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1.
Bioresour Technol ; 326: 124786, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33548818

RESUMO

In order to compare the effect of different mechanical-chemical coupling treatment on wheat straw and provide guidance for the subsequent preparation of cellulose nanomaterials, this paper systematically explored the impact of different scale mechanical fragmentation coupling various NaOH concentration treatment on the lignocellulosic components, micromorphology and cellulose crystal structure of wheat straw. The results showed that the relationship between hemicellulose and lignin removal with NaOH concentration can be expressed as exponential function Y = ai(1-exp(-biX)), and micro-nano-scale ball-milling coupling NaOH treatment can facilitate the removal of hemicellulose and lignin. Micromorphology analysis found that wet ball milling coupling NaOH one-step treatment can disintegrate cellulose fiber into crosslinked network structure of cellulose microfibrils. XRD results indicated that wet ball milling with NaOH solution was contributed to retaining cellulose crystal structure and conducive to cellulose crystalline transformation. In conclusion, wet ball milling coupling NaOH simultaneous treatment can be a promising pretreatment for cellulose nanomaterials preparation.


Assuntos
Celulose , Triticum , Hidrólise , Lignina , Hidróxido de Sódio
2.
Water Sci Technol ; 83(4): 975-984, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33617502

RESUMO

To improve the adsorption efficiency of layered double hydroxides (LDHs) for heavy metals, a novel sodium alginate (SA) intercalated MgAl-LDH (SA-LDH) was synthesized in this work. SA-LDH was characterized by XRD, FTIR, XPS and employed as adsorbent for Cd(II), Pb(II), Cu(II) elimination. Adsorbent dosage, initial pH and contact time, which are regarded as several key parameters, were optimized. The results showed that SA-LDH exhibited better adsorption performance compared with the pristine MgAl-LDH. The maximum adsorption capacities of SA-LDH for Cu(II), Pb(II) and Cd(II) reached 0.945, 1.176 and 0.850 mmol/g, respectively. The possible mechanisms were analyzed by XPS, XRD and FTIR. The results showed that Cd(II), Pb(II) and Cu(II) may be removed by SA-LDH via (i) bonding or complexation with Sur-OH or Sur-O- of SA-LDH, (ii) precipitation of metal hydroxides or carbonates, (iii) isomorphic substitution, and (iv) chelation with -COO- in the interlayers. This work provides an effective method for the development of LDH-based adsorbent and the treatment of wastewater containing heavy metals.


Assuntos
Cádmio , Poluentes Químicos da Água , Adsorção , Alginatos , Hidróxidos , Chumbo , Hidróxido de Sódio
3.
Food Chem ; 348: 129053, 2021 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-33508600

RESUMO

A combination of switchable-hydrophilicity liquid-liquid microextraction prior to magnetic nanoparticle-based dispersive solid-phase microextraction is proposed for the determination of erythrosine using UV/Vis spectrophotometry at 520 nm. Under optimum conditions (i.e., 1.0 mL octylamine as the extraction solvent, 1.5 mL of 10.0 M sodium hydroxide as the phase separation trigger, pH 4.0, 750 µL of acetone as the eluent, 10.0 mg of Fe3O4@XAD-16 as the adsorbent, and 15.0 mL of the sample solution), the method showed a superior analytical performance with limits of detection less than 25.9 ng mL-1, limits of quantitation less than 86.3 ng mL-1 and linear dynamic ranges ranging between 86.3 and 1000 ng mL-1. Percentage relative standard deviations were less than 4.1 and 7.2% for intra-day and inter-day, respectively. The method was successfully applied for the extraction and determination of erythrosine in food samples and other consumer products with recoveries in the range of 94.6-103.9% and within extraction time of 7.8 min per sample.


