Mmol Dm Research Articles

Removal of aqueous phenol catalysed by a low purity soybean peroxidase

AbstractThe application of a low purity soybean peroxidase (LP‐SBP), obtained from wasted seed hulls, as catalyst for phenol polymerisation in aqueous solution in the presence of hydrogen peroxide is described. The polymers formed precipitate out from solution and may be readily separated by physico‐chemical techniques. LP‐SBP offers the advantage of reduced cost compared with horseradish peroxidase (HRP). The SBP activity in fresh hulls was greater than in aged hulls and was preserved at −10 °C. There was a linear correlation between initial phenol concentration (1, 2, 5 and 10 mmol dm−3) and the minimum dosage of LP‐SBP required to precipitate 95% of the phenolic polymers. Polyethylene glycol (molecular weight, 6000) at 1000 mg dm−3 did not extend LP‐SBP lifetime. At all phenol concentrations tested, a retention time of about 100 min was sufficient to achieve yields of 95%.© 2002 Society of Chemical Industry

Effects of ion concentration and pH on hydroxyapatite deposition from aqueous solution onto titanium by the thermal substrate method.

A new hydrocoating method (the thermal substrate method) has been proposed for coating calcium phosphates, such as hydroxyapatite, onto titanium substrates in an aqueous solution. The influences of several solution properties on the thermal substrate method were examined. The solutions used included 3 mmol dm(-3) Ca(H(2)PO(4))(2) and 7 mmol dm(-3) CaCl(2) as a reference concentration solution. The ion concentration was changed from 0.1 to 2 times with respect to the reference concentration. The experimental studies were conducted under the following conditions: temperature = 140 degrees C, heating time = 10-20 min., pH = 4-8 and Ca/P = 0.0167-16.7. The type of precipitate changed, depending on the pH and ion concentration. In the reference solution with pH > 6, predominantly hydroxyapatite was precipitated onto titanium. By contrast, only CaHPO(4) was formed in the solution of pH 4. In the solution with an ion concentration of one-tenth the reference solution, CaHPO(4) was also precipitated. The addition of H(3)PO(4) to the 0.1-times solution accelerated the precipitation rate of HA. It is suggested that the PO(4) (3-) concentration was insufficient to form HA in the Ca/P = 1.67 solution.

The removal of iron and cobalt from aqueous solutions by ion exchange with Na‐Y zeolite: batch, semi‐batch and continuous operation

AbstractThe removal of single component and binary mixtures of divalent cobalt and iron from water by ion exchange with synthetic Y zeolite has been studied in batch, semi‐batch and continuous modes of operation; the initial metal solution concentration did not exceed 2 mmol dm−3. Binary Co/Na and Fe/Na ion exchange equilibrium isotherms (294 K) are presented wherein exchange site heterogeneity is evident in the case of the iron treatment. Under conditions of stoichiometric ion exchange, removal efficiencies for both cobalt and iron decrease with increasing metal concentration (0.2–2 mmol dm−3) and the values were similar for both metals. Removal of cobalt under transient conditions was found to be temperature dependent. In the fixed bed operation, break‐through behavior was sensitive to changes in both flow rate and inlet concentration. The break‐through profiles for both metals under competitive and non‐competitive conditions are presented; iron removal is lower in the presence of cobalt and vice versa. An in situ regeneration of the fully loaded zeolite by back exchange with sodium is considered and the exchange capacity of the regenerated zeolite is reported. The feasibility of employing cycles of heavy metal uptake/zeolite regeneration is addressed.© 2002 Society of Chemical Industry

Poly(β-phosphorylated nitrones): preparation and characterisation of a new class of spin trap

