خيارات البحث
النتائج 3251 - 3260 من 4,308
Vermicompost as a natural adsorbent: evaluation of simultaneous metals (Pb, Cd) and tetracycline adsorption by sewage sludge-derived vermicompost النص الكامل
2017
He, Xin | Zhang, Yaxin | Shen, Maocai | Tian, Ye | Zheng, Kaixuan | Zeng, Guangming
The simultaneous adsorption of heavy metals (Pb, Cd) and organic pollutant (tetracycline (TC)) by a sewage sludge-derived vermicompost was investigated. The maximal adsorption capacity for Pb, Cd, and TC in a single adsorptive system calculated from Langmuir equation was 12.80, 85.20, and 42.94 mg L⁻¹, while for mixed substances, the adsorption amount was 2.99, 13.46, and 20.89 mg L⁻¹, respectively. The adsorption kinetics fitted well to the pseudo-second-order model, implying chemical interaction between adsorbates and functional groups, such as –COOH, –OH, –NH, and –CO, as well as the formation of organo-metal complexes. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) specific surface area measurement were adopted to gain insight into the structural changes and a better understanding of the adsorption mechanism. The sewage sludge-derived vermicompost can be a low cost and environmental benign eco-material for high efficient wastewater remediation.
اظهر المزيد [+] اقل [-]Particle removal by vegetation: comparison in a forest and a wetland النص الكامل
2017
Liu, Jiakai | Zhai, Jiexiu | Zhu, Lijuan | Yang, Yilian | Liu, Jiatong | Zhang, Zhenming
Vegetation collection is one of the most effective scavenging methods but relevant studies are limited. It can be described by some abstract parameters such as collection rates and deposition fluxes within the canopy. In order to estimate the dry deposition within the canopy of particular matters (PMs) in Beijing, a highly particle-polluted city, and reveal the PM pollution-removal abilities of plants in wetlands and forests, concentration and meteorological data were collected during the daytime in an artificial forest and a wetland in the Olympic Park in Beijing. The dry depositions within the canopy and vegetation collection rates were calculated by a well-developed model and validated by measured deposition fluxes in 11 random experiment days. The experiment year was divided into three plant growth stages based on canopy density, and the day was divided into four different times. Two heights, 10 and 1.5 m, were defined in the forest while in the wetland, 0.5 and 1.5 m were defined. The results showed that in Beijing, the most severe pollution by PMs occurs in the non-leaf stage (NS), and the full-leaf stage (FS) is the cleanest stage. In NS, namely winter, more fossil fuel was used for worms in Beijing and peripheral areas and this might be the reason for the serious pollution condition. Within the canopy, PM deposition fluxes in the wetland are more than those in the forest, but the vegetation collection rates of the forest are higher. The lower temperature conditions led to more dry deposition, and the larger canopy contributed to the higher collection rates. During the daytime, over the year, the deposition of PM₁₀ in three plant growth stages is NS ≥ half-leaf stages (HS) ≥ FS, whereas the deposition of PM₂.₅ is NS ≥ FS ≥ HS, and during the daytime, the maximum deposition fluxes occur in 6:00–9:00 in the wetland while the minimum deposition values occur in 15:00–18:00. This phenomenon was related to the temporal variation of particle concentration.