Assuntos
Eritrosina/análise , Eritrosina/isolamento & purificação , Análise de Alimentos/métodos , Microextração em Fase Líquida/métodos , Nanopartículas de Magnetita/química , Microextração em Fase Sólida/métodos , Solventes/química , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Hidróxido de Sódio/química , Espectrofotometria
4.
Carbohydr Polym ; 255: 117383, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33436212

RESUMO

Cellulose nanofibrils were efficiently produced from eucalyptus fibers using a combined NaOH and enzymatic treatment followed by a pilot scale grinding process. The structural changes of fibers were assessed after NaOH treatments at 5, 10 and 15 wt% concentrations. A progressive shift from a cellulose I to a cellulose II crystalline structure was observed with X-ray diffraction (XRD) and nuclear magnetic resonance (NMR). The further enzymatic hydrolysis was improved for the NaOH treated samples. The increase of crystallinity indices due to enzymatic hydrolysis was of + 4.7 %, + 3.5 %, and +10.3 % for samples treated with NaOH 5, 10 and 15 wt% respectively, and DP values were drastically reduced to 340, 190 and 166 respectively. A morphological analysis underlined an optimum with the combination of NaOH 10 wt% and enzymatic hydrolysis. This treatment followed by the grinding process resulted in CNF with a rigid structure, with diameters ranging from 10 to 20 nm and lengths between 150 and 350 nm. A multi-scale analysis enabled to study the impact of this combined treatment on CNF properties and energy consumption. A decrease in mechanical properties of nanopapers was observed for the combined treatment and NaOH treatment alone compared to enzymatic hydrolysis alone, with Young's modulus of 8.94, 4.84 and 11.21 GPa respectively. However, optical properties were improved, with transmittance values of 42.2, 15.4 and 7.1 % respectively. This new pretreatment can therefore lead to CNF with tunable properties depending on the application, with possible industrialization thanks to the reduction of energy needs.


Assuntos
Celulose/química , Eucalyptus/química , Nanofibras/química , Hidróxido de Sódio/química , Biomassa , Cristalização , Módulo de Elasticidade , Hidrólise , Teste de Materiais/métodos , Nanofibras/ultraestrutura
5.
Carbohydr Polym ; 255: 117502, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33436255

RESUMO

Agrocybe cylindracea is a common source of active polysaccharides, but their fine structures are not clearly elucidated. In the present study, four fractions were purified from the alkaline extract of A. cylindracea (JACP), and their chemical components and structures were compared by HPAEC-PAD, methylation combined with GC-MS, and 1D/2D NMR analysis. Results showed the purified fractions' physicochemical properties, including monosaccharide compositions, molecular weights, viscosities and surface morphology considerably varied. JACP-30 was identified as a fucoglucogalactan with a α-(1 → 6)-galactopyranosyl as main chain. JACP-50p and JACP-80r were characterized as ß-(1 → 6)-glucans with side chains composed of terminal and 3-substituted ß-glucopyranosyl residues attached at O-3 for every three residues. Similarly, the backbone of JACP-80 was ß-(1 → 6)-linked glucopyranosyl and ß-(1 → 3,6)-linked glucopyranosyl residues at a ratio of 4:1. This work provides more information to the understanding of polysaccharides from A. cylindracea, further guiding its biological researches and developing the application in food and biomedicine industries.


Assuntos
Agrocybe/química , Polissacarídeos Fúngicos/química , Extração Líquido-Líquido/métodos , Monossacarídeos/química , beta-Glucanas/química , Sequência de Carboidratos , Polissacarídeos Fúngicos/classificação , Polissacarídeos Fúngicos/isolamento & purificação , Humanos , Metilação , Peso Molecular , Monossacarídeos/classificação , Monossacarídeos/isolamento & purificação , Hidróxido de Sódio/química , beta-Glucanas/classificação , beta-Glucanas/isolamento & purificação
7.
Bioresour Technol ; 325: 124677, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33493745

RESUMO

Waste activated sludge generated from wastewater treatment plants makes an abundant source of biomass. Its effective utilization through anaerobic digestion (AD) requires pretreatment to disintegrate the sludge matrix and increase organic matter availability. In this study, dewatered waste activated sludge (DWAS) was subjected to alkaline, photocatalytic, and alkaline-photocatalytic pretreatment for its disintegration and subsequent methane production using different concentrations of sodium hydroxide and titania nanoparticles. Individual pretreatment resulted in maximum disintegration degree (DDsCOD) of 11.3 and 5.2% at 0.8% NaOH and 0.6 gTiO2/L, respectively. Alkaline-photocatalytic pretreatment yielded 37% DDsCOD at 0.8% NaOH-0.4 g/L TiO2. As compared to control, AD at 0.4% NaOH and 0.5 g/L TiO2 pretreatments yielded maximum methane, which was 50.4 and 32.6% higher. Similarly, alkaline-photocatalytic pretreatment at 0.4% NaOH-0.5 g/L TiO2 yielded methane as 462 N mL/g VS, which was 71.1% higher. Modified Gompertz model fitted the methane yield data well.


