Efficient decomposition of perfluorocarboxylic acids and alternative fluorochemical surfactants in hot water

Decomposition of C5-C9 perfluorocarboxylic acids (PFCAs) and perfluoroether carboxylic acids (alternatives to PFCA-based surfactants) in hot water in a sealed reactor was investigated. Although PFCAs showed almost no decomposition in hot water at 80 degrees C in the absence of persulfate (S2O8(2-)), the addition of S2O8(2-) to the reaction system led to efficient decomposition, even at this relatively low temperature. The major products in the aqueous and gas phases were F- ions and CO2, respectively, and short-chain PFCAs were also detected in the aqueous phase. For example, when an aqueous solution containing perfluorooctanoic acid (PFOA, 374 microM) and S2O8(2-) (50.0 mM) was heated at 80 degrees C for 6 h, PFOA concentration in the aqueous phase fell below 1.52 microM (detection limit of HPLC with conductometric detection), and the yields of F- ions [i.e., (moles of F- formed) /(moles of fluorine content in initial PFOA)] and CO2 [i.e, (moles of CO2 formed) /(moles of carbon content in initial PFOA)] were 77.5% and 70.2%, respectively. This method was also effective in decomposing perfluoroether carboxylic acids, such as CF3OC2F4OCF2COOH, CF3OC2F4OC2F4OCF2COOH, and C2F5OC2F4OCF2COOH, which are alternatives to PFCA-based surfactants, producing F- and CO2 with yields of 82.9-88.9% and 87.7-100%, respectively, after reactions at 80 degrees C for 6 h. In addition, the method was successfully used to decompose perfluorononanoic acid in a floor wax solution. When PFOAwastreated at a higher temperature (150 degrees C), other decomposition reactions occurred: the formation of F- and CO2 was dramatically decreased, and 1H-perfluoroalkanes (C(n)F(2n+1)H, n = 4-7) formed in large amounts. This result clearly indicates that treatment with high-temperature water was not suitable for the decomposition of PFCAs to F-: surprisingly, the relatively low temperature of 80 degrees C was preferable.     

Reductive defluorination of perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS) is under increased scrutiny as an environmental pollutant due to recent reports of its worldwide distribution, environmental persistence, and bioaccumulation potential. The susceptibility of technical PFOS and PFOS branched isomers to chemical reductive dehalogenation with vitamin B12 (260 microM) as catalyst and Ti(III)-citrate (36 mM) as bulk reductant in anoxic aqueous solution at 70 degrees C and pH 9 was evaluated in this study. Defluorination was confirmed by fluoride release measurements of 18% in technical PFOS, equivalent to the removal 3 mol F-/mol PFOS, and 71% in PFOS branched isomers equivalent to the removal of 12 mol F-/mol PFOS. Degradation of PFOS was further confirmed by monitoring the disappearance of PFOS compounds with reaction time by suppressed conductivity ion chromatography, LC-MS/MS, and 19F NMR studies. The PFOS compounds differed in their susceptibility to reductive degradation by vitamin B12Ti(III) citrate. Chromatographic peaks corresponding to branched PFOS isomers disappeared whereas the peak corresponding to linear PFOS was stable. To our knowledge this is the first report of reductive dehalogenation of PFOS catalyzed by a biomolecule.     

Decomposition of environmentally persistent trifluoroacetic acid to fluoride ions by a homogeneous photocatalyst in water

Decomposition of trifluoroacetic acid (TFA) was achieved with a tungstic heteropolyacid photocatalyst H3PW12O40*6H2O in order to develop a technique for measures against TFA stationary sources. This is the first example of C-F bond cleavage in an environmentally harmful perfluoromethyl-group-containing compound using a homogeneous photocatalyst. The catalytic reaction proceeds in water at room temperature under UV-visible light irradiation in the presence of oxygen. The system produces only F- ions and CO2; the (mole of formed F-)/(mole of decomposed TFA) and (mole of formed CO2)/(mole of decomposed TFA) ratios were 2.91 and 2.09, respectively. GC/MS measurements showed no trace of other species such as environmentally undesirable CF4, which is the most stable perfluorocarbon and has a very high global warming potential. When the (initial TFA)/(initial catalyst) molar ratio was 20:1, the turnover number of TFA decomposition reached 5.58 by 72 h of irradiation, accompanying with no catalyst degradation. The catalytic reaction mechanism can be explained by a redox reaction between the catalyst and TFA, involving a photo-Kolbe process.     

