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Resultados 4471-4480 de 6,558
Facile preparation of L-cysteine–modified cellulose microspheres as a low-cost adsorbent for selective and efficient adsorption of Au(III) from the aqueous solution Texto completo
2020
Yang, Xin | Pan, Qi | Ao, Yinyong | Du, Jifu | Dong, Zhen | Zhai, Maolin | Zhao, Long
A facile method to synthesize adsorbent based on cellulose modified by amino acid was developed. The novel L-cysteine–functionalized adsorbent for Au(III) recovery was synthesized via radiation grafting technique. Glycidyl methacrylate (GMA) was grafted on the surface of microcrystalline cellulose microsphere (MCC); next, ring-opening reaction was performed to immobilize L-cysteine. The adsorption abilities of the adsorbent (CysR) were tested. Batch experiments suggested that the maximum adsorption capacity of Au(III) is 714.28 mg/g calculated by Langmuir model. The adsorption kinetic data was followed by pseudo-second-order model. CysR showed excellent selectivity for Au(III) even the concentration of competing ions was all ten times than that of Au(III). The column experiments revealed that Au(III) could be efficiently adsorbed by CysR competition with equal amounts of Ni(II) and Zn(II). Moreover, XPS analysis demonstrated that the adsorbed Au(III) was reduced to Au(I) and Au(0). The adsorption performance certified that CysR was a promising adsorbent for Au(III) recovery.
Mostrar más [+] Menos [-]Social benefits of improving water infrastructure in South Korea: upgrading sewage treatment plants Texto completo
2020
Ahn, Joongha | Moon, HyungBin | Shin, Jungwoo | Ryu, Jaena
A sewage treatment plant is considered an undesirable facility because of public concerns about odor, hygiene, and lowered house prices in the neighborhood. In South Korea, many aging sewage treatment plants need to be upgraded because they show inadequate performance on the removal of major pollutants. However, issues involved in such upgrades include social conflicts between the local government and residents, and economic feasibility. Examinations of social acceptability that include economic analyses are needed in order to fulfill social demand for upgrading the sewage treatment plants while simultaneously guaranteeing efficiency and minimizing social costs. This study investigates the social benefits of expanding and modernizing sewage treatment plants in South Korea using the contingent valuation method. Results show that Korean households, on average, are willing to pay 36,340 KRW (33.25 USD) per year for upgrading sewage treatment plants. About 47.73% of the project costs can be covered by the social benefits the Korean households enjoy. This study suggests that the Korean government needs to consider estimated social benefits in determining the scale and timeline of upgrade projects. The results of this study may help with stable implementation of upgrade projects for sewage treatment plants.
Mostrar más [+] Menos [-]Fractionation analysis and health risk assessment of heavy metals in six traditional Chinese medicines Texto completo
2020
Nan, Guanjun | Meng, Xianxin | Song, Ning | Liu, Zhengzheng | Liu, Yu | Yang, Guangde
Traditional Chinese medicines (TCMs) are widely used to treat various diseases in China and some countries, and TCM products are becoming increasingly available and popular worldwide. But TCMs are facing the challenge of heavy metal pollution. In this work, we examined the total contents and fractionations of Pb, Cd, Hg, and Cu in six TCMs (Angelicae Sinensis Radix (ASR), Chuanxiong Rhizoma (CR), Polygonati Rhizoma (PR), Astragali Radix (AR), Carthami Flos (CF), and Paeoniae Radix Rubra (PRR)) and evaluated the health risk of four heavy metals in these TCMs. The results showed that Cd, Pb, and Cu contents were considerably high and the amount of Cd in six TCMs, Pb in CR, ASR, AR, and CF, and Hg in ASR, PR, and PRR exceeded the limit values. The predominant fractions of Pb, Cd, and Cu were exchangeable and carbonate fractions in six TCMs; Hg mainly existed in organic and residual fractions. The average daily intake dose (ADD) and target hazard quotient (THQ) of Pb based on total content and total THQ of four heavy metals based on bioaccessible fractions in AR and PRR exceeded the safety guideline. These results indicated that the potential health risk could occur by taking these TCMs.