Assuntos
Esgotos , Purificação da Água , Anaerobiose , Metano , Hidróxido de Sódio , Eliminação de Resíduos Líquidos
8.
ACS Appl Mater Interfaces ; 13(2): 3186-3198, 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-33398989

RESUMO

Mesoscaled assemblies are organized in native collagen tissues to achieve remarkable and diverse performance and functions. In this work, a facile, low-cost, and controllable liquid exfoliation method was applied to directly extract these collagen mesostructures from bovine Achilles tendons using a sodium hydroxide (NaOH)/urea aqueous system with freeze-thaw cycles and sonication. A series of collagen fibrils with diameters of 26-230 nm were harvested using this process, and in situ observations under polarizing microscopy (POM) and using molecular dynamics simulations revealed the influence of the NaOH/urea system on the tendon collagen. FTIR and XRD results confirmed that these collagen fibrils preserved typical structural characteristics of type I collagen. These isolated collagen fibrils were then utilized as building blocks to fabricate free-standing collagen membranes, which exhibited good stability in solvents and outstanding mechanical properties and transparency, with potential for utility in optical and electronic sensors. Moreover, in vitro and vivo evaluations demonstrated that these new resulting collagen membranes had good cytocompatibility, biocompatibility, and degradability for potential applications in biomedicine. This work provides a new approach for collagen processing by liquid exfoliation with utility for the formation of robust collagen materials that consist of native collagen mesostructures as building blocks.


Assuntos
Tendão do Calcâneo/química , Materiais Biocompatíveis/química , Colágeno/química , Membranas Artificiais , Animais , Bovinos , Linhagem Celular , Colágeno/ultraestrutura , Feminino , Congelamento , Camundongos , Ratos Sprague-Dawley , Hidróxido de Sódio/química , Sonicação , Resistência à Tração , Ureia/química
9.
Food Chem ; 340: 128185, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33010647

RESUMO

In this study, sodium tripolyphosphate (STP) and tetrasodium pyrophosphate (TSPP) were utilized to modify duck egg white protein (EWP). The phosphorylated EWP was prepared as egg white gel (EWG) by adding sodium hydroxide. The phosphorus content of EWP reached 2.18 mg/g and 2.07 mg/g with the addition of STP and TSPP, respectively, after 2 h phosphorylation. The average particle size, absolute zeta potential value, and surface hydrophobicity of EWP increased significantly during phosphorylation. FTIR results indicate that phosphorylation reduced the random structure and α-helical content while increasing the content of ß-sheets and ß-turn. The mechanical and rheological properties of EWG decreased obviously after phosphorylation. A three-dimensional porous network microstructure was formed, and the gel with added TSPP had larger pores. Adding STP and TSPP to EWG weakened its salt and solvent sensitivity. The findings provide a direction for the exploration of gel properties after protein modification.


Assuntos
Álcalis/química , Patos , Proteínas do Ovo/química , Animais , Difosfatos/química , Géis , Interações Hidrofóbicas e Hidrofílicas , Tamanho da Partícula , Fosforilação , Reologia , Cloreto de Sódio/química , Hidróxido de Sódio/química
10.
Environ Pollut ; 270: 116244, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33321433

