Retention Of Cl Research Articles

Ore-forming process of the Huize super-large Pb-Zn deposit, SW China: Constraints from in situ elements and S-Pb isotopes

Study on the ore-forming process is crucial for comprehending the mechanisms of metal enrichment and facilitating mineral exploration. The Huize deposit in southwestern China is characterized by significant Pb and Zn resources, as well as economic coproducts of Ge and Ag. In spite of extensive studies, the key factors for ore deposition remain controversial. Mineral textures, in situ trace elements of dolomite, and S and Pb isotopes of sphalerite and galena from the contact zone between ore body and wall rocks were used to decipher this issue. The contact zone samples are further divided into three parts at the thin section scale: ore, transitional zone, and wall rock dolostone. In the ore part, dolomite is characterized by irregular replacement. In the transitional zone, dolomite displays a core-rim texture with dolomite in the core and Fe- and Mn-rich dolomite in the rim. In the wall rock part, the Fe- and Mn-rich dolomite occur as veins. From the ore, through the transitional zone, to the wall rock, the contents of Ca, Mg, and rare earth elements in dolomite increased, whereas the contents of Mn, Fe, In, and V decreased, indicating interaction between ore-forming fluids and dolostone. The LREE depletion of hydrothermal dolomite in three zones is caused by fluid-rock interaction and retention of Cl- complexes. Negative Eu and Ce anomalies indicate that fluids evolve from alkaline to weakly acidic at relatively low temperatures. The δ34S values of sphalerite generally decrease from the ore to the transitional zone, consistent with the kinetic fractionation of sulfur isotopes due to the precipitation of sulfides. The Pb isotopic composition of galena generally increases from the ore, transitional zone, to the wall rock, reflecting increased involvement of dolostone. The detailed ore-forming process can be summarized as follows. When hydrothermal fluids, with higher ore elements, higher δ34S value, and low Pb isotope composition, enter the wall rock that has relatively high Pb isotopic composition, intense fluid-rock interaction occurs, and elements and isotopes are exchanged, forming dolomite-dominated alteration and Pb-Zn sulfides. During this process, the fluids evolve from alkaline to neutral and weakly acidic. Therefore, we suggest that the change in the pH due to the replacement of dolostone has played an important role in ore deposition.

Enhanced Na+ and Cl− sequestration and secretion selectivity contribute to high salt tolerance in the tetraploid recretohalophyte Plumbago auriculata Lam.

Enhanced secretion of Na+ and Cl- in leaf glands and leaf vacuolar sequestration of Na+ or root retention of Cl-, combined with K+ retention, contribute to the improved salt tolerance of tetraploid recretohalophyte P. auriculata. Salt stress is one of the major abiotic factors threatening plant growth and development, and polyploids generally exhibit higher salt stress resistance than diploids. In recretohalophytes, which secrete ions from the salt gland in leaf epidermal cells, the effects of polyploidization on ion homeostasis and secretion remain unknown. In this study, we compared the morphology, physiology, and ion homeostasis regulation of diploid and autotetraploid accessions of the recretohalophyte Plumbago auriculata Lam. after treatment with 300mM NaCl for 0, 2, 4, 6, and 8 days. The results showed that salt stress altered the morphology, photosynthetic efficiency, and chloroplast structure of diploid P. auriculata to a greater extent than those of its tetraploid counterpart. Moreover, the contents of organic osmoregulatory substances (proline and soluble sugars) were significantly higher in the tetraploid than in the diploid, while those of H2O2 and malondialdehyde (MDA) were significantly lower. Analysis of ion homeostasis revealed that the tetraploid cytotype accumulated more Na+ in stems and leaves and more Cl- in roots but less K+ loss in roots compared with diploid P. auriculata. Additionally, the rate of Na+ and Cl- secretion from the leaf surface was higher, while that of K+, Mg2+, and Ca2+ secretion was lower in tetraploid plants. X-ray microanalysis of mesophyll cells revealed that Na+ mainly accumulated in different cellular compartments in the tetraploid (vacuole) and diploid (cytoplasm) plants. Our results suggest that polyploid recretohalophytes require the ability to sequester Na+ and Cl-(via accumulation in leaf cell vacuoles or unloading by roots) and selectively secrete these ions (through salt glands) together with the ability to prevent K+ loss (by roots). This mechanism required to maintain K+/Na+ homeostasis in polyploid recretohalophytes under high salinity provides new insights in the improved maintenance of ion homeostasis in polyploids under salt stress.

