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1.
Sheng Wu Gong Cheng Xue Bao ; 36(7): 1356-1364, 2020 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-32748593

RESUMO

Salinity is the most important factor for the growth of crops. It is an effective method to alleviate the toxic effect caused by salt stress using saline-alkali-tolerant and growth-promoting bacteria in agriculture. Seven salt-tolerant bacteria were screened from saline-alkali soil, and the abilities of EPS production, alkalinity reduction and IAA production of the selected strains were investigated. A dominant strain DB01 was evaluated. The abilities of EPS production, alkalinity reduction and IAA production of strain DB01 were 0.21 g/g, 8.7% and 8.97 mg/L, respectively. The isolate was identified as Halomonas aquamarina by partial sequencing analysis of its 16S rRNA genes, and had the ability to inhibit the growth of Fusarium oxysporum f. sp., Alternaria solani, Phytophthora sojae and Rhizoctonia cerealis. It also could promote root length and germination rate of wheat seedlings under salt stress. Halomonas aquamarina can provide theoretical basis for the development of soil microbial resources and the application in saline-alkali soil improvement.


Assuntos
Álcalis , Raízes de Plantas , Tolerância ao Sal , Microbiologia do Solo , Álcalis/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/genética , Halomonas/genética , Raízes de Plantas/microbiologia , RNA Ribossômico 16S/genética , Tolerância ao Sal/genética , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Solo/química , Triticum/microbiologia
2.
Nat Commun ; 11(1): 3783, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32728021

RESUMO

Current thermochemical methods to generate H2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable. If biomass is used as a source of H2, the process can be considered carbon-neutral. Seaweeds are among the less studied types of biomass with great potential because they do not require freshwater. Unfortunately, reaction pathways to thermochemically convert salty and wet biomass into H2 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H2 with substantially suppressed CO2 formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H2/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H2 production and in situ CO2 capture, while the Ni/ZrO2 catalyst enhanced the secondary H2 formation via steam methane reforming and water-gas shift reactions.


Assuntos
Carbono/isolamento & purificação , Hidrogênio/isolamento & purificação , Energia Renovável , Alga Marinha/química , Álcalis/química , Biomassa , Carbono/química , Catálise , Temperatura Alta , Hidrogênio/química , Vapor
3.
Huan Jing Ke Xue ; 41(3): 1449-1455, 2020 Mar 08.
Artigo em Chinês | MEDLINE | ID: mdl-32608648

RESUMO

Soil salinity and alkalinity are major problems that limit agricultural development across the world. The planting of halophytes and salt-tolerant plants could improve saline-alkaline soil character, while the microorganisms in saline-alkali soils play an important role in the growth of halophytes and salt-tolerant plants. In this study, four representative plants of maize, cotton, Phragmites australis (Cav.) Trin. ex Steud, and Suaeda salsa were selected in saline-alkali soil. Soil samples were collected to explore the relationship between the main bacterial communities of roots and non-roots and the physical and chemical properties and soil microbial diversity of saline-alkali soil. The results showed that the root microorganisms of Suaeda salsa affect the pH of the soil to some extent, and the soil salinity is negatively correlated with the soil nutrient content. The top five bacterial gates with higher relative abundance in all soil samples were α-Proteobacteria, Actinobacteria, Bacteroides, Chloroflexi, and Acidobacteria. Cotton, Phragmites australis(Cav.) Trin. ex Steud, and Suaeda salsa have large differences in salt-tolerant bacteria between root soils and non-root soils. High-throughput sequencing results show that salt tolerance is different between the three plant roots and non-root soils. Bacterial genus, such as Actinophytocola and Lechevalieria, differ greatly in cotton soil, Bacillus and Filobacillus differ greatly in Phragmites australis (Cav.) Trin. ex Steud. soil, and Echinicola differ greatly in the soil of Suaeda salsa. This research can provide a theoretical basis for promoting plant growth in saline-alkali soil.