RESUMO

This study investigated the competitive adsorption mechanisms of pharmaceuticals (i.e., naproxen, diclofenac, and ibuprofen) toward the pristine and NaOH-activated biochars from spent coffee wastes (SCW) in lake water and wastewater effluent. The kinetic and isotherm studies revealed that the improved physicochemical characteristics and physically homogenized surfaces of the pristine SCW biochar through the chemical activation with NaOH were beneficial to the adsorption of pharmaceuticals (competitive equilibrium adsorption capacity (Qe, exp): NaOH-activated SCW biochar (61.25-192.07 µmol/g) > pristine SCW biochar (14.81-20.65 µmol/g)). The adsorptive removal of naproxen (Qe, exp = 14.81-18.81 µmol/g), diclofenac (Qe, exp = 15.73-20.00 µmol/g), and ibuprofen (Qe, exp = 16.20-20.65 µmol/g) for the pristine SCW biochar showed linear correlations with their hydrophobicity (log D at pH 7.0: ibuprofen (1.71) > diclofenac (1.37) > naproxen (0.25)). However, their Qe, exp values for the NaOH-activated SCW biochar (naproxen (176.39-192.07 µmol/g) > diclofenac (78.44-98.74 µmol/g) > ibuprofen (61.25-80.02 µmol/g)) were inversely correlated to the order of their log D values. These results suggest that the reinforced aromatic structure of the NaOH-activated SCW biochar facilitated the π-π interaction. The calculated thermodynamic parameters demonstrated that the competitive adsorption of pharmaceuticals on the NaOH-activated SCW biochar compared to pristine SCW biochar occurred more spontaneously over the entire pH (5.0-11.0) and ionic strength (NaCl: 0-0.125 M) ranges. These observations imply that the NaOH-activated SCW biochar might be potentially applicable for the removal of pharmaceuticals in lake water and wastewater effluent.


Assuntos
Preparações Farmacêuticas , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Café , Interações Hidrofóbicas e Hidrofílicas , Lagos , Hidróxido de Sódio , Águas Residuárias , Água , Poluentes Químicos da Água/análise
11.
Chemosphere ; 262: 127940, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182111

RESUMO

Sodium hydroxide treated rice hulls were investigated to preconcentrate, remove, and recover metal ions including Be2+, Al3+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Sr2+, Ag+, Cd2+, Ba2+, and Pb2+ in both batch mode and column mode. Sodium hydroxide treatment significantly improved the removal efficiency for all metal ions of interest compared to the untreated rice hull. The removal kinetics were extremely fast for Co, Ni, Cu, Zn, Sr, Cd, and Ba, which made the treated rice hull a promising economic green adsorbent to preconcentrate, remove, and recover low-level metal ions in column mode at relatively high throughput. The principal removal mechanism is believed to be the electrostatic attraction between the negatively charged rice hulls and the positively charged metal ions. pH had a drastic impact on the removal for different metal ions and a pH of 5 worked best for most of the metal ions of interest. Processed rice hulls provide an economic alternative to costly resins that are currently commercially available products designed for metal ion preconcentration for trace metal analysis, and more importantly, for toxic heavy metal removal and recovery from the environment.


Assuntos
Metais Pesados/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Íons , Cinética , Oryza , Hidróxido de Sódio , Água
12.
Bioresour Technol ; 319: 124171, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33039842

RESUMO

The effect of NaOH catalytic ethanol pretreatment under various temperatures (130-180 °C) and time (15-90 min) on the chemical composition and enzymatic saccharification of sugarcane bagasse was investigated in this study. The results showed that NaOH catalytic ethanol pretreatment assisted delignification and the reservation of cellulose and hemicellulose. When sugarcane bagasse was pretreated at 180 °C for 30 min, a substantial glucose yield of 91.6% was obtained after hydrolysis for 72 h, representing 94.6% of glucose in pretreated residue. This yield was promoted with respect to the compositional change and surface alteration of pretreated substrate. With the supplement of Tween 80, the enzyme usage would be saved by 50% and the enzymolysis time could be shortened to 24 h while obtaining comparable glucose yield. This study provided an economical feasible and gradual process for the generation of glucose, which was followed by fermentation and conversion to platform chemicals.


