Úprava vzorku pro stanovení aniontů v důlní vodě s vysokým obsahem železa

Reliable analysis of anions in mine waters with high iron and sulfate contents is important for their characterization. However, both traditional and LC methods failed in direct anion analysis. The article describes two sample pretreatments - alkalization and cation exchange. The pretreated water samples were analyzed by potentiometric titration, spectrophotometry, ion chromatography with conductivity detector in suppressed regime and HPLC with diode array detector using indirect UV detection at 260 nm. Both the sample pretreatments enable determination of some anions, the former procedure being more suitable for the purpose. Potentiometric titration and spectrophotometry seem to be the most suitable due to low detection limits for all the selected anions ranging from 0.4 to 1.8 mg l-1. The application of ion chromatography and liquid chromatography with diode array detector for the purpose is also possible. However, due to very high detection limits of samples pretreated by cation exchange (26-121 mg l-1) and low recoveries of samples pretreated by alkalization (<17 %) for all the selected anions, HPLC-DAD is not suitable for analysis of real samples. Validation and analytical characteristics of the methods are given and discussed

Recovery of Cerium Dioxide from Spent Glass-Polishing Slurry and Its Utilization as a Reactive Sorbent for Fast Degradation of Toxic Organophosphates

The recovery of cerium (and possibly other rare earth elements) from the spent glass-polishing slurries is rather difficult because of a high resistance of polishing-grade cerium oxide toward common digestion agents. It was shown that cerium may be extracted from the spent polishing slurries by leaching with strong mineral acids in the presence of reducing agents; the solution may be used directly for the preparation of a ceria-based reactive sorbent. A mixture of concentrated nitric acid and hydrogen peroxide was effective in the digestion of partially dewatered glass-polishing slurry. After the removal of undissolved particles, cerous carbonate was precipitated by gaseous NH3 and CO2. Cerium oxide was prepared by a thermal decomposition of the carbonate precursor in an open crucible and tested as reactive sorbent for the degradation of highly toxic organophosphate compounds. The samples annealed at the optimal temperature of approximately 400°C exhibited a good degradation efficiency toward the organophosphate pesticide fenchlorphos and the nerve agents soman and VX. The extraction/precipitation procedure recovers approximately 70% of cerium oxide from the spent polishing slurry. The presence of minor amounts of lanthanum does not disturb the degradation efficiency

A simple molecular simulation strategy for rapid prediction of BTEX sorption on a surface-modified sorbent

Sorption of benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEX) molecules on Fe3O4@-SiO2@C-18 sorbent allows the idea of entering the BTEX between the C18 (octadecyl) chains. This process re-sembles BTEX+C18 mixing. Given the dominant effect of non-bond interactions, it should be possible to predict the sorption behavior using force field-based molecular simulations. Experimental data, i.e. sorption efficiency of Fe3O4@SiO2@C-18 towards BTEX in aqueous environment, were compared with results of two simulation strategies aimed at predicting sorption behavior using models significantly simplified compared to the real Fe3O4@SiO2@C-18 structure. The first strategy involved molecular dynamics performed on models containing only the shell with C18 chains in water with BTEX. The second strategy involved miscibility calculations (based on modified Flory-Huggins theory) performed on models containing only pairs of molecules: C18+BTEX and H2O+BTEX. Results of both simulation strategies are in good agreement with experimental data, i.e. BTEX sorption on Fe3O4@SiO2@C-18 can be studied using significantly simplified models. Given the speed of miscibility calculations and the simplicity of models used (pairs of molecules), the preparation of much larger models and time-consuming molecular dynamics simulations are not necessary. The sorption efficiency can be easily and quickly predicted by the miscibility calculations.Web of Science33art. no. 10219