Assuntos
Rizosfera , Solo , Álcalis , Rios , Plantas Tolerantes a Sal , Microbiologia do Solo
4.
Huan Jing Ke Xue ; 41(4): 1941-1949, 2020 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-32608703

RESUMO

The use of biochar to improve adversity of soil has received increasing attention. Enteromorpha prolifera biochar is used to repair coastal saline-alkali soil, which can not only utilize Enteromorpha prolifera but can also increase the scale of the coastal land reserve. In this study, the method of soil culture experiments was used to explore the effect and pathway of 0%-3% addition of Enteromorpha prolifera on the improvement of saline-alkali soil. The results showed that the optimum preparation temperature of Enteromorpha prolifera biochar suitable for saline-alkali soil improvement was 400℃, and the optimum addition amount was 1.5%. At the optimum level, although the biochar had a negative effect, such as increasing soil salinity (0.12%) and pH (1.49%), it also produced positive effects, such as reducing soil Na+/K+ by 55.73%, increasing mineral content, and improving water conductivity. Enteromorpha prolifera biochar improved soil physicochemical and biological properties, increased nutrient content, enhanced microbial activity, improved soil nutrient availability, and produced positive effects. These positive effects were characterized by reducing soil bulk density by 11.35%, increasing organic matter by 42.64%, increasing the proportion of organic carbon in total carbon by 3.84 times, increasing the proportion of available phosphorus in total phosphorus by 4.15 times, and increasing soil invertase activity by 2.39 times, urease activity by 1.18 times, and catalase activity 1.50 times. Therefore, the positive effect of Enteromorpha prolifera biochar on saline-alkali soil is more than negative, and it can be used for the improvement of coastal saline-alkali soil. This study provides a new path for the resource utilization of Enteromorpha prolifera and the improvement of the ecological environment of coastal saline-alkali soil.


Assuntos
Carvão Vegetal , Solo , Álcalis , Carbono
5.
Environ Sci Pollut Res Int ; 27(27): 34574-34582, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32681331

RESUMO

In this study, suitability of xylano-pectinolytic enzymes in pulping of wheat straw has been explored. The suitable biopulping conditions were optimized, with xylanase dose of 400 and pectinase dose of 120 IU/g wheat straw, 1:10 (g/ml) material to liquid ratio, 55 °C temperature, 3 h treatment time, 0.75% Tween 80 and pH 8.5. Enzymatic pretreatment efficiently increased the pulpability of wheat straw, generated pulp with higher yield, lower kappa number (15.67%) and rejections (59.65%) in comparison with chemical pulp. The brightness of pretreated wheat straw pulp with enzyme was 16.04% higher than that of the non-enzyme treated wheat straw pulp. The biopulping resulted in 12% reduction of pulping chemicals along with more residual alkali content, in order to achieve similar optical and chemical properties as obtained by 100% chemically treated pulp. Physical properties of pulp also improved after enzymatic pretreatment, increasing burst index (26.50%), tear index (18.22%) and breaking length (5.56%). The enzyme plus chemical (88% pulping chemicals) treated pulp showed improvement in brightness and whiteness, with reduction in yellowness at all bleaching stages. In comparison with chemically bleached pulp, biopulp with reduced alkali dose (88%) had higher breaking length (6.63%), double fold number (51.28%), tear index (2.83%), burst index (24.31%), along with increased viscosity (6.12%) and Gurley porosity (27.50%). These results clearly suggest that biopulping of wheat straw with xylano-pectinolytic enzymes can reduce chemical loading during soda-anthraquinone pulping and also improve the quality of paper. This is the first report demonstrating the biopulping of wheat straw using crude xylano-pectinolytic enzymes.


Assuntos
Endo-1,4-beta-Xilanases , Triticum , Álcalis , Cor , Papel , Poligalacturonase
6.
Ying Yong Sheng Tai Xue Bao ; 31(4): 1323-1332, 2020 Apr.
Artigo em Chinês | MEDLINE | ID: mdl-32530208

