RESUMO
Silica is regarded as a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, large volume variation and poor electrical conductivity are limiting factors for the development of SiO2 anode materials. To solve this problem, combining SiO2 with a conductive phase and designing hollow porous structures are effective ways. In this work, The Co(II)-EDTA chelate on the surface of diatom biosilica (DBS) frustules and obtained DBS@C-Co composites decorated with Co nanoparticles by calcination without a reducing atmosphere is first precipitated. The unique three-dimensional structure of diatom frustules provides enough space for the volume change of silica during lithiation/delithiation. Co nanoparticles effectively improve the electrical conductivity and electrochemical activity of silica. Through the synergistic effect of the hollow porous structure, carbon layer and Co nanoparticles, the DBS@C-Co-60 composite delivers a high reversible capacity of >620 mAh g-1 at 100 mA g-1 after 270 cycles. This study provides a new method for the synthesis of metal/silica composites and an opportunity for the development of natural resources as advanced active materials for LIBs.
RESUMO
Oxidative dissolution of stibnite (Sb2S3), one of the most prevalent geochemical processes for antimony (Sb) release, can be promoted by Sb-oxidizing microbes, which were studied under alkaline and neutral conditions but rarely under acidic conditions. This work is dedicated to unraveling the enhancement mechanism of stibnite dissolution by typical acidophile Acidithiobacillus ferrooxidans under extremely acidic conditions. The results of solution behavior showed that the dissolution of Sb2S3 was significantly enhanced by A. ferrooxidans, with lower pH and higher redox potential values and higher [Sb(III)] and [Sb(V)] than the sterile control. The surface morphology results showed that the cells adsorbed onto the mineral surface and formed biofilms. Much more filamentous secondary minerals were formed for the case with A. ferrooxidans. Further mineral phase compositions and Sb/S speciation transformation analyses showed that more secondary products Sb2O3/SbO2-, Sb2O5/SbO3-, SO42-, as well as intermediates, such as S0, S2O32- were formed for the biotic case, indicating that the dissolution of Sb2S3 and the Sb/S speciation transformation was promoted by A. ferrooxidans. These results were further clarified by the comparative transcriptome analysis. This work demonstrated that through the interaction with Sb2S3, A. ferrooxidans promotes S/Sb oxidation, so as to enhance S/Sb transformation and thus the dissolution of Sb2S3.
Assuntos
Acidithiobacillus , Antimônio/química , Minerais/química , Oxirredução , SolubilidadeRESUMO
Arsenic often coexists with metal sulfide minerals and occurs in different speciation and different toxicity in responding to Fe/S biooxidation. The differential inhibitive effects and fates of As(III) and As(V) during biooxidations of elemental sulfur (S0), ferrous ions (Fe2+) and pyrite (FeS2) by Sulfobacillus thermosulfidooxidans were studied. The results revealed that the arsenic species hardly changed for the biooxidation of S0, but dramatically changed for the biooxidation of Fe2+ and FeS2. Different transformation degree between As(III) and As(V) occurred for biooxidation of FeS2 in the presence of arsenic, where about 72% of As(III) was transformed to As(V) for the group with As(III) added, and 16% of As(V) was transformed to As(III) for that with As(V) added. Both formation and dissolution of amorphous ferric arsenate occurred during biooxidation of FeS2 with the addition of As(III) or As(V) and for the group grown on Fe2+ with added As(V), which were controlled by the changes of Fe/As molar ratio and pH value in the solution. Jarosite was detected for the group grown on Fe2+ and could adsorb As(III) and As(V). The inhibitive effects of As(V) were higher than As(III) when the strain grew on FeS2, which was contrary to those when the strain grew on S0 and Fe2+. The above results signify that the fates and inhibitive effects of arsenic are much related to each other, and such a relationship is significantly affected by the utilization of Fe/S energy substrates by the sulfur- and ferrous-oxidizing microorganisms.
