area can resolve the origins of the evaporate deposits; recent fluid inclusions data in the Khorat Plateau coincide with the predicted secular variation of seawater and are comparable to other fluid inclusions in Cretaceous marine halite, indicating these fluid inclusions are directly related to a marine transgression. Our analyses in this study shows that the average K+, Mg2+, and SO 4 2 - contents are 8.8, 5.0, and 6.8 g/l, respectively, in the primary fluid inclusions in halite of middle–late Eocene from the Yunying depression of China. These numbers are much less than those in the contemporary Spanish primary fluid inclusions in halite precipitated from seawater (16.4, 36.3, and 12.5 g/l for K+, Mg2+, and SO 4 2 - , respectively). Furthermore, Br contents of all fluid inclusion samples in halite from the Yunying depression are lower than 2 ppm (vs. 55–58 ppm at the base of Spanish contemporary marine halite), and their δ37Cl values range from −0.11‰ to +2.94‰ (vs. −0.09‰ to −0.24‰ in sylvite of Spanish deposit), indicating that the compositions of the middle–late Eocene brines trapped in halite in the Yunying depression of China are very different from those derived from the contemporary seawater, and are considered to be resulted from evaporation of an inland saline lake water with little influence of seawater.

Halogen abundances of natrocarbonatites and their alteration products from Oldoinyo Lengai (Tanzania) are compared to those of associated silicate rocks and to various calcite carbonatites from eleven occurrences worldwide. Fresh natrocarbonatites are extremely enriched in F (up to 3.6 wt.%), Cl (up to 5.9 wt.%) and Br (up to 100 μg/g). During meteoric alteration, however, the major Cl- and Br-bearing minerals (mainly sylvite and gregoryite) are easily dissolved, leaving behind residual materials with relatively low Cl (≤ 1000 μg/g) and Br (≤ 15 μg/g) contents. The comparatively low Cl/Br ratios suggest preferential leaching of Cl relative to Br during alteration. At the same time, F is passively enriched as fluorite remains relatively stable during alteration. In the associated silicate rocks at Oldoinyo Lengai concentrations of all three halogens increase from primitive olivine melilitite to evolved combeite–wollastonite nephelinite, demonstrating their incompatible behavior during magmatic differentiation. Relatively constant Cl/Br ratios, but strongly decreasing F/Cl ratios, in these samples are explained by moderately incompatible behavior for F compared to pronounced and very similar incompatibilities for Cl and Br. Our data further imply that during silicate–natrocarbonatite melt separation all three halogens show a strong affinity for the natrocarbonatite. F and Cl are equally enriched in the natrocarbonatite while Cl and Br are slightly fractionated from each other with a preferential partitioning of Cl relative to Br into the natrocabonatite melt.

The No. 2 porphyry Cu–Au deposit in the Xiongcun district forms part of the Gangdese porphyry copper belt of Tibet. This study clarifies the fluid evolution and ore precipitation mechanisms of the magmatic-hydrothermal system that formed the deposit by combining the results of fluid inclusion petrography, microthermometry, scanning electron microscope-cathodoluminescence imaging, and stable isotope analyses of multiple quartz-dominated veins. Four distinct sets of quartz-dominated veins and eight generations of quartz (Q1–Q8) within the veins were identified, namely from early to late, early barren quartz veins (V1) comprised of equigranular CL-bright Q1 quartz, quartz–pyrite–chalcopyrite ± magnetite veins (V2) containing early equigranular CL-bright Q1 quartz and later CL-gray or CL-dark Q2–3 (Q2 + Q3) quartz grains intergrown with Cu–Fe sulfides, quartz–molybdenite ± pyrite ± chalcopyrite veins (V3) comprised of quartz grains (Q4–Q6) characterized by subhedral comb-like textures with well-developed oscillatory growth zoning, and late quartz veins (V4) containing CL-gray Q7 quartz with euhedral growth zones and later CL-dark Q8 quartz. Fluid inclusions in these veins can be classified into six types: B40, B40H, B80, B15H, B15H+, and B15. The B40 and B40H inclusions; B80 inclusions; and B15, B15H, and B15H+ inclusions contain vapor bubbles occupying 30–60 vol%, >70 vol%, and 5–25 vol%, respectively; in addition, B15H, B15H+, and B40H inclusions contain transparent daughter minerals (halite, and in some cases, sylvite). Raman spectra showed that CO2 is only present in B40 and B80 inclusions. In the Q1 quartz in V1 and V2 veins, the dominant type of inclusions is B40, which have homogenization temperatures (Th) of 278 °C–389 °C (peaking at 310 °C–330 °C) and salinities of 2.0–12.8 wt% NaCl equiv. In Q2–3 quartz in V2 veins, all inclusion types were observed. These were trapped at temperatures of approximately 325 °C–340 °C and had salinities of 1.8–69.7 wt% NaCl equiv. In V3 veins, only B15H and B15 inclusions were observed, which had Th values of 171 °C–320 °C (peaking at 240 °C–260 °C) and 173 °C–317 °C (peaking at 210 °C–230 °C) and salinities of 28.7–33.9 wt% NaCl equiv and 5.6–23.1 wt% NaCl equiv, respectively. In V4 veins, only B15 inclusions were observed. Primary B15 inclusions in V4 veins yielded Th values of 166 °C–229 °C (peaking at 170 °C–200 °C) and salinities of 5.1–17.1 wt% NaCl equiv. The 3He/4He and 40Ar/36Ar ratios of the fluid inclusions exhibited the ranges of 0.08–0.84 Ra and 451.3–1567.8, respectively, and the δ18Ofluid and δDfluid values varied from −3.2‰ to 5.8‰ and −92.8‰ to −80.3‰, respectively. By integrating all results from the fluid inclusion, cathodoluminescence, and isotopic analyses, we conclude that the initial ore-forming fluids of the No. 2 deposit were low-salinity, CO2-rich single-phase fluids of magmatic origin. Subsequently, fluid immiscibility developed in the initial ore-forming fluids, generating hypersaline liquid and low-salinity vapor phases and leading to the separation of a CO2 phase plus chalcopyrite precipitation from the fluids. As meteoric water was injected into the hydrothermal system, the ore-forming fluids gradually evolved to become meteoric water-dominated, low temperature, low-salinity, and CO 2-poor; in addition, fluid-cooling due to the meteoric water input resulted in molybdenite precipitation.