C18-functionalized Fe3O4/SiO2 magnetic nano-sorbent for PAHs removal from water

Magnetic sorbents represent very promising materials for environmental applications due to their simple synthesis, separability in a magnetic field, low toxicity, wide range of possible modifications, and usability in heterogeneous systems. We report on the synthesis, characterization, and application of magnetically separable Fe3O4/SiO2 sorbent surface-modified with octadecyl chains (C18). Preparation of Fe3O4 cores by co-precipitation from Fe2+ and Fe3+ chlorides in an alkaline aqueous solution was followed by SiO2 shell synthesis and functionalization with C18. Fe3O4, Fe3O4/SiO2, and Fe3O4/SiO2-C18 samples were characterized by SEM, TOC, XRD, BET, and tested for purification of water contaminated by various polycyclic aromatic hydrocarbons (PAHs). Since PAHs are formed as by-products of pyrolysis, a rapidly evolving technology for transformation of waste into green chemicals, there is a need for efficient sorbents suitable for PAHs removal from the environment. The use of Fe3O4/SiO2-C18 for adsorption of 16 different PAHs has not yet been reported. The adsorption was examined by gas chromatography with mass spectrometry and studied using molecular modeling. Comparison of adsorption efficiency 7.7 for Fe3O4, Fe3O4/SiO2, and Fe3O4/SiO2- C18 revealed a positive effect of C18. When averaging all Fe3O4/SiO2-C18 doses tested (1-8 g/L), 7.7 > 80% and > 90% was found for 14 and 7 PAHs, respectively, out of a total of 16 tested PAHs. The highest 7.7 values were found for medium-heavy PAHs (178.2-228.2 g/mol). Exhibiting high efficiency and average capacity of similar to 1 mu g/g, the Fe3O4/SiO2-C18 is suitable for pre-concentration purposes of PAHs in analytical sample extractions from water.Web of Science24art. no. 10190

Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels

The phospholipid fatty acid (PLFA) content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS). Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm) of the input microbial suspension (R2 = 0.99). After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0) to their metabolic precursors (16:1ω7 + 18:1ω7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications

<i>Miscanthus</i> × <i>giganteus</i> Phytoremediation of Soil Contaminated with Trace Elements as Influenced by the Presence of Plant Growth-Promoting Bacteria

The phytoremediation of industrial crops is becoming popular for the revitalization of land contaminated by trace elements (TEs). This approach combines biomass production with the improvement of soil health. To implement phytoremediation and derive sufficient dry biomass, crop production must be adequately supported by agricultural practices, including the application of bioinoculants. The current study aims to test the influence of several plant growth-promoting bacteria (PGPB), isolated from TEs-contaminated soil—i.e., Stenotrophomonas maltophilia KP-13, Bacillus altitudinis KP-14, and Pseudomonas fluorescens KP-16 and their consortia on the phytoremediation of the industrial crop M. × giganteus cultivated in the same TEs-contaminated soil. Contrary to expectations, the effects of PGPB on the biomass harvest were low. The most significant increase was detected in leaf biomass treated with a consortium of tested PGPBs. More significant effects were detected in the uptake of individual TEs. The phytoparameters of translocation factor, comprehensive bioconcentration index and uptake index were used to characterize the behavior of the TEs; Cr; Mn; Ni; Cu; Zn; Sr; V; and Pb in the presence of isolates. Plants treated with PGPB strains accumulated minimal concentrations of Cu and Pb in their aboveground biomass, while a tendency for Zn accumulation in the leaves and stems, and Sr accumulation in the leaves was observed. The obtained results reveal the combinations of isolates that lead to the minimal uptake of TEs into the stems and the simultaneous increase in DW. This study provides more insight into the leading factors of phytoremediation supported by PGPB and can be helpful when M. × giganteus is grown on TEs-contaminated soils of different origins

Miscanthus &times; giganteus Phytoremediation of Soil Contaminated with Trace Elements as Influenced by the Presence of Plant Growth-Promoting Bacteria

