High Sulfur Concentrations Research Articles

Long-term characterization and resource potential evaluation of the digestate from food waste anaerobic digestion plants

The management of digestate from food waste (DFW) has become a big challenge for anaerobic digestion (AD) plants. It is crucial to understand the characteristics of DFW for its beneficial utilization. This study investigated the long-term characteristics of DFW from an industrial-scale AD plant in China for 16 months. The result showed that the characteristics of the DFW were relatively stable. The DFW contained considerable amounts of organic matter (23–40% of lignin and 12–26% of protein) and abundant nutrients (N, P, and K), with high concentrations of metals (e.g., 55.17 mg g−1 and 15.55 mg g−1 of Ca and Fe) and sulfur (1.40%) on a dry basis. Based on the results, pyrolysis and composting were evaluated as optional conversion ways of DFW. The pyrolysis temperature range of 500 °C to 600 °C was recommended for producing biochar. In this temperature range, the Brunauer-Emmett-Teller surface area of the produced biochar is over 120 m2 g−1. The composting offered the best potential for recovering the nutrients from DFW, but the high ammonia gas content (6970 ppm) should be paid attention to during composting.

Pyroxenite-hosted chalcopyrites from Sung Valley, Meghalaya, NE India: implications for the formation of both high- and low-temperature sulfides in plume-derived magma

Abstract Sulfides play a crucial role in the distribution of chalcophile elements in the Earth's mantle. In this work, combined petrography and mineral chemistry of sulfide and diopside in a pyroxenite from an ultramafic–alkaline–carbonatite complex of NE India, related to the Kerguelen plume, was carried out and a considerably high sulfur concentration in the parental melt of the pyroxenite was obtained. Two types of sulfide, with similar compositions, were detected in pyroxenite: Type A are multifaceted polygons, elliptical and spherical in shape, occurring as poikilitic inclusions in diopside; and Type B are intergranular sulfides of irregular shapes in silicate grains. These sulfides are often partially replaced by magnetite. Mineral chemistry suggests that both types of sulfide are products of re-equilibration of high-temperature monosulfide solid solution and represent a low-temperature ( c. 400°C) mineral phase of the Cu–Fe–S system. Petrographical features suggest that the sulfides were separated as immiscible melt droplets at the time of sulfur saturation and fractionation of diopside in the coexisting silicate magma. Our study implicates that both high- and low-temperature sulfides can form in the plume-associated ultramafic rocks.

Recovery of Zinc and Copper from Mine Tailings by Acid Leaching Solutions Combined with Carbon-Based Materials

Mine tailing storage represents an important environmental issue. The generation and dispersal of dust from mine tailings can contaminate air and surrounding soils. In addition, metals and soluble salts present in these wastes could pollute groundwater and surface water. The recovery of metals from mine tailings can contribute to minimize the environmental risk and to achieve a circular economy model. The main objective of the present work is to study the use of two carbon-based materials, a commercial activated carbon (AC) and a commercial charcoal (VC) in the leaching of zinc and copper from low-grade tailing waste. Experimental results obtained show that it is possible to achieve the recovery of more than 87 wt% of Zn after 6 h of leaching with different sulfuric acid solutions. The addition of carbon-based materials increases the extraction of Zn at high sulfuric acid concentrations (1 M) from 89% to 99%. The addition of VC significantly increases the extraction of Cu in leaching solution with high sulfuric acid concentration (1 M), from 41 to 61%. Future research will be necessary to optimize the properties of carbon-based materials and their recovery after leaching experiments in order to assess their potential for industrial application.