Mostrar más [+] Menos [-]Iron and molybdenum mixed oxide supported on Al-PILC for the catalytic oxidative desulfurization of dibenzothiophene in simulated diesel fuel Texto completo
2020
Tireli, Aline Auxiliadora | do Rosário Guimarães, Iara | Mello Mattos de Castro, Guilherme | Gonçalves, Mateus Aquino | de Castro Ramalho, Teodorico | Guerreiro, Mário Cesar
In this work, three novel catalysts were prepared by 2.5, 5.0, and 10.0 wt.% facile impregnation with an iron and molybdenum mixed oxide (Fe/Mo) on an aluminum pillared clay (Al-PILC) support. These materials were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), temperature programed reduction (TPR), and nitrogen (N₂) physisorption at 77 K. Characterizations indicated that the metal particles were dispersed on the surface of the three catalysts, and the interlayer d₀₀₁ spacing of the pillared material remained unchanged after the impregnation process. The catalytic tests showed good results for DBT oxidation using the synthesized catalysts, with high turnover frequency (TOF) values, particularly for the material with 5.0 wt.% Fe/Mo. Theoretical calculations were carried out at the density functional theory (DFT) level, to investigate how the DBT molecules were adsorbed onto the surface of the mixed oxide. The lowest energy proposal was obtained when both Fe and Mo were present at the active sites, indicating a possible synergistic effect of the metals on catalyst activity. Reuse tests indicated that the catalysts could be employed effectively for up to 3 cycles in a row, then a decrease in activity occurred and the active sites needed to be regenerated.
Mostrar más [+] Menos [-]Synthesis of mesoporous magnetic polypyrrole and its application in studies of removal of acidic, neutral, and basic pharmaceuticals from aqueous medium Texto completo
2020
Pires, Bruna Carneiro | Dutra, Flávia Viana Avelar | Borges, Keyller Bastos
As an alternative to traditional adsorbents, mesoporous magnetic polypyrrole (MMPPy) was first used as an adsorbent for the removal of acid, neutral, and basic pharmaceutical compounds considered aqueous pollutants. Ibuprofen (IBU, acid), caffeine (CAF, neutral), and bupropion (BUP, basic) were chosen as adsorbates and applied in adsorption studies. They proved to be pH dependent of the aqueous solution and the best results were found at pH 4 for IBU and CAF and pH 7 for BUP and 60 mg was the optimal amount of adsorbent to be used in the studies. Adsorption was extremely fast and the equilibrium was reached up to 180 s. The adsorption data of all analytes could be well interpreted by the pseudo second-order kinetic model and the dual-site Langmuir-Freundlich isotherm model. The adsorption capacities obtained by the dual-site Langmuir-Freundlich model were 53.67 mg g⁻¹, 16.74 mg g⁻¹, and 24.72 mg g⁻¹ for IBU, CAF, and BUP, respectively. Thermodynamic parameters revealed that IBU adsorption becomes spontaneous as temperature increases and CAF and BUP adsorption occurs through a non-spontaneous process. In addition, this study shows endothermic nature of the adsorption process. Analytes were desorbed using an aqueous solution at pH 10 for IBU, pH 7 for CAF, and pH 4 for BUP and then the material was regenerated successfully. The results suggest that MMPPy can be efficiently used in the removal of different organic analytes found in contaminated water.
Mostrar más [+] Menos [-]Exposure to arsenic and lead in children from Salamanca México, effects on telomeric lengthening and mitochondrial DNA Texto completo
2020
Alegría Torres, Jorge Alejandro | Pérez Rodríguez, Rebeca Yasmín | García Torres, Lizeth | Costilla Salazar, Rogelio | Rocha-Amador, Diana
Levels of urinary arsenic and levels of lead in blood were measured in children attending elementary schools located in an industrial zone in Salamanca, México. Its possible effects using telomere length and mitochondrial DNA copy number as biomarkers of genomic disequilibrium by oxidative stress were studied. Eighty-eight children (6–15 years old) were included and urine samples were collected for quantification of arsenic, while lead was measured in blood samples using inductively coupled plasma mass spectrometry (ICP-MS). DNA was isolated from peripheral blood and relative telomere length and the mitochondrial DNA copy number were determined by real-time PCR. The geometric mean of urinary arsenic was 54.16 μg/L (11.7–141.1 μg/L). Ninety-eight percent of the children were above 15 μg/L (biomonitoring equivalent value). With respect to the concentration of lead in blood, the mean was 3.78 μg/dL (LOD-22.61), where 24.5% of the participants had equal or above the reference value (5 μg/dL; Mexican Official Norm NOM-199-SSA1–2000, 2017). A positive association between urinary arsenic and telomere length was found (β = 0.161; 95% CI: 0.12; 0.301; P = 0.034), while lead blood concentrations were negatively associated with mitochondrial DNA copy number (β = − 0.198; 95% CI: − 2.81; − 0.17; P = 0.019), after adjusting by age, sex, and total white blood cell count. Differences in the mitochondrial DNA content were observed in children with lead blood levels from 2.5 μg/dL, (P ≤ 0.001), suggesting an effect at lead exposure levels considered acceptable (< 5 μg/dL). In conclusion, children living in an industrial area in Salamanca showed an exposure to arsenic and lead and an impact on telomere length and mitochondrial DNA content associated with arsenic and lead exposure, respectively.