Four new poly(β-phosphorylated nitrones), the 1,3,5-tris[N-(1-diethylphosphono-1-methylethyl)-N-oxidoiminiomethyl]benzene (TN) 1, the 1,3-bis[N-(1-diethylphosphono-1-methylethyl)-N-oxidoiminiomethyl]benzene (MDN) 2, the 1,4-bis[N-(1-diethylphosphono-1-methylethyl)-N-oxidoiminiomethyl]benzene (PDN) 3, and the 1,2-bis[N-(1-diethylphosphono)-1-methylethyl)-N-oxidoiminiomethyl]benzene (ODN) 4, derived from the mono-nitrone N-benzylidene-1-diethoxyphosphoryl-1-methylethylamine N-oxide (PPN) 5, were synthesised. The capacity of 1–4 to act as spin-trapping agents was investigated in phosphate buffers at pH 5.8 and 7.2. Complex EPR spectra were obtained for the spin adducts with ortho-dinitrone 4. The three other compounds efficiently trapped superoxide and several carbon-centred radicals, giving mono-spin adducts, although only weak signals were obtained with the hydroxyl radical. When the spin trap concentration was kept below 1 mmol dm−3, the formation of di-radicals also occurred. The half-lives of the superoxide spin adducts of 1–3 were in the range of 5–12 min and did not change significantly between pH 5.8 and 7.2. A competitive kinetic study showed that the trinitrone 1 trapped the methyl radical 1.9 times more rapidly than either α-(1-oxidopyridin-1-ium-4–yl)-N-tert-butylnitrone (POBN) or 5-diethoxyphosphoryl-5-methyl-4,5-dihydro-3H-pyrrole N-oxide (DEPMPO) at pH 7.2.

Production of L‐methionine by immobilized pellets of Aspergillus oryzae in a packed bed reactor

AbstractProduction of L‐methionine by immobilized pellets of Aspergillus oryzae in a packed bed reactor was investigated. Based on the determination of relative enzymatic activity in the immobilized pellets, the optimum pH and temperature for the resolution reaction were 8.0 and 60 °C, respectively. The effects of substrate concentration on the resolution reaction were also investigated and the kinetic constants (Km and Vm) of immobilized pellets were found to be 7.99 mmol dm−3 and 1.38 mmol dm−3 h−1, respectively. The maximum substrate concentration for the resolution reaction without inhibition was 0.2 mol dm−3. The L‐methionine conversion rate reached 94% and 78% when substrate concentrations were 0.2 and 0.4 mol dm−3, respectively, at a flow rate of 7.5 cm3 h−1 using the small‐scale packed bed reactor developed. The half‐life of the L‐aminoacylase in immobilized pellets was 70 days in continuous operation. All the results obtained in this paper exhibit a practical potential of using immobilized pellets of Aspergillus oryzae in the production of L‐methionine.© 2002 Society of Chemical Industry

The effects of elevated carbon dioxide on static and dynamic indices for tomato salt tolerance

Although there is consensus that water use efficiency increases at elevated concentrations of CO 2, there are few studies on the interacting effects of elevated CO 2 on plant salt tolerance. The objectives of this study were, (1) to determine the effect of ambient and twice ambient concentrations of CO 2 on tomato ( Lycopersicon esculentum Mill.) responses to salinity; (2) to compare the salt tolerance threshold values based on the classic root zone salinity [J. Irrig. Div. ASCE 103, (1977) 115], or ion flux to the shoot, a measure recently defined as Salinity Stress Index (SSI) by Dalton et al. [Plant Soil 192 (1997) 307; Plant Soil 219 (2000) 1; Plant Soil 229 (2001) 189]. For all salinities, the water use of the twice ambient CO 2 treatment was significantly reduced. The effect of twice ambient CO 2 was to increase the root zone salinity threshold value from 32 to 51 mmol dm −3 Cl. The threshold SSI value of 1.05 mmol Cl per g shoot DW for the twice ambient CO 2 treatment was almost identical to that of the ambient treatment and to those previously obtained when plant growth was modulated by root temperature (SSI=1.19 and 1.10 at 25 and 18 °C, respectively [Plant Soil 192 (1997) 307]) and photosynthetic photon flux density (PPFD) ((SSI=0.97 and 1.10 at 400 and 600 μmol m −2 s −1 PPFD respectively [Plant Soil 229 (2001) 189]). The twice ambient CO 2 treatment showed a slightly lower root/shoot ratio (0.138±0.001) than the ambient CO 2 treatment (0.156±0.014). Consistent with the predictions of the SSI, leaf chloride per plant and leaf chloride concentration showed significant reduction for the twice ambient CO 2 treatment which follows from the supposition that water and salt uptake are linked. Based on the SSI, it was shown that the intrinsic salt tolerance of tomato is invariant to an increase in atmospheric CO 2 as has been previously shown for root temperature and solar radiation, while at the same time, the root zone salinity threshold value is dependent on environmental factors.