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Arsênio , Clostridiales , Compostos Férricos , Minerais , Oxirredução , EnxofreRESUMO
PURPOSE: To explore the safety and efficacy of Ruiyun procedure for hemorrhoids (RPH) or RPH with the simplified Milligan-Morgan hemorrhoidectomy (sMMH) in the treatment of mixed hemorrhoids. METHODS: This is a randomized, controlled, balanced, multicenter study of 3000 patients with mixed hemorrhoids. The outcomes and postoperative complications were compared between 5 types of surgeries. RESULTS: The efficacy rate was the highest in patients who received RPH+sMMH and decreased in the following order: patients who received RPH alone, MMH alone, procedure for prolapse and hemorrhoids (PPH) alone, and PPH+sMMH ( P < .05). The operation time was the shortest in patients who received RPH alone and increased in the following order: patients who received RPH+sMMH, PPH alone, MMH alone, and PPH+sMMH ( P < .01). The duration of postoperative hospitalization stay was the shortest in patients who received RPH alone and increased in the following order: PPH alone, RPH+sMMH, PPH+sMMH, and MMH alone ( P < .01). The incidence of postoperative hemorrhage, uroschesis, anal fissure, crissum hematoma or thrombosis, and anorectal stenosis was significantly lower in patients who received RPH+sMMH than in patients who received the other 4 types of surgical treatments ( P < .05, P < .01). No significant differences in postoperative rectovaginal fistula and anal incontinence were observed between the 5 groups of patients. CONCLUSIONS: RPH with or without simplified MMH can reduce the incidence of postoperative complications and improve the curative efficacy in the treatment of patients with mixed hemorrhoids.
Assuntos
Hemorroidectomia/métodos , Hemorroidas/cirurgia , Complicações Pós-Operatórias/epidemiologia , Adulto , Feminino , Hemorroidectomia/efeitos adversos , Humanos , Tempo de Internação , Ligadura/efeitos adversos , Ligadura/métodos , Masculino , Pessoa de Meia-Idade , Duração da Cirurgia , Grampeamento Cirúrgico/efeitos adversos , Grampeamento Cirúrgico/métodos , Resultado do TratamentoRESUMO
Objective To observe the safety and efficacy of RPH with the simplified. Milligan-Mor- gan(M-M) surgery on mixed hemorrhoids. Methods Totally 1 200 patients with mixed hemorrhoid were assigned to the control group(600 cases) and the treatment group(600 cases) according to randomized, parallel controlled,multi-center trial design. Patients in the control group received PPH with the simplified M-M surgery, and patients in the treatment group received RPH with the simplified M-M surgery. Postop- erative complications, operation time,the postoperative hospitalization days and the efficacy were ob- served. Results Compared with the control group, the numbers of postoperation hemorrhage, postop- erative uroschesis, anal fissure and anorectal stenosis in treatment group were decreased(P <0. 01 , P < 0. 05), operation time and the postoperative hospitalization days were decreased (P <0. 01 , P <0. 05 ), the cure rate for 3 and 12 months after operation were increased (P <0. 01, P <0. 05). Conclusions RPH with the simplified M-M surgery could reduce the incidence of postoperative complications,improve the clinical cure rate and the curative effect in treatment of mixed hemorrhoids.
Assuntos
Hemorroidectomia , Hemorroidas , Complicações Pós-Operatórias , Constrição Patológica , Hemorroidectomia/métodos , Hemorroidas/cirurgia , Hospitalização , Humanos , Dor Pós-Operatória , Período Pós-Operatório , Resultado do TratamentoRESUMO
While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups.
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Acidianus/metabolismo , Acidithiobacillus/metabolismo , Metabolismo Energético , Ferro/metabolismo , Cobre/metabolismo , Compostos Ferrosos/metabolismo , Sulfetos/metabolismo , Propriedades de Superfície , Espectroscopia por Absorção de Raios XRESUMO
To better understand the biosynthetic pathway of flavonoids in Blumea balsamifera, and to increase the biosynthesis of flavone and flavonol amount, we carried out this research. Basing on transcriptome information, B. balsamifera flavonoids metabolic pathway was analyzed in KEGG data base. The result demonstrated that two metabolic pathways of flavonoids were found in KEGG data base. They were flavonoid biosynthesis pathway (No.ko00941) that contained 32 genes and flavone and flavonol biosynthesis pathway (No.ko00944) that contained 12 genes. Metabolic pathway of flavonoids in B. balsamifera was similar to that in other plants. Chalcone synthase (CHS) and Chalconeisomerase were much likely to be key enzymes on metabolic pathway of flavonoids in B. balsamifera. HCT was much relevant to biosynthesis of favones.
