Molecular Organic Substances Research Articles

Competitive Adsorption of 4-Hydroxybenzaldehyde and Toluene onto High Silica Zeolites

To evaluate the ability of zeolites to remove natural low molecular organic substances, p-hydroxybenzaldehyde (p-HBA), a phenolic compound derived from lignin, was chosen as a representative of naturally occurring dissolved organic substances. Two distinct high-silica zeolite materials, namely ZSM-5 and Y, were utilised for the study, and the adsorption process was investigated under a wide range of conditions. It has been observed that p-HBA is adsorbed by both zeolites, and the pH significantly impacts the adsorption of p-HBA, particularly within the low concentration range, while exerting minimal influence on the saturation capacity. For both zeolites, various isotherm models were assessed to accurately describe the adsorption data obtained from aqueous solutions of p-HBA. In addition, to comprehend the selectivity of the adsorbents towards natural organic substances and xenobiotics, the competitive adsorption of mixtures of p-HBA and toluene (TOL) was investigated. The zeolite’s saturation capacity for p-HBA diminishes with increasing contaminant concentration. Conversely, the adsorption of toluene remains minimally affected by p-HBA, and it has been demonstrated that toluene can displace adsorbed p-HBA from the zeolites’ sites. This finding has been confirmed by diffractometric study that indicates that TOL and p-HBA occupy “the same” adsorption sites. Furthermore, Rietveld refinements reveal the formation of p-HBA complexes interacting with the framework and stabilising the guest structures within the zeolite porosity. The results obtained are important for the selection of proper adsorbent for the removal of hydrocarbons in environmental application (natural waters).

PAC-UF Process Improving Surface Water Treatment: PAC Effects and Membrane Fouling Mechanism.

In this study, the water purification effect and membrane fouling mechanism of two powdered activated carbons (L carbon and S carbon) enhancing Polyvinylidene Fluoride (PVDF) ultrafiltration (UF) membranes for surface water treatment were investigated. The results indicated that PAC could effectively enhance membrane filtration performance. With PAC addition, organic removal was greatly enhanced compared with direct UF filtration, especially for small molecules, i.e., the S-UF had an additional 25% removal ratio of micro-molecule organics than the direct UF. The S carbon with the larger particle size and lower specific surface area exhibited superior performance to control membrane fouling, with an operation duration of S-UF double than the direct UF. Therefore, the particle size and pore structure of carbon are the two key parameters that are essential during the PAC-UF process. After filtration, acid and alkaline cleaning of UF was conducted, and it was found that irreversible fouling contributed the most to total filtration resistance, while the unrecoverable irreversible resistance ratio with acid cleaning was greater than that with alkaline cleaning. With PAC, irreversible UF fouling could be relieved, and thus, the running time could be extended. In addition, the membrane foulant elution was analyzed, and it was found to be mainly composed of small and medium molecular organic substances, with 12% to 21% more polysaccharides than proteins. Finally, the hydrophilicity of the elution was examined, and it was observed that alkaline cleaning mainly eluted large, medium, and small molecules of hydrophilic and hydrophobic organic matter, while acid cleaning mainly eluted small molecules of hydrophilic organic matter.

Oxy-fuel and air combustion performances and gas-to-ash products of aboveground and belowground biomass of Sedum alfredii Hance

The eco-friendly disposal choices of phytoremediation biomass still remain to be explored. This study characterized the combustions of Sedum alfredii Hance (SAH) in response to its aboveground (SAH-A) and belowground (SAH-B) parts, the oxy-fuel (CO2/O2) and air (N2/O2) atmospheres, temperature, and heating rate. The decomposition behaviors, gas-to-ash characteristics, thermo-kinetic parameters, and mineral transformations were quantified. In both atmospheres, the combustion performances were better for SAH-A than SAH-B at the same heating rate. In the range of 400.0–598.8 °C, the maximum mass loss rate of both samples obviously decreased and delayed with CO2 replacing N2 at the same oxygen concentration. The SAH-A and SAH-B combustions in both atmospheres emitted C- (CO2, CO, CH4, and small molecular organic substances) and N-containing (HCN and NH3) gases. In both atmospheres, the temperature dependency of the gas emissions remained the same. Both empirical indices and ternary phase diagrams indicated that both samples had a high deposition risk. Thermochemical equilibrium simulations were used to predict the slagging risk in response to ash mineral transformations. Our findings can provide new insights into the combustion dynamics of phytoremediation biomass and its effect on CO2 capture, utilization, and storage in mitigating climate change.

