Sulfate Precipitation Research Articles

Optimization of fracturing parameters for horizontal wells in high-sulfur gas reservoirs considering the effect of sulfur deposition

During the development of high-sulfur gas reservoirs, the precipitation and deposition of elemental sulfur can lead to a reduction in reservoir porosity and permeability. Previous studies focus on the well production with optimized operational parameters, but the effect of sulfur deposition is not included, which impacts fracturing parameters, well production, and economic evaluation. Therefore, this work proposes a reasonable approach for parameter optimization considering sulfur. The variation of porosity and permeability are first evaluated during sulfur deposition. After that, fracture half-length, fracture spacing, fracture conductivity, and fracture distribution are optimized with orthogonalization factor analysis, and the influence of sulfur deposition on different fracture parameters are detailed analyzed. The results shown that the fracture half-length and fracture conductivity are greatly affected by sulfur deposition. Finally, net profit value is applied to obtain the optimal fracture spacing interval. With economic evaluation, the optimal fracture spacing interval of 125 m∼ 150 m is determined considering the net profit and the payback period. This work provides a useful economic method for fracture parameter optimization high-sulfur gas reservoirs, which benefits for the development and production of gas reservoirs.

Jarosite formation in Permian-Triassic strata at Xiakou (South China): Implications for jarosite precipitation from H2S upwelling on Mars

Abstract The source of sulfuric acid and associated aqueous alteration of ancient martian sedimentary rocks remain under debate in the context of divergent models of jarosite formation. Here, we report the formation of sulfates, including jarosite in K-bentonites within shallow-water facies of the Permian-Triassic (P-T) transition at Xiakou in South China. In these strata, jarosite is dispersed in the clay matrix or forms aggregates in pore spaces, has a euhedral morphology, and coexists with variably 34S-depleted paragenetic gypsum and bassanite (δ34S = –37.23‰ to +3.20‰ VCDT). Subaqueous alteration of volcanic tuffs concurrently with oxidation of upwelled, biogenically sourced H2S is the process of jarosite formation in the Xiakou K-bentonites. This mechanism of jarosite precipitation and stability over geological time challenges the long-held view of acidic, water-limited conditions leading to iron(III) sulfate precipitation and would be consistent with possible microbial or nanobial life on early Mars.

Research advances on the mechanisms of reservoir formation and hydrocarbon accumulation and the oil and gas development methods of deep and ultra-deep marine carbonates

Based on the new data of drilling, seismic, logging, test and experiments, the key scientific problems in reservoir formation, hydrocarbon accumulation and efficient oil and gas development methods of deep and ultra-deep marine carbonate strata in the central and western superimposed basin in China have been continuously studied. (1) The fault-controlled carbonate reservoir and the ancient dolomite reservoir are two important types of reservoirs in the deep and ultra-deep marine carbonates. According to the formation origin, the large-scale fault-controlled reservoir can be further divided into three types: fracture-cavity reservoir formed by tectonic rupture, fault and fluid-controlled reservoir, and shoal and mound reservoir modified by fault and fluid. The Sinian microbial dolomites are developed in the aragonite-dolomite sea. The predominant mound-shoal facies, early dolomitization and dissolution, acidic fluid environment, anhydrite capping and overpressure are the key factors for the formation and preservation of high-quality dolomite reservoirs. (2) The organic-rich shale of the marine carbonate strata in the superimposed basins of central and western China are mainly developed in the sedimentary environments of deep-water shelf of passive continental margin and carbonate ramp. The tectonic-thermal system is the important factor controlling the hydrocarbon phase in deep and ultra-deep reservoirs, and the reformed dynamic field controls oil and gas accumulation and distribution in deep and ultra-deep marine carbonates. (3) During the development of high-sulfur gas fields such as Puguang, sulfur precipitation blocks the wellbore. The application of sulfur solvent combined with coiled tubing has a significant effect on removing sulfur blockage. The integrated technology of dual-medium modeling and numerical simulation based on sedimentary simulation can accurately characterize the spatial distribution and changes of the water invasion front. Afterward, water control strategies for the entire life cycle of gas wells are proposed, including flow rate management, water drainage and plugging. (4) In the development of ultra-deep fault-controlled fractured-cavity reservoirs, well production declines rapidly due to the permeability reduction, which is a consequence of reservoir stress-sensitivity. The rapid phase change in condensate gas reservoir and pressure decline significantly affect the recovery of condensate oil. Innovative development methods such as gravity drive through water and natural gas injection, and natural gas drive through top injection and bottom production for ultra-deep fault-controlled condensate gas reservoirs are proposed. By adopting the hierarchical geological modeling and the fluid-solid-thermal coupled numerical simulation, the accuracy of producing performance prediction in oil and gas reservoirs has been effectively improved.