EDXRF, FTIR, and XRD characterization of low calcium oxalate urinary stones collected from arid area

Low calcium oxalate urinary stones from the kidney, bladder, and ureter have been collected from the arid area (Taif, Saudi Arabia). After careful washing and drying of the collected stones, the samples were converted into a contamination‐free homogenous fine powder with a particles' size smaller than 50 μm. The processed urinary stone powders were studied using attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR), laboratory setup and synchrotron radiation X‐ray diffraction (XRD), and energy‐dispersive X‐ray fluorescence (EDXRF). The activated function groups, quantitative phase analysis, and the semi‐quantitative elemental analysis of the present urinary stones were identified. Seventeen elements were measured in most of the urinary stone samples. The significant elements are Ca, P, S, Cl, Zn, K, Fe, and Cu, whereas other elements were found alternatively in a few number of urinary stone samples. It was recognized that Ca exists with low concentration, which indicates the presence of different calcium phases even with low percentages. In 33% of the urinary stones, the phosphorus (P) was not measured, but there were high concentrations of sulfur (S) and low concentrations of Ca up to 2.15 ± 0.05%. The ATR‐FTIR results indicate that the most compounds of the present urinary stones were urea and cystine combined with low ratios of calcium oxalate and calcium phosphate compounds. The quantitative phase analysis of the XRD of selected samples proves the presence of the cystine, urea, and calcium oxalate phases with different weight percent.

Sulfur-Induced Growth of Coordination Polymer Derived-Straight Carbon Nanotubes on Carbon Nanofiber Network for Zn-Air Batteries.

Low-cost heteroatom-doped carbon nanomaterials have been widely studied for efficient oxygen reduction reaction and energy storage and conversion in metal-air batteries. A Masson pine twigs-like 3-dimensional network construction of carbon nanofibers (CNFs) with abundant straight long Co, N, and S-doped carbon nanotubes (CNTs) is developed by thermal treatment of Co-based polymer coated onto polyacrylonitrile nanofiber network together with thiourea at 900 °C, denoted as CNFT-Co9 S8 -900. It is interesting to note that the introduction of a high concentration of sulfur does not lead to the complete toxicity of catalysts, but promotes the axial growth to selectively form straight CNTs instead of curly bamboo-like CNTs. The highly graphitized in-situ grown Co, N, S-doped CNTs and the 3-dimensional N-doped CNF network provide both active catalytic sites and highly conductive paths, which are beneficial for oxygen reduction reaction (ORR). Thus, the optimal CNFT-Co9 S8 -900 performs the excellent ORR catalytic activity with a half-wave potential of 0.84 V and a diffusion-limited current density of 5.49 mA cm-2 . Furthermore, the CNFT-Co9 S8 -900-based Zn-air devices also possess a high power density of 136.9 mW cm-2 better than commercial Pt/C.

Gold deposit type and implication for exploration in the Abiete-Toko Gold District, South Cameroon: constraint from morphology and microchemistry of alluvial gold grains

The morphology and quantitative chemical analyses of fifty alluvial gold grains from fourteen studied sites were used to constraint gold deposit type and its implications to exploration in the Abiete-Toko Gold District in South Cameroon. The main results revealed that the gold grains show a core-rim zonation marked by Ag depleted rims as a result of leaching during transportation. The fineness of grains ranges from 826 to 1000 and their composition is almost binary gold-silver. Gold fineness refers to the relative amounts of Ag and Au present, given as a number out of 1000 and defined by Au/(Ag + Au)∗1000. The chemical composition of the gold grains are range as thus: 83.40–100 wt.% Au, 0.07–17.45 wt.% Ag, 0–0.96 wt.% Cu, 0–0.01 wt.% As, 0–0.02 wt.% Ni, 0–0.02 wt.% Co, 0–0.01 wt.% Se, 0–0.08 wt.% Hg and 0.003–0.03 wt.% S. The high sulphur concentrations of the gold grains probably imply primary deposition of gold by sulphidation; The ranges of Ni and Co concentrations suggest an interaction with greenstones. Such findings indicate that the Abiete-Toko area hosts a mesothermal-orogenic gold deposit. Exploration operations must target fractures and contact zones between ironstones, felsic gneiss and greenstones. Soil sampling is not recommended in this orogenic gold district due to the very thick and transported nature of the weathering mantle. Detailed mapping coupled to geophysical surveys are the recommended key exploration methods prior to drilling program.