Experimental study of chemical evolution and isotope fractionation of Cl and Br in pore water expelled during strong clay compaction

In sedimentary basins, clay compaction by burial can lead to fluid overpressure and is suspected to also generate fresh waters, but few geochemical tracers are available to assess this process both qualitatively and quantitatively. Our objective was to carry out experiments on the chemical - and halogen (Cl, Br) isotope evolutions of pore water expelled during clay compaction. For this, the smectite-rich bentonite MX80 and an illite-rich marl (Sainte-Suzanne) were equilibrated with ocean water. During two compaction experiments under high fluid pressure (45 MPa), mechanical stress (up to 150 MPa) and temperature (up to 150 °C), it was found that the chemistry and isotope behavior is considerably different between the swelling clay and the non-swelling clay.We saw a general decrease of the cat- and anion concentrations in the expelled water, for swelling clay while its concentration slightly increases in the remaining pore fluid. This was not the case for non-swelling clay. More freshening of the expelled water occurred during the compaction at higher temperature.We also observed a larger range of isotopic variation for Br (δ81Br from 0.9‰ up to 1.5‰) than for Cl (δ37Cl from −0.5‰ to −0.1‰) in the compaction experiments. During the compaction of illite-rich marl, no significant variation of Cl isotope (δ37Cl close to 0‰) was observed while the δ81Br value of the expelled water showed the same general increase (from 0.9‰ up to 1.5‰) as during the compaction of smectite-rich bentonite.We observed limited mineralogical transformations in terms of dissolution/precipitation processes. Therefore the surface chemistry of the clay in combination with decreasing porosity, in part, drive the anion and isotope evolution. We propose that significant retention of Cl and Br in the pore water of the compacted smectite-rich bentonite is indicative of ultrafiltration and that Cl and Br isotopes are promising tracers to consider when tracking the origin of low-salinity formation waters in sedimentary basins.

Transformation of HCl during pyrolysis of biomass and its model compounds

The release behavior of chlorine (Cl) during biomass pyrolysis has not been fully understood yet due to the complex transformation of hydrogen chloride (HCl). Here, we systematically investigate the transformation of HCl in vapor phase and its interactions with pyrolyzing biomass/char particles during biomass pyrolysis. Four biomass model compounds (cellulose, xylan, pectin, and alkali lignin) and an acid-washed wood were pyrolyzed in a fixed-bed reactor at 300–600 ℃ to produce Cl-free volatiles that reacted with the HCl injected downstream of the reactor. To explore the vapor–solid interactions of HCl with pyrolyzing biomass/char particles, the acid-washed wood was also pyrolyzed in a HCl atmosphere. The role of potassium (K) in the transformation of HCl was revealed via pyrolyzing a wood loaded with potassium carbonate (K2CO3). For all the experiments, the Cl distributed in char, heavy oil (condensed at 110 ℃), light oil (condensed at 0 ℃), and pyrolytic gases (as CH3Cl) was quantified. The results demonstrate that the vapor-phase reactions of HCl with the volatiles from pectin, lignin, and the acid-washed wood generate considerable amounts of methyl chloride (CH3Cl) but do not contribute to organic Cl in bio-oil. Increasing the temperatures of both pyrolysis and vapor-phase reaction promotes the generation of CH3Cl. The vapor–solid interactions of HCl with pyrolyzing biomass/char particles substantially enhance the formation of CH3Cl during the pyrolysis of the acid-washed wood at 300–500 ℃ because of the possible combination of HCl with the methyl radicals released in the initial stage of lignin pyrolysis. In addition, the vapor–solid interactions cause 120–490 μg/g feedstock of water-soluble Cl and 410–1120 μg/g feedstock of water-insoluble Cl being retained in the chars, which are produced from the capture of HCl by pores and carbon active sites in chars, respectively. The addition of K2CO3 catalyzes the cracking of lignin and thereby enhances the methylation of HCl in both vapor-phase reactions and vapor–solid interactions. It also increases the retention of Cl in the chars due to its capture by K.