RESUMO

Yellow River Delta is an important distribution area of coastal saline-alkali land in China. Revegetation is the main technology for ecological restoration during saline-alkali land amelioration. To explore the effects of different vegetation types on soil improvement in saline-alkali land and get the suitable model in the Yellow River Delta, four tree-grass compound models, Salix americana+Distichlis spicata, S. matsudana+D. spicata, Tamarix chinensis+Medicago sativa, and Fraxinus chinensis+T. chinensis+M. sativa, were set up, with pure S. americana forest as the control. Twenty indicators, including soil moisture physical parameters, saline-alkali content, soil nutrient contents, and microorganism quantity etc. were measured. Principal component analysis, cluster analysis and fuzzy mathematics were used to evaluate soil modification effect of different vegetation combinations. The results showed that all compound models significantly improved soil physical and che-mical properties in coastal saline-alkali land by increasing soil porosity, soil water storage, soil organic matter content, available nutrient content and soil microorganism quantity and reducing soil density. Among all the models, the tree-shrub-grass mixed model of F. chinensis+T. chinensis+M. sativa was the most effective in inhibiting salt and alkali stress and increasing soil nutrients and microorganism abundance, whereas the tree-grass mixed model of S. matsudana+D. spicata was the most effective in improving soil water physical properties. The combined effects of different vegetation patterns on soil amelioration in coastal saline-alkali land of the Yellow River Delta were arranged in order of F. chinensis+T. chinensis+M. sativa> S. matsudana+D. spicata> S. americana+D. spicata> T. chinensis+M. sativa.


Assuntos
Solo , Tamaricaceae , Álcalis , China , Rios
7.
Int J Syst Evol Microbiol ; 70(7): 4179-4185, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32558636

RESUMO

A novel moderately halophilic, filamentous actinobacterium, designated as XMNu-373T, was isolated from a saline-alkaline soil sample collected from the Mongolia Plateau, Dongwu County, Inner Mongolia Autonomous Region, PR China. The isolate grew optimally at 28‒37 °C, pH 7.0‒8.0 and with 2-5 % (w/v) NaCl. The substrate mycelia fragmented into rod-like elements, and the white aerial mycelia formed spore chains at maturity. The predominant menaquinone was MK-9(H4). The polar lipids were diphosphatidylglycerol, three unidentified phosphoglycolipids, an unidentified aminophospholipid, two phosphatidylinositol mannosides, four unidentified phospholipids, phosphatidylglycerol and two unidentified lipids. The major cellular fatty acids were iso-C16 : 0, anteiso-C17 : 0 and anteiso-C15 : 0. The genomic DNA G+C content was 66.2 mol%. It shared high 16S rRNA gene sequence similarities to Phytoactinopolyspora halotolerans YIM 96448T (96.1 %) and Phytoactinopolyspora endophytica EGI 60009T (96.0 %). Phylogenetic trees based on 16S rRNA gene sequences revealed that strain XMNu-373T resided in the clade of family Jiangellaceae, and it formed a monophyletic branch distinct from four other recognized type species in the subclade of the genus Phytoactinopolyspora. On the basis of polyphasic taxonomic evidence, strain XMNu-373T represents a novel species of the genus Phytoactinopolyspora, for which the name Phytoactinopolyspora mesophila sp. nov. is proposed. The type strain is XMNu-373T (=JCM 33740T=CGMCC 4.7654T).


Assuntos
Actinobacteria/classificação , Álcalis , Filogenia , Salinidade , Microbiologia do Solo , Actinobacteria/isolamento & purificação , Técnicas de Tipagem Bacteriana , Composição de Bases , China , DNA Bacteriano/genética , Ácido Diaminopimélico/química , Ácidos Graxos/química , Fosfolipídeos/química , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Solo/química , Vitamina K 2/análogos & derivados , Vitamina K 2/química
8.
Bioresour Technol ; 313: 123634, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32570076

RESUMO

This study aimed at evaluating the valorization of a typical yard waste, phoenix tree leaf (PTL), through mild alkali pretreatment followed by anaerobic digestion (AD). To this end, L9 Taguchi orthogonal biochemical methane potential (BMP) tests and semi-continuous AD experiments were conducted to examine the optimum pretreatment condition and the long term effect of alkali pretreatment on AD. The community structure evolutions were analyzed by high throughput 16S rRNA gene pyrosequencing. The results indicated that alkali pretreatment was effective on decrystallization and releasing more surface of PTL for enzyme attacking. The methane yield was positively correlated with lignin removal (R2=0.8242). In semi-continuous mode, 151.5±7.9 mL/g VS of the methane yield was obtained for alkali pretreated PTL, which was 80% higher than that of untreated one. Microbial community analysis indicated that alkali pretreatment led to a higher abundance of dominated bacteria (Bacteroidetes and Clostridia) and archaea of Methanosaeta.