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Asteraceae/metabolismo , Vias Biossintéticas , Flavonoides/biossíntese , TranscriptomaRESUMO
In order to provide a theoretical basis for the regulation of active ingredient, the terpenoids metabolic pathway and specific enzymes in Blumea balsamifera are investigated. Basing on transcriptome information, B. balsamifera terpenoids metabolic pathway was analyzed in KEGG data base. Four metabolic pathway of terpenoids were found in KEGG data base. They were terpenoid backbone biosynthesis, monoterpenoid biosynthesis, diterpenoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, contained 103, 10, 29,59 genes, respectively. Through the analysis of the enzyme and product in the pathway, the result showed that there were 8 kinds of monoterpenes, 3 kinds of diterpenes, 3 kinds of triterpenes and sesquiterpenes. The mainly key enzymes were deoxyxylulose 5-phosphate synthase, HMG-CoA reductase and allyl transferase system. In B. balsamifera, there were relatively few monoterpenes synthetic enzymes, while the type of products was much more than other terpenes. This may be relate to the non-specific catalytic characteristic of monoterpene synthase. It is expected to improve the yield of terpenoids in B. balsamifera by analysis the pathways and regulation the key enzymes.
Assuntos
Asteraceae/metabolismo , Redes e Vias Metabólicas , Terpenos/metabolismo , Diterpenos/metabolismo , Monoterpenos/metabolismo , Sesquiterpenos/metabolismo , Triterpenos/metabolismoRESUMO
Objective: To study the effects of different plant density and harvest time on the yield and quality of Miao medicine Blumea balsamifera, in order to provide a theoretical basis for Good Agriculture Practice( GAP). Methods: Two factors trails were used to research the influence of plant density and harvest time on the yield and quality of Blumea balsamifera. The plant density were located at 50 cm × 90 cm,50 cm × 60 cm,50 cm × 30 cm and 30 cm × 30 cm, and the harvest time were set up at mid-October, mid-November and mid-December. The experiments were designed with randomized block design. Results: Yield and quality were both affected by the plant density and harvest time. Yield per unit area and volatile oil yield per unit area were increased significantly with the increasing of plant density. Yield per unit area and volatile oil yield per unit area were peaked at the plant density of 111 112 plants / hm~2 which could obtain high-yield at the mid-December, which were 1 546. 68 kg / hm~2 and 96. 6 L / hm~2,respectively. The content of total flavonoids were peaked at the plant density of 22 223 plants / hm~2 and 111 112 plants / hm~2,which were 2. 50 and 2. 53 mg/g,respectively. Harvest time had no significant effect on the flavonoids content. Conclusion: The suitable plant density of transplanted root tillers of Blumea balsamifera is 111 112 plants / hm~2 and the optimum harvest time is December.
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Asteraceae , Agricultura , Flavonoides , Óleos VoláteisRESUMO
Bio-oxidation of elemental sulfur (S(0)) is very important in bioleaching and sulfur cycle. S(0) was proposed to be first activated by reacting with reactive thiol groups (-SH) of outer membrane proteins, forming -S n H (n ≥ 2) complexes. The differential expression of -SH of moderately thermophilic Sulfobacillus thermosulfidooxidans and extremely thermophilic Acidianus manzaensis grown on Fe(2+) and S(0) was investigated by synchrotron radiation-based scanning transmission X-ray microscopy (STXM) imaging and micro-beam X-ray fluorescence (µ-XRF) mapping. The STXM imaging and µ-XRF mapping of extracellular -SH were based on the analysis of Ca(2+) bound on the cell. By comparing Ca(2+) of the cells with and without labeling by Ca(2+), the distribution and content of thiol groups were obtained. The results showed that, for both S. thermosulfidooxidans and A. manzaensis, the expression of extracellular -SH of S(0)-grown cells was higher than that of Fe(2+)-grown cells. Statistical analysis indicated that the expression of extracellular -SH for S. thermosulfidooxidans and A. manzaensis grown on S(0) was 2.37 times and 2.14 times, respectively, to that on Fe(2+). These results evidently demonstrate that the extracellular thiol groups are most probably involved in elemental sulfur activation and oxidation of the acidophilic sulfur-oxidizing microorganisms.