Impact of monovalent cations on the separation performance of graphene oxide membrane for different organic matters.

Graphene oxide (GO) membrane has become a promising membrane due to its advantages of high flux, good anti-pollution performance, and controllable cost. Since wastewater contains inorganic ions and organic substances, the effect of inorganic ions on the removal of organic matters has attracted attention. This study investigated the impact of monovalent cations (Na+ and K+) on the removal of different organic matters by GO membranes. The results showed that the removal by GO membranes of both macromolecular organic compounds (humic acid, sodium alginate, and bull serum albumin) and small molecular organic substances (new coccine, methyl orange, and methylene blue) were high (>75%). The coexisting Na+ caused the increase in flux and the decrease in removal of small molecular organic matters, while the impact on the removal of macromolecular organic matters was weak. The impact of the coexisting K+ was weaker than Na+. With the crosslinking of ethylenediamine, the structure of GO membrane was more stable. The impacts of Na+ on the flux and separation performance of crosslinked membranes were less than that of non-crosslinked membranes. This suggests that crosslinked GO membrane has more potential for practical wastewater treatment.

In English

The aim of the investigation is to develop multifunctional adsorbent, which is able to remove both inorganic ions and molecular organic substances from aqueous solutions. Oxidized graphene has been obtained by Hammer’s method. The composite, which includes hydrated zirconium dioxide and graphene oxide (» 2 mass. %), has been synthesized by deposition from sol containing dispersed particles of the carbon material. The adsorbent as well as its constituents were investigated with methods of XRD analysis, FTIR spectroscopy, TEM and standard contact porosimetry involving octane (ideally wetting liquids) and water as working liquids. Strong hydration of graphene oxide in water has been found: the volume of micro- and mesopores in water medium is higher than that in octane. It means that the oxidized graphene behaves similarly to ion exchange polymers. This is evidently due to its hydrophilic functional groups (hydroxyle carboxyl and epoxy groups). High specific surface area of graphene oxide reaches 1200 (in the organic solvent) or 2250 m 2 g –1 (in aqueous medium). It has been shown that graphene covers the particles of the inorganic matrix loosening its structure within the wide interval of pore size (from 10 nm to 1.5 µm). As found, adsorption isotherms of Pb(II) and HCrO 4 - ions obeys with Langmuir model. The filler improves adsorption of Pb(II) ions increasing the capacity in 1.7 times due to its expressed cation exchange properties. Contrary, anion exchange function of the composite is depressed, since the sheets of graphene oxide screen adsorption centers of the inorganic matrix. Other reason can be electrostatic repulsion of anions due to the shift of the point of zero charge of the composite to acidic field. By reason of the carbon filler, the oxide material acquires the capability to adsorb both slightly dissociated (phenol) and molecular (lactose) organic substances. When the initial content of phenol is 5 mg dm –3 , it is possible to reduce its content in water down to maximal permeable concentration. After adsorption, the content of lactose is much lower than this parameter. It means, that the composite provides practically complete removal of organics from water.

Absorption and subcellular distribution of cadmium in tea plant (Camellia sinensis cv. "Shuchazao").

