Refinar búsqueda
Resultados 3151-3160 de 4,936
Graphene oxide wrapped copper-benzene-1,3,5-tricarboxylate metal organic framework as efficient absorbent for gaseous toluene under ambient conditions Texto completo
2019
Dai, Yexin | Li, Meng | Liu, Fang | Siuvai, Ming | Wang, Yongqiang | Zhao, Chaocheng
The ultrasonic-assisted hydrothermal and ethanol activation method was proposed to synthesize copper-benzene-1,3,5-tricarboxylate (Cu-BTC) metal organic framework and Cu-BTC/graphene oxide (GO) composites (Cu-BTC@GO). The dynamic adsorption behavior of toluene on two adsorbents was studied and compared with that of GO and reduced graphene oxide (RGO). The Cu-BTC@GO exhibited high adsorption capacity (183 mg/g) for toluene, which is nearly three times as much as that of Cu-BTC (62.7 mg/g) with the GO mass fraction of 20%. Furthermore, the adsorption of toluene on Cu-BTC@GO composites was positively correlated with the initial concentration of toluene and the adsorbent dosage, and negatively correlated with the temperature. The adsorption data of toluene on Cu-BTC@GO composites were well in accordance with pseudo-first kinetics model. Langmuir model had a better fit than Freundlich model. The adsorption thermodynamic results showed that the adsorption process was mainly physical adsorption and the adsorption process was spontaneous at low temperature. After five adsorption–desorption cycles, the adsorption efficiency can still reach 82.1%.This study will help to draw a promising roadmap to describe the adsorption performance of Cu-BTC@GO composites for toluene.
Mostrar más [+] Menos [-]Removal of Pb(II) from aqueous solutions by adsorption on magnetic bentonite Texto completo
2019
Zou, Chenglong | Jiang, Wei | Liang, Jiyan | Sun, Xiaohang | Guan, Yinyan
Bentonite is a porous clay material that shows good performance for adsorbing heavy metals and other pollutants for wastewater remediation. In our previous study, magnetic bentonite (M-B) was prepared to solve the separation problem and improve the operability. In this study, we investigated the influence of various parameters on the Pb(II) adsorption of M-B, and it showed effective performance. About 98.9% adsorption removal rate was achieved within 90 min at adsorbent dose of 10 g/L for initial Pb(II) concentration of 200 mg/L at 40 °C and pH 5. The adsorption kinetic fit well by the pseudo-second-order model, and also followed the intra-particle diffusion model up to 90 min. Moreover, adsorption data were successfully reproduced by the Langmuir isotherm; the maximum adsorption capacity was calculated as 80.40 mg/g. The mechanism of interaction between Pb(II) ions and M-B was ionic exchange, surface complexation, and electro-static interactions. Thermodynamics study indicated that the reaction of Pb(II) adsorption on M-B was endothermic and spontaneous; increasing the temperature promoted adsorption. This study was expected to provide a reference and theoretical basis for the treatment of Pb-containing wastewater using bentonite materials.
Mostrar más [+] Menos [-]Unprecedented high percentage of food waste powder filler in poly lactic acid green composites: synthesis, characterization, and volatile profile Texto completo
2019
Cecchi, Teresa | Giuliani, Arianna | Iacopini, Federica | Santulli, Carlo | Sarasini, Fabrizio | Tirillò, Jacopo
The attractive qualities of plastics lead us, around the world, to an enormous need for plastic goods, which results in their unsustainable overconsumption. Bio-based products are the core concept of circular economy, yet this sector suffers from the high cost of their production. In practice, biopolymers, such as polylactic acid (PLA), are still limitedly used, due to their expensiveness and not outstanding technological properties. A circular and sustainable solution would be to use waste from the food industry as filler that contributes to reduce the cost of PLA-based materials, thereby encouraging their widespread use. At the same time, this would be a circular approach to wisely upgrade food waste and prevent pollution. Ceramic food waste powder fillers from egg shells and from mussel shells were compounded with PLA at 180 °C to obtain composites, which contain an unprecedented high amount of filler, equal to 140 over 100 parts of PLA. We analyzed volatile organic compounds emitted from PLA and, for the very first time, from its composites via headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The molecular fingerprint of the volatiles comprises only three aldehydes, a ketone, and two lactides. Volatiles typical of fossil plastics, that are causative factors of hormone disruption or reproductive dysfunction, are effectively missing. Scanning electron microscopy, used to examine the structure of the composite, indicates that both the egg shells and the mussel shells are suitable fillers, in that they form a sufficiently strong interface with the polymer.