Impact of dissolved wastewater constituents on peroxidase‐catalyzed treatment of phenol

AbstractThe impact of dissolved wastewater constituents on the treatment of synthetic phenol solutions using horseradish peroxidase (HRP) and hydrogen peroxide was investigated under a variety of reaction conditions. The constituents studied included various inorganic salts, organic compounds and heavy metals. Higher H2O2 doses were required to treat phenol in the presence of sodium sulfite, thiosulfate and sulfide; however, enhanced levels of phenol conversion were achieved once sufficient H2O2 was supplied. Sulfide and cyanide inhibited phenol transformation. The inhibition of sulfide was overcome by supplying sufficient H2O2 to oxidize the sulfide to sulfur. However, increasing the H2O2 dose was ineffective in attempting to overcome the strong inhibiting effect of cyanide. Among the heavy metal ions tested, only Mn(II) substantially inhibited phenol removal when it was present at a concentration of 1 mmol dm−3. The presence of inorganic salts including NaCl, CaCl2, MgCl2, NH4Cl and (NH4)2SO4 reduced phenol conversion as compared with the treatment in distilled‐deionized water. This can be attributed to the increased ionic strength of the solution.© 2002 Society of Chemical Industry

Polypyrrole-Glucose Oxidase 효소전극의 배위자 크기에 따른 전기화학적 특성

We synthesized polypyrrole (PPy) by electrolysis of the pyrrole monomer solution containing support electrolyte, KCl and/or p-toluene sulfonic acid sodium salt (p-TS). The electrochemical behavior, was investigated using cyclic voltammetry and AC impedance. In the case of using electrolyte p-TS, the oxidation potential of the PPy was about -02 V vs Ag/AgCl reference electrode, while the potential was about 0 V for using electrolyte KCl. The falloff of the oxidation potential gave a sign of an improvement in the electron hopoing mechanism on the backbone. The AC impedance plot gave a hint of betterment of mass transport. PPy doped with p-TS improved in mass transport or diffusion. That was because the PPy doped with p-TS was more porous than PPy with KCl. We attained an effect of good kinetic parameters, in the case of PP-GOx enzyme electrodes doped with p-TS, which were determined by 58 mmol dm<TEX>$\^$</TEX>-3/ for apparent Michaelis constant and by 581 ㎂ for maximum current respectively.

Solubilization of cholesterol and polycyclic aromatic compounds into sodium bile salt micelles (Part 2)

The aqueous solubility of cholesterol was determined over the temperature range from 288.2 to 318.2 K with intervals of 5 K by the enzymatic method. The solubility was (3.7±0.3)×10 −8 mol dm −3 (average±S.D.) at 308.2 K. The maximum additive concentrations of cholesterol into the aqueous micellar solutions of sodium deoxycholate (NaDC), sodium ursodeoxycholate (NaUDC), and sodium cholate (NaC) were spectrophotometrically determined at different temperatures. The cholesterol solubility increased in the order of NaUDC<NaC<NaDC; for example, 0.10 for NaUDC, 0.61 for NaC, and 2.99 mmol dm −3 for NaDC at the concentration of 60 mmol dm −3 and at 308.2 K. The same solubilization experiments were made at 308.2 K using polycyclic aromatic compounds (benzene, naphthalene, anthracene, pyrene) as a reference. Their solubility increase for the bile salts was in the same order as above. Thermodynamic analysis was made for the solubilization, where a micelle was regarded as a chemical species. The average number of solubilizate per micelle was less than unity throughout the experiments. From the Gibbs energy change for solubilization at the different mean aggregation numbers, the function of bile salt micelles was discussed from the viewpoint of molecular structure of solubilizates. The Δ G 0 value for cholesterol was most negative among the solubilizates studied, which reflected that solubilization of cholesterol into bile salt micelles brought about largest thermodynamic stabilization.