This study of the hypabyssal kimberlite with particularly fresh olivine from the Palaeogene Koala pipe (Ekati cluster, Slave craton, Canada) is focused on reconstruction of the kimberlite parental melt. The Koala kimberlite sample is a typical ultramafic rock (archetypal or Group-I kimberlite) containing large abundance of forsteritic olivine set in a carbonate-rich matrix. The euhedral olivine-II shows significant zoning in terms of forsterite content and trace elements. Only the rims of olivine-II are considered to be magmatic — they are uniform in terms of Fo (91.5 ± 0.2 mol%) and host primary crystal (apatite, Cr-spinel) and melt inclusions. The magmatic spinel phenocrysts are strongly zoned from titanian magnesian chromite to pleonaste, with the cores having the same composition as spinel inclusions in olivine. The primary and pseudo-secondary melt inclusions in both magmatic Cr-spinel and olivine comprise a complex assemblage of daughter phases, dominated by carbonate minerals (dolomite, eitelite (Na 2 Mg(CO 3 ) 2 ), shortite Na 2 Ca 2 (CO 3 ) 3 , nyerereite Na 2 Ca(CO 3 ) 2 , zemkorite (Na,K) 2 Ca(CO 3 ) 2 , and fairchildite (K 2 Ca(CO 3 ) 2 )). In addition to the dominant carbonates, the melt inclusions contain phosphates, chlorides and sulphates (bradleyite (Na 3 Mg(PO 4 )(CO 3 ), halite, sylvite, aphthitalite (Na 0.25 K 0.75 ) 2 SO 4 )), but the silicate component is represented by tetraferriphlogopite only. The melt inclusions in olivine studied in heating experiments show immiscibility of two carbonate liquids on heating and cooling, and homogenise at low temperature 2 O, SrO and BaO (in wt.%, 0.37–0.65, 1.17–2.40, 2.37–4.18, respectively). Such compositions are compared to secondary calcite replacing nyerereite and shortite in the natrocarbonatite lavas of the modern Oldoinyo Lengai volcano. The results on mineralogy, composition and homogenisation temperature of melt inclusions and the groundmass of the Koala kimberlite imply that the parental kimberlite liquid was a Si-poor Ca–Mg carbonate, enriched in alkali elements, lithophile trace elements, phosphorus, chlorine and sulphur.

This work presents a preliminary study on the energy recovery of two date palm residues (date stone and date rachis) provided from Tunisia. Rachis residues were transformed into pellets while date stones were used as received. Physicochemical characteristics such as ultimate and proximate analyses and calorific values were determined. Date palm residues were combusted in a domestic pellet boiler according to European EN 303-5 standard. High calorific values of both residues as well as combustion efficiencies close to 80% obtained during combustion tests indicate that these residues are a promising alternative to produce renewable energy in Tunisia. Further adjustments (airflow and fuel feed rates) are necessary to improve boiler efficiencies. High air excess were observed and consequently cooled down the fume temperature. CO and dust emission factors were in the same order of magnitude than expected for EN 303-5 certification. Bottom and fly ashes were characterized by DRX and Fluorescence X. With high contents of chlorine and ash in the rachis pellets, combustion of this sample leads to high emission factors of dust. Further investigations are required for rachis pellets to reach biofuel standards. Elemental chlorine remains in solid residues as bottom and fly ashes under Halite and Sylvite species.