Assuntos
Saccharum , Celulose , Etanol , Hidrólise , Hidróxido de Sódio , Tensoativos
13.
Water Sci Technol ; 82(9): 1932-1949, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33201856

RESUMO

In this study, activated carbon (AC) was prepared from agro-waste betel nut husks (BNH) through the chemical activation method. Different characterization techniques described the physicochemical nature of betel nut husks activated carbon (BNH-AC) through Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and pH point of zero charge. Later, the produced AC was used for methylene blue (MB) adsorption via numerous batch experimental parameters: initial concentrations of MB dye (25-250 mg/L), contact time (0.5-24 hours) and initial pH (2-12). Dye adsorption isotherms were also assessed at three temperatures where the maximum adsorption capacity (381.6 mg/g) was found at 30 °C. The adsorption equilibrium data were best suited to the non-linear form of the Freundlich isotherm model. Additionally, non-linear pseudo-second-order kinetic model was better fitted with the experimental value as well. Steady motion of solute particles from the boundary layer to the BNH-AC's surface was the possible reaction dynamics concerning MB adsorption. Thermodynamic study revealed that the adsorption process was spontaneous and exothermic in nature. Saline water emerged as an efficient eluent for the desorption of adsorbed dye on AC. Therefore, the BNH-AC is a very promising and cost-effective adsorbent for MB dye treatment and has high adsorption capacity.


Assuntos
Azul de Metileno , Poluentes Químicos da Água , Adsorção , Areca , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Azul de Metileno/análise , Hidróxido de Sódio , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Poluentes Químicos da Água/análise
14.
J Environ Manage ; 276: 111272, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32871466

RESUMO

In this study, carbonized material was produced using sodium hydroxide treated Sugar cane bagasse (SB), and synthesized materials ware used to prepare Sodium Alginate/SBAC composite beads which were further used as an adsorbent to remove malachite green dye (MG) present in water. Physiochemical characteristics of composite beads were analyzed using FTIR, SEM, TGA, and BET. Adsorption equilibrium data showed excellent fit to the Freundlich model (R2 = 0.994) than to the Langmuir model (R2 = 0.925). Adsorption kinetics study indicated that the MG removal process would be better described by the pseudo-second-order kinetic model. The thermodynamic study suggested the spontaneous and endothermic nature of MG adsorption. By using response surface methodology, the optimum conditions for MG adsorption on composite beads were found to be 115.43 min, 0.3 g/L and pH 8 for contact time, adsorbent mass, and pH respectively and MG adsorption efficiency was 97.88%. The fixed-bed column data were evaluated using several kinetic models and among them, Thomas model showed the best agreement with investigation results. These results revealed that synthesized composite beads have a high affinity toward MG and it could be reasonable, eco-friendly adsorbent for dye removal from wastewater.


Assuntos
Saccharum , Poluentes Químicos da Água , Adsorção , Alginatos , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Corantes de Rosanilina , Hidróxido de Sódio
15.
J Chromatogr A ; 1627: 461390, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823096

RESUMO

A dispersive solid phase extraction method was combined with deep eutectic solvent-based solidification of floating organic drop-dispersive liquid-liquid microextraction and used for the extraction/preconcentration of some organophosphorus pesticides residues from edible oil samples. The extracted analytes were quantified with gas chromatography-nitrogen phosphorous detector. In this procedure, the sample lipids are saponified with a sodium hydroxide solution and then the analytes are adsorbed onto a primary secondary amine sorbent. After that the analytes are desorbed with acetone as an elution/dispersive solvent and mixed with choline chloride: 3,3-dimethyl butyric acid deep eutectic solvent and the mixture is rapidly dispersed into deionized water. Then, the obtained cloudy solution is centrifuged and placed into an ice bath. The extraction solvent is solidified on the top of the solution. Finally, it is removed and dissolved in acetonitrile, and 1 µL of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.06-0.24 and 0.20-0.56 ng mL-1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 170-192 and 68-77%, respectively. The method had an acceptable precision with relative standard deviations less than ≤9.2% for intra- (n=6) and inter-day (n=6) precisions at four concentrations (3, 10, 50, and 250 ng mL-1, each analyte). Finally the method was used for determination of the analytes in five edible oil samples.


