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1.
Environ Sci Technol ; 53(16): 9542-9552, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31313918

RESUMO

The geochemical behaviors of phosphate-containing species at mineral-water interfaces are of fundamental importance for controlling phosphorus mobility, fate, and bioavailability. This study investigates the sorption and hydrolysis of polyphosphate (a group of important long-chained phosphate molecules) on aluminum oxides in the presence of divalent metal cations (Ca2+, Cu2+, Mg2+, Mn2+, and Zn2+) at pH 6-8. γ-Al2O3 with three particle sizes (5, 35, and 70 nm) was used as an analogue of natural aluminum oxides to investigate the particle size effect. All metal cations enhanced polyphosphate hydrolysis at different levels, with Ca2+ showing the most significant enhancement, and the difference in the enhancement might be due to the intrinsic affinity of metal cations to polyphosphate. In the presence of Ca2+, the hydrolysis rate decreased with increasing mineral particle size. Solid-state 31P nuclear magnetic resonance spectroscopy (NMR) revealed the main surface P species to be amorphous calcium phosphate precipitates, phosphate groups in polyphosphate that formed direct bonds with the mineral surface as inner-sphere complexes, and phosphate groups in polyphosphate that were not directly bonded to the mineral surfaces. Our results reveal the critical roles of mineral-water interface processes and divalent metal cations on controlling polyphosphate speciation and transformation and phosphorus cycling.

2.
J Am Chem Soc ; 141(16): 6680-6689, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-30932488

RESUMO

While sodium-ion batteries (SIBs) hold great promise for large-scale electric energy storage and low speed electric vehicles, the poor capacity retention of the cathode is one of the bottlenecks in the development of SIBs. Following a strategy of using lithium doping in the transition-metal layer to stabilize the desodiated structure, we have designed and successfully synthesized a novel layered oxide cathode P2-Na0.66Li0.18Fe0.12Mn0.7O2, which demonstrated a high  capacity of 190 mAh g-1 and a remarkably high capacity retention of ∼87% after 80 cycles within a wide voltage range of 1.5-4.5 V. The outstanding stability is attributed to the reversible migration of lithium during cycling and the elimination of the detrimental P2-O2 phase transition, revealed by ex situ and in situ X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy.

3.
Environ Microbiol ; 21(7): 2415-2425, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30972877

RESUMO

Polyphosphates and phosphomonoesters are dominant components of marine dissolved organic phosphorus (DOP). Collectively, DOP represents an important nutritional phosphorus (P) source for phytoplankton growth in the ocean, but the contribution of specific DOP sources to microbial community P demand is not fully understood. In a prior study, it was reported that inorganic polyphosphate was not bioavailable to the model diatoms Thalassiosira weissflogii and Thalassiosira pseudonana. However, in this study, we show that the previous finding was a misinterpretation based on a technical artefact of media preparation and that inorganic polyphosphate is actually widely bioavailable to Thalassiosira spp. In fact, orthophosphate, inorganic tripolyphosphate (3polyP), adenosine triphosphate (ATP) and adenosine monophosphate supported equivalent growth rates and final growth yields within each of four strains of Thalassiosira spp. However, enzyme activity assays revealed in all cultures that cell-associated hydrolysis rates of 3polyP were typically more than ~10-fold higher than degradation of ATP and the model phosphomonoester compound 4-methylumbelliferyl phosphate. These results build on prior work, which showed the preferential utilization of polyphosphates in the cell-free exudates of Thalassiosira spp., and suggest that inorganic polyphosphates may be a key bioavailable source of P for marine phytoplankton.

