Search results for "Environmental engineering"
showing 10 items of 2674 documents
Application of Molecular Imprinted Polymers for Selective Solid Phase Extraction of Bisphenol A
2016
Abstract Selective molecularly imprinted polymers (MIPs) with bisphenol A as template were synthesized using the non-covalent imprinting approach. MIPs were prepared using thermally initiated polymerization with 1,1’-azobis(cyclohexanecarbonitryle) (ACHN) as initiator and ethylene glycol dimethacrylate (EDMA) as a cross-linking agent. The tested functional monomers included methacrylic acid, acrylamide, and 4-vinylpyridine. The selectivity of the BPA-MIP for the solid phase extraction of bisphenol A was tested in samples containing other related alkylphenols. The polymers prepared in acetonitrile using methacrylic acid or acrylamide as monomer showed the highest selectivity towards target a…
The role of hydrology on enhanced weathering for carbon sequestration II. From hydroclimatic scenarios to carbon-sequestration efficiencies
2021
Abstract Enhanced weathering (EW) scenarios are analyzed using the model presented in Cipolla et al. (2020). We explore the role of different hydroclimatic forcing on carbon-sequestration efficiencies. We also investigate whether increasing soil carbon content improves weathering conditions. We link olivine weathering rates to pH variations and quantify the suitability of hydroclimatic regimes to EW, based on rainfall intensity and frequency. The results show that the amount of CO 2 reacting with olivine and ending up in solution in the form of HCO 3 − and CO 3 2 − increases with mean annual precipitation (MAP) up to 2000 mm, but then tapers off for higher MAPs. On the contrary, the sequest…
Chemical characterization of peat fulvic acid fractions
1993
Abstract Milled peat fulvic acid (FA) preparation was fractionated by XAD-8 and conventional extraction methods. The fractions were further analyzed by IR and NMR and subjected to cupric oxide (CuO) oxidation. Carbohydrates of polydisperse FA were mostly not retained in the XAD-8 fractionation. The intensity of the signals due to double bonded carbons was much greater in the 13 C and proton NMR spectrum of the XAD-8 retained fraction than in the spectra of the XAD-8 non-retained or XAD-8 non-treated fractions. In CuO oxidation the main products of all FA fractions were 4-hydroxybenzaldehyde and 4-hydroxyacetophenone, both indicators of 4-hydroxyphenylpropane building blocks. Their concentra…
Well water quality in Latvia
1996
A total of 2500 water samples from drinking water shallow wells and boreholes in rural areas of Latvia were collected. The samples were analyzed for 20 parameters. Well waters in Latvia can be characterized by a high content of organic (humic) substances. Mean values for analyzed water parameters are: 0.17 mg/1 NH4, 0.016 mg/1 NO2, 2.90 mg/1 NO3, 0.028 mg/1 PO4, 25.53 mg/1 Cl, 0.12 mg/1 Fe, 7.4 pH, 784 μ/cm conductivity, 24 degrees in PtCo scale color, 7.5 mgequiv/1 total hardness. Comparison with water quality criteria adopted in the USA and European Communiy indicate that water quality is often unsatisfactory. For example, nitrate concentrations exceed standards in nearly 20% of the surve…
The Influence of Natural and Model Forms of Humic Acids on the Dynamic Parameters of Model Membranes
2016
Abstract In this paper the influence of humic acid concentrations extracted from Histosols (HA-A) and their model forms (HA-B) separated from humic substances commercially produced by Carl Roth GmbH + Co.KG on the dynamic properties of liposome membranes was determined. Differences in the quality of the humic acids (HA-A and HA-B) were determined by the 1HNMR and FTIR methods. Liposomes from the sonication of egg yolk lecithin (EYL) in an aqueous solution and synthetic Dipalmitoylphosphatidylcholine (DPPC) were used. Fluidity of liposome membranes was determined by the EPR technique with spin probes (TEMPO, 16DOIXYL). The electrical parameters of membranes were found using a Keithley 6517 e…
Enzymatic activity of circular sortase A under denaturing conditions: An advanced tool for protein ligation
2014
Abstract Staphylococcus aureus sortase A is a transpeptidase that is extensively used in various protein research applications. Sortase A is highly selective and does not require any cofactors for the catalysis of protein ligation and, importantly, can be produced in high yields. However, the primary disadvantage of this transpeptidase is its inability to access the recognition site within the highly structured regions of folded substrates. To overcome this problem, we developed an Escherichia coli expression system that produces milligram quantities of circularly closed sortase A; efficient enzyme cyclization was achieved by Synechocystis sp. PCC6803 intein-mediated post-translational spli…
Sequiterpene-related compounds as endocrine disrupters in Oncopeltus fasciatus, and potential reduced glutathione synthesis modifiers
1999
Sesquiterpene lactones have been found to exhibit effects on insect growth and development. In this study, the bioactivity of natural lactones extracted from Centaurea mariolensis and some structurally related synthetic derivatives has been investigated. Assays have also been carried out in order to determine the potential of these lactones as modifiers of reduced glutathione (GSH) synthesis.
Exploring the limits of anaerobic biodegradability of urban wastewater by AnMBR technology
2018
[EN] Anaerobic membrane bioreactors (AnMBRs) can achieve maximum energy recovery from urban wastewater (UWW) by converting influent COD into methane. The aim of this study was to assess the anaerobic biodegradability limits of urban wastewater with AnMBR technology by studying the possible degradation of the organic matter considered as non-biodegradable as observed in aerobic membrane bioreactors operated at very high sludge retention times. For this, the results obtained in an AnMBR pilot plant operated at very high SRT (140 days) treating sulfate-rich urban wastewater were compared with those previously obtained with the system operating at lower SRT (29 to 70 days). At 140 days SRT the …
A Novel Gas Chromatographic Method to Measure Sorption of Dense Gases into Polymers
2006
A novel experimental approach to determine the solubility of gaseous compounds inside polymers is here described. The method is based on the gas chromatographic determination of the composition of the fluid phase at equilibrium with the polymer. To take into account the effect of the volume swelling on the measurement a suitable probe, nonabsorbable by the polymer, was added to the fluid phase. Under the adopted configuration the apparatus can operate up to 35 MPa and 80°C. This experimental technique has been used to determine the solubility of carbon dioxide in poly(vinylidene fluoride) using argon as a probe. The latter was chosen because it is negligibly absorbed by the polymer and does…
Extreme thermophilic (70°C), VFA-fed UASB reactor: performance, temperature response, load potential and comparison with 35 and 55°C UASB reactors
1999
Abstract The paper evaluates the reactor performance, load potential and temperature response of a 70°C, VFAs-fed UASB reactor, seeded with mesophilic granular sludge. Batch experiments were, in addition, conducted to assess the effect of temperature on the achievable residual VFAs in the 70°C effluent. The performance of similarly-fed and seeded 35 and 55°C UASB reactors was also tested. At a short HRT (2–3 h) and a moderate VLR of 12–20 g COD l−1 d−1, the 70°C UASB achieved 66–74% VFAs removal (acetate and butyrate 84–90%, propionate