Photodegradation of perfluorooctane sulfonate by UV irradiation in water and alkaline 2-propanol

Perfluorooctane sulfonate (PFOS) is the environmentally concerned compound because of its persistence and bioaccumulative properties. Since photodegradation of PFOS is not yet experimentally confirmed, photodegradation study of PFOS in water and alkaline 2-propanol solution was conducted. Aqueous and alkaline 2-propanol solution of PFOS (40 microM) was irradiated with a low-pressure mercury lamp (254 nm, 32 W) by internal irradiation for 10 d, and then PFOS, fluoride and sulfate ions, and the other degradation products were analyzed. Photodegradation of PFOS was confirmed in both media. PFOS was degraded by 8% after 1 day and by 68% after 10 days irradiation compared to the initial concentration in water. In alkaline 2-propanol, 76 and 92% of PFOS was degraded after 1 and 10 days irradiation, respectively. Photodegradation of PFOS in alkaline 2-propanol was much faster and effective than in water, as the photodegradation rate constants were 0.93 days(-1) in alkaline 2-propanol and 0.13 days(-1) in water, respectively. Formation of fluoride and sulfate was also confirmed by ion chromatography and X-ray diffraction analysis. From observation of the degradation products, two major degradation pathways of PFOS were considered: via C8HF17 and C8F17OH, respectively, resulting in short-chain fluorinated compounds such as C7HF15 and C7F15OH by stepwise removal of CF2. Formation of short-chain fluorocarbons such as CF4, C2F6, and C3F8 were also confirmed. This is the first study to confirm photodegradation of PFOS in water and alkaline 2-propanol.     

Decomposition of environmentally persistent perfluorooctanoic acid in water by photochemical approaches

The decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water by UV-visible light irradiation, by H202 with UV-visible light irradiation, and by a tungstic heteropolyacid photocatalyst was examined to develop a technique to counteract stationary sources of PFOA. Direct photolysis proceeded slowly to produce CO2, F-, and short-chain perfluorocarboxylic acids. Compared to the direct photolysis, H2O2 was less effective in PFOA decomposition. On the other hand, the heteropolyacid photocatalyst led to efficient PFOA decomposition and the production of F- ions and CO2. The photocatalyst also suppressed the accumulation of short-chain perfluorocarboxylic acids in the reaction solution. PFOA in the concentrations of 0.34-3.35 mM, typical of those in wastewaters after an emulsifying process in fluoropolymer manufacture, was completely decomposed by the catalyst within 24 h of irradiation from a 200-W xenon-mercury lamp, with no accompanying catalyst degradation, permitting the catalyst to be reused in consecutive runs. Gas chromatography/mass spectrometry (GC/MS) measurements showed no trace of environmentally undesirable species such as CF4, which has a very high global-warming potential. When the (initial PFOA)/(initial catalyst) molar ratio was 10: 1, the turnover number for PFOA decomposition reached 4.33 over 24 h of irradiation.     

Decomposition Kinetics of Glucose and Fructose in Subcritical Water Containing Sodium Chloride

The kinetics of the decomposition and isomerization of glucose and fructose in pure water and water containing sodium chloride (1–20 % w/w) under subcritical conditions at 180–220 °C was investigated. The addition of sodium chloride in subcritical water accelerated the decrease of glucose, and the rate was expressed by the Weibull equation. Although the isomerization of glucose to fructose was observed in parallel with decomposition, the yield of fructose was lower at higher sodium chloride concentrations. Mannose was also formed from glucose with very low yield. It was seen that fructose decomposed much faster than glucose, in pure and salty subcritical water. The decomposition of fructose obeyed first-order kinetics in the initial stages of the reaction and could be expressed by the autocatalytic model in the later stages. The formation of glucose and mannose from fructose was not observed under any of the conditions investigated.     