Improving energy storage ability of acid-treated carbon fibers via simple sonication and heat treatments for flexible supercapacitors

Fiber-type supercapacitor (FSC) is indispensable for soft electronics. Modifying substrate without depositing electroactive material can prevent electroactive material from peeling off and enhance flexibility of FSC. Acid treatment is one of the most effective methods to enhance energy storageability of carbon fiber (CF) via inducing functional groups and creating defects for charge accumulation. In this work, it is firstly to apply sonication and heat treatments on CF electrodes in acid mixture to enhance hydrogen ion diffusion path and acid etching rate. The highest specific capacitance (CL) of 319.0 mF/cm is obtained at 20 mV/s for the CF electrode prepared using full sonication for 45 min and heat treatment at 80 °C at last 25 min, while the untreated CF electrode only shows CL value of 8.3 mF/cm. The FSC with optimized CF electrodes shows maximum energy density of 12 μWh/cm at 250 μW/cm. After 10,000 times repeated charge/discharge process, CL retention of 78% and Coulombic efficiency of 88% are achieved. Excellent flexibility is attained with high CL retentions with bending angle of 180° and bended for 1000 times. Other energy supplying methods are expected to promote the acid treatment on CF and create more efficient FSC in near future.

Optimization of printed sensors to monitor sodium, ammonium, and lactate in sweat

We describe the optimization of a flexible printed electrochemical sensing platform to monitor sodium ion (Na+), ammonium ion (NH4+), and lactate in human sweat. We used previously reported material systems and adapted them to scalable fabrication techniques. In the case of potentiometric Na+ and NH4+ sensors, ion-selective electrodes (ISEs) required minimum optimization beyond previously reported protocols, while a reference electrode had to be modified in order to achieve a stable response. We incorporated a carbon nanotube (CNT) layer between the membrane and the silver/silver chloride (Ag/AgCl) layer to act as a surface for adsorption and retention of Cl−. The resulting reference electrode showed minimal potential variation up to 0.08 mV in the solutions with Cl concentration varying from 0.1 mM to 100 mM. Increasing the ionophore content in the NH4+ ISE sensing membrane eliminated an offset in the potential readout, while incorporating CNTs into the sensing membranes had a marginal effect on the sensitivity of both Na+ and NH4+ sensors. Na+ and NH4+ sensors showed a stable near-Nernstian response with sensitivities of 60.0 ± 4.0 mV and 56.2 ± 2.3 mV, respectively, long-term stability for at least 60 min of continuous operation, and selectivity to Na+ and NH4+. For the lactate sensor, we compared the performance of the tetrathiafulvalene mediated lactate oxidase based working electrode with and without diffusion-limiting polyvinyl chloride membrane. The working electrodes with and without the membrane showed sensitivities of 3.28 ± 8 A/mM and 0.43 ± 0.11 μA/mM with a linear range up to 20 mM and 30 mM lactate, respectively.