Assuntos
Ferro/metabolismo , Compostos de Sulfidrila/metabolismo , Sulfolobaceae/metabolismo , Enxofre/metabolismo , Acidianus/metabolismo , Oxirredução , Microtomografia por Raio-XRESUMO
OBJECTIVE: Combination of different planting direction and layer were set to choose the best technology of cultivation of Gastrodia elata f. elata. METHODS: To improve the yield and quality of Gastrodia elata f. elata, randomized block design experiments were carried out to investigate the yield and quality, and to analyze their economic effectiveness in bionic wild cultivation. RESULTS: Length, width, thickness and weight of southern direction's Gastrodia elata f. elata developed better than the northeast direction. The three planting layer levels on growth effect of Gastrodia elata f. elata was the 3rd layer > the 2nd layer > the 1st layer. In six treatments, combination of southern direction-the 3rd layer was the best technology of cultivation of Gastrodia elata f. elata, which had the best growth condition, the highest yield significantly higher than other treatments, and the best economic benefits. CONCLUSION: Southern direction associated with the 3rd layer is the best combination to planting Gastrodia elata f. elata in bionic wild cultivation. The planting ways not only improve the yield and quality, but also save land.
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Agricultura/métodos , Gastrodia/crescimento & desenvolvimento , Plantas Medicinais/crescimento & desenvolvimentoRESUMO
OBJECTIVE: To study the content of mineral elements and the principal components in Gastrodia elata. METHOD: Mineral elements were determined by ICP and the data was analyzed by SPSS. RESULT: K element has the highest content-and the average content was 15.31 g x kg(-1). The average content of N element was 8.99 g x kg(-1), followed by K element. The coefficient of variation of K and N was small, but the Mn was the biggest with 51.39%. The highly significant positive correlation was found among N, P and K . Three principal components were selected by principal components analysis to evaluate the quality of G. elata. P, B, N, K, Cu, Mn, Fe and Mg were the characteristic elements of G. elata. CONCLUSION: The content of K and N elements was higher and relatively stable. The variation of Mn content was biggest. The quality of G. elata in Guizhou and Yunnan was better from the perspective of mineral elements.
Assuntos
Medicamentos de Ervas Chinesas/análise , Gastrodia/química , Minerais/análise , Análise de Componente PrincipalRESUMO
BACKGROUND/AIMS: Cardiac action potential duration (APD) is regulated by heart rate, leading to the trans-membrane movement of inorganic ions. Whether the alteration of heart rate can affect the expression of transient receptor potential canonical channels (TRPCs), further studies should be made. We investigated the changes of APD at different stimulus frequencies and their influences on the expression of TRPCs in rabbit ventricular myocardium. METHODS: Monophasic action potential (MAP) was recorded by contact electrode technique in different programmed stimulus frequencies on rabbit ventricular epicardium in vivo, and the expression of TRPCs was detected using RT-PCR and Western blot. RESULTS: At the frequency range of 4.5-7.5 Hz, APD gradually shortened with the increase of stimulus frequency, showing the property of significant frequency dependence in rabbit ventricular myocardium in vivo. Compared with 4.5 Hz group, TRPC3 mRNA and protein expression increased in 6 Hz and 7.5 Hz groups by way of frequency dependence. Both amiodarone (AM) and neferine (Nef) could prolongate APD and showed characters of frequency independence at the designed frequency. In contrast with 4.5 Hz control group, it was Nef treatment group rather than AM treatment group that could obviously increase the expression of TRPC3 mRNA and protein. CONCLUSIONS: At the frequency range of 4.5-7.5 Hz, frequency-dependent shortening of APD was associated with the expression of TRPC3. AM and Nef exhibited frequency-independent lengthening of the APD. Nef may prolong APD via the increasement of TRPC3.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Amiodarona/farmacologia , Benzilisoquinolinas/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Miocárdio/metabolismo , Canais de Cátion TRPC/biossíntese , Potenciais de Ação/fisiologia , Animais , Ventrículos do Coração/metabolismo , RNA Mensageiro/biossíntese , CoelhosRESUMO
Light and scanning electron microscopy (SEM) were used to examine the first zoeal stage of four ghost crabs, Ocypode ceratophthalmus (Pallas, 1772), O. cordimanus Latreille, 1818, O. sinensis Dai, Song & Yang, 1985 and O. stimpsoni Ortmann, 1897. Finding diagnostic characters to distinguish between the four species proved difficult because their setal appendage patterns were identical. However the rectangular and pockmarked patterns on the ventral carapace are rather pronounced in O. ceratophthalmus and O. stimpsoni but weak in O. cordimanus and O. sinensis. The spinulation on the furca of the telson is less in O. cordimanus than in the other three species.