Catalyzed oxidation of arsenic(III) by hydrogen peroxide on the surface of ferrihydrite: an in situ ATR FTIR study

Knowledge of arsenic redox kinetics is crucial for understanding the impact and fate of As in the environment and for optimizing As removal from drinking water. Rapid oxidation of As(III) adsorbed to ferrihydrite (FH) in the presence of hydrogen peroxide (H2O2) might be expected for two reasons. First, the adsorbed As(III) is assumed to be oxidized more readily than the undissociated species in solution. Second, catalyzed decomposition of H2O2 on the FH surface might also lead to As(III) oxidation. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to monitor the oxidation of adsorbed As(III) on the FH surface in situ. No As(III) oxidation within minutes to hours was observed prior to H2O2 addition. Initial pseudo-first-order oxidation rate coefficients for adsorbed As(III), determined at H2O2 concentrations between 8.4 microM and 8.4 mM and pH values from 4 to 8, increased with the H2O2 concentration according to the equation log k(ox) (min(-1)) = 0.17 + 0.50 log [H2O] (mol/L), n = 21, r2 = 0.87. Only a weak pH dependence of log k(ox) was observed (approximately 0.04 logarithm unit increase per pH unit). ATR-FTIR experiments with As(III) adsorbed onto amorphous aluminum hydroxide showed that Fe was necessary to induce As(III) oxidation by catalytic H2O2 decomposition. Supplementary As(III) oxidation experiments in FH suspensions qualitatively confirmed the findings from the in situ ATR-FTIR experiments. Our results indicate that the catalyzed oxidation of As(III) by H2O2 on the surface of iron (hydr)oxides might be a relevant reaction pathway in environmental systems such as surface waters, as well as in engineered systems for As removal from water.     

Efficient decomposition of environmentally persistent perfluorocarboxylic acids by use of persulfate as a photochemical oxidant

Photochemical decomposition of persistent perfluorocarboxylic acids (PFCAs) in water by use of persulfate ion (S2O8(2-)) was examined to develop a technique to neutralize stationary sources of PFCAs. Photolysis of S2O8(2-) produced highly oxidative sulfate radical anions (SO4-), which efficiently decomposed perfluorooctanoic acid (PFOA) and other PFCAs bearing C4-C8 perfluoroalkyl groups. The major products were F- and CO2; also, small amounts of PFCAs with shorter than initial chain lengths were detected in the reaction solution. PFOA at a concentration of 1.35 mM (typical of that in untreated wastewater after an emulsifying process in fluoropolymer manufacture) was completely decomposed by a photochemical system with 50 mM S2O8(2-) and 4 h of irradiation from a 200-W xenon-mercury lamp. The initial PFOA decomposition rate was 11 times higherthan with photolysis alone. All sulfur-containing species in the reaction solution were eventually transformed to sulfate ions by this method. This method was successfully applied to the decomposition of perfluorononanoic acid contained in a floor wax solution.     

Decomposition kinetics of monoacyl glycerol and fatty acid in subcritical water under temperature-programmed heating conditions

The decompositions of monocaprylin, monocaprin, monolaurin and their corresponding fatty acids in subcritical water were measured under temperature-programmed heating conditions where the reaction temperature was linearly increased from room temperature to 350 °C at specified rates to estimate the activation energies E_i and the frequency factors k_i0 for the decompositions. The decompositions of both monoacyl glycerol and fatty acid obeyed first-order kinetics, and the decomposition of a monoacyl glycerol proceeded consecutively to form its constituent fatty acid and then further decomposition compounds. There was a tendency for both the E_i and k_i0 values for a monoacyl glycerol or fatty acid with a longer acyl chain to be smaller, and it was shown that the enthalpy–entropy compensation held for the decompositions of monoacyl glycerols and fatty acids as well as for those of fatty acid esters with various acyl and alkyl chains in subcritical water.     

Subcritical (hot/liquid) water dechlorination of PCBs (Aroclor 1254) with metal additives and in waste paint