Cl/Br and δ37Cl evolution in seawater expelled during the compaction of MX-80 smectite

During a high pressure (up to 150 MPa) high temperature (up to 150°C) compaction experiment of MX-80 smectite equilibrated with ocean water, it was found that the Cl and Br concentrations in the expelled solution are progressively being decreased while simultaneously being increased in the compacted clay. This significant retention of Cl and Br in the pore water of the compacted clay is indicative of ultrafiltration by the clay. Despite the size difference between the two anions no significant chemical partitioning between Cl and Br is observed in the expelled water. The δ37Cl value of the expelled water shows a sharp decrease (from -0.1 ‰ down to -0.5‰) during the first steps of compactions (between 45MPa – 21°C and 65MPa – 30°C) and then remains stable until 125MPa – 120°C. The largest impact on anion and stable isotope composition is seen during the earlier phases of the compaction. It is supposed that the surface chemistry of the clay in combination with decreasing porosity result in re-equilibration of compressed and overlapping diffuse double layers which in part, drive the anion and δ37Cl evolution.

Modeling salinization and recovery of road salt-impacted lakes in temperate regions based on long-term monitoring of Lake George, New York (USA) and its drainage basin

Road salt mitigates winter highway icing but accumulates in watershed soils and receiving waters, affecting soil chemistry and physical, biological, and ecological processes. Despite efforts to reduce salt loading in watersheds, accumulated cations and Cl− continue to impact tributaries and lakes, and the recovery process is not well understood. Lake George, New York (USA) is typical of many temperate lakes at risk for elevated Cl− concentrations from winter deicing; the lake salt concentration increased by ~3.4% year−1 since 1980. Here, we evaluated the ionic composition in Finkle Brook, a major watershed draining to Lake George, studied intermittently since 1970 and typical of other salt-impacted Lake George tributaries. Salt loading in the Lake George basin since the 1940s displaced cations from exchange sites in basin soils; these desorbed cations follow a simple ion-exchange model, with lower sodium and higher calcium, magnesium and potassium fluxes in runoff. Reduced salt application in the Finkle Brook watershed during the low-snow winter of 2015–2016 led to a 30–40% decline of Cl− and base cations in the tributary, implying a Cl− soil half-life of 1–2 years. We developed a conceptual model that describes cation behavior in runoff from a watershed that received road salt loading over a long period of time, and then recovery following reduced salt loading. Next, we developed a dynamic model estimating time to steady-state for Cl− in Lake George with road salt loading starting in 1940, calibrating the model with tributary runoff and lake chemistry data from 1970 and 1980, respectively, and forecasting Cl− concentrations in Lake George based on various scenarios of salt loading and soil retention of Cl−. Our Lake George models are readily adaptable to other temperate lakes with drainage basins where road salt is applied during freezing conditions and paved roads cover a portion of the watershed.

In situ investigation of halide incorporation into perovskite solar cells

Abstract

Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory.

Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl− ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl− ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl− ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl− reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH.

Soil as a reservoir for road salt retention leading to its gradual release to groundwater

Road salt application elevates Na and Cl concentrations throughout the year in many surface water and groundwater systems. This study explores the role of soils in extending the lag time between road salt application and the delivery of Na and Cl to shallow groundwater in a temperate environment. Intact soil cores were collected near karst springs at both an urban and a rural site at distances of 1 m, 5 m, and 13 m from nearby roads that experience winter salting. Cores were manipulated in the lab to simulate various field conditions; treatments included irrigation with: 1) deionized (DI) water (DI group) as a control, 2) NaCl solution (salt group) to mimic prolonged exposure to road salt, or 3) NaCl followed by DI water (recovery group) to mimic winter road salting followed by dilute rainfall in spring. In the first NaCl irrigation of the salt and recovery groups, soils retained 62% of the applied Cl and 66% of the applied Na on average, which was largely stored in the porewater. Throughout the 5 week study, Ca, Mg, and K were elevated and the pH was depressed in leachate from salt group compared to DI group cores due to cation exchange. Likewise, cation exchange enhanced Na retention so that salt and recovery group cores retained half of the applied Na at the end of the experiment, compared to a quarter of the Cl. Na and Cl retention were greater for soils from the rural site, which is characterized by higher organic matter (OM) and sand content, faster infiltration, and lower bulk density than for the urban site, which has higher bulk density and more silt and clay. Furthermore, extractable Cl in untreated field soils was positively correlated with soil water content, OM, and sand content, suggesting that these properties may control retention. We assume Cl retention to be the result of porewater retention, microbial uptake, and chlorination of soil OM. After the addition of 2000 mg Cl to the salt group cores, non-conservative Cl behavior ceased because the retention capacity of the soils had been exhausted. Recovery rates during DI flushes of recovery group cores indicate that these soils slowly release Na and Cl for at least 2.5–5 months following salt application. This gradual release from soils helps to explain the year-round persistence of high salt concentrations in some surface waters and groundwaters.