اظهر المزيد [+] اقل [-]Environmental analysis of waste foundry sand via life cycle assessment النص الكامل
2017
Mitterpach, Jozef | Hroncová, Emília | Ladomerský, Juraj | Balco, Karol
The aim of this manuscript is to provide an environmental assessment of the creation and use of waste foundry sand (WFS) via an LCA in a foundry for grey cast iron. A life cycle impact assessment was carried out using SimaPro 8. This environmental analysis assessed the impact of creating waste foundry sand (WFS) in a foundry, Hronec (Slovakia, Central Europe). According to BREF, this foundry is classified as an iron foundry with a production capacity greater than 20 t/day with processes typical for grey cast iron foundries. Molten metal is poured into single-use sand moulds. We identified those factors influencing the creation and use of WFS which significantly affect the quality of the environment. The use of WFS from the production of cores in regenerated moulding mixtures with installed circuits brings marked minimisation of material and energy inputs in the processes of creating WFS and it positively influences the consumption of resources and the quality of the ecosystem. Space for lessening the impact of WFS processes upon the consumption of resources and ecosystem quality is mainly found in recycling WFS in the building sector. In the next step, it is necessary to thoroughly verify the eco-toxicological properties of not only the created WFS and other foundry waste, but mainly the building products for which this waste is used. In terms of transportation, it is important that waste is recycled at local level. The processes of creating WFS have a marked influence upon all the selected waste categories (consumption of resources, ecosystem quality, human health). By minimising material inputs into processes and the effective adjustment of production technology, a foundry can significantly lessen the impacts of processes for creating WFS upon the environment.
اظهر المزيد [+] اقل [-]Metal-resistant rhizobacteria isolates improve Mucuna deeringiana phytoextraction capacity in multi-metal contaminated soils from a gold mining area النص الكامل
2017
Boechat, Cácio Luiz | Giovanella, Patricia | Amorim, Magno Batista | de Sá, Enilson Luiz Saccol | de Oliveira Camargo, Flávio Anastácio
Phytoremediation consists of biological techniques for heavy metal remediation, which include exploring the genetic package of vegetable species to remove heavy metals from the environment. The goals of this study were to investigate heavy metal and bioaugmentation effects on growth and nutrient uptake by Mucuna deeringiana; to determine the metal translocation factor and bioconcentration factor and provide insight for using native bacteria to enhance heavy metal accumulation. The experiment was conducted under greenhouse conditions using a 2 × 4 factorial scheme with highly and slightly contaminated soil samples and inoculating M. deeringiana with three highly lead (Pb⁺²)-resistant bacteria Kluyvera intermedia (Ki), Klebsiella oxytoca (Ko), and Citrobacter murliniae (Cm) isolated from the rhizosphere of native plants identified as Senecio brasiliensis (Spreng.) Less., Senecio leptolobus DC., and Baccharis trimera (Less) DC., respectively. The increased heavy metal concentrations in soil samples do not decrease the root dry mass of M. deeringiana, concerning the number and dry weight of nodules. The shoot dry mass is reduced by the increasing concentration of heavy metals in soil associated with Kluyvera intermedia and Klebsiella oxytoca bacteria. The number of nodules is affected by heavy metals associated with Citrobacter murliniae bacteria. The bacteria K. intermedia, C. murliniae, and K. oxytoca increase the lead and cadmium available in the soil and enhanced metal uptake by Mucuna deeringiana. The M. deeringiana specie has characteristics that make it hyperaccumulate copper and zinc. The translocation and bioconcentration factors for M. deeringiana characterize it as a promising candidate to phytostabilize multi-metal contaminated soils.
اظهر المزيد [+] اقل [-]Photocatalytic air purifiers for indoor air: European standard and pilot room experiments النص الكامل
2017
Costarramone, N. | Cantau, C. | Desauziers, V. | Pécheyran, C. | Pigot, T. | Lacombe, S.
At the European level (CEN/TC386), some efforts are currently devoted to new standards for comparing the efficiency of commercial photocatalytic material/devices in various application fields. Concerning prototype or commercial indoor photocatalytic air purifiers designed for volatile organic compounds (VOC) abatement, the methodology is based on a laboratory airtight chamber. The photocatalytic function is demonstrated by the mineralization of a mixture of five VOCs. Experimental data were obtained for four selected commercial devices and three commercial materials: drop of VOC concentration, but also identification of secondary species (with special attention to formaldehyde), mineralization rates, and Clean Air Delivery Rate (CADR). With two efficient air purifiers, these laboratory experiments were compared to the results in two experimental rooms (35–40 m³) where air pollution was introduced through wooden floor and furniture. The systems’ ageing was also studied. The safety of the commercial products was also assessed by the determination of nanoparticle release. Standardized tests are useful to rank photocatalytic air purifiers and passive materials and to discard inefficient ones. A good correlation between the standard experiments and the experimental room experiments was found, even if in the latter case, the concentration of lower weight VOCs drops less quickly than that of heavier VOCs.