Evaluation of the Anthropogenic Metal Pollution at Osisko Lake: Sediments Characterization for Reclamation Purposes

The anthropogenic pollution of lake ecosystems by human activities (e.g., mining industries) is recognized as a serious issue. The Osisko urban lake located in Rouyn-Noranda (Quebec, Canada) was used partially as a waste disposal facility for many decades, causing a heavy pollution. The main undertakings of this study are (i) assessing the mineralogical and geochemical properties of lake Osisko sediments, and (ii) studying the pollution that occurred within lake water due to the sediments’ reactivity. Water and sediments across the lake were collected in different sensitive locations. Within the sediment samples, two parts were distinguished: a small layer of black vase over grey sediments. The black vase resembled organic matter while the gray sediment seemed close to clean lake sediments. The collected samples were characterized for their physical (particle size distribution, specific gravity and specific surface area), chemical (minor and major elements as well as total sulfur and carbon) and mineralogical (X-ray diffraction and scanning electron microscope) properties. Additionally, the reactivity of sediments was studied using weathering cells to quantify chemical species leaching and their releasing rates. The results showed that the vase was the only contaminated part with high concentrations of sulfur and metals such as copper, zinc and iron. Geochemical data showed that the composite sample and the vase potentially cause contaminated acid drainage if they are exposed to atmospheric conditions. Indeed, the pH values of the leachates from both samples were between 4 and 6, while those corresponding to sediments remained around circumneutral values. Quantitatively, the contaminant release from the tested samples was variable. Indeed, the Fe cumulative concentrations were around 200, 80 and 20 mg/kg for the vase, composite and sediment samples, respectively. Similarly, the Zn cumulative concentrations were around 4500, 4200, and below the detection limit for vase, composite and sediment samples, respectively. The same tendency was observed for Cu, S, and Fe. Thus, sediments within Osisko lake present a risk for water contamination if they are resuspended or dredged out of the lake. Consequently, they should be stabilized before their disposal. The samples’ high Cu contents also offer the possibility of their reprocessing.

Experiential investigation on the effect of heavy fuel oil substitution by high sulfur petcoke on the physico-mechanical features and microstructure of white cement composites

The current research paper study the effects of producing white cement using high sulfur petroleum coke (WCPC) instead of using HFO (WCHFO). White Cement production needs huge amounts of thermal units from HFO and it the most consumed energy all over the world. There are many interest to burn alternative energy sources aiming to decrease in combustion cost and secure the surround environment. Current combustion technologies allow the burning of fuel With a high percentage of sulfur such as PC, to have the least environmental damage and generate the least amount of fly ash. HFO contains one third or less of sulfur (S) than high sulfur PC. High concentration of sulfur in white cement/clinker granules cause a series of adverse effects on its applications due to formation of big amounts of anhydrite (CaSO4-insoluble) & aphthitalite (3K2SO4·Na2SO4) and reduce the formation of thenardite (Na2SO4) leaves cracks, endearments and yellowish color for skin coat, painting and decoration applications. High sulfur content in white cement (WCPC) comes from high sulfur in fuel and accordingly increases the setting time, compressive strength, workability and sodium equivalent (Na2OEq) content, while it reduce cement whiteness reflection (Ry) degree. XR, XRD and physical properties of fuels are performed reflected high sulfur and alkali concentration. SEM morphology analysis has been tested showing improving in WCpC microstructure.

Integrated geochemical characterization and geological modeling of organic matter-rich limestones and oils from Ajeel Oilfield in Mesopotamian Basin, Northern Iraq