Acidogenic mineral additions increased Ca mobilization in prepartum sows.

Increased sow milk production is associated with an increase in unexplained sow mortality during prepartum and early postpartum periods. This association has led to purported claims of hypocalcemic disorders. Assuming similar responses as dairy cows, feeding anionic mineral salts in late gestation and early lactation may reduce potential hypocalcemia related disorders in sows. Two experiments using CAD-MATE (Granco Minerals, Petersburg, VA), an acidogenic mineral supplement (AMS), were designed to determine the amount required to increase urinary Ca excretion and to identify renal compensatory responses to acid loads in sows. In Exp. 1, 30 multiparous gestating sows (Landrace × Large White) were fed 1 of 6 diets with either 0, 0.5, 1.0, 1.5, 2.0, or 2.5% AMS additions for 14 d. Diets provided a range (33 to -216 mEq/kg) of cation-anion balance, calculated as Na + K - Cl - S. Two 24-h urine samples were collected via bladder catheters for mineral analysis. One venous blood sample was drawn from 2 sows per diet on d 14. In Exp. 2, twelve sows were fed 1 of 3 diets to provide either 0, 1.5, or 2.5% AMS. Three 24-h composites of urine and fecal excreta were collected and analyses were used to calculate apparent mineral retention. Venous blood pH (range 7.41 to 7.33) and base excess (range 5.4 to 0.5 mmol/L) decreased (linear, < 0.10), but blood ionized Ca (range 1.28 to 1.37 mmol/L) increased (linear, < 0.05) proportionally to dietary AMS additions. Blood anion gap was not affected by diet. Urine pH decreased (linear, < 0.10) with additions of AMS (range 7.47 to 5.52). In Exp. 2, urinary SO (range 134 to 396 mEq/d) and NH (range 84 to 323 mEq/d) excretion increased ( < 0.05) with AMS additions. Urinary Mg, Na, and K excretion did not differ among treatments. Fecal excretion of Ca, Mg, and P increased ( < 0.05) in sows fed diets with 2.5% AMS. Fecal K, Na, and Cl excretion did not differ among treatments. Apparent Ca retention decreased ( < 0.05) with AMS additions, but apparent Mg and Cl retention increased ( < 0.05). In conclusion, AMS induced a renal compensated acid load as exhibited by urinary ion excretion patterns and maintenance of blood gas values within physiological ranges. Feeding diets with 1.5 or 2.5% AMS increased urinary and fecal Ca excretion and decreased apparent Ca retention implying an increase in mobilization of body Ca pools in prepartum sows.

Cellular chloride and bicarbonate retention alters intracellular pH regulation in Cftr KO crypt epithelium.