A hydroponic experiment was performed to investigate the Cd absorption and subcellular distribution in tea plant, Camellia sinensis. Increased Cd accumulation potential was observed in the tea plant in a Cd-enriched environment, but most of the Cd was absorbed by the roots of C. sinensis. The Cd in all the root fractions was mostly distributed in the soluble fraction, followed by the cell wall fraction. By contrast, the Cd was least distributed in the organelle fraction. The adsorption of Cd onto the C. sinensis roots was described well by the Langmuir isotherm model than the Freundlich isotherm. Most of the Cd (38.6 to 59.4%) was integrated with pectates and proteins in the roots and leaves. Fourier transform infrared spectroscopy (FTIR) analysis showed that small molecular organic substances, such as amino acids, organic acids, and carbohydrates with N-H, C=O, C-N, and O-H functional groups in the roots, bonded with Cd(II). The Cd accumulation in the C. sinensis leaves occurred in the cell wall and organelle fractions. C. sinensis has great capability to transport Cd, thereby indicating pollution risk. The metal homeostasis of Fe, Mn, Ca, and Mg in C. sinensis was affected when the Cd concentration was 1.0-15.0mg/L.

CO2 efflux by rapid decomposition of low molecular organic substances in soils

Decomposition rates of the [2-14C]-glucose and [2-14C]-glycine in four different soils of the long-term field trial of Moscow were investigated in a 3-months laboratory experiment in which 14CO2 respiration was measured. A model with three decomposition components and two distribution parameters was developed and validated with the data of the experiment. The decay rate constants of free [2-14C]-glucose (4–32 day-1) were slower than those of [2-14C]-glycine (16–44 day-1). The calculated use efficiency for microbial biosynthesis of the second carbon atom was 47% for glucose and 31% for glycine. The potential half-life of labelled carbon in the microbial soil biomass ranged from 0.6 to 4.4 days, depending on the soil type and the initial amount of added substrate. The calculated total utilisation of carbon by the soil biomass from glycine was about 2–5 times lower than that of glucose. The modelled 14C incorporation into the microbial soil biomass reached its maximum on the first day of the incubation experiment and did not exceed 22% of the 14C input. Both of the investigated substances decomposed most rapidly in the soil samples from sites that have not being fertilised with organic or mineral fertilisers during an 81-years period.

Heterogeneous Turnover of Molecular Organic Substances from Crop Soils as Revealed by 13 C Labeling at Natural Abundance with Zea mays

Understanding the dynamics of soil organic matter is of major importance for agronomical and environmental studies. In particular, soil organic matter holds soil physical stability and thus prevents erosion; soil organic matter stores pollutants; and soil organic carbon impacts climate change as either a source or sink of atmospheric CO2. However, knowledge on the dynamics of soil carbon is still incomplete, particularly at the molecular level. Here, using a recently developped analytical technique that allows measuring the 13C isotope composition of individual substances within a complex organic mixture I show that plant-wax derived soil n alkanes have a higher turnover than bulk soil organic matter. Soil samples were collected in a field experiment where maize was cropped 23 years. Since maize, a C4 plant, is 13C-enriched versus previous vegetation made of C3 plants, cropping maize introduces 13C-enriched carbon in the soil over time. This labelling at natural abundance thus allows to distinguish maize-derived carbon from initial C3 plant-derived carbon. The 13C composition of bulk soil carbon was measured by isotope ratio monitoring mass spectrometry (IRMS), whereas that of individual soil n-alkanes was measured by gas chromatography-IRMS. The results show that after 23 years of maize cropping the increase of 13C composition is faster for the C31 soil n-alkane (+7.6‰) than for bulk soil carbon (+5.6‰). This finding evidences the faster turnover of soil n-alkanes, which is rather unexpected because n-alkanes are chemically stable compounds. Using a first order kinetic model, it is estimated that the complete C turnover will last 192 years for bulk soil carbon and 148 years for the plant-derived soil n-alkane.

13C Labelling of soil n-hentriacontane (C 31) by maize cultivation

The fate of plant carbon into molecular organic substances from soils can be followed by stable carbon analysis. Soil organic matter has thus been progressively labelled with 13C at natural abundance by cultivation of Zea mays, a C 4 plant, on a soil which was previously under isotopically distinct C 3 vegetation. The molar carbon percentage of maize n-hentriacontane within soil n-hentriacontane has been calculated by isotopic means and amounts to around 50% after 23 years of maize cultivation.

