خيارات البحث
النتائج 4081 - 4090 من 8,010
Efficient separation and recovery of Re(VII) from Re/U bearing acidic solutions using aminotriazole modified cellulose microsphere adsorbents النص الكامل
2021
Wen, Di | Hua, Rong | Dong, Zhen | Xie, Kangjun | Qi, Wei | Zhao, Long
In this work, aminotriazole-modified microcrystalline cellulose microsphere (3-ATAR) containing an abundant nitrogen content as promising adsorbent was prepared via a radiation grafting method for the selective recovery ReO₄⁻ in the presence of UO₂²⁺ in acidic solution. A series of batch and column adsorption experiments including monocomponent and binary systems were designed for evaluating the adsorption and separation performance of Re(VII) onto 3-ATAR. The 3-ATAR exhibited a good adsorption capacity (max 146.4 mg·g⁻¹) of Re(VII) and a rapid adsorption rate, with equilibrium time of 45 min. In binary solution, the high selectivity coefficients (βRₑ/M) indicated that 3-ATAR could separate and recover Re(VII) from U(VI) and other metal ions (Cu(II), Cr(III), Ni(II), Zn(II)). In particular, it was found that the adsorption of Re was almost unaffected in U/Re-bearing solutions no matter how much the U(VI) was changed. In the column experiment, when the concentration of U(VI) was 40 times higher than that of Re(VII), 3-ATAR manifested high Re(VII) selectivity over U(VI) from a synthetic uranium ore leachate. This work demonstrated that 3-ATAR could provide an efficient, selectively, sustainable, and industrially feasible way for Re(VII) to be recovered from uranium ore leachate and other prospective sources.Graphical abstract
اظهر المزيد [+] اقل [-]Solar photocatalysis as strategy for on-site reclamation of agro-wastewater polluted with pesticide residues on farms using a modular facility النص الكامل
2021
Garrido, Isabel | Fenoll, José | Flores, Pilar | Hellín, Pilar | Pérez-Lucas, Gabriel | Navarro, Simón
One of the consequences of phytosanitary treatments applied to crops is the generation of a great volume of agro-wastewater having pesticide residues. These pollutants can be considered a serious threat to the environment and human health due to their capacity to affect distant areas remaining for a long time after their application. We have assessed the degradation of five pesticides in agro-waste water produced in two farms by the cleaning pesticide containers and phytosanitary treatment equipment used in the farms. For this purpose, a pilot facility was installed in both farms and advanced oxidation treatments were conducted using natural sunlight by means of Na₂S₂O₈ and heterogeneous photocatalysis (TiO₂/Na₂S₂O₈). The remaining percentages obtained at the end of the experiments ranged from 5 to 90.1% for chlorantraniliprole, 5 to 82.3% for difenoconazole, 0.02 to 19.1% for metalaxyl, 1.4 to 74.4% for myclobutanil, and 0.3 to 61% for triadimenol. We observed a correlation between the higher remaining percentages and the total initial concentration of pollutant because of other commercial formulations applied in the farms. The results showed that this equipment could be used to eliminate or reduce the presence of pesticide residues in agro-waste water using an innovative facility installed in the farms and a renewable and economical source of energy (sunlight).
اظهر المزيد [+] اقل [-]Contamination of habu (Protobothrops flavoviridis) in Okinawa, Japan by persistent organochlorine chemicals النص الكامل
2021
Tashiro, Yutaka | Goto, Akitoshi | Kunisue, Tatsuya | Tanabe, Shinsuke
Persistent organochlorine chemicals (OCs), including chlordane compounds (CHLs), DDTs, PCBs, and chlorinated dioxins and related compounds (DRCs), were examined in the adipose tissue and liver from 33 specimens of habu (Protobothrops flavoviridis), a species of venomous pit viper endemic to the Japanese Southwest Islands. The median concentrations of CHLs, DDTs, and PCBs in adipose tissue of 22 habus collected from an urban area were 4400 ng g⁻¹ lipid weight (lw), 610 ng g⁻¹ lw, and 1600 ng g⁻¹ lw, respectively. Their DDT and PCB concentrations were higher in comparison with the specimens from a rural area. Liver of 10 specimens from the urban area were subjected to DRCs analysis, and PCDDs, PCDFs, and DL-PCBs were detected with median values of 1300, 350, and 150,000 pg g⁻¹ lw, respectively. Among PCDD/F congeners, octa-CDD was detected at the highest concentrations in seven liver samples, but considerable concentrations of penta- and hexa-CDD/Fs were found in two samples. Relatively higher concentrations of PCB, DDTs, and PCDD/Fs were found in habus collected within 1 km of the boundary of military facilities, suggesting that OCs from some unknown sources of these OCs inside and/or around some of the facilities accumulated in habus.
