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121.
The chromium(VI) biosorption onto guava seeds, as an alternative method for Cr6+ removal from aqueous solutions, was investigated. The parameters affecting kinetics and equilibrium of Cr6+ adsorption onto guava seeds were studied. An external mass-transfer diffusion coefficient k and intra-particle diffusion coefficient ki were determined to measure the rate-limiting step of adsorption. A single external mass-transfer diffusion model and intra-particle diffusion models were used. The effects of initial pH, sorbent mass, and initial Cr6+ concentrations on mass-transfer coefficients were investigated. The external mass-transfer coefficient has an average value of 7.2×10-3 cm s-1, while the intra-particle mass-transfer diffusion coefficient was 0.34 mg g-1 min-0.5. This indicates that external diffusion to the guava seeds surface and intra-particle diffusion are both involved in the sorption process. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models with an average correlation coefficient R2=0.98. The maximum removal of Cr6+ was obtained at pH 1 (about 100% for adsorbent dose of 15 g l-1 and 25 mg l-1 initial concentration of Cr6+). The results indicated that the guava seeds exhibit acceptable sorption capacity. 相似文献
122.
Highly activated carbon from the seed husk of Casuarina Casuarinas equisetifolia, a worldwide famous plant, have been prepared and tested for the removal of toxic Cr(VI) from its aqueous solution. The adsorbent was investigated for influences of initial chromium concentration (75, 100, 125, and 150 mg l-1), pH, contact time, and quantity of carbon on removal of Cr(VI) from aqueous solution at room temperature (25±2 °C). The adsorption kinetic of Cr(VI) was studied, and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R2≥0.99). The Langmuir and Freundlich models fit the isotherm data well. Furthermore, the Gibbs free energy was obtained for each system and was found to be-5.29 kJ mol-1 for removal of Cr(IV). The negative value of Δ G° indicates the feasibility and spontaneous nature of adsorption. The results indicate that acidic pH (1.05) supported the adsorption of Cr(IV) on activated carbon. The maximum adsorption capacity of Cr(VI) on activated carbon was about 172.4 mg g-1 at pH 1.05. 相似文献
123.
124.
Fajraoui Afef Nasr Jalel Ben Lacoste Catherine Dony Philippe Odof Serge Amar Mohamed Ben Halouani Foued El 《Journal of Polymers and the Environment》2022,30(4):1673-1681
Journal of Polymers and the Environment - In the context of sustainable development and natural products valorization, new ecological materials enter a logic aimed at removing the causes of... 相似文献
125.
Environment Systems and Decisions - Early warning systems for weather events are becoming widespread as technological capacities develop. For warnings to be effective, they must allow enough lead... 相似文献
126.
Mohamed Laabd Hafsa Chafai Nouh Aarab Abdelhadi El Jaouhari Mohammed Bazzaoui Hassan Kabli Habiba Eljazouli Abdallah Albourine 《Environmental Chemistry Letters》2016,14(3):395-400
Adsorbents in the form of powders are commonly used to filtrate organic compounds in waters. However, this technique requires the separation of the solid phase from the solution after adsorption experiments. Here we propose the use of films as adsorbents. We synthesized polyaniline films by chemical oxidative polymerization of aniline on red ceramic brick. This film was tested to remove trimellitic, hemimellitic and pyromellitic acids as model molecules of the biodegradation of aquatic humic substances. We evaluated the effect of pH, contact time and initial concentration. Our results show that optimal adsorption conditions required 45 min of solid/liquid contact at pH 7 and an initial concentration of 20 mg/l. The maximum adsorption capacities for hemimellitic, trimellitic and pyromellitic acids are 154.83 for hemimellitic acid, 161.88 for trimellitic acid and 175.26 mg/g for pyromellitic acid. The adsorption efficiency of the polyaniline film decreased only by 13 % after four cycles. Overall, we conclude that polyaniline films are promising separable adsorbents compared to conventional adsorbents for removal of aromatic polycarboxylic acids from water. 相似文献
127.