The current study focuses on the organic geochemical and basin modeling of organic matter-rich limestones and oil samples from the Ajeel Oilfield. The objective was to characterize the organic matter and its hydrocarbon-generating potential, and its relevance to future hydrocarbon exploration in the northwestern Mesopotamian Basin. The organic biomarker results of the extracted bitumen samples indicated that the Sargelu, Naokelekan, and Chia Gara limestones received abundant planktonic-bacterial organic matter input, with a limited terrestrial contribution. Lipid-rich organic matter that originates from phytoplankton and bacteria with low amounts of terrestrial organic matter suggest a high abundance of Type-II or mixed-II/III kerogen as the original organic matter at time of sedimentation.Bulk property and geochemical analyses of the recovered oil samples, with mediumAPI gravities between 31 and 33°, and relatively high sulfur concentrations of up to 3.95 wt%, suggest that examined oil samples were derived mainly from Type II-S kerogen at moderate maturity stages. Biomarker ratios and parameters, as well as carbon isotopes, further indicated that these oils were derived from marine carbonate-rich source rocks deposited under reducing environmental conditions. These biomarker fingerprints and carbon isotopes show a genetic link between the oil examined samples and the extracted rocks of the Sargelu, Naokelekan, and Chia Gara source rocks and represent a mix of these carbonate-rich source rocks. Therefore, these source rocks contained kerogen Type II-S with high sulfur, and generated commercial oil at relatively low thermal maturity of early to moderate stages, as demonstrated from maturity parameters such as Tmax and PI as well as several biomarker ratios.Burial/maturity models with kerogen Type–II–S kinetic parameter revealed that the Sargelu, Naokelekan, and Chia Gara intervals began to generate oil at slightly lower thermal maturity (maturity levels = 0.55–0.79 EASY%Ro). As a result, about 10%–50% of the organic-matter was converted to oil during the Late Paleocene. The basin models also suggested that the organic-rich units including Sargelu and Naokelekan source rocks reached higher maturity levels, with TR of 71%–79% in the Early Miocene (20 Ma) and continued to the present. Trapping large quantities of oil lead to the high pressures and expulsion of these oils. The high conversion ratios further suggested large oil volumes accumulated in the northwestern Mesopotamian Basin were mainly originated from the Middle-Late Jurassic Sargelu and Naokelekan source rocks.

Leak failure at the TP316L welds of a water pipe caused by microbiologically influenced corrosion

Water leaking through a pinhole from an ASTM A312-TP316L stainless steel pipe was investigated. The pipes had been used for transferring a large amount of potable water. Multiple leaks were found at the circumferential welds of the pipe after a short term of service. An analysis using an optical microscope, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) was conducted to explore the root cause of the failure.The results demonstrated that the perforation of the pipe was due to localized corrosion initiated from the inside at the many small pits penetrating to the outside of the pipe. Corrosion pits were located near the heat-affected zone (HAZ), which is the area most susceptible to a corrosion attack. The microbiologically influenced corrosion (MIC) was identified as the primary cause of perforation failure. Corrosion attacks occurred predominantly at the microstructure of ferrite stringers. Spheroidal corpuscles were observed with a high concentration of sulfur, which indicated that sulfate-reducing bacteria (SRB) were creating a biofilm, accelerating the MIC corrosion process. Slightly concave surfaces near the weld of the pipe exhibited evidence of bacterial attack or residue of microorganisms, where the leak occurred.

Investigation of the mechanism for fireside corrosion in coal-fired boilers in South Africa

SYNOPSIS Furnace wall tubes from 600 MW subcritical boilers at three coal-fired power stations were sampled and the fireside deposits examined to determine the mechanism of fireside corrosion. This involved an in-depth investigation into the morphology and composition of the fireside deposits and the conditions of the furnace that enable this type of attack. SEM-EDS analysis revealed high concentrations of oxygen, iron, and sulphur, QEMSCAN and XRD analyses identified the presence of Fe3O4, Fe2O3, FeS, and FeS2. Differential thermal analysis showed thermal activities at temperatures of 500-600°C, 900-1100°C, and 1100-1250°C, which are associated, respectively, with FeS2 oxidation to FeS and Fe2O3, at 475-525°C, formation of aluminosilicates at 925-1100°C, and melting of FeS around 1190°C. The absence of sodium and potassium eliminates the contribution of molten alkali sulphates to the corrosion. The consistent coexistence of iron sulphide and iron oxide is indicative of the substoichiometric conditions in the furnace, while the detection of pyrite suggests that the coal is not completely combusted, which points to a poor combustion process. These observations were affirmed by gas analysis at one of the stations, where very high levels of carbon monoxide were measured at the furnace wall (> 14 000 ppm) and furnace exit (> 3500 ppm). The high CO concentrations are indicative of limited combustion caused by limited O2. These reducing conditions promote the formation of FeS-rich deposit, which is the corrosive species responsible for degradation. Keywords: fireside corrosion, sulphidation, coal-fired boiler, furnace wall tubes.