Assuntos
Álcalis , Árvores , Anaerobiose , Biocombustíveis , Metano , RNA Ribossômico 16S
9.
Int J Syst Evol Microbiol ; 70(7): 4139-4144, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32501784

RESUMO

Strains of Echinicola, thought to play vital roles in the environment for their high enzyme production capacity during decomposition of polysaccharides, are ubiquitous in hypersaline environments. A Gram-negative, non-spore forming, gliding, aerobic bacterial strain, designated LN3S3T, was isolated from alkaline saline soil sampled in Tumd Right Banner, Inner Mongolia, northern PR China. Strain LN3S3T grew at 10-40 °C (optimum, 30 °C), pH 5.0-9.0 (optimum, pH 8.0) and with 0-12.5 % NaCl (optimum, 2.0 %). A phylogenetic tree based on the 16S rRNA gene sequences showed that strain LN3S3T clustered with Echinicola rosea JL3085T and Echinicola strongylocentroti MEBiC08714T, sharing 97.0, 96.7 and <96.50 % of 16S rRNA gene sequence similarities to E. rosea JL3085T, E. strongylocentroti MEBiC08714T and all other type strains. MK-7 was the major respiratory quinone, while phosphatidylethanolamine, two unidentified phospholipids, an unidentified aminophospholipid, an unidentified lipid and two unidentified aminolipids were the major polar lipids. Its major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The genome consisted of a circular 5 550 304 bp long chromosome with a DNA G+C content of 44.0 mol%. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values of strain LN3S3T to E. rosea JL3085T and E. strongylocentroti MEBiC08714T were 82.5 and 81.5 %, 87.5 and 86.0 %, and 39.1 and 35.1 %, respectively. Based on physiological, genotypic and phylogenetic analyses, strain LN3S3T could be discriminated from its phylogenetic relatives. Echinicola soli sp. nov. is therefore proposed with strain LN3S3T (=CGMCC 1.17081T=KCTC 72458T) as the type strain.


Assuntos
Álcalis , Bacteroidetes/classificação , Filogenia , Salinidade , Microbiologia do Solo , Técnicas de Tipagem Bacteriana , Bacteroidetes/isolamento & purificação , Composição de Bases , China , DNA Bacteriano/genética , Ácidos Graxos/química , Hibridização de Ácido Nucleico , Fosfolipídeos/química , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Solo/química , Vitamina K 2/análogos & derivados , Vitamina K 2/química
10.
Bioresour Technol ; 314: 123685, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32593784

RESUMO

Alkali-extracted xylan from lignocellulosics is a promising feedstock for production of prebiotic xylooligosaccharides (XOS). An integrated process was established combining autohydrolysis, nanofiltration and xylanase hydrolysis. Results show that after autohydrolysis 48.37% of xylan was degraded into oligomers and dissolved into the autohydrolysate, of which 57.83% were XOS. By-products and xylose were removed by nanofiltration with discontinuous diafiltration, while high recovery yields of XOS (84.15%) and xylan (87.45%) were obtained. High yields of XOS were obtained by adding xylanase to the autohydrolysates; after enzymatic hydrolysis an XOS yield of 96-98% was obtained. The enzymatic hydrolysates showed positive prebiotic effects on B. adolescentis with an increase in cell concentration by 4.8-fold after fermentation for 24 h. The main products were short-chain fatty acids with carbon balanced during the whole fermentation process. This integrated strategy resulted in a final XOS conversion of 41.22% contrasted to the initial xylan in raw alkali-extracted xylan.