Chemical decolorization of the azo dye CI Reactive Orange 96 by various organic/inorganic compounds

Batch experiments were performed to investigate the possibility and kinetics of chemical decolorization of the reactive mono-azo dye CI Reactive Orange 96 (RO 96) with various compounds such as cysteine, ascorbate, Ti(III)-citrate, Fe(II)-sulfate, and yeast extract. Cysteine and ascorbate (10 mmol dm−3 respectively) decolorized RO 96 (0.19 mmol dm−3) in the absence of oxygen. Increasing the concentration of either reductant (to 20 or 38 mmol dm−3) enhanced the decolorization rate, showing first-order kinetics with respect to both the concentration of the dye and of cysteine or ascorbate. The rate constants, k, for cysteine and ascorbate were 0.0003 and 0.0010 dm3mmol−1 h−1 respectively at pH 7.1 and 33 °C. Ti(III)-citrate (10 mmol dm−3) decolorized RO 96 (0.20 mmol dm−3) within 5 min, independent of the presence of oxygen. Fe(II)-sulfate was not effective in the decolorization of RO 96 at pH 8, whereas a rapid decolorization occurred at pH 12. This study suggests that a variety of abiotic processes may be involved in decolorization under anaerobic conditions. © 2002 Society of Chemical Industry

Heterogeneous Asymmetric Reactions. 29. Enantioselective Hydrogenation of Ethyl Benzoylformate over Dihydrocinchonidine-Modified Platinum–Alumina Catalyst in Acetic Acid

The enantioselective hydrogenation of ethyl benzoylformate to (R)-ethyl mandelate over dihydrocinchonidine (DHCD)-modified Pt/Al2O3 catalyst in acetic acid was studied as a function of modifier concentration, hydrogen pressure and reaction temperature. The maximum enantioselectivity obtained under optimized conditions (DHCD concentration 1 mmol dm-3, 25 bar H2, 0 °C, AcOH/toluene 1:1) was 98% ee. The difference between the rates of racemic and enantioselective hydrogenation was less significant than in the case of ethyl pyruvate. This indicates that the high reaction rate in the enantioselective heterogeneous hydrogenation of α-ketoesters is not a necessary condition of the chiral induction.

Particulate organic matter in Antarctic summer sea ice: concentration and stable isotopic composition

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 238:1-13 (2002) - doi:10.3354/meps238001 Particulate organic matter in Antarctic summer sea ice: concentration and stable isotopic composition H. Kennedy1,*, D. N. Thomas1, G. Kattner2, C. Haas2, G. S. Dieckmann2 1School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey LL59 5EY, Wales, UK 2Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27515 Bremerhaven, Germany *E-mail: h.a.kennedy@bangor.ac.uk ABSTRACT: The chemical and isotopic data from sea ice collected over a wide area of the Weddell Sea, Antarctica, during the austral summer/early autumn illustrate the range of environmental conditions under which ice algae grow. A range of ice types and features were sampled including intact and layered ice floes and surface ponds. Sea ice communities were found in all these environments but the highest biomasses were found either at the base of ice floes, or in the interior of layered floes with quasi-continuous horizontal gaps at or shortly below the water level. In the layered floes, particulate organic carbon (POC) measured in the ice layer immediately overlying the gap water (280 to 6014 µmol dm-3) was in excess of what would be predicted if algal growth had occurred in a closed environment. The chemical composition of the gap water was strongly affected by biological activity in the overlying ice, which acts as a physical support for the algae retained within its matrix. The lowest range of POC (27 to 739 µmol dm-3) conformed to predictions of algal growth in a closed system and samples were collected from the interior of ice floes where there was essentially no potential for nutrient exchange. The surface ponds displayed nitrate (NO3-) exhaustion and total dissolved inorganic carbon (ΣCO2) reductions consistent with nutrient limited algal growth. The stable carbon isotopic composition of the particulate organic matter (POM) across all habitat types sampled (δ13CPOC -10.0 to -27.3‰) displayed a wide range but was much less variable than the range of POC concentrations might have implied. The assumption that the highest biomass of algae in sea ice will result in the most positive δ13CPOC values cannot be generally applied. The isotopic composition of dissolved inorganic carbon (δ13CΣCO2) in gap waters and surface ponds varied from 0.15 to 3.0‰ and was shown to be commensurate with the changes predicted from NO3- deficits caused by algal growth. KEY WORDS: POM · Antarctic sea ice · Ice macroalgae · Carbon isotopic composition Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 238. Online publication date: August 08, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Electrochemical treatment of dilute cyanide solutions containing zinc complexes by oxidation at carbon felt (Sigratherm)