اظهر المزيد [+] اقل [-]Application of neural network and time series modeling to study the suitability of drain water quality for irrigation: a case study from Egypt النص الكامل
2021
Abdel-Fattah, Mohamed K. | Mokhtar, Ali | Abdo, Ahmed I.
Limited water resources are one of the major challenges facing Egypt during the current stage. The agricultural drainage water is an important water resource which can be reused for agriculture. Thus, the current study aims to assess the quality of drainage water for irrigation purpose through monitoring and predicting its suitability for irrigation. The chemical composition of Bahr El-Baqr water drain, especially salinity, as well as ions are mainly involved in calculating indicators of water suitability for irrigation, i.e., Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO⁻³, Cl⁻, and SO₄²⁻. Further analysis was carried out to evaluate the irrigation water quality index (IWQI) through integrated approaches and artificial neural network (ANN) model. Further, ARIMA models were developed to forecast IWQI of Bahr El-Baqr drain in Egypt. The results indicated that the computed IWQI values ranged between 46 and 81. Around 11% of the samples were classified as excellent water, while 89% of the samples were categorized as good water. The results of IWQI showed a standard deviation of 8.59 with a mean of 62.25, indicating that IWQI varied by 13.79% from the average. ANN model showed much higher prediction accuracy in IWQI modeling with R² value greater than 0.98 during training, testing and validation. A relatively good correlation was obtained, between the actual and forecasted IWQI based on the Akaike information criterion (AIC); the best fit models were ARIMA (1,0) (0,0) without seasonality. The determination coefficient (R²) of ARIMA models was 0.23. Accordingly, 23% of IWQI variability could be explained by different model parameters. These findings will support the water resources managers and decision-makers to manage the irrigation water resources that can be implemented in the future.
اظهر المزيد [+] اقل [-]Associations between apolipoprotein B and selected perfluoroalkyl substances among diabetics and nondiabetics النص الكامل
2021
Jain, Ram B. | Ducatman, Alan
Previous population investigation of perfluoroalkyl substances (PFAS) features associations with lipids in a number of populations; these investigations have seldom included consideration of apolipoproteins. Apolipoprotein B (Apo B) fractions were considered in this descriptive analysis because they are essential to the assembly, transport, and cellular uptake of lipid classes associated with poorer health outcomes, and they are associated with incident and prevalent disease. Regression models stratified by diabetes and lipid lowering medication (LLM) status for data from National Health and Nutrition Examination Survey for 2007–2014 were fitted to interrogate associations between selected PFAS and Apo B for US adults aged ≥ 20 years. Adjusted concentrations of Apo B were positively associated with perfluorooctanoic acid (PFOA β = 0.03878, p < 0.01), perfluorooctane sulfonic acid (PFOS β = .02029, p = 0.02), and perfluorononanoic acid (PFNA β = .01968, p = .03) for nondiabetics who were not taking lipid lowering medications. These associations were not seen among diabetic participants, except for perfluorodecanoic acid (PFDA) in those taking LLMs (β = 0.03831, p = 0.02). We also note that LLMs have an inferred greater impact on Apo B in the diabetics compared to the nondiabetic populations. We have considered several sources of confounding and think the data are most consistent with a weak causal association that PFAS exposure increases Apo B. The rodent toxicology literature also contains evidence that PFAS disrupt fatty acid trafficking including Apo B, although how the specific findings may relate to circulating human Apo B concentrations is unclear. We therefore advocate for attempts to replicate the findings in other populations and to consider additional types of mechanistic studies.