Mostrar más [+] Menos [-]The effect of biochar on severity of soil water repellency of crude oil-contaminated soil Texto completo
2020
Ebrahimzadeh Omran, Samaneh | Shorafa, Mehdi | Zolfaghari, Ali Asghar | Soltani Toolarood, Ali Ashraf
Crude oil contamination adversely affects soil water repellency. In this study the effect of biochar on this soil characteristic has been investigated in the laboratory. Soil sample was collected from a field located near Pars Oil Company, at the top depth of 0–15 cm below surface. After air-drying and passing through a 2-mm sieve, the soil was artificially contaminated with four levels of crude oil (1:0, 1:25, 1:16.6, and 1:12.5 ratios). Biochars used in this research were generated from beechwood and maize residues at three different pyrolysis temperatures (350 °C, 550 °C, and 750 °C). Chemical functionality of all biochar samples was determined using Fourier-transform infrared spectrometry. Sufficient amounts of beechwood and maize biochars, passed through a 0.053-mm and 2-mm sieves, were mixed into crude oil-contaminated soil at the rate of 0, 0.5, 1, and 2% of total dry soil weight. The mixed samples were then laboratory incubated for 90 days at 24 °C and 10% soil moisture. Water repellency was measured using water drop penetration time (WDPT). The experimental results showed that functional groups on the biochars’ surfaces produced at the studied temperatures were distinct. Beechwood and fine size of biochar showed more ability in reducing the hydrophobicity. The produced biochars, at higher temperature, had more potential to alleviate water repellency due to the strong interactions between functional groups of biochars and crude oil. The highest amount of biochar used (2%) significantly alleviated water repellency.
Mostrar más [+] Menos [-]Synthesis and application of Cu-BTC@ZSM-5 composites as effective adsorbents for removal of toluene gas under moist ambience: kinetics, thermodynamics, and mechanism studies Texto completo
2020
Li, Meng | Li, Yuwei | Li, Wei | Liu, Fang | Qi, Xuejin | Siuvai, Ming | Wang, Yongqiang | Zhao, Chaocheng
Metal organic frameworks (MOFs) are excellent adsorbents that provide abundant specific surface area, adjustable pore structure, and rich active sites. The purpose of this study was to prepare composites with hydrophobic and high microporous specific surface area and to adsorb toluene gas in moist ambience. An ethanol activation-assisted hydrothermal method was proposed to synthesize copper-benzene-1,3,5-tricarboxylic acid (Cu-BTC) metal-organic framework, Cu-BTC, and ZSM-5 molecular sieve composites (Cu-BTC@ZSM-5). The dynamic adsorption process of toluene on different adsorbents was investigated, and the results showed that the toluene adsorption capacity of Cu-BTC@ZSM-5 (158.6 mg/g) was 2.53 times higher than Cu-BTC (62.7 mg/g), when the ZSM-5 content is 5% and the humidity is 30%RH. Compared with other factors, the humidity inhibited the adsorption of toluene on Cu-BTC@ZSM-5. Langmuir model and the pseudo-second kinetics model can better describe the adsorption behavior of Cu-BTC@ZSM-5. The thermodynamic results showed the adsorption process was a spontaneous exothermic process at low temperature and mainly physical adsorption. The relative regenerability can still up to 80.4% after six cycles. The adsorption mechanisms of Cu-BTC@ZSM-5 were pore-filling adsorption, π-π interaction, cation-π bonding, and hydrophobic interactions. This study will help to design a systematic route to evaluate the adsorption performance of Cu-BTC@ZSM-5 for toluene.