اظهر المزيد [+] اقل [-]Protective effects of Eruca sativa (rocket) on abamectin insecticide toxicity in male albino rats النص الكامل
2017
Meligi, Noha M. | Hassan, Hanaa Fawzy
The extensive use of insecticides has hazardous effects since they can damage human health as well as the environment. Abamectin has been widely used in veterinary medicine and as a pesticide in agriculture. It is considered as one of the most commonly used insecticides in Egypt. The focus of the present study is to examine the toxic effects of sublethal dose (1 mg/kg b.wt.) of abamectin (Crater 3.37% EC) in male albino rats and to evaluate the efficiency of Eruca sativa suspension to ameliorate the abamectin toxicity. The present study was achieved using 18 male albino rats. Rats were divided into three groups: normal control group, abamectin-treated group, and abamectin + E. sativa-treated group. Rats of the third group were orally administrated a mixture of sublethal dose of abamectin (1 mg/kg b.wt.) and E. sativa suspension (5 g/kg b.wt.) three times a week for 28 days. At the end of the study period, blood samples were collected from all groups to measure the various hematological and biochemical parameters. The results revealed that rats, after abamectin exposure, exhibited general signs of toxicity and disturbance in the hematological and biochemical parameters. In addition, administration of E. sativa suspension ameliorated the hematological and biochemical parameters. These findings suggested that the exposure to abamectin might be responsible for hypertension, liver and kidney dysfunction, lipid profile disturbance, and oxidative stress, reflected in hematological and biochemical parameters. It was also found that the administration of E. sativa suspension reduced the detrimental impact of abamectin on some hematological and biochemical parameters.
اظهر المزيد [+] اقل [-]Interpretation of single and competitive adsorption of cadmium and zinc on activated carbon using monolayer and exclusive extended monolayer models النص الكامل
2017
Sellaoui, Lotfi | Dotto, GuilhermeL. | Lamine, AbdelmottalebBen | Erto, Alessandro
In this work, a modeling analysis based on experimental tests of cadmium/zinc adsorption, in both single-compound and binary systems, was carried out. All the experimental tests were conducted at constant pH (around neutrality) and temperature (20 °C). The experimental results showed that the zinc adsorption capacity was higher than that of cadmium and it does not depend on cadmium presence in binary system. Conversely, cadmium adsorption is affected by zinc presence. In order to provide good understanding of the adsorption process, two statistical physics models were proposed. A monolayer and exclusive extended monolayer models were applied to interpret the single-compound and binary adsorption isotherms of zinc and cadmium on activated carbon. Based on these models, the modeling analysis demonstrated that zinc is dominant in solution and more favorably adsorbed on activated carbon surface. For instance, in single-compound systems, the number of ions bound per each receptor site was n (Zn²⁺) = 2.12 > n (Cd²⁺) = 0.98. Thus, the receptor sites of activated carbon are more selective for Zn²⁺ than for Cd²⁺. Moreover, the determination of adsorption energy through the adopted models confirmed that zinc is more favored for adsorption in single-compound system (adsorption energies equal to 12.12 and 7.12 kJ/mol for Zn and Cd, respectively) and its adsorption energy does not depend on the cadmium presence in binary system. Finally, the adsorption energy values suggested that single-compound and binary adsorption of zinc and cadmium is a physisorption.