The phytoremediation of industrial crops is becoming popular for the revitalization of land contaminated by trace elements (TEs). This approach combines biomass production with the improvement of soil health. To implement phytoremediation and derive sufficient dry biomass, crop production must be adequately supported by agricultural practices, including the application of bioinoculants. The current study aims to test the influence of several plant growth-promoting bacteria (PGPB), isolated from TEs-contaminated soil&mdash;i.e., Stenotrophomonas maltophilia KP-13, Bacillus altitudinis KP-14, and Pseudomonas fluorescens KP-16 and their consortia on the phytoremediation of the industrial crop M. &times; giganteus cultivated in the same TEs-contaminated soil. Contrary to expectations, the effects of PGPB on the biomass harvest were low. The most significant increase was detected in leaf biomass treated with a consortium of tested PGPBs. More significant effects were detected in the uptake of individual TEs. The phytoparameters of translocation factor, comprehensive bioconcentration index and uptake index were used to characterize the behavior of the TEs; Cr; Mn; Ni; Cu; Zn; Sr; V; and Pb in the presence of isolates. Plants treated with PGPB strains accumulated minimal concentrations of Cu and Pb in their aboveground biomass, while a tendency for Zn accumulation in the leaves and stems, and Sr accumulation in the leaves was observed. The obtained results reveal the combinations of isolates that lead to the minimal uptake of TEs into the stems and the simultaneous increase in DW. This study provides more insight into the leading factors of phytoremediation supported by PGPB and can be helpful when M. &times; giganteus is grown on TEs-contaminated soils of different origins

Indication of Importance of Including Soil Microbial Characteristics into Biotope Valuation Method

Soil is a key part of a biotope and microorganisms are dominant components contributing to soil functions. Conversely, established methods for valuation of biotopes according to Natura 2000 rely predominantly on the communities living on the surface. Here, we aimed to assess soil microbial biomass and community structure on five localities with range of biotope values by means of phospholipid fatty acid (PLFA) profiling. PLFA figures were affected both by sampling season (spring vs. autumn) and locality. In spring, the living microbial biomass (estimated by PLFAtot) exhibited poor correlation to biotope values. These were, on the contrary, correlated to trans/cis PLFA, an indicator of microbial stress, (i.e., lower stress in higher-rated biotopes), and fungal/bacterial PLFA (i.e., higher-rated biotopes contained more fungi). The attempt to model biotope values from microbial characteristics explained a maximum of ~50% of the variability; the best predictors were the trans/cis stress indicator, percentage of actinobacterial PLFA, and ratio of PLFA of Gram-positive to Gram-negative bacteria. These results show that soil microbial characteristics present partly new information and indicate the need to amend the procedures of biotope assessment. Soil PLFA profiling could serve as suitable methods for this purpose

The influence of diesel contaminated soil on Miscanthus x giganteus biomass thermal utilization and pyrolysis products composition

The second-generation energy crop Miscanthus x giganteus (Mxg) demonstrated ability to produce adequate biomass yield even in marginal or contaminated soils. This renewable biomass can be utilized energetically or transformed into various biobased products and thus contribute to decrease of primary resources and fossil fuel use. To evaluate potential effects on energetic biomass properties Mxg was grown in diesel contaminated soils. Traces of total petroleum hydrocarbons were found solely in the leaves, however most likely resulting from air contamination. No differences were detected in the elemental composition of the raw biomass. Biomass combustion heat value reached average of 17.23 ± 0.21 MJ kg−1; contamination-originated leaves had slightly but significantly decreased heat values (14.41 ± 1.10 MJ kg−1) while heat of other parts was comparable to control. Thermogravimetric curves, simulating thermic utilization processes, were comparable both under oxygen (combustion) and nitrogen (pyrolysis). No diesel impacts were observed on the pyrolysis products yield. Higher amounts of CH4, C2H6, C3H4, C3H6 and C3H8 were detected in the pyrolysis gas from aboveground biomass from contaminated soil. Diesel contamination decreased significantly biochar surface. Concentrations of acids and esters in biooil were increased on the expense of concentrations of furans in the case of samples from contaminated soils. No significant effect on phenols and ketones concentrations in the biooil was observed. The amount of acetic acid, as the main biooil component, increased in the above- and below-ground plant parts along with the higher diesel concentrations in soil. Despite slight changes detected, the parameters of the biomass produced in diesel-contaminated soils present no obstacle to its energetic utilization and Mxg can be recommended for productive phytomanagement of such soils.Web of Science406art. no. 13698