Biodegradation of Organic Substances by Biological Activated Carbon – Simulation of Bacterial Activity on Granular Activated Carbon

Biodegradation of organic substances by attached bacteria on biological activated carbon (BAC) was studied to clarify the advantages of granular activated carbon (GAC) as support media over conventional media without adsorption capacity with regard to biodegradation activity and community structure of attached bacteria. Anthracite (AN) was used as reference support medium without adsorbability. Low molecular organic substances with different biodegradability and adsorbability (phenol, glucose, benzoic acid and m-aminobenzoic acid) were fed into completely mixed BAC and AN reactors. The rate of biodegradation by BAC reactors fed with biodegradable organic substances was approximately 3 times as high as that by AN reactors. The difference in adsorbability of organic substances onto GAC had little effects on the rate of biodegradation. The structure of GAC with micro and macro pores did not provide better habitat for attached bacteria with regard to the size of population in comparison with anthracite without pores. The rates of biodegradation per attached bacteria for biodegradable organic substances in the BAC reactors were from 1.7 to 4.9 times higher than those in the AN reactors. GAC, as a bacterial support media, stimulated the biodegradation activity of each bacteria without increase in their population and probably with little change in their species composition. Although the number of attached bacteria on BAC was not different significantly from that on anthracite, m-aminobenzoic acid with low biodegradability was degraded only by the GAC reactor.

生物活性炭による低濃度有機化合物の分解除去

Biodegradation of organic substances by attached bacteria on biological activated carbon (BAC) was studied to clarify the advantages of granular activated carbon (GAC) as a support medium over conventional medium without adsorption capacity with regard to biodegradation activity and community structure of attached bacteria. Anthracite (AN) was used as a reference support medium without adsorbability. Low molecular organic substances with different biodegradability and adsorbability (phenol, benzoic acid, glucose and m-aminobenzoic acid) were fed into completely mixed BAC and AN reactors. The rates of biodegradation by BAC reactors fed with the biodegradable organic substances were approximately 3 times as high as those by AN reactors. The difference in adsorbability of the organic substances onto GAC had little effect on the rate of biodegradation. m-Aminobenzoic acid with low biodegradability was degraded only by the BAC reactor. The structure of GAC with micro and macro pores did not provide better habitat for attached bacteria with regard to the size of population in comparison with AN without pores. Bacterial floras on GAC was probably little difference from those on anthracite. Therefore GAC as a bacterial support medium stimulated the biodegradation activity of each bacterium without increase in the population and probably with little change in the species composition.

Osmolality and electrolyte concentration of hemolymph and the problem of ion and volume regulation of cells in higher insects

1. 1. The study was carried out on 22 species of insects from 5 orders. The osmolality of their hemolymph varied from 319 to 421 mOsm/kg H 2O, concentration of Na + 4.6 to 118 mM/l, K + 6.3 to 73mM/l, Ca 2+ 3.6 to 12.9 mM/l, Mg 2+ 2.3 to 76 mM/l. The most abundant cation in the hemolymph of insects from higher orders is either K + or Mg 2+. 2. 2. In the muscles of lower and higher insects K + is usually within 80–120 mM/kg wet wt. 3. 3. Most Ca 2+ and Mg 2+ in hemolymph is bound with protein and low molecular anions, concentration of free Ca 2+ is 0.9-2.1mM/l Mg 2+ 3.7–8.0 mM/l. 4. 4. It is concluded that, in insects, potassium hemolymph, cell volume regulation and accumulation of ions in the cell, are ensured by an increased osmolality of hemolymph due to a high percentage contribution of low molecular organic substances which are retained in the hemolymph due to the absence of filtration apparatus in the Malpighian tubules.