4.
Water Environ Res ; 91(8): 797-804, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30993735

RESUMO

The recovery and reuse of phosphorus (P) from wastewater treatment process is a critical and viable target for sustainable P utilization. This study explores a novel approach of integrating ultrafine mineral particles into hydrogel matrixes for enhancing the capacity of phosphate adsorption. Dolomite-alginate (DA) hydrogel beads were prepared by integrating ball-milled, ultrafine dolomite powders into calcium cross-linked alginate hydrogel matrix. The adsorption isotherms followed a Langmuir-Freundlich adsorption model with higher specific adsorption capacity than those reported in literature. The kinetics of phosphate adsorption suggest that the adsorption is diffusion controlled. Investigation of adsorption capacity at different pH showed a maximum adsorption capacity in the pH range of 7-10. Lastly, we demonstrated that the DA beads are capable of slowly releasing most of the adsorbed phosphate, which is an important criterion for them to be an effective phosphorous fertilizer. This study, using DA composite hydrogel as an example, demonstrates a promising strategy of immobilizing ultrafine mineral adsorbents into biocompatible hydrogel matrix for effective recovery of phosphorous resource from wastewater. PRACTITIONER POINTS: Integration of dolomite and alginate hydrogel beads is demonstrated using ball milling. Ball milling process increases the specific adsorption capacity of dolomite on phosphorus. Adsorption isotherms, kinetics, and pH effects of the dolomite-alginate beads are investigated. The dolomite-alginate beads can be used as slow-release phosphorus fertilizer.


Assuntos
Alginatos/química , Carbonato de Cálcio/química , Fertilizantes , Magnésio/química , Fosfatos/isolamento & purificação , Adsorção
5.
Sci Total Environ ; 668: 216-223, 2019 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-30852198

RESUMO

Associations of organic carbon (OC) with iron (Fe) oxide minerals play an important role in regulating the stability of OC in soil environments. Knowledge about the fate and stability of Fe-OC complexes is impaired by the heterogeneity of OC. Additional biogeochemical variables in soil environments, such as redox conditions and microbes, further increase complexity in understanding the stability of mineral-associated soil OC. This study investigated the fate and stability of model organic compounds, including glucose (GL), glucosamine (GN), tyrosine (TN), benzoquinone (BQ), amylose (AM), and alginate (AL), complexed with an Fe oxide mineral, ferrihydrite (Fh), during microbial reduction. During a 25-d anaerobic incubation with Shewanella putrefaciens CN32, the reduction of Fe followed the order of Fh-BQ > Fh-GL > Fh-GN > Fh-TN > Fh-AL > Fh-AM. In terms of OC released during the anaerobic incubation, Fh-GN complexes released the highest amount of OC while Fh-AM complexes released the lowest. Organic carbon regulated the reduction of Fe by acting as an electron shuttle, affecting microbial activities, and associating with Fh. Benzoquinone had the highest electron accepting capacity, but potentially can inhibit microbial activity. These findings provide insights into the roles of different organic functional groups in regulating Fe reduction and the stability of Fh-bound OC under anaerobic conditions.


Assuntos
Compostos Férricos/metabolismo , Modelos Químicos , Compostos Orgânicos/metabolismo , Anaerobiose
6.
Environ Sci Technol ; 53(9): 5369-5377, 2019 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-30912650

RESUMO

In recent years, recovery of rare earth elements (REEs) from coal fly ashes (CFAs) has been considered as a promising resource recovery option. Yet, quantitative information on REE speciation in CFAs and its correlation with REE extractability are not well established. This study systematically investigated the REE speciation-extractability relationship in four representative CFA samples by employing multiple analytical and spectroscopic techniques across the micro to bulk scale and in combination with thermodynamic calculations. A range of REE-bearing phases are identified, such as REE oxides, REE phosphates, apatite, zircon, and REE-bearing glass phase. REEs can occur as discrete particles, as particles encapsulated in the glass phase, or distribute throughout the glass phase. Although certain discrepancies exist on the REE speciation quantified by X-ray adsorption spectroscopy and acid leaching due to intrinsic limitations of each method, both approaches show significant fractions of REE oxides, REE phosphates, apatite, and REE-bearing Fe oxides. This study contributes to an in-depth understanding of the REE speciation-distribution-extractability relationship in CFAs and can help identify uncertainties associated with the quantification of REE speciation. It also provides a general methodology for future studies on REE speciation in complex environmental samples and a knowledge basis for the development of effective REE recovery techniques.