Evolution of Physical and Chemical Characteristics of Atmospheric Precipitation and Its Significant Impacts on the Environment in Beijing

Atmospheric precipitation samples were collected in 2018, 2019, and 2021 in Beijing to study the concentrations and changes of the main metal elements and water-soluble ions； the wet deposition fluxes of heavy metals, water-soluble ions, dissolved inorganic nitrogen, and sulfur in the atmospheric precipitation and their impacts on the ecological environment； and the scavenging mechanisms of the typical precipitation to atmospheric pollutants during the study period. The results showed that the precipitation in Beijing during the study period was mostly neutral or alkaline, and the frequency of acid rain occurrence was very low, only accounting for 3.06%. The total concentrations of major metal elements in 2018, 2019, and 2021 were （4 787.46 ±4 704.31）, （7 663.07 ±8 395.05）, and （2 629.13 ±2 369.51） μg·L-1, respectively. The total equivalent concentrations of ions in 2018, 2019, and 2021 were （851.68 ±649.16）, （973.98 ±850.94）, and （644.31 ±531.16） μeq·L-1, respectively. The interannual changes in major metal elements and ions followed the order of 2019 > 2018 > 2021. The seasonal average total concentrations of major metal elements in spring, summer, autumn, and winter were （9 624.25 ±7 327.92）, （4 088.67 ±5 710.14）, （3 357.68 ±3 995.64）, and （6 203.19 ±3 857.43） μg·L-1, respectively, and the seasonal average total equivalent concentrations of ions in spring, summer, autumn, and winter were （1 014.71 ±512.21）, （729.83 ±589.90）, （724.35 ±681.40）, and （1 014.03 ±359.67） μeq·L-1, respectively, all presenting the order of spring > winter > summer > autumn. NO3- and SO42- were the main acid-causing ions in precipitation, whereas NH4+ and Ca2+ were the main acid-neutralizing ions. The wet deposition fluxes of the heavy metal Cd were very low [（0.05 ±0.01） mg·（m2·a）-1], only accounting for （0.13 ±0.04）% of the total wet deposition fluxes of main metal elements； however, its soil safety years were 291 years, significantly lower than those of other heavy metals, displaying that its ecological risk was relatively the highest. The total wet precipitation flux of water-soluble ions NH4+, Ca2+, NO3-, and SO42- accounted for （85.72 ±2.18）% of the wet precipitation flux of total ions, suggesting that their comprehensive impact on the ecological environment might have been higher. DIN wet deposition flux was mainly characterized by NH4+-N, which had a positive impact on the ecological environment in summer. SO42--S wet deposition flux was higher in summer, so its positive impact on the ecological environment was also greater. The scavenging effects of atmospheric precipitations to pollutants from the air were impacted by various factors, and the synergism effects of these factors could directly influence the scavenging mechanisms of precipitation to pollutants.