اظهر المزيد [+] اقل [-]Overestimation of orthophosphate monoesters in lake sediment by solution 31P-NMR analysis النص الكامل
2017
Zhang, Wenqiang | Jin, Xin | Tang, Wenzhong | Shan, Baoqing
Solution ³¹P nuclear magnetic resonance spectroscopy (³¹P-NMR) is a useful method for analyzing organic phosphorus (Pₒ). Unfortunately, the extraction conditions, which are highly alkaline and require long extraction times, make this analysis less effective. In this research, according to the lability of orthophosphate monoesters (mono-Pₒ) and orthophosphate diesters (diesters-Pₒ), we verified the hypothesized overestimation of mono-Pₒ in lake sediment using solution ³¹P-NMR. We set three scenes to redistribute the mono-Pₒ and diesters-Pₒ. Six components, including eight mono-Pₒ species, were detected in the NaOH–EDTA extracts of sediment samples using ³¹P-NMR. The results showed that mono-Pₒ (212.7 mg kg⁻¹) was the dominant Pₒ in the surface sediment. In the three scenes, mono-Pₒ decreased from 212.7 to 112.0 mg kg⁻¹, and diesters-Pₒ increased from 31.9 to 132.7 mg kg⁻¹. The ratio of mono-Pₒ to diesters-Pₒ increased from 6.7 to 0.8. Therefore, we deduced that the concentration of mono-Pₒ was overestimated, while that of diesters-Pₒ was underestimated, in most research because of the high pH and long extraction process. Diesters-Pₒ might be an important labile P source during the P “exhausted” period.
اظهر المزيد [+] اقل [-]Proximate composition and mineral contents in the body wall of two species of sea cucumber from Oman Sea النص الكامل
2017
Barzkar, Noora | Attaran Fariman, Gilan | Taheri, Ali
The proximate composition and mineral contents of Stichopus horrens and Holothuria arenicola from Chabahar Bay were analyzed and investigated. During the present study, we aimed to demonstrate the nutritive value. The approximate percent composition of moisture, protein, fat, and ash were 92.8, 3.47, 0.4, and 3.33% in S. horrens and 93, 4.4, 0.6, and 2% in H. arenicola, respectively. Atomic absorption spectrophotometry of the ashes indicated the body wall of two species of sea cucumbers contained higher amounts of both macro minerals (92.5 mg/100 g Mg in S. horrens and 115 mg/100 g Mg in H. arenicola; 106.25 mg/100 g Ca in S. horrens and 83.25 mg/100 g Ca in H. arenicola) and trace elements (521.781 mg/100 g Fe in S. horrens; 60.354 mg/100 g Fe in H. arenicola, and 0.096 mg/100 g Zn in S. horrens; 0.04 mg/100 g Zn in H. arenicola). For both species, there were high content of protein and essential mineral. Also, they have low content of fat in the body wall of two species in the experiment.
اظهر المزيد [+] اقل [-]Enzyme-based solutions for textile processing and dye contaminant biodegradation—a review النص الكامل
2017
Chatha, Shahzad Ali Shahid | Asgher, Muhammad | Iqbal, Hafiz M. N.
The textile industry, as recognized conformist and stake industry in the world’s economy, is facing serious environmental challenges. In numerous industries, in practice, various chemical-based processes from initial sizing to final washing are fascinating harsh environment concerns. Some of these chemicals are corrosive to equipment and cause serious damage itself. Therefore, in the twenty-first century, chemical and allied industries quest a paradigm transition from traditional chemical-based concepts to a greener, sustainable, and environmentally friendlier catalytic alternative, both at the laboratory and industrial scales. Bio-based catalysis offers numerous benefits in the context of biotechnological industry and environmental applications. In recent years, bio-based processing has received particular interest among the scientist for inter- and multi-disciplinary investigations in the areas of natural and engineering sciences for the application in biotechnology sector at large and textile industries in particular. Different enzymatic processes such as chemical substitution have been developed or in the process of development for various textile wet processes. In this context, the present review article summarizes current developments and highlights those areas where environment-friendly enzymatic textile processing might play an increasingly important role in the textile industry. In the first part of the review, a special focus has been given to a comparative discussion of the chemical-based “classical/conventional” treatments and the modern enzyme-based treatment processes. Some relevant information is also reported to identify the major research gaps to be worked out in future.
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