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Braquiúros/anatomia & histologia , Braquiúros/classificação , Animais , Feminino , Larva/anatomia & histologia , Larva/classificação , Especificidade da EspécieRESUMO
In order to get to know the imitation of wild Gastrodia elata in life history and phenology period, by G. elata f. elata forest wild simulated cultivation in Dafang county, Guizhou province, observing and recording its morphological characteristics of each growth and development stage. This experiment summarized the law of its life history over 24 months, amplified the characteristics of each 5 phenology periods over the sexual and asexual reproduction of wild simulated cultivated G. elata f. elata in Guizhou. Which the results could clear the process of wild simulated cultivated G. elata f. elata in Guizhou, and provide a theoretical support for the standard technical of the simulated wild G. elata.
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Gastrodia/crescimento & desenvolvimento , Gastrodia/fisiologia , Estágios do Ciclo de Vida/fisiologia , ReproduçãoRESUMO
OBJECTIVE: To provide reference in selecting premium provenance and improve the cultivation techniques of Polygonum multiflorum. METHODS: Field survey, routine field-observation and sampling fixed plant for analysis in lab were adopted. RESULTS: The growing adaptability of Polygonum multiflorum was very strong, which growed flourishly in the condition with adequate light, ample rainfall, rich heat and fertile soil; Along with the lower of latitude, the vegetative period was prolonged and reproductive stage was delayed, which prolonged the time of roots' nutrition acquisition. Time for root shoot ratio increasing continuously of low latitude germplasms was higher than that of higher latitude germplasms. CONCLUSION: Polygonum multiflorum germplasms have different biological characteristics because of different regions and habitats, which can provide useful reference for selecting premium provenance and adjusting measures to local conditions in different areas.
Assuntos
Ecossistema , Plantas Medicinais/fisiologia , Polygonum/fisiologia , Tempo (Meteorologia) , Altitude , China , Raízes de Plantas/crescimento & desenvolvimento , Caules de Planta/crescimento & desenvolvimento , Plantas Medicinais/crescimento & desenvolvimento , Polygonum/crescimento & desenvolvimento , Estações do Ano , SoloRESUMO
The domoic acid (DA) produced by certain species of the marine pennate diatom genus Pseudo-nitzschia is highly neurotoxic and can induce nerve excitability and neurotoxicity by binding with ionotropic glutamate receptors, causing amnesic shellfish poisoning in humans who consume seafood contaminated with DA. In recent years, poisoning of humans caused by DA has occurred around the world, which has attracted increasing attention, and studies on DA production by Pseudo-nitzschia have become the hotpot. This article reviews the progress in the biosynthesis of DA by the typical diatom Pseudo-nitzschia, in which the metabolic pathway of the biosynthesis of DA and its precursors, i.e., geranyl pyrophosphate and L-glutamate, and the various environmental factors affecting DA production including temperature, light intensity, nutrients, trace metals, and alien bacteria are discussed. The detection methods of DA (including bioassays, enzyme linked immunosorbent assays, high performance liquid chromatography, capillary electrophoresis and biosensors), as well as the morphology and toxigenicity of Pseudo-nitzschia are also presented.