Review of Sulfate Removal in Low Concentration Brine Solutions

Sulfate is a common ion present in natural water bodies at low concentrations and as effluent in different metallurgical processes. The discharge of sulfate in rivers and waterbodies can cause direct and indirect damage to the environment. Regulatory agencies have been increasing the constraints in sulfate content limit for discharge focused on human equity and environmental protection. A common practice is the precipitation of sulfate with lime, but the remaining solution still has ca. 1,500 mg L-1 of sulfate, which is not acceptable for disposal or reuse. This work describes the main routes for sulfate removal such as chemical precipitation, biological degradation, ion exchange, and separation through membranes and discusses the main advantages and issues of each approach. One of the main challenges is to scale up the tests and show the performances at the industrial level. The subject must be the focus of constant study to obtain relevant results so that usual technologies are replaced by more innovative, cheap and efficient methods.

Fractional precipitation of copiapite-halotrichite efflorescent salts on Au[sbnd]Cu mine tailings under semi-arid climates in northern Chile

The oxidation of pyrite involves a series of chemical reactions that, depending on climatic conditions, can give rise to different mineral phases and morphologies. When oxidation takes place in semi-arid climate, the development of efflorescent salts on the surface of mine tailings is characteristic. These salts are mainly composed of Fe, Al and Mg sulfates and may accumulate valuable metals liberated through the dissolution of tailing minerals.This research aims to describe the evolution of salt precipitation from the economic and environmental perspective. For this purpose, we sampled efflorescent salts formed during the summer season on the surface of a tailing impoundment located in the north of Chile. The materials underwent comprehensive characterization utilizing X-ray techniques and scanning electron microscopy.The findings reveal a fractional precipitation in the crystallized salts. In an advanced oxidation system, characterized by multiple seasons of crystallization, dissolution and oxidation, the dry season begins with the precipitation of sulfates from a highly acidic solution dominated by Fe3+. This solution results from the dissolution and oxidation of the previous season sulfates. This initial stage is characterized by the presence of jarosite and gypsum, which are subsequently replaced by ferricopiapite. Towards the progress of the dry season, copiapite becomes more magnesian and precipitates alongside coquimbite and alunogen. Finally, halotrichite and pickeringite begin to crystallize. Base metal cations such as Co, Cu, Mn, Ni and Zn are preferentially incorporated into halotrichite-pickeringite sulfates during the most advanced evaporation phase.

A Predictive Model for Wellbore Temperature in High-Sulfur Gas Wells Incorporating Sulfur Deposition

HSG (high-sulfur gas) reservoirs are prevalent globally, yet their exploitation is hindered by elevated levels of hydrogen sulfide. A decrease in temperature and pressure may result in the formation of sulfur deposits, thereby exerting a notable influence on gas production. Test instruments are susceptible to significant corrosion due to the presence of hydrogen sulfide, resulting in challenges in obtaining bottom hole temperature and pressure test data. Consequently, a WTD (wellbore temperature distribution) model incorporating sulfur precipitation was developed based on PPP (physical property parameter), heat transfer, and GSTP (gas–solid two-phase) flow models. The comparison of a 2.53% temperature error and a 4.80% pressure error with actual field test data indicates that the established model exhibits high accuracy. An analysis is conducted on the impact of various factors, such as production, sulfur layer thickness, reservoir temperature, and reservoir pressure, on the distribution of the wellbore temperature field and pressure field. Increased gas production leads to higher wellhead temperatures. The presence of sulfur deposits reduces the flow area and wellhead pressure. A 40% concentration of hydrogen sulfide results in a 2 MPa pressure drop compared to a 20% concentration. Decreased reservoir pressure and temperature facilitate the formation of sulfur deposits at the wellhead.