Observations during Reactions and Melting of Freely Suspended Solid Particles

AbstractWith the three‐plate‐capacitor method, as described previously by the author, reactions and heating processes in freely suspended particles (diameter 5‐50 μm) were investigated by using the diffraction pattern of a laser beam. Change of weight can be registered, during operation, by the a. c. and d. c. voltage connected to a capacitor. This device enables information to be obtained, from inside the droplets, on the gradient of density or the precipitation of small particles and on the formation and solution process of a crystal nucleus in anorganic and low molecular organic substances. The behaviour of high polymer materials was studied during heating in the central region ca. 4 μm of the droplet.The diffraction patterns are similar to those of crystals (micells), but they do not show any crystal nucleus in the center. The application of heat, up to the softening point, gradually diffuses this cell arrangement. Such phenomena have not previously been studied within a droplet.

Development of mass blooms of photosynthetic bacteria on sheltered beaches in Scapa Flow, Orkney Islands

SynopsisMass blooms of purple sulphur bacteria belonging to the generaThiocapsaandChromatium(> 108viable cells/g dry wt sediment) develop in localised areas at the sand/air interface on a number of sheltered beaches in Scapa Flow each summer. These anaerobic bacteria grow phototrophically using H2S as e−donor and develop in association with other groups of phototrophic and heterotrophic bacteria. Oxygen consumption by the heterotrophs is greater than O2production by the algae and diffusion from the surface and this rapidly leads to anaerobic conditions in the sub-surface sediments (0–10 mm depth). Under these conditions, significant populations of sulphate reducing bacteria develop (circa 105viable cells/g dry wt sediment) and reduce SO2−/4 to S2−during the anaerobic oxidation of low molecular weight organic substrates. Sulphide generated in this process is used as the e−donor in photosynthesis by the purple sulphur bacteria and in turn is re-oxidised to SO2−/4. Sulphate reduction is dependent upon the availability of oxidisable low molecular organic substrates which are produced, as metabolic end-products, during the microbial decomposition of algal detritus. Blooms ofThiocapsaandChromatiumspp. were most pronounced on beaches such as Scapa, Waulkmill and Swanbister, which in localised areas, have high total organic carbon contents (5–12% w/w). The factors regulating the development of these localised mass developments of anaerobic phototrophic bacteria in apparently aerobic environments are discussed.

Orientation of polymers together with low molecular organic substances

Binary oriented containing polymers and low molecular organic substances have been prepared. The specimens examined were mixtures of oriented crystals of both components forming two independent textures with a single axis. One texture consists of polymeric crystallites, and the other of crystals of the low molecular substance. The polymeric crystals invariably formed axial textures. The crystals of the low molecular component could be oriented in the form of either axial or planar textures. Binary textures are obtainable with mixtures of fixed compositions by press moulding at T pm above the melting point of the polymer. Oriented systems were obtained for the following pairs: ferrocene-PE, anthracene-PE, ferrocene-POE, ε-caprolactam-POE, naphthalene-POE, ferrocene-POM and anthracene-PP. In the case of dicyanodiamide-PE, pentaerithrite-PE, urea-PE, pentaerithrite-POE, urea-POE and hydroquinone-PE orientation of the low-molecular component could not be obtained at the same time as orientation of the polymer. On analysing the thermal behaviour of the mixed components it was found that coorientation takes place in pairs where the low molecular component dissolves in the polymer melt, after which both components crystallize simultaneously while cooling, though the components crystallize independently of one another.

The chemistry of cervical mucus.

The constituents of cervical mucus are water 90%; inorganic salts 1%; small amounts of low molecular organic compounds; and small amounts of high molecular organic substances including glycogen. The bulk of the solid material is formed by glycoproteins normally 1-6%. While the qualitative composition of the cervical secretion seems to be essentially constant there are considerable quantitative variations between the ovulatory and anovulatory phases. The physiological role of cervical mucus and its main function is to act as a protective barrier to the interior of the uterine cavity.