Omar El‐Anwar 《Disasters》2013,37(3):489-515
The widespread destruction that follows large‐scale natural disasters, such as Hurricane Katrina in August 2005, challenges the efficacy of traditional temporary housing methods in providing adequate solutions to housing needs. Recognising these housing challenges, the Congress of the United States allocated, in 2006, USD 400 million to the Department of Homeland Security to support Alternative Housing Pilot Programs, which are intended to explore the possibilities of providing permanent and affordable housing to displaced families instead of traditional temporary housing. This paper presents a new methodology and optimisation model to identify the optimal configurations of post‐shelter housing arrangements to maximise the overall net socioeconomic benefit. The model is capable of quantifying and optimising the impacts of substituting temporary housing with alternative housing on the social and economic welfare of displaced families as well as the required additional costs of doing so. An application example is presented to illustrate the use of the model and its capabilities. 相似文献
128.
Dissipation behavior and hazard assessment of the fungicide fenhexamid applied to grapes were investigated under climatic conditions in Egypt. Fenhexamid residues were extracted from grape samples with ethyl acetate. The extract was cleaned up by QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, and determined by gas chromatographic method (GC-μECD). The average recoveries ranged between 94.2% and 99.4% with associated relative standard deviation not exceeding 12%. The estimated limit of quantification for fenhexamid was 0.1 mg/kg. The field results showed that fenhexamid dissipated rapidly from grapes and had a half-life of approximately 4.21 days. Hazard assessment was evaluated by using the hazard quotient (HQ). Data showed that the HQ value was significantly less than HQ = 1. Results indicate that hazard of fenhexamid use in grape even at 1.5-fold higher than recommended dosage was negligible to humans. This study could provide guidance for safe and reasonable use of fenhexamid in grapes and prevent health problems to consumers. However, further hazard assessment studies are needed to ascertain the hazard of fenhexamid residues on grape to vulnerable groups, including children, pregnant women, and elderly consumers. 相似文献
129.
AbstractThe toxicity of glyphosate at 3.6?mg L?1 to maize seedlings raised from un-treated seeds and the effectiveness of seed pretreatment by soaking in 0.25?mmol L?1 ascorbic acid (AsA) solution for mitigation of toxicity were evaluated in hydroponic culture. Glyphosate dramatically reduced the growth of roots and photosynthetic pigments in the leaves but increased protein content in the leaves. Superoxide dismutase activity and AsA concentration in the roots were increased, and guaiacol peroxidase (GPOX) activity was unaffected. Pretreatment with AsA improved the dry mass of the roots and shoots, increased the protein content in roots and leaves, and significantly decreased the activity of GPOX in roots. The positive effect of AsA treatment was not associated with more efficient functioning of the antioxidative system. 相似文献
130.
Environmental risk assessment of cobalt and manganese from industrial sources in an estuarine system
F. Barrio-Parra J. Elío E. De Miguel J. E. García-González M. Izquierdo R. Álvarez 《Environmental geochemistry and health》2018,40(2):737-748
A total of 74 samples of soil, sediment, industrial sludge, and surface water were collected in a Mediterranean estuarine system in order to assess the potential ecological impact of elevated concentrations of Co and Mn associated with a Terephthalic (PTA) and Isophthalic (PIPA) acids production plant. Samples were analyzed for elemental composition (37 elements), pH, redox potential, organic carbon, and CaCO3 content, and a group of 16 selected samples were additionally subjected to a Tessier sequential extraction. Co and Mn soil concentrations were significantly higher inside the industrial facility and around its perimeter than in background samples, and maximum dissolved Co and Mn concentrations were found in a creek near the plant’s discharge point, reaching values 17,700 and 156 times higher than their respective background concentrations. The ecological risk was evaluated as a function of Co and Mn fractionation and bioavailability which were controlled by the environmental conditions generated by the advance of seawater into the estuarine system during high tide. Co appeared to precipitate near the river mouth due to the pH increase produced by the influence of seawater intrusion, reaching hazardous concentrations in sediments. In terms of their bioavailability and the corresponding risk assessment code, both Co and Mn present sediment concentrations that result in medium to high ecological risk whereas water concentrations of both elements reach values that more than double their corresponding Secondary Acute Values. 相似文献