اظهر المزيد [+] اقل [-]Heavy metals in playgrounds in Lublin (E Poland): sources, pollution levels and health risk النص الكامل
2021
Zgłobicki, Wojciech | Telecka, Małgorzata | Skupiński, Sebastian
In the paper, the pollution of playgrounds in Lublin with heavy metals was assessed. Since playgrounds are a place of activity of children—the most vulnerable group of city residents, identifying the degree of pollution and the related health hazards is particularly important. 50 playgrounds were investigated, and samples were collected from three types of places: soil in the playgrounds, soil beneath the swings and soil in the sandpits (a total of 91 samples); heavy metal levels were determined in the < 0.05-mm fraction. The mean heavy metal levels were Cd—4.7 mg kg⁻¹, Cr—192.4 mg kg⁻¹, Cu—16.3 mg kg⁻¹, Hg—0.027 mg kg⁻¹, Ni—12.7 mg kg⁻¹, Pb—41 mg kg⁻¹, and Zn—79.8 mg kg⁻¹, and they were in the following order when normalised to the geochemical background: Cd > Cr > Zn > Pb > Hg > Ni > Cu. The highest mean levels occurred in the case of soil collected from beneath the swings (Cd, Cr, Ni and Zn) or soil in the playgrounds (Cu, Hg and Pb). Geochemical indices such as Igₑₒ and EF indicate the lack of pollution or low level of pollution with Cu, Cr, Ni, Zn and Pb. Moderate or considerable pollution with Cd and, sporadically, with Hg occurred in some playgrounds. A significant ecological risk was found for all samples due to the presence of Cd and, for about 20% of the samples, the concentration of Hg. In all the cases analysed, the values of health hazard indices (HI, CR) for children are very low and well below the hazard threshold for each element.
اظهر المزيد [+] اقل [-]Concentration-dependent enantioselective accumulation of chiral polychlorinated biphenyls in Nelumbo nucifera Gaertn. root from contaminative sediment النص الكامل
2021
Dai, Shouhui | Qiu, Jing | Wang, Min
Nelumbo nucifera Gaertn. (lotus) roots were collected from contaminated sediments which were artificially adding different concentrations of chiral polychlorinated biphenyls (PCBs) to investigate the effect of concentration on the accumulation characteristics and chiral signatures of PCBs in lotus root during its growth period of 150 days. Under high PCB exposure concentration, the biota-sediment accumulation factors (BSAFs) of PCBs 91, 95, and 136 in the lotus root were up to 0.25–0.46 and 8.10–10.5 times higher than those under low-exposure concentration (0.024–0.052). The BSAFs of PCBs 149, 176, and 183 under high-exposure concentration were up to 0.24–0.44, while they were undetected at low concentration. The significant difference observed in the BSAFs based on different concentrations indicates that the lotus root accumulation efficiency toward chiral PCBs increases with the contaminate concentration. Although the (–)-enantiomers of PCBs 91, 95, and 136 were all preferentially accumulated in lotus root under two exposure concentrations, the extent of the preferential accumulation of (–)-PCB 95 decreased with increasing exposure concentration throughout the whole growth period (30–150 days). In addition, the (–)-enantiomers of PCBs 91 and 136 also showed the same tendency during most of the growth period. Conclusively, the exposure concentrations are an important influence factor on the enantioselective accumulation of chiral PCBs in lotus root.