Contrasting magma chemistry in the Candelaria IOCG district caused by changing tectonic regimes

Iron oxide-copper-gold (IOCG) deposits are a vital source of copper and critical elements for emerging clean technologies. Andean-type IOCG deposits form in continental arcs undergoing extension, and they have a temporal relationship with magmatism although they do not exhibit a close spatial relation with the causative intrusions. The processes required to form IOCG deposits and their potential connections to iron oxide–apatite (IOA)-type mineralization remain poorly constrained, as well as the characteristics of magmatism linked to both deposit types. Here we combine zircon U–Pb geochronology with zircon trace element geochemistry of intrusive rocks associated with the Candelaria deposit, one of the world’s largest IOCG deposits, to unravel distinctive signatures diagnostic of magmatic fertility. Our results reveal a marked transition in the geochemistry of intrusions in the Candelaria district, characterized by changes in the redox state, water content and temperature of magmas over time. The oldest magmatic stage (~ 128–125 Ma), prior to the formation of the Candelaria deposit, was characterized by zircon Eu/Eu* ratios of 0.20–0.42, and redox conditions of ΔFMQ − 0.4 to + 1.0. The earliest magmatic stage related to the formation of Fe-rich mineralization at Candelaria (118–115 Ma) exhibits low zircon Eu/Eu* ratios (0.09–0.18), low oxygen fugacity values (ΔFMQ ~− 1.8 to + 0.2) and relatively high crystallization temperatures. In contrast, the youngest stage at ~ 111–108 Ma shows higher zircon Eu/Eu* (~ 0.37–0.69), higher oxygen fugacity values (ΔFMQ ~ + 0.4 to + 1.3) and a decrease in crystallization temperatures, conditions that are favorable for the transport and precipitation of sulfur and chalcophile elements. We conclude that Candelaria was formed through two distinct ore-forming stages: the first associated with a reduced, high temperature, water-poor magma developed under a low tectonic stress, followed by a more oxidized, water-rich, and low temperature magmatic event related to a compressional regime. The first event led to Fe-rich and S-poor IOA-type mineralization, while the second event with geochemical signatures similar to those of porphyry copper systems, generated the Cu- and S-rich mineralization. This late stage overprinted preexisting IOA mineralization resulting in the formation of the giant Candelaria IOCG deposit.

Detoxification of copper and zinc from anaerobic digestate effluent by indigenous bacteria: Mechanisms, pathways and metagenomic analysis

The presence of organic-complexed copper and zinc in anaerobic digestate effluent (ADE) poses persistent ecological toxicity. This study investigated the detoxification performance and biotic responses of indigenous bacteria against ethylene diamine tetraacetic acid (EDTA)-complexed Cu(II) and Zn(II). Heavy metals (HMs) stress induced reactive oxygen species (ROS) generation and enhanced extracellular polymeric substances (EPS) secretion. At a Cu(II) influent concentration of 20.0 mg·L−1, indigenous bacteria removed 88.2% of Cu(II) within nine days. The majority of copper and zinc sequestered by bacteria were stored in the cell envelope, with over 50% of copper and 60% of zinc being immobilized. Transmission electron microscopy mapping (TEM-mapping) revealed significant mineralization of copper and zinc on the cell wall. Proteins abundant in EPS, alongside humic acid-like substances, effectively adsorbed HMs. Indigenous bacteria exhibited the capacity to reduce cupric to the cuprous state and cupric is preferentially reduced to cuprous before reaching reducing capacity saturation. Sulfur precipitation emerges as a crucial pathway for Zn(II) removal. Metagenomic analysis indicated that indigenous bacteria upregulated genes related to HMs homeostasis, efflux, and DNA repair, enhancing its resistance to high concentrations HMs. This study provided theoretical guidance for employing bacterial consortia to eliminate HMs in complex aquatic environments.

A comparison of dual-enzyme immobilization by magnetic nanoparticles and magnetic enzyme aggregates for cascade enzyme reactions