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR), an anion channel providing a major pathway for Cl(-) and HCO3 (-) efflux across the apical membrane of the epithelium. In the intestine, CF manifests as obstructive syndromes, dysbiosis, inflammation, and an increased risk for gastrointestinal cancer. Cftr knockout (KO) mice recapitulate CF intestinal disease, including intestinal hyperproliferation. Previous studies using Cftr KO intestinal organoids (enteroids) indicate that crypt epithelium maintains an alkaline intracellular pH (pHi). We hypothesized that Cftr has a cell-autonomous role in downregulating pHi that is incompletely compensated by acid-base regulation in its absence. Here, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein microfluorimetry of enteroids showed that Cftr KO crypt epithelium sustains an alkaline pHi and resistance to cell acidification relative to wild-type. Quantitative real-time PCR revealed that Cftr KO enteroids exhibit downregulated transcription of base (HCO3 (-))-loading proteins and upregulation of the basolateral membrane HCO3 (-)-unloader anion exchanger 2 (Ae2). Although Cftr KO crypt epithelium had increased Ae2 expression and Ae2-mediated Cl(-)/HCO3 (-) exchange with maximized gradients, it also had increased intracellular Cl(-) concentration relative to wild-type. Pharmacological reduction of intracellular Cl(-) concentration in Cftr KO crypt epithelium normalized pHi, which was largely Ae2-dependent. We conclude that Cftr KO crypt epithelium maintains an alkaline pHi as a consequence of losing both Cl(-) and HCO3 (-) efflux, which impairs pHi regulation by Ae2. Retention of Cl(-) and an alkaline pHi in crypt epithelium may alter several cellular processes in the proliferative compartment of Cftr KO intestine.

A mass-balance study on chloride fluxes in a large central European catchment during 1900–2010

Using data on long-term monitoring of water quality, mass budgets, and empirical models, we quantified chloride (Cl) leaching from major diffuse and point sources in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900–2010), with the major aim to evaluate the influence of historical changes in land use and management practices on Cl leaching from agricultural land. The Cl input to farmland in synthetic fertilizers, livestock feed, and atmospheric deposition tripled in the 1950s–1980s (from 23 to 64 kg ha−1 year−1 on average), and then abruptly decreased to ~14 kg ha−1 year−1 during 1990–2010. The proportion of drained agricultural land rapidly increased from 4 % in the 1950s to its maximum of 43 % in the 1990s. Until the 1950s, the Cl leaching from agricultural land followed a simple dose–response function. Then, agricultural soils retained on average 16 ± 4 kg ha−1 year−1 of Cl during 1959–1985, when the most important changes in land use and management practices occurred, and subsequently became a net Cl source of 11 ± 3 kg ha−1 year−1 on average during 1986–2010, when Cl input to soils declined and drainage of new land ceased. Our data suggest that the temporal changes in the Cl storage in agricultural land are associated with changes in Cl concentrations in both permanent soil water and soils. Physico-chemical conditions in freshly drained soils, namely elevated aeration and high concentrations of soil organic matter (SOM), and high Cl inputs probably resulted in a Cl immobilization in soils by formation of organic chlorine (Clorg) and adsorption that was higher than the Cl production from Clorg mineralization and desorption. In contrast, Clorg mineralization and Cl desorption exceeded the Cl retention during the consecutive period of low Cl inputs and decreasing SOM concentrations in agricultural soils. Our study implies that changes in land use and agricultural management can significantly affect dose–response functions even for Cl, which is traditionally considered and modelled as a conservative ion.