No disposal option exists for "mixed wastes" such as paint scrapings that are co-contaminated with polychlorinated biphenyls (PCBs) and radioactive metals. Either removal or destruction of the PCBs is required prior to disposal. Comparison of subcritical water dechlorination (350 degrees C, 1 h) of Aroclor 1254 in paint scrapings (180 ppm) and of standard Aroclor 1254 showed significantly enhanced dechlorination in the presence of paint. While no significant degradation was observed for standard Aroclor (no paint), the dechlorination of PCBs in paint was 99, 99, and 80% for the hepta-, hexa-, and pentachlorinated congeners, respectively, indicating that metals in the paint enhanced the dechlorination reactions. Adding metals to the standard Aroclor (no paint) reactions enhanced PCB dechlorination in subcritical water in descending order of activity: Pb approximately = Cu > Al > Zn > Fe. In the presence of both zerovalent and divalent lead and zerovalent copper in subcritical water (350 degrees C, 1 h), 99% of the Aroclor 1254 mixture (tetra- to heptachlorinated biphenyls) was dechlorinated. High dechlorination (ca. 95%) was also achieved with zerovalent aluminum. In contrast to other metals, lead retained its degradation ability at a lower temperature of 250 degrees C after 18 h. The high degradation efficiency achieved using metal additives in water at reasonable temperatures and pressures demonstrates the potential for subcritical water dechlorination of PCBs in paint scrapings and, potentially, in other solid and liquid wastes.     

Heterogeneous decomposition of CHF2OCH2CF3 and CHF2OCH2C2F5 over various standard aluminosilica clay minerals in air at 313 K

The heterogeneous decomposition of CHF2OCH2C2F5, a potential substitute for hydrofluorocarbons, over aluminosilica clay minerals in air, was confirmed to occur at 313 K in a closed-circulation reactor. HC(O)OCH2C2F5, the gaseous main product was produced through hydrolytic elimination of F atoms from the CHF2OCH2- group. CHF2OCH2CF3 also decomposed to HC(O)OCH2CF3 over the clay minerals. The pseudo-first-order rate constants were determined for the decompositions over eight types of clay minerals (19 samples). The various clay minerals had different abilities to decompose these hydrofluoroethers. The decomposition rates per Brunauer-Emmett-Teller surface area and the conversion ratios to HC(O)OCH2C2F5 or HC(O)OCH2CF3 for the reactions over kaolinite, halloysite, and illite were high in comparison to those for the same reactions over montmorillonite, hectorite, and nontronite. The dependence of this heterogeneous reaction on temperature and relative humidity indicates that, in the environment, the reaction could be important only in hot, dry regions. The results did not suggest that sunlight would directly accelerate the decay of CHF2OCH2CF3 or CHF2OCH2C2F5. In the presence of clay-containing soils in arid areas, this hydrolytic oxidation reaction may significantly affect both the lifetime and the degradation products of CHF2OCH2CF3 and CHF2OCH2C2F5 in the troposphere.     

Decomposition of hydrogen peroxide and organic compounds in the presence of dissolved iron and ferrihydrite

This work examines the contribution of solution phase reactions, especially those involving a chain reaction mechanism, to the decomposition of hydrogen peroxide (H2O2) and organic compounds in the presence of dissolved iron and ferrihydrite. In solutions at pH 4, where Fe was introduced as dissolved Fe(III), both H2O2 and 14C-labeled formic acid decomposed at measurable rates that agreed reasonably well with those predicted by a kinetic model of the chain reaction mechanism, using published rate constants extrapolated to pH 4. The ratio of the formic acid and H2O2 decomposition rates, as well as the dramatic effect of tert-butyl alcohol on these rates, confirmed that a solution chain reaction mechanism involving *OH controlled the decomposition kinetics of both compounds. In the presence of ferrihydrite as the iron source, the ratio of the rate of formic acid decomposition to that of H2O2 decomposition was significantly lower than that observed in the presence of only dissolved Fe. Moreover, neither rate diminished drastically upon addition of tert-butyl alcohol, indicating that the solution phase chain reaction is not a dominant decomposition pathway of H2O2 and formic acid. Relative decomposition rates of formic acid and a second *OH probe, benzoic acid, were consistent with oxidation of these compounds by *OH. These observations can be reproduced by a kinetic model including (a) decomposition of H2O2 at the iron oxide surface, producing *OH with lower yield than the reaction sequence with dissolved Fe, and (b) low concentrations of dissolved Fe in the presence of ferrihydrite, preventing propagation of the solution phase chain reaction.     