Mostrar más [+] Menos [-]Removal efficiency of commonly prescribed antibiotics via tertiary wastewater treatment Texto completo
2019
Burch, Kayla D. | Han, Bangshuai | Pichtel, John | Zubkov, Tykhon
Wastewater treatment plants (WWTPs) have been identified as “hot spots” of antibiotics release to the environment. Treatment operations at WWTPs may remove a significant proportion of antibiotics from influent wastewater; however, the effects of tertiary treatment processes on antibiotics removal are not well understood. The objective of this review is to summarize the current literature regarding antibiotics removal from common tertiary processes at full-scale municipal WWTPs and to reveal the research gaps and inform future research directions. Chlorination, ultraviolet (UV) irradiation, and sand filtration were reviewed due to their popularity of application in the USA. The majority of studies of antibiotics removal via tertiary wastewater treatment have been conducted in EU nations, the USA, Australia, and China. Chlorination significantly reduces antibiotics concentrations in wastewater effluents. In comparison, sand filtration and UV irradiation are less effective. However, a large discrepancy of removal efficiencies is apparent across different studies of these treatment processes. Increases in antibiotics concentration following tertiary treatment have also been observed. Possible reasons for the discrepancies, such as sorption to filtered particles, sampling strategies, specific operating parameters of wastewater treatment plants, and deconjugation, are discussed. It is concluded that the effects of tertiary treatment on antibiotic removal efficiency are still arguable, and caution must be taken when sampling wastewater in full-scale WWTPs for comparison of removal efficiencies of antibiotics.
Mostrar más [+] Menos [-]Opportunities and challenges in the remediation of metal-contaminated soils by using tobacco (Nicotiana tabacum L.): a critical review Texto completo
2019
Rehman, Muhammad Zia ur | Rizwan, Muhammad | Sohail, Muhammad Irfan | Ali, Shafaqat | Waris, Aisha A. | Khalid, Hinnan | Naeem, Asif | Ahmad, Hamaad Raza | Rauf, Arslan
The successful phytoextraction of potentially toxic elements (PTEs) from polluted soils can be achieved by growing non-food and industrial crops. Tobacco (Nicotiana tabacum L.) is one of the main industrial crops and is widely grown in many countries. Tobacco can uptake high concentrations of PTEs especially in aboveground biomass without suffering from toxicity. This review highlighted the potential of tobacco for the phytoextraction of heavy metals and tolerance mechanisms under metal stress. Different management practices have been discussed which can enhance the potential of this plant for metal extraction. Finally, suitable options for the management/disposal of biomass enriched in excess metal have been elaborated to prevent secondary pollution.
Mostrar más [+] Menos [-]Siting and sizing of distributed generators based on improved simulated annealing particle swarm optimization Texto completo
2019
Su, Hongsheng
Distributed power grids generally contain multiple diverse types of distributed generators (DGs). Traditional particle swarm optimization (PSO) and simulated annealing PSO (SA-PSO) algorithms have some deficiencies in site selection and capacity determination of DGs, such as slow convergence speed and easily falling into local trap. In this paper, an improved SA-PSO (ISA-PSO) algorithm is proposed by introducing crossover and mutation operators of genetic algorithm (GA) into SA-PSO, so that the capabilities of the algorithm are well embodied in global searching and local exploration. In addition, diverse types of DGs are made equivalent to four types of nodes in flow calculation by the backward or forward sweep method, and reactive power sharing principles and allocation theory are applied to determine initial reactive power value and execute subsequent correction, thus providing the algorithm a better start to speed up the convergence. Finally, a mathematical model of the minimum economic cost is established for the siting and sizing of DGs under the location and capacity uncertainties of each single DG. Its objective function considers investment and operation cost of DGs, grid loss cost, annual purchase electricity cost, and environmental pollution cost, and the constraints include power flow, bus voltage, conductor current, and DG capacity. Through applications in an IEEE33-node distributed system, it is found that the proposed method can achieve desirable economic efficiency and safer voltage level relative to traditional PSO and SA-PSO algorithms, and is a more effective planning method for the siting and sizing of DGs in distributed power grids.