Assuntos
Microextração em Fase Líquida/métodos , Compostos Organofosforados/análise , Praguicidas/análise , Óleos Vegetais/química , Extração em Fase Sólida/métodos , Solventes/química , Acetonitrilos/química , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Soluções , Sonicação , Fatores de Tempo
16.
J Chromatogr A ; 1626: 461350, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797830

RESUMO

In ionexchange chromatography, the pH gradient mode becomes more and more popular today for the analysis of therapeutic proteins as this mode can provide higher or alternative selectivity to the commonly used salt gradient mode. Ideally, a linear pH response is expected when performing linear gradients. However up to now, only a very few buffer systems have been developed and are commercially available which can perform nearly linear pH responses when flowing through a given column. It is also known that a selected buffer system (mobile phase) can work well on one column but can fail on other column. The goal of this study was to practically evaluate the effects that ionexchange columns (weak and strong exchangers) might have on effluent pH, when performing linear pH gradient separations of therapeutic monoclonal antibodies. To attain this objective, the pH was monitored on-line at the column outlet using a specific setup. To make comprehensive observations of the phenomenon, four different mobile phase conditions and five cation exchange columns (weak and strong exchangers) were employed. The obtained pH responses were systematically compared to responses measured in the absence of the columns. From this work, it has become clear that both the column and mobile phase can have significant effects on pH gradient chromatography and that their combination must be considered when developing a new method. Phase systems (column + mobile phase) providing linear pH responses are indeed the most suitable for separating mAbs with different isoelectric points and, with them, it is possible to elute mAbs across wide retention time ranges and with high selectivity.


Assuntos
Cromatografia por Troca Iônica/métodos , Anticorpos Monoclonais/análise , Cátions/química , Ácido Cítrico/química , Concentração de Íons de Hidrogênio , Troca Iônica , Força Próton-Motriz , Hidróxido de Sódio/química , Taurina/análogos & derivados , Taurina/química
17.
PLoS One ; 15(8): e0237612, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32790731

RESUMO

Seventeen glass vessels and twenty glass beads recovered from the excavations at the ancient city of Malindi and the archaeological site of Mambrui in Kenya, east Africa were analysed using electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results show that all of the glass samples are soda-lime-silica glass. They belong to the high alumina -plant ash glass type, characterised by high alumina and relatively low calcium contents, widely distributed in eastern (10th- 16th centuries AD) and southern Africa (13th - 15th centuries AD), Central Asia (9th- 14th centuries AD) and southeast Asia (12th- 13th centuries AD), made with plant ashes and sands. This is an understudied glass type for which previous research has indicated there were three types. When compared with published research on such glasses using Zr, Ti, Ba, Cr, La, Li, Cs, Na2O, MgO and CaO we have identified at least four different compositional groups of v-Na-Al glass: Types A, B, C and D. By comparing the results with contemporary v-Na-Al glass vessels and beads from Central Asia, Africa, and southeast Asia we show that most of the Malindi and Mambrui glass share similar characteristics to the compositions of Mapungubwe Oblate and some of the Madagascar glass beads from southern Africa. They belong to Type A v-Na-Al glass which is characterised by an elevated level of Ti and Ba and a relatively high ratios of Cr/La, relatively low Zr concentrations and low ratios of Zr/Ti. Differences in Zr, Li, MgO and Na2O concentrations in Type A glass indicates that there are subgroups which might derive from different glass workshop(s) specialising in Type A v-Na-Al glass production. Comparison with the chemical compositions of glass from Ghazni, Afghanistan and Termez, Uzbekistan, and by using lead isotope analysis, we suggest v-Na-Al glass was manufactured in Central Asia and possibly worked into vessels and beads there.