A new device to simulate the performance of rubber dams for dental applications

Rubber dams employed for endodontic treatment are commonly based on natural rubber latex compounds and it is essential that they remain unbroken throughout the different procedures. The in-use failure of some types of rubber dams can be related to the time spent under tension in contact with saliva and/or to sodium hypochlorite. Five different types of commercial rubber dams were assessed with respect to physico-mechanical properties (crosslink density, stress at break, tear strength and stress relaxation), morphological aspects (Scanning Electron Microscopy), and elemental analyses (energy-dispersive X-ray spectrometry). Moreover, a special bench apparatus was developed to mimic actual conditions of rubber dams during endodontic procedures. Results showed that the device performance was reliable and comparable to observations during clinical activity corroborated by the stress relaxation test. Samples based on sulfur curing system with predominance of accelerator has better performance under stress relaxation tests than those samples with higher concentration of sulfur.

Exploring the acid enrichment application of piperidinium-functionalized cross-linked poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes in electrodialysis

The use of electrodialysis (ED) fabricated with proton blocking anion exchange membranes (AEMs) is a promising method to realize waste acid reclamation. To develop AEMs with low proton leakage, in this work, we designed a series of N-methylpiperidine (MPRD)-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) cross-linked by weak base 1,3-di-4-piperidylpropane (DiPRD). Our investigations demonstrate the weak base cross-linker could enhance the density of membrane matrix and reduce the hydrophilicity of AEM matrix, which have been verified by thermogravimetric analysis and water absorption with low swelling ratio of 2.43%. Benefit from the unique structure with denser membrane matrix and additional protonated weak base piperidine structure, the acid blocking performance of the optimized crosslinked AEM was enhanced with the H+ concentration of 1.98 M in concentrate cell during 24 h-ED process at current density of 20 mA cm−2 (initial H+ concentration: 1.0 M), outperforming the AEM without cross-linking structure (1.73 M). Nevertheless, it was found that the small-sized proton diffusion in ion-nanochannels of AEM and the aged membrane matrix in ED process with high sulfuric acid concentration resulted in proton leakage to some degree. As a result, a trade-off between the proton blocking and sulfate ion transport of the cross-linked AEMs is achieved. It is believed that this study can provide a guideline for designing advanced proton blocking AEMs.

Biofuel characteristics and combustion emissions of poultry litter and lignocellulosic biomass

AbstractBroiler chicken industry generate different kinds of organic wastes mainly poultry litters (PL), which presenting high energy potential, but significant incineration burdens due to the mineral compositions. In the present study, the combustion potential of PL and locally available biomass co‐combustion candidates were evaluated based on proximate, ultimate, ash constitute, and exhaust gas emission. High heating values measured for PL samples were in the range of 13.5–14.6 MJ/kg and low heating values were 12.9–13.6 MJ/kg, respectively. The ultimate analysis result of PL was as follows; C (46.5 ± 1.3%), O (44.8 ± 0.7%), H (3.6 ± 0.3%), N (3.9 ± 0.3%), and S (0.9 ± 0.1%). Ash deposit challenging minerals were abundant in PL, in contrasting to the lignocellulosic biomass; wood residue (WR), hazelnut shell (HS), corn stalk (CS), and giant reed (GR), which can serve mitigation potential. High nitrogen and sulfur concentrations in PL had significantly increased the NOx and SO2 emissions but confirming related standards. Despite the high exhaust gas and ash emissions, the energy recovery practices of PL co‐combustion with lignocellulosic biomas allow environmentally safe management option for PL.