Assuntos
Cinza de Carvão , Metais Terras Raras , Adsorção , Carvão Mineral , Vidro
7.
Environ Sci Technol ; 52(22): 13202-13211, 2018 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-30358985

RESUMO

The kinetics and mechanism of thiol oxidation by Mn oxides undergoing dynamic structural transformation under environmentally relevant conditions remain poorly understood. In this study, thiol/disulfide pair concentrations were simultaneously determined in situ using voltammetric microelectrodes during the interaction of four common thiols (cysteine, homocysteine, cysteamine, and glutathione) with fresh and aged δ-MnO2 at pH 7.0. The reaction kinetics was first order with respect to thiol and zero order with respect to Mn oxides. A transient intermediate sulfur surface species observed during the reaction provides evidence for a mechanism involving two successive one-electron transfer steps. The reaction kinetics of fresh and aged δ-MnO2 was investigated with cysteine and compared to that of manganite, a Mn(III) oxyhydroxide phase. The reactivity of aged δ-MnO2 decreased as a result of structural transformation to cryptomelane but remained higher than that of manganite, suggesting the potential roles of transient Mn(III) surface intermediate in promoting the reduction of Mn(IV) in δ-MnO2 and cryptomelane (compared to Mn(III) in manganite). This study demonstrates the importance of correlating Mn oxide mineral structure and redox reactivity and extends the potential for thiols commonly found in sedimentary environments to be utilized as electron shuttles during dissimilatory Mn reduction.

8.
Environ Sci Technol ; 52(5): 3016-3026, 2018 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-29431994

RESUMO

Phosphorus (P) in animal manures is an important P pool for P recycling and reclamation. In recent years, thermochemical techniques have gained much interests for effective waste treatment and P recycling. This study comparatively characterized the transformation of P during two representative thermochemical treatments (pyrolysis and hydrothermal carbonization, HTC) of four animal manures (swine, chicken, beef, and dairy manures) by combining nuclear magnetic resonance spectroscopy, X-ray absorption spectroscopy, and sequential extraction. For both pyrolysis and HTC treatments, degradation of organic phosphate and crystallization of Ca phosphate minerals were observed and were highly dependent on treatment temperature. Extensive crystallization of Ca phosphate minerals occurred at temperatures above 450 °C during pyrolysis, compared to the lower temperature (175 and 225 °C) requirements during HTC. As a result, P was immobilized in the hydrochars and high temperature pyrochars, and was extracted primarily by HCl. Because Ca is the dominating P-complexing cation in all four manures, all manures showed similar P speciation and transformation behaviors during the treatments. Results from this work provided deeper insights into the thermochemical processes occurred during the pyrolysis and HTC treatments of biological wastes, as well as guidance for P reclamation and recycling from these wastes.

9.
Environ Sci Technol ; 52(3): 1183-1190, 2018 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29359927

RESUMO

Polyphosphates are a group of phosphorus (P) containing molecules that are produced by a wide range of microorganisms and human activities. Although polyphosphates are ubiquitous in aquatic environments and are of environmental significance, little is known about their transformation and cycling. This study characterized the polyphopshate-hydrolysis mechanisms of several representative phosphatase enzymes and evaluated the effects of polyphosphate chain length, light condition, and calcium (Ca2+). 31P nuclear magnetic resonance (NMR) spectroscopy was used to monitor the dynamic changes of P molecular configuration during polyphosphate hydrolysis and suggested a terminal-only degradation pathway by the enzymes. Such mechanism enabled the quantification of the hydrolysis rates by measuring orthophosphate production over time. At the same initial concentration of polyphosphate molecules, the hydrolysis rates were independent of chain length. The hydrolysis of polyphosphate was also unaffected by light condition, but was reduced by the presence of Ca2+. The released orthophosphates formed Ca-phosphate precipitates in the presence of Ca2+, likely in amorphous phases. Results from this study lay the foundation for better understanding the chemical processes governing polyphosphate transport and transformation in various environmental settings.