Assuntos
Prebióticos , Xilanos , Álcalis , Endo-1,4-beta-Xilanases , Glucuronatos , Hidrólise , Oligossacarídeos
11.
J Environ Manage ; 270: 110869, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32507745

RESUMO

This work recovered the dredged sediment around Kaohsiung Harbor, Taiwan, for preparing lightweight aggregates (LWA), of which physicochemical properties as affected by the addition of basic-oxygen-furnace (BOF) slag and waste glass were investigated. LWA properties included water absorption, particle density, compressive strength, shrinkage, and microstructure of sintered pellets were evaluated to ensure feasibility of dredged harbor sediment reutilization technique. Results showed that adding appropriate amount of glass powders (~7%) to the mixtures of sediment and slag significantly reduced the water absorption (as low as 2.2%) of the sintered pellets and increase the compressive strength (as high as 23.1 MPa) of LWA, which were found to be controlled by open porosity and shrinkage. Excessive addition of glass (>10%) led to increase in internal pore sizes of the sintered pellets, and thus reduced the compressive strength. The alkali-silica reactivity (ASR) of the LWA was innocuous according to the ASTM C289 test. Sintering and glass addition improved the stability of heavy metal and environmental compatibility of the LWA. The recycling of waste sediment, slag, and glass for LWA production can provide an alternative for the disposal of dredge harbor sediment and has positive impact on waste reduction, which not only can reduce secondary contamination to the environment, but also can contribute to circular economy.


Assuntos
Álcalis , Aço , Materiais de Construção , Resíduos Industriais/análise , Reciclagem , Dióxido de Silício , Taiwan
12.
Sci Total Environ ; 729: 139055, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32388132

RESUMO

Two types of silica-composited biochars were prepared by mixing swine manure or rice straw with alkali-fused fly ash (AFFA) followed by pyrolysis. A 10% (w/w) AFFA modification improved the specific surface area, pore volume, and average pore size of the biochars. Certain surface oxygen-containing functional groups (i.e., -OH and CO) in the biochars were protected, and silicon-oxygen bonds (i.e., O-Si-O and OSi) were strengthened considerably by AFFA modifications during high-temperature pyrolysis. The adsorption capacity of biochar for methylene blue (MB) was enhanced after AFFA modification, and a modified biochar with the highest adsorption capacity was prepared at a pyrolysis temperature of 700 °C, pyrolysis holding time of 2 h, and an AFFA proportion of 10%. The MB adsorption capacity of the modified biochars significantly increased when the pH of the solution increased (from 3 to 13). The adsorption data were well described by a pseudo-second-order model and Langmuir isotherms. The maximum MB adsorption capacities of the modified swine manure and rice straw biochars were 143.76 mg/g and 131.58 mg/g, respectively. The adsorption capacities of the AFFA-modified biochars were 10.7-112.3% higher than those of the unmodified biochars. The enhanced MB adsorption capacities of the former appear to be attributed to their increased specific surface areas, increased porosities, strong oxygen-containing functional groups, and high contents of exchangeable sodium ions. These results indicate that industrial and agricultural wastes can be reused to produce novel silica-composited biochars with high MB removal capacity. Accordingly, these biochars could be effectively used to treat wastewater and thus to mitigate solid waste disposal-related problems.


Assuntos
Cinza de Carvão , Adsorção , Álcalis , Animais , Carvão Vegetal , Azul de Metileno , Dióxido de Silício , Suínos
14.
Phys Rev Lett ; 124(19): 199602, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32469581

Assuntos
Álcalis , Termômetros , Vidro
15.
PLoS One ; 15(5): e0232853, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32374780

RESUMO

OBJECTIVE: The choice of the most suitable litter treatment should be based on scientific evidence. This systematic review assessed the effectiveness of litter treatments on ammonia concentration, pH, moisture and pathogenic microbiota of the litter and their effects on body weight, feed intake, feed conversion and mortality of broilers. METHODS: The systematic literature search was conducted using PubMed (Medline), Google Scholar, ScienceDirect and Scielo databases to retrieve articles published from January 1998 to august 2019. Means, standard deviations and sample sizes were extracted from each study. The response variables were analyzed using the mean difference (MD) or standardized mean difference (SMD), (litter treatment minus control group). All variables were analyzed using random effects meta-analyses. RESULTS: Subgroup meta-analysis revealed that acidifiers reduce pH (P<0.001), moisture (P = 0.002) ammonia (P = 0.011) and pathogenic microbiota (P <0.001) of the litter and improves the weight gain (P = 0.019) and decreases the mortality rate of broilers (P<0.001) when compared with controls. Gypsum had a positive effect on ammonia reduction (P = 0.012) and improved feed conversion (P = 0.023). Alkalizing agents raise the pH (P = 0.035), worsen feed conversion (P<0.001), increase the mortality rate (P <0.001), decrease the moisture content (P<0.001) and reduce the pathogenic microbiota of the litter (P<0.001) once compared to controls. Superphosphate and adsorbents reduce, respectively, pH (P<0.001) and moisture (P = 0.007) of the litter compared to control groups. CONCLUSION: None of the litter treatments influenced the feed intake of broilers. Meta-analyses of the selected studies showed positive and significant effects of the litter treatments on broiler performance and litter quality when compared with controls. Alkalizing was associated with worse feed conversion and high mortality of broilers.