Assuntos
Compostos de Cálcio/química , Vidro/química , Óxidos/química , Plantas/química , Dióxido de Silício/química , Hidróxido de Sódio/química , Oligoelementos/análise , Oligoelementos/história , África Oriental , Óxido de Alumínio , Arqueologia , História do Século XV , História do Século XVI , Oceano Índico , Marcação por Isótopo/métodos , Quênia , Espectrometria de Massas
18.
Br J Anaesth ; 125(5): 773-778, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32859360

RESUMO

BACKGROUND: Increasing fresh gas flow (FGF) to a circle breathing system reduces carbon dioxide (CO2) absorbent consumption. We assessed the environmental and economic impacts of this trade-off between gas flow and absorbent consumption when no inhalational anaesthetic agent is used. METHODS: A test lung with fixed CO2 inflow was ventilated via a circle breathing system of an anaesthetic machine (Dräger Primus or GE Aisys CS2) using an FGF of 1, 2, 4, or 6 L min-1. We recorded the time to exhaustion of the CO2 absorbent canister, defined as when inspired partial pressure of CO2 exceeded 0.3 kPa. For each FGF, we calculated the economic costs and the environmental impact associated with the manufacture of the CO2 absorbent canister and the supply of medical air and oxygen. Environmental impact was measured in 100 yr global-warming potential, analysed using a life cycle assessment 'cradle to grave' approach. RESULTS: Increasing FGF from 1 to 6 L min-1 was associated with up to 93% reduction in the combined running cost with minimal net change to the 100 yr global-warming potential. Most of the reduction in cost occurred between 4 and 6 L min-1. Removing the CO2 absorbent from the circle system, and further increasing FGF to control CO2 rebreathing, afforded minimal further economic benefit, but more than doubled the global-warming potential. CONCLUSIONS: In the absence of inhalational anaesthetic agents, increasing FGF to 6 L min-1 reduces running cost compared with lower FGFs, with minimal impact to the environment.


Assuntos
Anestésicos Inalatórios/química , Dióxido de Carbono/química , Poluição Ambiental/análise , Gases/química , Anestesia com Circuito Fechado , Anestesia por Inalação , Anestésicos Inalatórios/economia , Poluição Ambiental/economia , Poluição Ambiental/prevenção & controle , Gases/economia , Aquecimento Global , Humanos , Pulmão/fisiologia , Modelos Anatômicos , Respiração Artificial , Hidróxido de Sódio
19.
Water Sci Technol ; 81(7): 1452-1460, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32616697

RESUMO

In the process of preparing magnetic palygorskite from waste pickling liquor of the steel industry, the dosage of NaOH will affect the properties of the magnetic palygorskite. The experimental results showed that magnetic palygorskite can be effectively prepared when NaOH dosage is between 255 and 330 g/L. Vibration sample magnetometry proved that different NaOH dosages can affect the saturation magnetization of magnetic palygorskite. The catalytic performance of five catalysts synthesized with different NaOH dosages hardly changed after five cycles of Fenton-like catalytic degradation of tetracycline (TC). The magnetic palygorskite prepared by this method had good catalytic performance even when the catalyst preparation conditions were magnified ten times, which can provide a reference for large-scale preparation of magnetic palygorskite.


Assuntos
Poluentes Químicos da Água/análise , Compostos de Magnésio , Fenômenos Magnéticos , Compostos de Silício , Hidróxido de Sódio
20.
Sci Total Environ ; 744: 140900, 2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-32702543

RESUMO

A novel pretreatment using NaOH/Urea (NU) solution at outdoor cold-winter conditions was developed to enhance the enzymatic saccharification and hythane production from rice straw (RS). Results revealed that the reducing sugar conversion of RS reached 90.02% after NU pretreatment at outdoor freezing temperature. Chemical composition analysis showed that the lignin removal was up to 62.74% with cellulose and hemicellulose loss of 0.56% and 18.87% after 3%-6% NU pretreatment at 100% solid loading for 3 months. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the surface of pretreated RS exposed more cellulose and hemicellulose due to the disruption of resistant structure of lignocellulose. Subsequently, the enzymatic hydrolysate of pretreated RS was used as substrate to produce hythane by two-stage fermentation with the yield of 225.1 mL H2/g sugar and 112.8 mL CH4/g sugar. The energy conversion efficiency of hythane fermentation attained 10.4%, which was 22.8% and 190.5% higher than that for single H2 and CH4 fermentation. These results demonstrated that NU pretreatment at outdoor cold-winter conditions was practically and feasible way for improved hythane recovery from lignocellulosic biomass.


Assuntos
Oryza , Temperatura Baixa , Hidrólise , Lignina , Hidróxido de Sódio , Ureia
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