10.
Water Res ; 132: 260-269, 2018 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-29331913

RESUMO

Thermal and hydrothermal treatments are promising techniques for sewage sludge management that can potentially facilitate safe waste disposal, energy recovery, and nutrient recovery/recycling. Content and speciation of heavy metals in the treatment products affect the potential environmental risks upon sludge disposal and/or application of the treatment products. Therefore, it is important to study the speciation transformation of heavy metals and the effects of treatment conditions. By combining synchrotron X-ray spectroscopy/microscopy analysis and sequential chemical extraction, this study systematically characterized the speciation of Zn and Cu in municipal sewage sludges and their chars derived from pyrolysis (a representative thermal treatment technique) and hydrothermal carbonization (HTC; a representative hydrothermal treatment technique). Spectroscopy analysis revealed enhanced sulfidation of Zn and Cu by anaerobic digestion and HTC treatments, as compared to desulfidation by pyrolysis. Overall, changes in the chemical speciation and matrix properties led to reduced mobility of Zn and Cu in the treatment products. These results provide insights into the reaction mechanisms during pyrolysis and HTC treatments of sludges and can help evaluate the environmental/health risks associated with the metals in the treatment products.


Assuntos
Cobre/química , Esgotos/química , Zinco/química , Carbono/química , Microanálise por Sonda Eletrônica , Eliminação de Resíduos , Eliminação de Resíduos Líquidos/métodos , Espectroscopia por Absorção de Raios X
11.
Zhonghua Wei Chang Wai Ke Za Zhi ; 20(11): 1263-1268, 2017 Nov 25.
Artigo em Chinês | MEDLINE | ID: mdl-29178096

RESUMO

OBJECTIVE: To determine the incidence, risk factors and clinical outcomes of postoperative delirium in colorectal cancer patients over 60 years. METHODS: Consecutive 382 patients older than 60 years undergoing colorectal cancer surgery at Shenzhen Second People's Hospital from June 2013 to June 2016 were recruited prospectively in this study. These patients were evaluated daily after surgery for 7 days by confusion assessment method. Clinical outcomes were compared between patients with and without postoperative delirium, including postoperative complications, length of hospital stay, and mortality within 30 days. Logistic regression analysis was used to identify independent predictors of postoperative delirium. RESULTS: There were 230 male and 152 female patients with median age of 67(range 60 to 92) years. Among them, 213 had colon cancer and 169 had rectal cancer. Postoperative delirium developed in 46(12.0%) patients, and most deliriums (78.3%) were diagnosed within 3 days after surgery. Patients with postoperative delirium had more complications [30.4%(14/46) vs. 17.3%(58/336), P=0.032], higher mortality [6.5%(3/46) vs. 1.8%(6/336), P=0.047], and longer postoperative hospital stay (median 14 days vs. 9 days, P=0.008). Univariate analysis revealed that advanced age, male, higher Charlson comorbidity index, higher American Society of Anesthesiologists Classification, lower preoperative blood albumin concentration, history of psychiatric disease, history of cerebrovascular disease, alcohol abuse, emergent operation, and perioperative blood transfusion were significantly related to the development of postoperative delirium. Logistic regression analysis identified that advanced age (OR=1.06, 95%CI: 1.01 to 1.13), history of psychiatric disease (OR=10.89, 95%CI: 2.73 to 41.59) and perioperative blood transfusion (OR=2.37, 95%CI: 1.11 to 7.32) were independent risk factors of postoperative delirium. CONCLUSIONS: Postoperative delirium is relatively common in elderly patients over 60 years undergoing colorectal cancer surgery. The high morbidity of postoperative complication and mortality associated with postoperative delirium warrant implementation of preoperative risk assessment and postoperative screening protocol for postoperative delirium. Comprehensively preventive strategies should be carried out for high-risk patients, e.g. advanced age, history of psychiatric disease, and perioperative blood transfusion.


Assuntos
Neoplasias Colorretais/cirurgia , Delírio , Complicações Pós-Operatórias , Idoso , Idoso de 80 Anos ou mais , Neoplasias do Colo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Risco
12.
Nat Commun ; 8(1): 1590, 2017 11 17.
Artigo em Inglês | MEDLINE | ID: mdl-29150598

RESUMO

The chromium (Cr) isotope system has emerged as a potential proxy for tracing the Earth's atmospheric evolution based on a redox-dependent framework for Cr mobilization and isotope fractionation. Although studies have demonstrated that redox-independent pathways can also mobilize Cr, no quantitative constraints exist on the associated isotope fractionations. Here we survey the effects of common environmental ligands on the dissolution of Cr(III)-(oxy)hydroxide solids and associated Cr isotope fractionation. For a variety of organic acids and siderophores, δ53Cr values of dissolved Cr(III) are -0.27 to 1.23‰, within the range of previously observed Cr isotope signatures in rock records linked to Cr redox cycling. Thus, ligand-promoted dissolution of Cr-containing solids, a redox-independent process, must be taken into account when using sedimentary Cr isotope signatures to diagnose atmospheric oxygen levels. This work provides a step towards establishing a more robust framework for using Cr isotopes to track the evolution of the Earth's atmosphere.