Assuntos
Criação de Animais Domésticos/métodos , Galinhas/fisiologia , Abrigo para Animais , Ácidos/análise , Ácidos/farmacologia , Ácidos/toxicidade , Álcalis/análise , Álcalis/farmacologia , Álcalis/toxicidade , Amônia/análise , Ração Animal , Animais , Doenças das Aves/mortalidade , Peso Corporal , Galinhas/crescimento & desenvolvimento , Comportamento Alimentar , Abrigo para Animais/estatística & dados numéricos , Umidade , Concentração de Íons de Hidrogênio , Microbiota , Gerenciamento de Resíduos , Ganho de Peso
16.
J Environ Manage ; 265: 110350, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32421549

RESUMO

The existence of leachable Cr(Ⅵ) in chromite ore processing residue (COPR) makes it hazardous waste. Therefore, resourceful utilization of COPR is necessary to protect the ecosystem and living biota from hazardous effect of Cr(Ⅵ) caused by its leaching. In this study, detoxification and immobilization of COPR was carried out through introduction of ascorbic acid (AA) in alkali-activated cementitious materials. Several dosages of AA were treated with water extractable/soluble Cr(Ⅵ) to achieve the optimum dosage which could be further utilized in solidification process. While, the compressive strength was developed through utilizing different modulus of water glass, liquid to solid ratios and curing temperatures. The results showed that 0.3% of AA was enough to reduce the Cr(Ⅵ) into Cr(Ⅲ), and highest compressive strength of 120 MPa was achieved after using the modulus of 1.6, liquid to solid ratio of 0.24 and curing temperature of 30 °C. The solidified samples having AA had not exceeded the toxicity limit up to 60% addition of COPR, and samples without addition of AA were effective for solidification of 20% COPR. Regarding mechanism, the compressive strength, leaching behavior and microscopic analysis i.e. X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electron microscope with energy dispersive spectrometry (SEM-EDS) showed that immobilization of chromium was carried out through physical and chemical means.


Assuntos
Álcalis , Resíduos Industriais , Ácido Ascórbico , Cromo , Ecossistema
17.
J Environ Manage ; 267: 110638, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32421671

RESUMO

To solve the problems of low early strength and severe plastic cracking caused by high volume fly ash used in cement-based materials. Triethanolamine (TEA), calcium hydroxide (Ca(OH)2), and sodium silicate (Na2SiO3) or sodium sulfate (Na2SO4) were selected to conduct a ternary doping test. The compressive strength of samples was measured to determine the best ratio, content, and time effect of the activator, and its action mechanism was studied by various micro test. The quantitative calculation model of main hydration products was established in the fly ash-cement system. Based on the simulation of molecular dynamics, the structure of NASH gel was studied under alkali activation. The results show that the optimal mixing mass ratio of TEA:Ca(OH)2:Na2SiO3 is 2:75:25 and the optimal dosage is 1.02% of the cementitious material. There are a large number of needle-like ettringite, petaloid hydrated calcium aluminate and clusters of hydrated calcium silicate gel in the system, whereas the amount of plate-like CH decreased significantly at hydration for 14 days. The Si/Al is three and aluminium coordination is predominantly tetrahedral, and the order of bonds stability and atoms mobility are Si-O > Al-O > Na-O and Na > O > Al> in the NASH gel, respectively. Under the Na+ and alkali environment, the Si(OH)4 and Al(OH)4- formed polycondensation reaction to reform polymers Si-O-Si and Al-O-Si, forming a large amount of NASH gel.