Low concentrations of surfactants enhance siderophore-promoted dissolution of goethite

Surface-active agents (surfactants) are released by many soil bacteria and plant roots and are also important as environmental contaminants. Their presence at interfaces could influence important biogeochemical processes in soils such as ligand-controlled dissolution, an important process in biological iron acquisition. To investigate their potential influence on ligand-controlled dissolution of iron oxides, we studied the dissolution kinetics of goethite (alpha FeOOH) at pH 6 in the presence of the bacterial siderophore desferrioxamine B (DFOB) and the anionic surfactant sodium dodecyl sulfate (SDS). The adsorption isotherm of SDS on goethite showed an increase in the slope at concentrations ranging between 300 and 400 microM SDS in solution. This increase in slope suggested the onset of admicelle formation. Adsorption of DFOB onto goethite increased strongly with increasing concentrations of adsorbed SDS. Small concentrations of SDS (5 microM) resulted in a 3-fold acceleration of DFOB-controlled goethite dissolution in the presence of 80 microM DFOB, compared to the suspensions without SDS. The effects of SDS on the goethite dissolution rates were less pronounced at higher SDS concentrations, and became negligible above 600 microM total SDS. The dissolution rates of goethite were not proportional to the adsorbed DFOB concentrations, as would be expected for ligand-controlled dissolution. We speculate that increasing concentrations of adsorbed SDS result in a change in DFOB surface speciation from inner-sphere to outer-sphere complexes and, consequently, the ligand-controlled dissolution rates are not linearly related to the adsorbed DFOB concentration. Our results provide the first evidence for an important role of biosurfactants in biological iron acquisition involving siderophores.     

CHARACTERIZATION OF A CHEMICALLY CONJUGATED β-GALACTOSIDASE BIOREACTOR1

A chemically prepared conjugate of avidin and E. coli β-galactosidase was adsorbed to biotinylated controlled-pore glass beads and used in a fluidized-bed bioreactor to assess the feasibility of bioselective adsorption immobilization technology. Biotinylated 200 nm pore diameter porous glass beads were prepared by reaction of 3-aminopropyl-glass beads with sulfosuccinimidyl-6-(biotinamido) hexanoate. Avidin and biotinylated β-galactosidase were sequentially adsorbed to the matrix. The fluidized-bed bioreactor was characterized with respect to β-galactosidase activity using both a lactose solution and o-nitrophenyl β-D-galactopyranoside (ONPG) as substrates. A lactose solution (4.5%, pH 7) was assayed for lactose hydrolysis at various flow rates. The bioreactor was operated for three months at 65–75% lactose hydrolysis with no loss in enzyme activity. The biocatalyst was characterized by amino acid analysis to determine the amount of each of the two proteins adsorbed. Results indicated 162 μ protein/mg beads of which 36% was avidin and 64% was β-galactosidase corresponding to 1 mole of avidin per mole of β-galactosidase monomer. Biocatalyst activity using ONPG as the substrate was 430 μmoles/min/mg protein, yielding a specific activity of 672 μmoles/min/mg β-galactosidase. These results lead to the conclusion that biospecific adsorption of the β-galactosidase conjugate onto biotinylated glass beads via avidin results in a biocatalyst that is stable and retains a high specific activity.     

Efficient electrochemical oxidation of perfluorooctanoate using a Ti/SnO2-Sb-Bi anode

The electrochemical decomposition of persistent perfluorooctanoate (PFOA) with a Ti/SnO2-Sb-Bi electrode was demonstrated in this study. After 2 h electrolysis, over 99% of PFOA (25 mL of 50 mg·L(-1)) was degraded with a first-order kinetic constant of 1.93 h(-1). The intermediate products including short-chain perfluorocarboxyl anions (CF3COO-, C2F5COO-, C3F7COO-, C4F9COO-, C5F11COO-, and C6F13COO-) and F- were detected in the aqueous solution. The electrochemical oxidation mechanism was revealed, that PFOA decomposition first occurred through a direct one electron transfer from the carboxyl group in PFOA to the anode at the potential of 3.37 V (vs saturated calomel electrode, SCE). After that, the PFOA radical was decarboxylated to form perfluoroheptyl radical which allowed a defluorination reaction between perfluoroheptyl radical and hydroxyl radical/O2. Electrospray ionization (ESI) mass spectrum further confirmed that the oxidation of PFOA on the Ti/SnO2-Sb-Bi electrode proceeded from the carboxyl group in PFOA rather than C-C cleavage, and the decomposition processes followed the CF2 unzipping cycle. The electrochemical technique with the Ti/SnO2-Sb-Bi electrode provided a potential method for PFOA degradation in the aqueous solution.     