13.
Environ Sci Technol ; 51(18): 10284-10298, 2017 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-28876917

RESUMO

Phosphorus (P) is an essential nutrient for all organisms, thus playing unique and critical roles at the food-energy-water nexus. Most P utilized by human activities eventually converges into various solid biowastes, such as crop biomass, animal manures, and sewage sludges. Therefore, integration of efficient P recovery practices into solid biowaste management will not only significantly reduce the dependence on limited geological P resources but also reduce P runoff and related water contamination issues associated with traditional waste management strategies. This study reviews the applications of (hydro)thermal techniques for the treatment of solid biowastes, which can greatly facilitate P recovery in addition to waste volume reduction, decontamination, and energy recovery. Research showed that P speciation (including molecular moiety, complexation state, and mineralogy) can experience significant changes during (hydro)thermal treatments, and are impacted by treatment techniques and conditions. Changes in P speciation and overall properties of the products can alter the mobility and bioavailability of P, and subsequent P reclamation and recycling efficiency of the treatment products. This review summarizes recent progresses in this direction, identifies the challenges and knowledge gaps, and provides a foundation for future research efforts targeting at sustainable management of nutrient-rich biowastes.


Assuntos
Fósforo , Reciclagem , Esgotos , Agricultura , Animais , Humanos , Esterco , Gerenciamento de Resíduos
14.
Environ Sci Process Impacts ; 19(6): 793-811, 2017 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-28488712

RESUMO

Quartz crystal microbalances (QCMs) provide a new analytical opportunity and prospect to characterize many environmental processes at solid/liquid interfaces, thanks to their almost real-time measurement of physicochemical changes on their quartz sensor. This work reviews the applications of QCMs in probing the interactions of organic molecules, nanomaterials (NMs) and microbes with solid surfaces. These interfacial interactions are relevant to critical environmental processes such as biofilm formation, fate and transport of NMs, fouling in engineering systems and antifouling practices. The high sensitivity, real-time monitoring, and simultaneous frequency and dissipation measurements make QCM-D a unique technique that helps reveal the interaction mechanisms for the abovementioned processes (e.g., driving forces, affinity, kinetics, and the interplay between surface chemistry and solution chemistry). On the other hand, QCM measurement is nonselective and spatially-dependent. Thus, caution should be taken during data analysis and interpretation, and it is necessary to cross-validate the results using complementary information from other techniques for more quantitative and accurate interpretation. This review summarizes the general methodologies for collecting and analyzing raw QCM data, as well as for evaluating the associated uncertainties. It serves to help researchers gain deeper insights into the fundamentals and applications of QCMs, and provides new perspectives on future research directions.


Assuntos
Biofilmes/crescimento & desenvolvimento , Monitoramento Ambiental/métodos , Nanoestruturas/análise , Compostos Orgânicos/análise , Técnicas de Microbalança de Cristal de Quartzo , Quartzo/química , Adsorção , Animais , Técnicas Biossensoriais , Humanos , Cinética , Modelos Teóricos , Propriedades de Superfície
15.
Environ Sci Technol ; 51(6): 3250-3259, 2017 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-28244747

RESUMO

Iron oxides are important structural and biogeochemical components of soils that can be strongly altered by redox-driven processes. This study examined the influence of temporal oxygen variations on Fe speciation in soils from the Luquillo Critical Zone Observatory (Puerto Rico). We incubated soils under cycles of oxic-anoxic conditions (τoxic:τanoxic = 1:6) at three frequencies with and without phosphate addition. Fe(II) production, P availability, and Fe mineral composition were monitored using batch analytical and spectroscopic techniques. The rate of soil Fe(II) production increased from ∼3 to >45 mmol Fe(II) kg-1 d-1 over the experiment with a concomitant increase of an Fe(II) concentration plateau within each anoxic period. The apparent maximum in Fe(II) produced is similar in all treatments, but was hastened by P-amendment. Numerical modeling suggests the Fe(II) dynamics can be explained by the formation of a rapidly reducible Fe(III) phases derived from the progressive dissolution and re-oxidation of native Fe(III) oxides accompanied by minor increases in Fe reducer populations. The shift in Fe(III) reactivity is evident from Fe-reducibility assays using Shewanella sp., however was undetectable by chemical extractions, Mössbauer or X-ray Absorption spectroscopies. More broadly, our findings suggest Fe reduction rates are strongly coupled to redox dynamics of the recent past, and that frequent shifts in redox conditions can prime a soil for rapid Fe-reduction.