Immobilized enzymes have been widely used for their efficiency, economy, and environment friendly. In this case, a simpler and effective immobilization method has been developed. In this study, the enzyme immobilized by magnetic beads with genipin (MGE) was prepared by mixing genipin-modified nano-Fe3O4 with (R)− 1-phenylethanol dehydrogenase ((R)-PEDH) and recombinant glucose dehydrogenase (rGDH), and the magnetic cross-linked enzyme aggregates (MCLEAs) was prepared by stirring a mixture of the sulfur precipitate of the (R)-PEDH and rGDH, poly-L-lysine, and cross-linkers. When o-phthalaldehyde (o-PA) was used as a cross-linking agent for the MCLEAs preparation, a protein loading of 99.9% and 62.93% recovery activity of (R)-PEDH and 70.12% of rGDH were obtained. Compared to the MGE, the MCLEAs possessed better enzyme activity recovery. Furthermore, this study tried the synthesis of (R)− 1-(furan-2-yl) ethanol by the immobilized enzymes and obtained a concentration of 1.10 mM for the MCLEAs and 0.24 mM for the MGE at 48 h. This study explored a facile method for co-immobilization of (R)-PEDH and rGDH to synthesize (R)− 1-(furan-2-yl) ethanol.

Vanadium niobium carbide (VNbCTx) bimetallic MXene derived V5S8-Nb2O5@MXene heterostructures for efficiently boosting the adsorption and catalytic performance of lithium polysulfide.

To alleviate the shuttle effect in lithium-sulfur (Li-S) batteries, the electrocatalytic conversion of polysulfides serves as a vital strategy. However, achieving a synergy that combines robust adsorption with high catalytic activity continues to pose significant challenges. Herein, a simple solid-state sintering method is employed to transform vanadium-niobium carbide MXene (VNbCTx) into a heterogeneous structure of V5S8-Nb2O5@VNbCTx MXene (denoted as V5S8-Nb2O5@MX). The Nb2O5 component immobilizes lithium polysulfides (LiPSs) at the electrode through its strong chemical affinity, while the V5S8 fraction serves as an outstanding electrochemical catalyst, enhancing the reaction kinetics of sulfur precipitation. Furthermore, the VNbCTx MXene precursor scaffold is preserved through the conversion and uniformly distributed throughout the composite, exhibiting excellent electrical conductivity. Thanks to the synergistic "capture-adsorption-catalysis" action on LiPSs, the V5S8-Nb2O5@MX composite effectively restrains the shuttle effect. The as-prepared Li-S battery demonstrates a significant increase in specific capacity, reaching 1508 mA h g-1 at 0.1C and maintaining a capacity decay of approximately 0.027% per cycle after 500 cycles at 1C and 766.1 mA h g-1 at 5C. Even under a high sulfur loading of 5.75 mg cm-2, the battery can maintain a specific capacity of 596.6 mA h g-1 and exhibit significant cycling stability after 100 cycles. DFT calculations indicate that the V5S8-Nb2O5@MX heterostructure exhibits a higher binding energy of 5.34 eV and a lower decomposition barrier energy of 0.68 eV, presenting potential advantages in accelerating the conversion reactions of LiPSs. Our research offers a straightforward approach for designing metal oxide-sulfide heterostructured catalysts that deliver superior performance and enhance the electrocatalytic conversion of LiPSs, clearing the path for high performance Li-S batteries.