Perfluoroalkyl acids in the Atlantic and Canadian Arctic Oceans

We report here on the spatial distribution of C(4), C(6), and C(8) perfluoroalkyl sulfonates, C(6)-C(14) perfluoroalkyl carboxylates, and perfluorooctanesulfonamide in the Atlantic and Arctic Oceans, including previously unstudied coastal waters of North and South America, and the Canadian Arctic Archipelago. Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) were typically the dominant perfluoroalkyl acids (PFAAs) in Atlantic water. In the midnorthwest Atlantic/Gulf Stream, sum PFAA concentrations (∑PFAAs) were low (77-190 pg/L) but increased rapidly upon crossing into U.S. coastal water (up to 5800 pg/L near Rhode Island). ∑PFAAs in the northeast Atlantic were highest north of the Canary Islands (280-980 pg/L) and decreased with latitude. In the South Atlantic, concentrations increased near Rio de la Plata (Argentina/Uruguay; 350-540 pg/L ∑PFAAs), possibly attributable to insecticides containing N-ethyl perfluorooctanesulfonamide, or proximity to Montevideo and Buenos Aires. In all other southern hemisphere locations, ∑PFAAs were <210 pg/L. PFOA/PFOS ratios were typically ≥1 in the northern hemisphere, ～1 near the equator, and ≤1 in the southern hemisphere. In the Canadian Arctic, ∑PFAAs ranged from 40 to 250 pg/L, with perfluoroheptanoate, PFOA, and PFOS among the PFAAs detected at the highest concentrations. PFOA/PFOS ratios (typically ?1) decreased from Baffin Bay to the Amundsen Gulf, possibly attributable to increased atmospheric inputs. These data help validate global emissions models and contribute to understanding of long-range transport pathways and sources of PFAAs to remote regions.     

Reaction Behavior of Glucose and Fructose in Subcritical Water in the Presence of Various Salts

Glucose and fructose were treated in subcritical water in the presence of alkali or alkaline earth metal chlorides. All salts accelerated the conversion of saccharides, and alkaline earth metal chloride greatly promoted the isomerization of glucose to fructose. In contrast, alkali metal salts only slightly promoted this isomerization and facilitated the decomposition of glucose to byproducts such as organic acids. The selectivity of the glucose-to-fructose isomerization was higher at lower conversions of glucose and in the presence of alkaline earth metal chlorides. The pH of the reaction mixture also greatly affected the selectivity, which decreased rapidly at lower pH due to the generated organic acids. At low pH, decomposition of glucose became dominant over isomerization, but further conversion of glucose was suppressed. This result was elucidated by the suppression of the alkali-induced isomerization of glucose at low pH. Fructose underwent decomposition during the treatment of the fructose solution, but its isomerization to glucose was not observed. The added salts autocatalytically promoted the decomposition of fructose, and the reaction mechanism of fructose decomposition differed from that of glucose.     

An experimental and kinetic modeling study of the reaction of CHF3 with methane

The gas-phase reaction of CHF3 with CH4 has been studied experimentally and computationally. The motivation behind the study is that reaction of CHF3 with CH4 provides a possible route for synthesis of CH2=CF2 (C2H2F2). Experiments are carried out in a plug flow, isothermal alpha-alumina reactor at atmospheric pressure over the temperature range of 973-1173 K. To assist in understanding the reaction mechanism and the role of the reactor material involved in the reaction of CHF3 with CH4, the reaction of CHF3 with CH4, pyrolysis of CH4, and pyrolysis of CHCIF2 have been studied in the presence of alpha-alumina or alpha-AIF3 particles under various conditions. Under all conditions studied for the reaction of CHF3 and CH4, the major products are C2F4, C2H2F2, and HF. Minor products include C2H2, C2H4, C2H3F, C2HF3, C3F6, CO2, and H2. C2H6, CH2F2, and CHF2CHF2 are detected in trace amounts. The initial step is the gas-phase unimolecular decomposition of CHF3, producing CF2 and HF. It is proposed that CF2 decomposes on the surface of alpha-alumina, producing F radicals that are responsible for the activation of CH4. A reaction scheme developed on the basis of the existing NIST HFC and GRI-Mech 3.0 mechanisms is used to model the reaction of CHF3 with CH4. Generally satisfactory agreement between experimental and modeling results is obtained on the conversion levels of CHF3 and CH4 and rates of formation of major products. Using the software package AURORA, the reaction pathways leading to the formation of major products are elucidated.     