The electrochemical oxidation of dilute solutions containing cyanide complexes of zinc using a carbon felt anode is described. The composition of the solution was determined using stability constants for particular complexes. The application of a GFA5 electrode enables the oxidation of cyanides (10 mmol dm−3) in 99.2% at 0.7 V and 30 C (1.5 Q t). Under these conditions, the electrical energy consumption is about 24 kWh (kg CN−)−1. Modification of the anode surface with copper oxides allows a cyanide conversion degree of 99.6% at 0.7 V and 17.5 C (0.875 Q t with electrical energy consumption of 17.6 kWh (kg CN−)−1. However, modification of the anode resulted in 75% destruction.

A SELECTIVE KINETIC METHOD FOR THE ESTIMATION OF BENZYL ALCOHOL IN CLOSELY RELATED MIXTURES

Ethylenebis(biguanide)silver(III) ion quantitatively oxidises benzyl alcohol and its derivatives (XC6H4CH2OH; X = H, CH3, Cl or NO2, substituents in ortho or para position). The difference in reaction rates for different alcohols has been utilised in developing a kinetic method for the estimation of benzyl alcohol (2.0–40.0 mmol dm−3) in the presence of a large number of closely related alcohols and hydroxy compounds. The relative standard deviation for ten replicate measurements of 5 mmol dm−3 benzyl alcohol is 1.5%. The method was satisfactorily applied to analyse real samples.

Simultaneous ion chromatographic separation of anions and cations on poly(aspartic acid) functionalized silica.

Poly(aspartic acid)-silica (PolyCAT A), originally designed for the cation-exchange chromatography of proteins, is proposed for the simultaneous ion chromatographic separation of inorganic anions and cations. This is possible owing to the zwitterion-exchange properties of this stationary phase, which are attributed to the presence of both protonated aminopropyl and dissociated carboxylic groups in poly(aspartic acid) attached to the silica. The retention of alkali metal (Li+, Na+, K+), alkaline earth metal (Mg2+, Ca2+), ammonium and inorganic anions (Cl-, H2PO4-, Br-, NO2-, I-, IO3-, NO3-, ClO4-, SCN-) was tested in aqueous solutions of sulfuric, perchloric, sulfosalicylic, citric, oxalic, maleic and aspartic acids with conductimetric detection. The effect of eluent pH, together with the concentration and characteristics of the eluting ions, were studied. Under optimum conditions (0.3 mmol dm(-3) H2SO4-0.2 mmol dm(-3) Li2SO4 eluent), the simultaneous separation of three anions (Cl-, H2PO4-, NO3-) and four cations (Na+, K+, Mg2+, Ca2+), on a PolyCAT A column (200 x 4.6 mm id, 5 microm film thickness) was achieved in 9 min.

Precipitation of calcite in the presence of inorganic phosphate

Abstract The precipitation of calcite from Ca(HCO3)2 solutions was studied over a wide range of dissolved inorganic phosphorus concentrations (0–500 μmol dm−3 KH2PO4) and a dissolved calcium concentration of 2.5 mmol dm−3 at 10 °C. At low phosphorus concentrations (

Hydroxyapatite coating on titanium by thermal substrate method in aqueous solution.