Simulation of Lithium-Sulfur Batteries and Optimization of Cathode Structure

Recently, the spread of the mobile devices and clean energy, the demand for high-power and high-capacity secondary batteries has been growing. However, the energy density of lithium-ion batteries (LiB) that is widely used nowadays is reaching its design limit. Instead of LiB, lithium-sulfur batteries (LiSB) are expected as one of the next-generation secondary batteries. Compared to LiB, LiSB has the advantages of higher energy density, lower cost, and easier weight saving. In LiB, the driving force is the insertion and desorption reaction of lithium ions between the cathode and anode, while in LiSB, is the complex sulfur dissolution and precipitation reaction. In LiSB, the electrolyte determines the dissolution and precipitation of sulfur, which is thought to have a significant impact on battery characteristics. Therefore, new electrolyte systems are being developed daily and techniques to elucidate the reaction mechanisms are needed. Furthermore, the effect of carbon black, a conductive material, on battery characteristics has also been considered. In this study, we investigated the optimal initial lithium ion concentration and calculation focused on the precipitation form of each carbon species for the design of optimal electrode structures.Kumaresan's one-dimensional model [1] based on porous electrode theory was used. Sulfur was used as the cathode active material and lithium metal as the anode active material. Electron and ionic potentials were calculated from the electro-neutrality condition, concentration distribution in the electrolyte was calculated from the non-stationary mass balance equation, and electrochemical reactions at the interface between active material and electrolyte were calculated using the Butler-Volmer equation. Furthermore, stepwise reactions were considered by incorporating the electrochemical reaction of sulfur and the dissolution and precipitation reactions into the concentration distribution and the interfacial reactions. The temperature in the electrode layer was assumed to be constant, and no heat loss or side reactions due to overvoltage were assumed to occur. In LiSB, sulfur dissolved in the electrolyte on the cathode surface is sequentially reduced as polysulfide ions as the discharge progresses. It then combines with lithium ions transferred from the anode and expands to about 1.8 times. Therefore, based on our previous research [2], the effect of the expansion and contraction of the electrode particles was reflected by dynamic changes in the structural properties of the electrode layer.Ionic conductivity and transport number are important parameters that affect the properties of the electrolyte. The higher the lithium ion concentration, the higher the transport number, but the lower the ionic conductivity [3]. In this study, we focused on sulfolane-based electrolyte and investigated the effect of initial lithium ion concentration on discharge capacity by incorporating the relationship between ionic conductivity and transport number into a model. As a result, the discharge capacity reached its maximum when the initial lithium ion concentration was 3.0 M. In the static state, the ionic conductivity was highest around 1.6 M, but considering the operating conditions during discharge, the concentration distribution became be more remarkable due to the low transport number, which may have resulted in excessive Li2S precipitation near the separator. As an extension to the microstructure of the electrode layer, we focused on carbon black (CB). Two types of CB (KB, MCND) were targeted. When MCND and KB were used as CB under the same conditions in the experiment, it was confirmed that the discharge characteristics of MCND were significantly better than those of KB. In LiSB, Li2S precipitation has a significant effect on discharge characteristics. Therefore, we focused on the pores of both CBs. We reconstructed the binarized structure from X-ray CT images of both CBs, hypothetically precipitated Li2S in the pores, and calculated the relative conductivity. The relative conductivity represents the transport property and is highly dependent on the structure of the electrode layer. As a calculation result, the relative conductivity of KB became significantly smaller as the porosity decreased. From the above, the transport properties in both CBs were confirmed by calculation.As described above, it was suggested that an optimum lithium ion concentration exists, and the effect of different CB structures on transport properties was qualitatively evaluated. In the future, it is necessary to confirm the validity of the optimal concentration through experiments and to quantitatively evaluate the effect of different CB.AcknowledgmentThis study was supported by JST ALCA-SPRING Grant JPMJAL1301, Japan.

Improvement of extractive desulfurization for Iraqi refinery atmospheric residual

Extractive desulfurization (EDS) process of petroleum fuels via effective solvents has been widely investigated in recent decades and has an excellent future as an alternative technique to HDS process. This study was focused on removal of sulfur compounds from heavy Iraqi atmospheric residual oil (IARO) via EDS process without affecting its other properties. Different hydrocarbon solvents (light naphtha, n-heptane and n-hexane), solvent to oil ratios (4/1, 8/1, and 12/1), extraction times (30, 60, and 120 min), and extraction temperatures (30 °C, 60 °C and 90 °C) were investigated on the precipitation of sulfur in Iraqi atmospheric oil residue. The results were showed that increasing of solvent to oil ratio, extraction times, and extraction temperatures enhanced the performance of EDS process. The experimental results proved that 96% of sulfur compounds were eliminated from heavy residual oil using effective n-hexane as solvent under moderate operating conditions as follow: extraction temperature of 90 °C, extraction time of 60 min, and solvent to oil ratio of 12/1. This study prove that extractive desulfurization via hexane-like solvents at the best experimental conditions can achieve satisfactory sulfur removal efficiency of heavy oil via safe, fast, economically and effective process.