Release of Chlorine during Mallee Bark Pyrolysis

Mallee bark (75–150 μm) was pyrolyzed at 400–900 °C under various conditions to investigate chlorine (Cl) release and distribution among char, tar, and gas. All Cl species in the bark are in form of water-soluble chlorides. In a fixed-bed pyrolysis reactor, the release of Cl is insensitive to pyrolysis temperature between 400 and 900 °C, with Cl completely released with volatiles (∼77% in tar and ∼23% in gas). In a drop-tube/fixed-bed reactor, under continuous feeding, the amount of Cl released at 400 °C is similar to that in the fixed-bed reactor. However, Cl retention in char increases with temperature, reaching a maximum at 600 °C (∼42%), and then decreases with further temperature increases (e.g., only ∼6% at 900 °C). In the same drop-tube/fixed-bed reactor under pulsed feeding conditions, Cl release and distribution follow similar trends but to a lesser extent. The results confirm that volatile–char interactions also play important roles in Cl release and distribution among products during biomass pyrolysis and that Cl in char is thermally unstable at elevated temperatures. Calculations by difference further suggest that substantial Cl (47–84%) is present in tars. Quantification of Cl in tar was then carried out experimentally via in situ combustion of biomass volatiles produced using a two-column pyrolysis/combustion reactor. The results confirm the presence of substantial organically bounded Cl in tar. The mass balances of Cl in char, tar, and gas achieve ∼100% closure during biomass pyrolysis in the fixed-bed reactor between 400 and 900 °C, as well as that during biomass pyrolysis in the drop-tube/fixed-bed reactor below 600 °C. However, at temperatures >600 °C, 100% Cl mass balance cannot be achieved during in situ combustion of volatiles and the data suggest that some Cl react with inorganic species (e.g., Na and K) in the gaseous phase to form alkali chlorides, which are deposited on the reactor wall.

Transformation of chlorine in NaCl-loaded Victorian brown coal during the gasification in steam

This study is to examine the changes in Cl volatilizations and chemical forms in NaCl-loaded Victorian brown coal during gasification in steam at 800°C using Cl K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The char samples were prepared in a novel one-stage fluidised-bed/fixed-bed quartz reactor at a fast heating rate. The samples were then collected and sealed in an argon-filled bag in order to minimise possible oxidation of char and Cl by air prior to analysis by XANES. Char-steam reactions were found to significantly affect the transformation of Cl, including the possible formation of chlorine-containing organic structures. On the other hand, volatile-char interactions during the gasification appeared to enhance the Cl retention and prevent the formation of organic chlorine compounds in chars.

PH Optimum of the Photosystem II H2O Oxidation Reaction: Effects of PsbO, the Manganese-Stabilizing Protein, Cl– Retention, and Deprotonation of a Component Required for O2 Evolution Activity

Hydroxide ion inhibits Photosystem II (PSII) activity by extracting Cl(-) from its binding site in the O(2)-evolving complex (OEC) under continuous illumination [Critchley, C., et al. (1982) Biochim. Biophys. Acta 682, 436]. The experiments reported here examine whether two subunits of PsbO, the manganese-stabilizing protein, bound to eukaryotic PSII play a role in protecting the OEC against OH(-) inhibition. The data show that the PSII binding properties of PsbO affect the pH optimum for O(2) evolution activity as well as the Cl(-) affinity of the OEC that decreases with an increasing pH. These results suggest that PsbO functions as a barrier against inhibition of the OEC by OH(-). Through facilitation of efficient retention of Cl(-) in PSII [Popelkova, H., et al. (2008) Biochemistry 47, 12593], PsbO influences the ability of Cl(-) to resist OH(-)-induced release from its site in the OEC. Preventing inhibition by OH(-) allows for normal (short) lifetimes of the S(2) and S(3) states in darkness [Roose, J. L., et al. (2011) Biochemistry 50, 5988] and for maximal steady-state activity by PSII. The data presented here indicate that activation of H(2)O oxidation occurs with a pK(a) of ∼6.5, which could be a function of deprotonation of one or more amino acid residues that reside near the OEC active site on the D1 and CP43 intrinsic subunits of the PSII reaction center.

Dust-Firing of Straw and Additives: Ash Chemistry and Deposition Behavior

In the present work, the ash chemistry and deposition behavior during straw dust-firing were studied by performing experiments in an entrained flow reactor. The effect of using spent bleaching earth (SBE) as an additive in straw combustion was also investigated by comparing with kaolinite. During dust-firing of straw, the large (>∼2.5 μm) fly ash particles generated were primarily molten or partially molten spherical particles rich in K, Si, and Ca, supplemented by Si-rich flake-shaped particles. The smaller fly ash particles (<∼2.5 μm) were predominantly formed from the nucleation, condensation, and coagulation of the vaporized K, Cl, S, and P species. Approximately 70% of K in the fly ash from straw combustion was water-soluble, and KCl was estimated to contribute to more than 40% of the water-soluble K. With the addition of SBE to straw dust-firing, the Cl retention in ash was reduced, the SO2 emission was increased, and the formation of water-soluble alkali species was decreased. Compared to kaolinite...