Effect of sulfur precursor concentration on the structures and optical properties of CdS nanowire array on Cd foil by solvothermal method

CdS nanowire array on foil has been fabricated through a solvothermal method, which is uniform, regular and approximately perpendicular to the Cd foil. With the variation of sulfur precursor concentration, the relative intensity of (100), (002) and (101) peak are variable. The nanostructured CdS show the preferential (002)-orientation growth. At the sulfur concentration of 0.1 mol/l, 0.2 mol/l and 0.3 mol/l, CdS nanowires are approximately perpendicular to the Cd foil. At the high sulfur concentration, the characterization of array is destroyed. The band gap, which are estimated from the absorptance spectra using the Kubelka-Munk method, increase with the increasing sulfur precursor concentration until the concentration reaches up to 0.4 mol/l and no longer increases. It is very important to understand the relation between the experimental parameters and the physical properties of the CdS nanowires.

Mineral Deposit Formation in Gas Engines During Combustion of Biogas from Landfills and Municipal WWTP

Abstract The biogas produced in municipal wastewater-treatment plants (WWTP) should be cleaned before it can be used as a fuel in internal combustion engines. Efficient running of such engines is possible only subject to using high quality biogas and lubricating oil. Otherwise, biogas impurities in course of complex chemical reactions may form deposits on various engine parts as well as seriously contaminate the lubricating oil. In this paper, mineral deposits containing high concentration of bismuth, silicon, sulphur, calcium and zinc are studied. Silicon deposits demonstrating strong friction properties are formed during combustion of volatile silica compounds. As these deposits build up, abrasion problems, ignition failure and even engine failure result. The bismuth containing deposits comes from bearings degradation, zinc and calcium were derived from the additives present in commercially available lubricating oil, while lead, aluminium, copper, nickel, iron and chromium were introduced by engine wear phenomena. The highest bismuth content was located at the engine cylinder heads and the lowest at the exhaust elements, whereas highest calcium content was registered on the pistons. Silicon containing deposits are highest in the exhaust and lowest at the engine head. Zinc deposits are highest at the piston.

Elucidating the effect of impurities present in different crude glycerol sources on lipid and citric acid production by Yarrowia lipolyticaSKY7

AbstractBACKGROUNDCrude glycerol is an industrial by‐product of biodiesel producing companies and requires a high cost for purification. In fact, it is a good carbon source and can be used for lipid production from oleaginous microbes. However, crude glycerol has several impurities that may impact the cellular metabolism for lipid production.RESULTSIn this study, crude glycerol from different sources was employed for lipid production and the effect of its impurities on the biomass and lipid production was investigated on Yarrowia lipolytica SKY7, which is a well‐known yeast for lipid and citric acid production. Growth inhibition was observed in BIOCARDEL, BIOLIQ, and ROTHSAY glycerol when compared with pure glycerol. This was due to high sodium concentrations in BIOCARDEL, high potassium concentrations in BIOLIQ, and high sulphur concentrations in ROTHSAY glycerol. Among three crude glycerol sources, the highest lipid concentration (14.78 g L−1) was obtained using BIOCARDEL glycerol at 96 h. However, the higher citric acid concentrations of 18.70 g L−1 in ROTHSAY glycerol and 12.00 g L−1 in BIOLIQ were obtained at 96 h when compared with 8.30 g L−1 in BIOCARDEL glycerol.CONCLUSIONA high potassium and sulphur concentration in glycerol medium inhibits cell growth and lipid production in Yarrowia lipolytica SKY7, while it favors citric acid production. © 2020 Society of Chemical Industry

Geochemical characteristics of crude oils and basin modelling of the probable source rocks in the Southern Mesopotamian Basin, South Iraq