Mostrar más [+] Menos [-]Effect of mobile phone radiation on oxidative stress, inflammatory response, and contextual fear memory in Wistar rat Texto completo
2020
Singh, Kumari Vandana | Gautam, Rohit | Meena, Ramovtar | Nirala, Jay Prakash | Jha, Sushil Kumar | Rajamani, Paulraj
In the present lifestyle, we are continuously exposed to radiofrequency electromagnetic field (RF-EMF) radiation generated mainly by mobile phones (MP). Among other organs, our brain and hippocampus in specific, is the region where effect of any environmental perturbation is most pronounced. So, this study was aimed to examine changes in major parameters (oxidative stress, level of pro-inflammatory cytokines (PICs), hypothalamic-pituitary-adrenal (HPA) axis hormones, and contextual fear conditioning) which are linked to hippocampus directly or indirectly, upon exposure to mobile phone radiofrequency electromagnetic field (MP-RF-EMF) radiation. Exposure was performed on young adult male Wistar rats for 16 weeks continuously (2 h/day) with MP-RF-EMF radiation having frequency, power density, and specific absorption rate (SAR) of 1966.1 MHz, 4.0 mW/cm², and 0.36 W/kg, respectively. Another set of animals kept in similar conditions without any radiation exposure serves as control. Towards the end of exposure period, animals were tested for fear memory and then euthanized to measure hippocampal oxidative stress, level of circulatory PICs, and stress hormones. We observed significant increase in hippocampal oxidative stress (p < 0.05) and elevated level of circulatory PICs viz. IL-1beta (p < 0.01), IL-6 (p < 0.05), and TNF-alpha (p < 0.001) in experimental animals upon exposure to MP-RF-EMF radiation. Adrenal gland weight (p < 0.001) and level of stress hormones viz. adrenocorticotropic hormone (ACTH) (p < 0.01) and corticosterone (CORT) (p < 0.05) were also found to increase significantly in MP-RF-EMF radiation-exposed animals as compared with control. However, alteration in contextual fear memory was not significant enough. In conclusion, current study shows that chronic exposure to MP-RF-EMF radiation emitted from mobile phones may induce oxidative stress, inflammatory response, and HPA axis deregulation. However, changes in hippocampal functionality depend on the complex interplay of several opposing factors that got affected upon MP-RF-EMF exposure.
Mostrar más [+] Menos [-]Association between ambient temperature and daily emergency hospitalizations for acute coronary syndrome in Yancheng, China Texto completo
2020
Guo, Shumei | Niu, Yue | Cheng, Yuexin | Chen, Renjie | Kan, Julia | Kan, Haidong | Li, Xu | Li, Jiading | Cao, Jingyan
Acute coronary syndrome (ACS) is a major public health concern worldwide. Few studies have directly evaluated the associations between ambient temperature and ACS incidence. To explore the association between ambient temperature and ACS emergency hospitalizations in the area of subtropical monsoon climate, data on ACS emergency hospitalizations were collected from two highest-ranking hospitals in the central urban area of Yancheng, China, from January 1, 2013, to December 31, 2018. We applied the time-series method to investigate the potentially lagged and non-linear effects of ambient temperature on ACS using the generalized linear model combined with the distributed lag non-linear model after adjusting for time trend, day of the week, holiday, and relative humidity. We identified a total of 5303 cases of ACS emergency hospitalizations during the study period. The exposure-response curves between ambient temperature and ACS hospitalizations were inverse “J-shaped.” The effects of extreme low temperature on ACS hospitalizations occurred on the present day and lasted for 3 days, followed by the harvesting effect. The effects of extreme high temperature occurred on the present day and lasted for 5 days. The cumulative relative risks of ACS were 2.14 [95% confident interval (CI): 1.32 to 3.47] for extremely low temperature and 1.66 (95% CI: 1.33 to 2.06) for extremely high temperature over the lag of 0–5 days, compared with the reference temperature (25.0 °C). Both low and high temperatures were significantly associated with higher risks of emergency hospital admissions for ACS in Yancheng, China.
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