اظهر المزيد [+] اقل [-]Chromium retention potential of two contrasting Solanum lycopersicum Mill. cultivars as deciphered by altered pH dynamics, growth, and organic acid exudation under Cr stress النص الكامل
2021
Javed, Muhammad Tariq | Tanwir, Kashif | Abbas, Saghir | Saleem, Muhammad Hamzah | Iqbal, Robina | Chaudhary, Hassan Javed
Chromium (Cr), being a persistent toxic heavy metal, triggered the retardation of plant’s metabolic processes by initiating changes in rhizospheric zone. Current study focused the Cr accumulation potential of two tomato (Solanum lycopersicum Mill.) cultivars through alterations of rhizospheric pH and exudation of organic acids together with plant’s ionomics and morpho-physiological responses. Four-week-old seedlings of tomato cultivars (cv. Nakeb and cv. Nadir) were maintained in hydroponic solutions supplemented with 0, 100, 200, and 300 mg/L K₂Cr₂O₇ and a start pH of 6.0. The pH of the growth medium was monitored twice a day up to 6 days as well as mineral contents and morpho-physiological attributes were recorded by harvesting half of plants after 1 week. The remaining half plants were shifted to rhizoboxes for the collection of root exudates. After 6 days, cv. Nakeb exhibited medium acidification by 0.7 units while cv. Nadir showed basification by 0.6 units under 300 mg/L treatment. Increase in applied Cr levels enhanced the root and shoot Cr accumulation in both cultivars with concomitant reduction in growth and accumulation of nutrients (Fe, Zn, K, Mg, and Ca). However, this reduction in biomass and nutrient acquisition was predominant in cv. Nakeb as compared to cv. Nadir. The release of organic acid exudates (citric, acetic, maleic, tartaric, and oxalic acids) was also recorded higher in cv. Nadir at 300 mg/L applied Cr level. This enhanced production of organic acids caused greater retention of mineral nutrients and Cr in cv. Nadir, probably due to growth medium basification. Enhanced exudations of di- and tri- carboxylic organic acids together with accumulation of mineral nutrients are the physiological and biochemical indicators which confer this genotype a better adaptation to Cr polluted biotic systems. Furthermore, it was perceived that organic acid and rhizospheric pH variation response by studied tomato cultivars under Cr stress is an important factor to be considered in food safety and metal remediation programs.
اظهر المزيد [+] اقل [-]Efficient mineralization of gaseous benzyl chloride by VUV/UV photodegradation in humid air النص الكامل
2021
Sun, Xue | Li, Chaolin | Ren, Liyuan | Wang, Wenhui
VUV/UV photodegradation technology, which is free of catalysts or oxidants, has been regarded as an efficient method to decompose gaseous VOCs. However, the mineralization of gaseous VOCs by VUV/UV photodegradation has seldom been discussed systematically. In this work, the mineralization of benzyl chloride in humid air is comprehensively investigated and the potential contributors in the system (i.e., light wavelength, O₂ and H₂O) are discussed. As a result, more than 95.0% benzyl chloride is mineralized at 40 min in humid air with 80% relative humidity (RH) despite its initial concentrations (i.e., ranging from 4 to 20 ppm). It is found that both 185-nm VUV light and H₂O significant contribute to the efficient mineralization of benzyl chloride in humid air, while O₂ only has a limited effect to the efficient mineralization of benzyl chloride in humid air. The introduction of H₂O into the VUV/UV photodegradation can reduce the emission of ozone obviously. These findings are significant inspiration to application of the VUV/UV photodegradation technology on the treatment of gaseous VOCs in the actual air atmosphere.
اظهر المزيد [+] اقل [-]Efficient toluene adsorption/desorption on biochar derived from in situ acid-treated sugarcane bagasse النص الكامل
2021
Qu, Yuan | Xu, Li | Chen, Yi | Sun, Shikuan | Wang, Yu | Guo, Limin
Carbon-based materials with great adsorption performance are of importance to meet the needs of industrial gas adsorption. Having massive agricultural wastes of sugarcane bagasse, China could use this waste into wealth. However, the comprehensive utilization of sugarcane bagasse as precursor for biochar that can be used as adsorbent has not been extensively explored. In this study, a series of in situ sulfuric acid–modified biochar was prepared by hydrothermal carbonization process. The prepared biochar (SBAC-7) has a combination of two main advantages that are high microporosity (micropore surface area = 1106 m²/g) and being rich in S-containing functional groups on the surface. In particular, SBAC-7 showed an excellent adsorption capacity of toluene (771.1 mg/g) at 30 °C, which is nearly 3 times as high as that of the commercial activated carbons. Meanwhile, it showed great stability and cyclic regeneration performance with five toluene adsorption-desorption test cycles. This study provides a high-performance biochar for the adsorption-desorption cycle in practical engineering applications, and would contribute to the sustainable “sugarcane production–bagasse utilization” circular economy.
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