Assuntos
Cinza de Carvão , Materiais de Construção , Álcalis , Alumínio , Força Compressiva
18.
Bioresour Technol ; 312: 123535, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32454440

RESUMO

In order to explore the effects of different mechanical fragmentation on cellulose separation and cellulose polymorphic transformation of wheat straw during alkali treatment, one coarse milled (CM) and two ball milled wheat straw samples (BM30 and BM120) were treated with different NaOH concentrations (1%-10%), and the lignocellulosic compositions and crystalline-structural various were quantitative and qualitative characterized. The quantitative equations between cellulose content and NaOH concentration of different mechanical treated samples were YCM = 69.8-35.1exp(-0.64X)), YBM30 = 71.3-35.1exp(-0.86X)) and YBM120 = 73.5-35.1exp(-1.82X)). The enhancement effect of cellulose separation with the increasing mechanical fragmentation intensity is mainly due to the increasing hemicellulose solubilization. X-ray diffraction results reveals that the NaOH concentration required for cellulose crystalline transformation of CM, BM30 and BM120 is 10%, 8% and 2%, respectively. In conclusion, mechanical fragmentation contributes to cellulose separation and cellulose crystalline transformation under lower NaOH concentration.


Assuntos
Celulose , Triticum , Álcalis , Hidróxido de Sódio , Difração de Raios X
19.
Bioresour Technol ; 311: 123517, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32413643

RESUMO

To overcome the recalcitrance of residual lignins in acid-pretreated larch (AL), a combined acid and alkali pretreatment with in-situ lignin modification was developed in this study. The results showed that introducing in-situ lignin modification with 2-naphthol to acid pretreatment (160 and 180 oC) improved the enzymatic digestibility of AL by 12.7-14.4%, through suppressing lignin repolymerization. The obviously higher improvement (57.8-88.3%) was achieved by applying alkali post-treatment (90 oC) with poly (ethylene glycol) diglycidyl ether (PEGDE) on AL, mainly due to the function of in-situ lignin modification with PEGDE for reducing enzyme non-productive binding on lignins. More importantly, the synergism of 2-naphthol and PEGDE modification facilitated the enzymatic hydrolysis of AL more significantly. Its beneficial mechanism was explored by investigating the effects of in-situ lignin modification on lignin properties, including extraction yields, functional groups, and enzyme affinity of lignins. Results will give insights into establishing an efficient pretreatment of softwood biomass.


Assuntos
Larix , Lignina , Ácidos , Álcalis , Hidrólise
20.
Sci Total Environ ; 731: 138938, 2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32408208

RESUMO

Because salinity of coastal soils is drastically increasing, the application of biochars to saline-alkali soil amendments has attracted considerable attention. Various Solidago-canadensis-L.-derived biochars prepared through pyrolysis from 400 to 600 °C were applied to coastal saline-alkali soil samples to optimise the biochar pyrolysis temperature and investigate its actual ecological responses. All biochars reduced the soil bulk density and exchangeable sodium stress and increased soil water-holding capacity, cation exchange capacity, and organic matter content. Principal-component-analysis results showed that pyrolysis temperature played an important role in the potential application of biochars to improve the coastal saline-alkali soil, mainly contributed to ameliorating exchangeable sodium stress and decreasing biochar-soluble toxic compounds. Furthermore, soil bulk density and organic matter, as well as carboxylic acids, phenolic acids and amines of biochar were major driving factors for bacterial community composition. Compared to low-temperature biochar (pyrolyzed below 550 °C), which showed higher toxicity for Brassica chinensis L. growth due to the higher content of carboxylic acids, phenols and amines, high-temperature biochar (pyrolyzed at or above 550 °C) possessed less amounts of these toxic functional groups, more beneficial soil bacteria and healthier for plant growth. Therefore, high-temperature biochar could be applied as an effective soil amendment to ameliorate the coastal saline-alkali soil with acceptable environmental risk.


Assuntos
Solo , Solidago , Álcalis , Carvão Vegetal , Pirólise , Temperatura
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