Biochar as a Fuel: 4. Emission Behavior and Characteristics of PM1 and PM10 from the Combustion of Pulverized Biochar in a Drop-Tube Furnace

Six biochar samples were produced from both slow and fast pyrolysis of mallee bark at 400–550 °C, respectively; such temperatures are typically used for biochar and/or bio-oil production in practice. Under the pyrolysis conditions, the biochar yields range from 26.7 to 37.0% and the majority (78.5–100.0%) of alkali and alkaline earth metallic (AAEM) species (mainly Na, K, Mg, and Ca) in biomass are retained in the biochars, while the retention of Cl in biochars is only 2.0–33.4%. The raw biomass and its derived biochar samples were then combusted in a laboratory-scale drop-tube furnace (DTF) at 1300 °C to investigate the emission behavior and characteristics of sub-micrometer particulate matter (PM1) and PM with an aerodynamic diameter less than 10.0 μm (PM10). The particle size distribution (PSD) of PM10 from raw biomass combustion has a bimodal size distribution, while the PSDs of PM10 from biochar combustion generally show a unimodal distribution. Although most inorganic species are retained in the biochar during pyrolysis, it is interesting to note that the combustion of biochars leads to a substantial reduction in the emission of PM1 (and the mass of Na, K, and Cl in PM1) that dominantly consists of PM with a size less than 0.1 μm (PM0.1) in comparison to biomass combustion, apparently because of the removal of volatiles and Cl from the raw biomass during pyrolysis for biochar preparation. The results imply that the combustion of volatiles (including the released inorganic species), which is particularly important during biomass combustion, is mainly responsible for PM1 emission. Meanwhile, considerable increases in the emission of coarser particulate matter with an aerodynamic diameter between 1 and 10 μm (PM1−10) and the mass of Mg and Ca in PM1−10 are also evident during biochar combustion, most likely as a result of more porous structure and increased ash loading of biochars.

Ru-based catalysts for glycerol hydrogenolysis—Effect of support and metal precursor

Hydrogenolysis of biomass-derived glycerol is an alternative route for the production of value-added chemicals, such as 1,2-propanediol. Ru-based (γ-Al2O3, SiO2, ZrO2) catalysts were prepared by the wet impregnation method and evaluated in glycerol hydrogenolysis at 240°C and 8MPa H2. The effect of the refractory oxide and metal precursor (RuCl3·xH2O, RuNO(NO3)3) used for catalyst preparation was examined. The nature of the oxidic support was found to influence the ability of the catalyst to both activate the glycerol substrate and selectively convert it to propanediol. Among the tested catalysts, Ru/Al2O3 prepared with the chloride precursor exhibited the highest activity (69%) and the lowest selectivity to 1,2-propanediol due to excessive hydrogenolysis of 1,2-propanediol to 1-propanol. Ru/SiO2 prepared with the nitrate precursor yielded to the highest selectivity to 1,2-propanediol (65%) at 20% conversion level. The characterization of the catalytic materials revealed a correlation between catalytic activity for the hydrogenolysis reaction and total acidity, as the yield to hydrogenolysis products increased with the concentration of the acid sites. The use of different metal precursors affected the catalytic activity and product selectivity mainly in the case of γ-Al2O3 used as support, but with SiO2 support as well. The supported Ru samples prepared using the chloride precursor showed higher activity compared to the corresponding materials prepared with nitrate, but selectivity to 1,2-propanediol was lower due to the promotion of excessive hydrogenolysis to propanols. These effects were attributed to the retention of Cl− ions on the support surface, as evidenced by TEM-EDS.