A new hydrocoating method (the thermal substrate method) is proposed for coating calcium phosphates such as hydroxyapatite (HA), on titanium substrates in an aqueous solution. Several factors (e.g., the type of ion source, the heating time and temperature, and the surface roughness of the substrate) affected the characteristics of the precipitate formed by this method. The solution used included 3 mmol dm(-3) Ca(H(2)PO(4))(2) and 7 mmol dm(-3) CaCl(2), and its pH was adjusted to 6.5. The experimental studies were conducted under the following conditions: temperature 45-160 degrees C, heating time 10-20 min, and surface roughness of substrate #120-#2000 grid ground using energy paper. A high quality of precipitate, whose predominant component was HA, was obtained on titanium substrates by the thermal substrate method in an aqueous solution. No significant difference in the precipitates was found with the type of ion source. The amount of HA precipitate increased with increasing temperature and with increasing heating time. The features of the precipitate were different, depending on the surface roughtness of the substrate: HA regularly nucleated along the grooves of the rough surface (#120 and #400 grid), and in the case of the fine surface (#1200-#2000 grid), a uniform precipitation occurred.

Silicic acid (Si(OH) 4) is a significant influence upon the atomic absorption signal of aluminium measured by graphite furnace atomic absorption spectrometry (GFAAS)

We have identified silicic acid (Si(OH) 4) as an important modifier of the absorbance signal of aluminium measured by graphite furnace atomic absorption spectrometry (GFAAS). The presence of Si(OH) 4 enhanced the signal by as much as 50%. The extent of the enhancement was dependent upon both [Al] and [Si(OH) 4] and was maximal when [Al]≤4.44 μmol dm −3 and [Si(OH) 4]≥0.50 mmol dm −3. The enhancement of the Al absorbance signal was not linearly related to [Si(OH) 4] and the effect was, generally, saturated, for all [Al] tested, at [Si(OH) 4]≥0.50 mmol dm −3. Si(OH) 4 was significantly more effective in enhancing the Al absorbance signal than Mg(NO 3) 2. However, the co-occurrence of 10 mmol dm −3 Mg(NO 3) 2 and 2 mmol dm −3 Si(OH) 4 in samples abolished the enhancement due to Si(OH) 4. The presence of Si(OH) 4 in samples could result in an overestimation of the Al content of those samples by as much as 50%. Errors in the measurement of Al in samples containing Si(OH) 4 could be prevented using matrix-matched calibration standards. Our observation could have serious implications for the determination of Al in aqueous samples of both geochemical and biological interest. It may also point towards the application of Si(OH) 4 as a novel and effective matrix modifier in the determination of Al by GFAAS since the inclusion of Si(OH) 4 in standards and samples improved the limit of detection of Al from ca 8 nmol dm −3 to 3 nmol dm −3.

Advanced oxidation processes for the degradation of p‐hydroxybenzoic acid 2: Photo‐assisted Fenton oxidation

AbstractOxidation of p‐hydroxybenzoic acid in aqueous solution by the photo‐assisted Fenton reaction (Fe2+ + H2O2 + UV) has been studied. The effects of ferrous ion concentration (0.05, 0.14 and 0.29 mmol dm−3), temperature (10, 20, 30 and 40 °C), and initial hydrogen peroxide concentration (0.7, 1.4, 2.2 and 2.9 mmol dm−3) on the p‐hydroxybenzoic acid conversion were established. Experimental results indicate that the kinetics of this oxidation process fits pseudo‐first‐order kinetics well. The overall kinetic rate constant was split into two components: direct oxidation by UV radiation (photolysis) and oxidation by free radicals (mainly OH·) generated in the system. The importance of these two reaction paths for each specific value of ferrous ion concentration, temperature and initial hydrogen peroxide concentration was evaluated. A semi‐empirical expression is proposed for the overall reaction rate which takes into account both oxidation pathways and is a function of operating variables.© 2001 Society of Chemical Industry

Obtaining the 'best values' of stability constants: the protonation constants of five thioether carboxylates as a case study.

Computer speciation models often require large numbers of equilibrium constant values. For this purpose, state-of-the-art methods for experimental constant determination, best value constant selection from published values, and constant prediction based on quantitative structure-activity relationships, are evaluated through their application to the study of the protonation constants of five thioether carboxylates in aqueous solution at 37 degrees C and I = 150 mmol dm(-3) (NaCl).