Experimental timing of pyrite oxidation under various leaching conditions: consequences for rates of weathering in geological profiles

Pyrite (FeS2) is one of the most abundant sulfides on Earth and has already been studied in numerous ways for decades because of its rapid oxidation and the associated environmental impacts. This study proposes a new experimental physico-chemical approach (air, tridistilled water and water drip exposure) to determine the oxidation rate of pyrite using surface and depth data via XPS (X-ray Photoelectron Spectroscopy) analyses. Our experimental study of almost pure pyrite reveals a maximum oxidation rate of 11.7 ± 1.8 nm day−1 for drip exposure with precipitation of sulfates or Fe-oxides depending on the experimental condition. The oxidation rates obtained under various experimental conditions may be extrapolated to weathering rates of different zones of supergene profiles/ores (leached zone, saprolite and cementation zone). The extrapolation suggests a maximum rate of 4.3 ± 0.6 m Ma−1, which is consistent with data obtained by isotope dating of weathering profiles. Under geological conditions however, the oxidation rate of pyrite may be influenced by additional parameters, such as the nature of the host rock, its porosity/permeability, the climate, the influence of an oxidizing environment, and the mineralization of secondary minerals.

Wet‐Oxidative Desulfurization as a Flexible and Greener Way for H2S Removal from Acid Gases

AbstractIn wet‐oxidative gas desulfurization processes, absorbed H2S is directly converted to sulfur by a redox catalyst dissolved in a circulating scrubbing solution. High flexibility is achieved through the availability of different catalyst classes. In this work, a process based on the Takahax process was investigated in a pilot plant under industrially relevant conditions with coke oven gas. A stable plant operation without sulfur precipitation was achieved by a suitable choice of the operating conditions. The solid‐free operating window was determined and a sulfur redissolution strategy developed.

Effect of Sulfide on the Processes of Transformation of Nitrogen Compounds and the Microbial Community Composition in the Anammox Bioreactor

Anammox is one of the most important processes in the global nitrogen cycle and the basis for an efficient technology of nitrogen removal from wastewater. The effect of the presence of sulfide in wastewater on the transformation of nitrogen compounds by the anammox community has been insufficiently studied. The present work dealt with the effect of sulfide on nitrogen removal efficiency and the dynamics of nitrogen species in a laboratory sequencing batch bioreactor modeling the functioning of the anammox community carrying out ammonium oxidation via nitritation and anammox and nitrite oxidation. The 16S rRNA gene profiling of the community of the anammox-activated sludge attached to the stationary carrier revealed members of the key physiological groups: ammonium oxidizers of the genus Nitrosomonas, nitrite oxidizers of the genus Nitrosospira, and anammox bacteria of the genera Candidatus Brocadia and Ca. Jettenia, as well as members of other bacterial genera. Nitrate removal was not sensitive to sulfide at concentrations up to 50 mg S/L and decreased by 17% at 100 mg/L. The threshold of sulfide sensitivity for group I nitrifiers was ~50 mg/L, while anammox bacteria were resistant to sulfide concentrations of up to 100 mg S/L in the incoming water. Group II nitrifiers were probably the most sulfide-sensitive components of the community. A drastic increase in the abundance of members of the family Hydrogenophilaceae at elevated sulfide concentrations, together with the precipitation of elemental sulfur, may indicate sulfide oxidation either by molecular oxygen or via nitrate reduction; this finding requires further investigation. This is the first report on the different effects of sulfide on the growth rate of members of the nitrifying genus Nitrosomonas, increasing/decreasing or not affecting it for different phylotypes at elevated sulfide concentrations.