Assuntos
Compostos Férricos/química , Solo/química , Florestas , Ferro/química , Oxirredução
16.
Chemosphere ; 176: 255-265, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28273533

RESUMO

The fate and toxicity of zinc oxide nanoparticles (ZnO NPs) in nature are affected by solution chemistry such as pH, anions, and natural organic matter (NOM). Inorganic polyphosphates are environmentally ubiquitous phosphorus (P) species that may change the speciation and environmental fate of ZnO NPs. In this study, the interactions of polyphosphates with ZnO NPs and the impacts on ZnO NP dissolution and transformation were investigated and compared with orthophosphate (P1). The results revealed that pyrophosphate (P2), tripolyphosphate (P3), and hexametaphosphate (P6) enhanced whereas P1 inhibited the dissolution of ZnO NPs. In addition, P1, P2, and P3 promoted the transformation of ZnO NPs into zinc phosphate (Zn-P) precipitates via interactions with dissolved Zn2+. However, P6-promoted ZnO NP dissolution was through the formation of soluble Zn-P complexes due to the strong capability of P6 to chelate with Zn2+. The transformation of ZnO NPs in the presence of P3 was affected by reaction time, pH, and P/Zn molar ratio. P3 first formed inner-sphere surface complexes on ZnO NPs, which gradually transformed into crystalline Zn2HP3O10(H2O)6 precipitates. This study provided a new perspective for understanding the reactivity of various forms of inorganic phosphate species with ZnO NPs in the natural environment.


Assuntos
Precipitação Química , Nanopartículas/química , Fosfatos/química , Polifosfatos/química , Óxido de Zinco/química , Solubilidade , Compostos de Zinco
17.
Environ Sci Technol ; 51(6): 3223-3232, 2017 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-28218537

RESUMO

The role of microbial activities on the transformation of chromium (Cr) remediation products has generally been overlooked. This study investigated the stability of Cr(III)-Fe(III)-(oxy)hydroxides, common Cr(VI) remediation products, with a range of compositions in the presence of common microbial exudates, siderophores and small organic acids. In the presence of a representative siderophore, desferrioxamine B (DFOB), iron (Fe) was released at higher rates and to greater extents relative to Cr from all solid phases. The presence of oxalate alone caused the release of Cr, but not of Fe, from all solid phases. In the presence of both DFOB and oxalate, oxalate acted synergistically with DFOB to increase the Fe, but not the Cr, release rate. Upon reaction with DFOB or DFOB + oxalate, the remaining solids became enriched in Cr relative to Fe. Such incongruent dissolution led to solid phases with different compositions and increased solubility relative to the initial solid phases. Thus, the presence of microbial exudates can promote the release of Cr(III) from remediation products via both ligand complexation and increased solid solubility. Understanding the potential reaction kinetics and pathways of Cr(VI) remediation products in the presence of microbial activities is necessary to assess their long-term stability.


Assuntos
Cromo , Sideróforos , Compostos Férricos , Hidróxidos , Ferro , Oxirredução , Solubilidade
18.
Water Res ; 100: 439-447, 2016 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-27232988