TiO2-induced heterogeneous photodegradation of a fluorotelomer alcohol in air

Degradation of C4F9C2H4OH in air over TiO2 particles was examined in this first report of gas-solid heterogeneous photochemical degradation of fluorotelomer alcohols (FTOHs), which may be precursors of perfluorocarboxylic acids (PFCAs) in the environment. Photoirradiation (>290 nm) of C4F9C2H4OH in air flowing over TiO2 produced CO2, via C4F9CH2CHO, C4F9CHO, CnF(2n+1)COF (n=2 and/or 3), and COF2, in that order. X-ray photoelectron spectroscopy of the Ti02 surface showed a decrease in the amount of fluorine bonded to carbon and an increase in the amount of F- as the degradation of C4F9C2H4OH in air proceeded. Of the carbon content in the initial C4F9C2H4OH (78.8 ppmv), 90.7% was transformed to CO2, and the predominant fluorine species produced on the TiO2 surface was F-. Fluorotelomer unsaturated acids, which are considered to be toxic and have been observed in the biodegradation of FTOHs, did notform. Increased relative humidity in the air accelerated the decomposition of the reaction intermediates, which led to increased CO2 and F- formation. This result indicates that humidity is a key factor for counteracting FTOHs in indoor air. Although perfluoroalkyl substances such as PFCAs in water reportedly undergo little photodegradation over TiO2, our data show that mineralization of C4F9C2H4OH in air can be achieved with TiO2.     

Enzymatic hydrolysis of heated whey: iron-binding ability of peptides and antigenic protein fractions

This study evaluated the influence of various enzymes on the hydrolysis of whey protein concentrate (WPC) to reduce its antigenic fractions and to quantify the peptides having iron-binding ability in its hydrolysates. Heated (for 10 min at 100°C) WPC (2% protein solution) was incubated with 2% each of Alcalase, Flavourzyme, papain, and trypsin for 30, 60, 90, 120, 150, 180, and 240 min at 50°C. The highest hydrolysis of WPC was observed after 240 min of incubation with Alcalase (12.4%), followed by Flavourzyme (12.0%), trypsin (10.4%), and papain (8.53%). The nonprotein nitrogen contents of WPC hydrolysate followed the hydrolytic pattern of whey. The major antigenic fractions (β-lactoglobulin) in WPC were degraded within 60 min of its incubation with Alcalase, Flavourzyme, or papain. Chromatograms of enzymatic hydrolysates of heated WPC also indicated complete degradation of β-lactoglobulin, α-lactalbumin, and BSA. The highest iron solubility was noticed in hydrolysates derived with Alcalase (95%), followed by those produced with trypsin (90%), papain (87%), and Flavourzyme (81%). Eluted fraction 1 (F-1) and fraction 2 (F-2) were the respective peaks for the 0.25 and 0.5 M NaCl chromatographic step gradient for analysis of hydrolysates. Iron-binding ability was noticeably higher in F-1 than in F-2 of all hydrolysates of WPC. The highest iron contents in F-1 were observed in WPC hydrolysates derived with Alcalase (0.2 mg/kg), followed by hydrolysates derived with Flavourzyme (0.14 mg/kg), trypsin (0.14 mg/kg), and papain (0.08 mg/kg). Iron concentrations in the F-2 fraction of all enzymatic hydrolysates of WPC were low and ranged from 0.03 to 0.05 mg/kg. Fraction 1 may describe a new class of iron chelates based on the reaction of FeSO₄·7H₂O with a mixture of peptides obtained by the enzymatic hydrolysis of WPC. The chromatogram of Alcalase F-1 indicated numerous small peaks of shorter wavelengths, which probably indicated a variety of new peptides with greater ability to bind with iron. Alcalase F-1 had higher Ala (18.38%), Lys (17.97%), and Phe (16.58%) concentrations, whereas the presence of Pro, Gly, and Tyr was not detected. Alcalase was more effective than other enzymes at producing a hydrolysate for the separation of iron-binding peptides derived from WPC.