Riverine sulfate sources and behaviors in arid environment, Northwest China: Constraints from sulfur and oxygen isotopes

The fate of riverine sulfate ion (SO42-) and its environmental effects in arid environment are difficult to evaluate due to its complicated sources and strongly coupled behaviors with water cycle which is significantly modified by humans. To understand the sulfur cycle in aquatic systems in arid environment, the chemical and sulfur and oxygen isotopic compositions (δ34SSO4 and δ18OSO4) of major rivers around the Badain Jaran Desert, northwestern China, were investigated. These rivers had averaged SO42- content at 1336 µmol/L, over 10 times higher than the global average. The δ34SSO4 and δ18OSO4 values ranged from -5.3‰ to +11.8‰ and +1.6‰ to +12.8‰, respectively. The end-member analysis and the inverse model showed that riverine sulfate was mainly derived from evaporites dissolution (0-87%), sulfide oxidation (13%-100%) and precipitation (0-33%), indicating heterogeneity in sulfur sources and behaviors along the river drainage with the lithology variations and climate gradients. Multiple isotopic tools combining with hydro-chemistry compositions could be applied to reveal sulfur cycle in arid environment. Based on the calculation, sulfide oxidation plays the primary role in the headwater and upstream in the Qilian-Mountains area, where sulfide is widely exposed. While the proportion of evaporites dissolution contributing to riverine sulfate is much higher in downstream in a drier environment. Besides, less precipitation and higher temperature can lead to more intensive evaporation, affecting the process of sulfide oxidation and enhancing the rates of evaporites dissolution and sulfate precipitation in the basin.

A Robust Procedure for Determination of Immunosuppressants Cyclosporine A and Tacrolimus in Blood Samples with Detection of LC–MS/MS

The immunosuppressants monitoring is crucial in the treatment of transplant patients to avoid the risk of organ rejection. So it is vital to develop an accurate method to obtain precise and reliable results. Herein, a liquid chromatography tandem mass spectrometry (LC–MS/MS) based method was developed and validated, which could simultaneously realize the accurate quantification of cyclosporine A and tacrolimus with a total run time of 4.5 min. Unlike the previously described methods, the highlight of this assay is that there is no using zinc sulfate in the protein precipitation of the whole blood sample, which can effectively prolong the lifespan of mass spectrometry. In addition, the linearity, matrix effect, carryover, accuracy, intraday and interday precision of this method were investigated. The linear range of tacrolimus and cyclosporine were 1–40 ng/mL and 50–2000 ng/mL, respectively; The correlation coefficients (R2) were both greater than 0.995. The intraday and interday precision of cyclosporine and tacrolimus were ≤ 10%. The lower limit of quantitation (LLOQ) of tacrolimus and cyclosporine A were 1 ng/mL and 50 ng/mL, respectively. The main features of this method are good accuracy, sensitivity, specificity, rapidness, robustness and high throughput. It is suitable for therapeutic drug monitoring of cyclosporine A and tacrolimus in routine clinical diagnostics.

Selective Removal of Sulfate from Water by Precipitation with a Rigid Bis‐amidinium Compound

AbstractA simple, readily prepared biphenyl bis‐amidinium compound (1⋅Cl2) is able to selectively precipitate sulfate from water. The precipitant is effective at concentrations as low as 1 mM and shows complete selectivity against monovalent anions, and high selectivity even against CO32− and HPO42−. It is highly effective (>90 % sulfate removed) in both seawater and highly acidic conditions relevant to mining waste‐streams. X‐ray crystallography reveals that 1⋅SO4 forms a tightly packed, anhydrous, structure where each sulfate anion receives eight hydrogen bonds from amidinium N−H hydrogen bond donors.

Selective Removal of Sulfate from Water by Precipitation with a Rigid Bis-amidinium Compound.

A simple, readily prepared biphenyl bis-amidinium compound (1⋅Cl2 ) is able to selectively precipitate sulfate from water. The precipitant is effective at concentrations as low as 1 mM and shows complete selectivity against monovalent anions, and high selectivity even against CO3 2- and HPO4 2- . It is highly effective (>90 % sulfate removed) in both seawater and highly acidic conditions relevant to mining waste-streams. X-ray crystallography reveals that 1⋅SO4 forms a tightly packed, anhydrous, structure where each sulfate anion receives eight hydrogen bonds from amidinium N-H hydrogen bond donors.