Bulk property and geochemical analyses were performed on 15 crude oil samples collected from the Early Cretaceous clastic reservoirs in the oilfields of the southern Mesopotamian Basin, South Iraq. Specific gravities ranging between 25.4 and 31.6 API and relatively high sulfur concentrations of up to 1.97 wt % suggest that the samples were generated from kerogen Type II-S at relatively low maturity level. Biomarker ratios and parameters as well as carbon isotope ratios, indicate that the oils were derived from marine carbonate-rich source rocks deposited under reducing environmental conditions during the Jurassic to Early Cretaceous. Furthermore, biomarker maturity suggests two maturity subgroups for the samples based on their sulfur concentrations and specific gravity values. Sub-group (A) is characterized by oils generated from low-mature source rocks from the Late Jurassic-Early Cretaceous Sulaiy Formation; while the relatively high mature oils of sub-group (B) were generated from organic-rich intervals in the Jurassic Sargelu and Najmah formations. Basin model results revealed that these formations reached a peak oil-generation window at different times, expelling various quantities of oil. The basin model results further suggest that the organic-rich interval in the Sulaiy Formation began to expel little amounts of oil, corresponding to transformation ratio (TR) between 50 and 63% since the Late Miocene to present-day, while the organic-rich intervals in the Sargelu and Najmah formations were the earliest to expel significant amounts of oil, with relatively high TR values of 50–90% during the end of the Late Cretaceous to Early Eocene and continued to the present-day. These generated oils subsequently migrated to the shallow stratigraphic reservoir intervals through the vertical pathway of faults, and are currently extracted for use in the oil industry.

Dissecting MicroRNA-mRNA Regulatory Networks Underlying Sulfur Assimilation and Cadmium Accumulation in Poplar Leaves.

The process of cadmium (Cd) accumulation and detoxification under different sulfur levels remains largely unknown in woody plants. To investigate the physiological and transcriptomic regulation mechanisms of poplars in response to different sulfate (S) supply levels and Cd exposure, we exposed Populus deltoides saplings to one of the low, moderate and high S levels together with either 0 or 50 µM Cd. Cd accumulation was decreased in low S-treated poplar leaves, and it tended to be increased in high S-supplied leaves under the Cd exposure condition. Sulfur nutrition was deficient in low S-supplied poplars, and it was improved in high S-treated leaves. Cd exposure resulted in lower sulfur level in the leaves supplied with moderate S, it exacerbated a Cd-induced sulfur decrease in low S-treated leaves and it caused a higher sulfur concentration in high S-supplied leaves. In line with the physiological changes, a number of mRNAs and microRNAs (miRNAs) involved in Cd accumulation and sulfur assimilation were identified and the miRNA-mRNA networks were dissected. In the networks, miR395 and miR399 members were identified as hub miRNAs and their targets were ATP sulfurylase 3 (ATPS3) and phosphate 2 (PHO2), respectively. These results suggest that Cd accumulation and sulfur assimilation are constrained by low and enhanced by high S supply, and Cd toxicity is aggravated by low and relieved by high S in poplar leaves, and that miRNA-mRNA regulatory networks play pivotal roles in sulfur-mediated Cd accumulation and detoxification in Cd-exposed poplars.

Selective copper recovery by membrane distillation and adsorption system from synthetic acid mine drainage

Acid mine drainage (AMD) which involves high sulfur and heavy metals concentrations and furthermore are acidic in character, has been a major environmental and economic issue due to the associated toxicity and treatment costs. A large quantity of AMD in nature has a variety of resources including water and heavy metals such as Cu, Al, Fe and Ni. In this study, the valuable resource of Cu was selectively recovered from model AMD solution through membrane distillation and adsorption systems. Direct contact membrane distillation (DCMD) system enabled to concentrate the Cu concentration in AMD by more than 2.5 times while recovering 80% of high-quality water for reuse purposes. For adsorption, mesoporous silica material was used after multi-modification with Mn and amine grafting to enhance the adsorption capacity as well as selectivity for Cu. Under acidic conditions, heavy metals cannot be adsorbed on amine grafted SBA-15. Therefore, the pH of synthetic AMD (pH = 2.2) had to be adjusted to the 5.0–5.2 range, in order to enable adsorption of Cu on modified SBA-15 (this is to prevent protonation of amine groups grafted on prepared SBA-15). Moreover, an increase in pH helped to precipitate more than 99% of Fe and Al (predominant metals in AMD). Cu adsorption on modified SBA-15 was 24.53 mg/g for KOH-treated AMD. However, Cu adsorption on modified SBA-15 decreased by 26% (18.11 mg/g) for NaOH-treated AMD. Cu adsorption with modified SBA-15 significantly improved to 55.75 mg/g when the Cu concentration was concentrated by DCMD.