Mostrar más [+] Menos [-]Correction to: Occurrence and risk assessment of trace metals and metalloids in sediments and benthic invertebrates from Dianshan Lake, China Texto completo
2019
Wu, Yan | Zhou, Yihui | Qiu, Yanling | Chen, Da | Zhu, Zhiliang | Zhao, Jianfu | Bergman, Åke
The article Occurrence and risk assessment of trace metals and metalloids in sediments and benthic invertebrates from Dianshan Lake, China, written by Yan Wu, Yihui Zhou, Yanling Qiu, Da Chen, Zhiliang Zhu, Jianfu Zhao and Åke Bergman
Mostrar más [+] Menos [-]Sorption of iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy Texto completo
2019
Köhler, Fabian | Riebe, Beate | Scheinost, Andreas C. | König, Claudia | Hölzer, Alex | Walther, Clemens
The environmental fate of iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11–41% to 62–85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.
Mostrar más [+] Menos [-]Innovation and CO2 emissions: the complimentary role of eco-patent and trademark in the OECD economies Texto completo
2019
Mensah, Claudia Nyarko | Long, Xingle | Dauda, Lamini | Boamah, Kofi Baah | Salmān, Muḥammad
Increasing global emissions has led to research on the role of innovations play combating emissions. Mitigations from innovation perspective have mainly been focused on the role of patent, ignoring the role of trademarks. We therefore investigate the mitigating power of patent and trademarks in the OECD economies, benchmarking patent as the traditional mitigation strategy. Examining the complimentary role, we created an interaction term between patent and trademark. Our study divided the OECD economies into four subpanels which are OECD America, OCED Asia, OECD Europe, and OECD Oceania. We employed the Im, Pesaran and Shin W-stat, Augmented Dickey-Fuller, and Phillips Perron unit root tests, as well as cross-sectional dependence and Westerlund cointegration tests for the preliminary test on the variables. We also adopted ARDL approach to cointegration, Granger causality test, and OLS in examining the relationship between CO₂ and patent, trademark, urbanization, and economic growth. Findings show that jointly, eco-patents and trademarks mitigate CO₂ emissions. Also, bidirectional or unidirectional causal relationship was established between our variables of study, an indication that most of our variables can be used in forecasting one other.
Mostrar más [+] Menos [-]Persistence of tetraniliprole and reduction in its residues by various culinary practices in tomato in India Texto completo
2019
Kaushik, Ekta | Dubey, Jatiender Kumar | Patyal, Surender Kumar | Katna, Sapna | Chauhan, Avinash | Devi, Nisha
A field experiment was conducted to study the persistence and dissipation pattern of a new molecule tetraniliprole on tomato fruits and soil. Tetraniliprole was sprayed at the rate of 60 g a.i. ha⁻¹ and 120 g a.i. ha⁻¹on the tomato crop. Tomato fruit samples were analyzed as per the method described by Bosta and Nageswara (Asian J Res Chem 8:383-388, 2015). The residues of tetraniliprole and its metabolite chinazolinon were estimated on HPLC equipped with RP C₁₈ column and photo diode array detector. Initial deposits of tetraniliprole were 0.865 and 1.747 mg kg⁻¹ on fruits and 0.092 and 0.177 mg kg⁻¹ in the soil, respectively, from the two treatments at the rate 60 g a.i. ha⁻¹ and 120 g a.i. ha⁻¹. The residues on fruits dissipated to half in 2.7 and 3.49 days, respectively. Based on the persistence studies, a waiting period of 15 days is suggested on tomato fruit from consumer’s safety point of view. The pesticide residues, left to a variable extent in the tomato after harvesting, are beyond the control of consumers and have deleterious effects on human health; hence, their residues reduction by various culinary processes were highlighted. Treated tomato fruit samples collected at 1, 3, and 5 days after application were also subjected to common household practices. Washing of tomato fruits by tap, lukewarm, and saline water reduce tetraniliprole residues up to 37.63, 44.67, and 61.49%, respectively. Microwave cooking of tomato provided >12% better relief from tetraniliprole residues in comparison with open pan cooking of 72.21%. Chinazolinon residues, a metabolite of tetraniliprole, were not detected in any analyzed processed tomato fruit sample.
Mostrar más [+] Menos [-]