RESUMO

(Hydro)thermal treatments of sewage sludge is a promising option that can simultaneously target safe waste disposal, energy recovery, and nutrient recovery/recycling. The speciation of phosphorus (P) in sludge is of great relevance to P reclamation/recycling and soil application of sludge-derived products, thus it is critical to understand the effects of different treatment techniques and conditions on P speciation. This study systematically characterized P speciation (i.e. complexation and mineral forms) in chars derived from pyrolysis and hydrothermal carbonization (HTC) of municipal sewage sludges. Combined sequential extraction and P K-edge X-ray absorption near edge structure (XANES) spectroscopy analysis revealed the dependence of P transformation on treatment conditions and metal composition in the feedstocks. Pyrolysis of sludges decreased the relative abundance of phytic acid while increased the abundance of Al-associated P. HTC thoroughly homogenized and exposed P for interaction with various metals/minerals, with the final P speciation closely related to the composition/speciation of metals and their affinities to P. Results from this study revealed the mechanisms of P transformation during (hydro)thermal treatments of sewage sludges, and might be applicable to other biosolids. It also provided fundamental knowledge basis for the design and selection of waste management strategies for better P (re)cycling and reclamation.


Assuntos
Fósforo , Esgotos/química , Reciclagem , Solo/química , Espectroscopia por Absorção de Raios X
19.
Environ Sci Technol ; 50(5): 2389-95, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26836650

RESUMO

As an important component of soil organic matter (SOM), the transformation of pyrogenic carbon plays a critical role in the biogeochemical cycles of carbon and other redox-active elements such as iron (Fe). Herein, we studied the influences of wheat straw-derived biochars on the microbial reduction of 100 mM of hematite by the dissimilatory metal reducing bacteria Shewanella oneidensis MR-1 under anoxic conditions. The long-term microbial reduction extent and initial reduction rate of hematite were accelerated by more than 2-fold in the presence of 10 mg L(-1) biochar. Soluble leachate from 10 mg L(-1) biochar enhanced Fe(III) reduction to a similar degree. Microbially prereduced biochar leachate abiotically reduced hematite, consistent with the apparent electron shuttling capacity of biochar leachate. Electron paramagnetic resonance (EPR) analysis suggested that biochar leachate-associated semiquinone functional groups were likely involved in the redox reactions. In addition to electron shuttling effects, biochar particles sorbed 0.5-1.5 mM biogenic Fe(II) and thereby increased the long-term extent of hematite reduction by 1.4-1.7 fold. Our results suggest that Fe redox cycling may be strongly impacted by pyrogenic carbon in soils with relatively high content of indigenous pyrogenic carbon or substantial application of biochar.


Assuntos
Carvão Vegetal/metabolismo , Compostos Férricos/metabolismo , Shewanella/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Transporte de Elétrons , Meio Ambiente , Ferro/química , Oxirredução , Solubilidade , Temperatura Ambiente
20.
Environ Sci Technol ; 49(24): 14466-74, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26633236

RESUMO

(Hydro)thermal treatments of sewage sludge from wastewater treatment process can significantly reduce waste volume and transform sludge into valuable products such as pyrochar and hydrochar. Given the global concern with phosphorus (P) resource depletion, P recycling/reclamation from or direct soil application of the derived chars can be potential P recycling practices. In order to evaluate P recyclability as well as the selection and optimization of treatment techniques, it is critical to understand the effects of different treatment techniques and conditions on P speciation and distribution. In the present study, we systematically characterized P speciation in chars derived from thermal (i.e., pyrolysis) and hydrothermal treatments of municipal sewage sludge using complementary chemical extraction and nuclear magnetic resonance (NMR) spectroscopy methods. P species in the raw activated sludge was dominated by orthophosphate and long-chain polyphosphates, whereas increased amounts of pyrophosphate and short-chain polyphosphates formed after pyrolysis at 250-600 °C. In contrast, hydrothermal treatments resulted in the production of only inorganic orthophosphate in the hydrochar. In addition to the change of molecular speciation, thermal treatments also altered the physical state and extractability of different P species in the pyrochars from pyrolysis, with both total P and polyphosphate being less extractable with increasing pyrolysis temperature. Results from this study suggest that P speciation and availability in sludge-derived chars are tunable by varying treatment techniques and conditions, and provide fundamental knowledge basis for the design and selection of waste management strategies for better nutrient (re)cycling and reclamation.


Assuntos
Fósforo/análise , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Fracionamento Químico , Espectroscopia de Ressonância Magnética , Fósforo/química , Polifosfatos/química , Reciclagem , Temperatura Ambiente , Águas Residuárias/química
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