Assuntos
Diatomáceas , Síndromes Neurotóxicas , Intoxicação por Frutos do Mar , Humanos , Diatomáceas/metabolismo , Ácido Caínico/análise , Ácido Caínico/metabolismo , Redes e Vias MetabólicasRESUMO
OBJECTIVE: To study the seed germination characteristic and optimal germination condition of wild Disporum cantoniense. METHODS: Used wild Disporum cantoniense seed as the test materials, the rate of water absorption of the seed was determined. The germination rates under different conditions, along a temperature gradient (15, 20, 25 and 30 degres C), in light or dark, on top or between wet filter papers, and keeping or removing the seed coat, were determined respectively using petri dish method. At the same time germination trends were observed. RESULTS: The thousand seed weight was 33.24 g, and the seed water-absorbing reached saturation pot after soaking for 30 h. Higher germination rates were respectively recorded at 25 degrees C, between filter papers, and in dark after 24 h soaking in the pretreatment solution. CONCLUSION: The optimal condition for the germination of the seed of wild Disporum cantoniense is as follow: keeping testa, seed soaking for 24 h in seed germination agent and being incubated between wet filter papers in dark at 25 degrees C.
Assuntos
Germinação , Liliaceae/crescimento & desenvolvimento , Plantas Medicinais/crescimento & desenvolvimento , Sementes/fisiologia , Luz , Liliaceae/fisiologia , Plantas Medicinais/fisiologia , Sementes/crescimento & desenvolvimento , Temperatura , ÁguaRESUMO
It is well known that speciation transformations of As(III) vs. As(V) in acid mine drainage (AMD) are mainly driven by microbially mediated redox reactions of Fe and S. However, these processes are rarely investigated. In this study, columns containing mine water were inoculated with two typical acidophilic Fe/S-oxidizing/reducing bacteria [the chemoautotrophic Acidithiobacillus (At.) ferrooxidans and the heterotrophic Acidiphilium (Aph.) acidophilum], and three typical energy substrates (Fe2+, S0, and glucose) and two concentrations of As(III) (2.0 and 4.5 mM) were added. The correlation between Fe/S/As speciation transformation and bacterial depth distribution at three different depths, i.e., 15, 55, and 105 cm from the top of the columns, was comparatively investigated. The results show that the cell growth at the top and in the middle of the columns was much more significantly inhibited by the additions of As(III) than at the bottom, where the cell growth was promoted even on days 24-44. At. ferrooxidans dominated over Aph. acidophilum in most samples collected from the three depths, but the elevated proportions of Aph. acidophilum were observed in the top and bottom column samples when 4.5 mM As(III) was added. Fe2+ bio-oxidation and Fe3+ reduction coupled to As(III) oxidation occurred for all three column depths. At the column top surfaces, jarosites were formed, and the addition of As(III) could lead to the formation of the amorphous FeAsO4â 2H2O. Furthermore, the higher As(III) concentration could inhibit Fe2+ bio-oxidation and the formation of FeAsO4â 2H2O and jarosites. S oxidation coupled to Fe3+ reduction occurred at the bottom of the columns, with the formations of FeAsO4â 2H2O precipitate and S intermediates. The formed FeAsO4â 2H2O and jarosites at the top and bottom of the columns could adsorb to and coprecipitate with As(III) and As(V), resulting in the transfer of As from solution to solid phases, thus further affecting As speciation transformation. The distribution difference of Fe/S energy substrates could apparently affect Fe/S/As speciation transformation and bacterial depth distribution between the top and bottom of the water columns. These findings are valuable for elucidating As fate and toxicity mediated by microbially driven Fe/S redox in AMD environments.
RESUMO
The bio-oxidative dissolution of arsenopyrite, the most severe arsenic contamination source, can be mediated by organic substances, but pertinent studies on this subject are scarce. In this study, the bio-oxidative dissolution of arsenopyrite by Sulfobacillus thermosulfidooxidans and arsenic immobilization were evaluated in the presence of humic acid (HA). The mineral dissolution was monitored through analyses of the parameters in solution, phase and element speciation transformations on the mineral surface, and arsenic immobilization on the surfaces of cells and jarosites-HA. The results show that the presence of HA enhances the dissolution of arsenopyrite, e.g., 7.1% of arsenopyrite was in the residue after 12 d of bio-oxidation compared to 19.3% in the absence of HA. Meanwhile, the presence of HA led to changes of the fates of As and Fe and no accumulation of elemental sulfur (S0) or ferric arsenate on the mineral surface. Moreover, a flocculent porous structure was formed on the surfaces of both microbial cells and jarosites, on which a large amount of arsenic was adsorbed. These results clearly indicate that HA can simultaneously promote the dissolution of arsenopyrite and arsenic immobilization, which may be significant for bioleaching of arsenopyrite-bearing contaminated sites.