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Aims: To estimate dietary intakes of folate and vitamin B12 (vital nutrients during the early stages of human development) in women of childbearing age (15 40 years). Study design: Baseline data were collected from 1668 women recruited to an intervention trial. Materials: An interviewer-administered food frequency questionnaire (101 items, 15 food-groups) was developed to obtain intakes in the past month. Data were recorded as frequencies ranging from three times/day to once/month or less. Daily folate and B12 intakes were calculated, assuming standard portion sizes, and using published nutrient-content tables and (for GLVs) laboratory analysis. Outcome measures: Adequacy of intakes according to ICMR Recommended Daily Allowances (RDAs; folate 100 mg/day; B12 1 mg/day).

The kinetics, reaction pathways and product distribution of oxidation of tetrachloroethylene (PCE) by potassium permanganate (KMnO4) were studied in phosphate-buffered solutions under constant pH, isothermal, completely mixed and zero headspace conditions. Experimental results indicate that the reaction is first-order with respect to both PCE and KMnO4 and has an activation energy of 9.3±0.9kcal/mol. The second-order rate constant at 20 °C is 0.035±0.004M−1s−1, and is independent of pH and ionic strength (I) over a range of pH 3–10 and I∼0–0.2 M, respectively. The PCE–KMnO4 reaction may proceed through further oxidation and/or hydrolysis reaction pathways, greatly influenced by the acidity of the solution, to yield CO2(g), oxalic acid, formic acid and glycolic acid. Under acidic conditions (e.g., pH 3), the further oxidation pathway will dominate and PCE tends to be directly mineralized into CO2 and chloride. Under neutral (e.g., pH 7) and alkaline conditions (e.g., pH 10), the hydroxylation pathway dominates the reaction and PCE is primarily transformed into oxalic acid prior to complete PCE mineralization. Moreover, all chlorine atoms in PCE are rapidly liberated during the reaction and the rate of chloride production is very close to the rate of PCE degradation.

The extent of oxidation of dissolved-phase and pure-phase trichloroethylene (TCE) by potassium permanganate (KMnO4) in a sandy aquifer matrix and the impact of reaction products (H+ and MnOx) on pH, metal ion leaching and permeability of the aquifer medium near TCE source zones during KMnO4 flushing were investigated using laboratory-scale column experiments. The results of three column experiments indicated that KMnO4 completely dechlorinated TCE, evidenced by ∼100% chloride recovery, when TCE was present in dissolved phase or pure phase in the aquifer matrix. Two other column experiments were conducted to investigate the impact of H+ and MnOx on the aquifer medium near TCE source zones. KMnO4 flushing of the aquifer medium with residual pure TCE showed significant decreases in the pH levels (e.g. from 6.7 to ∼2.0) of the column effluents, and large quantities of MnOx precipitates were retained in the columns. The decrease in the pH levels in the columns led to an increase in the iron content of the column effluents. Two bromide tracer tests indicated that MnOx precipitates reduced approximately 20% of the pore space in the columns. In addition, characterization of MnOx by X-ray diffraction (XRD) and infrared (IR) spectroscopy demonstrated that the TCE–KMnO4 reaction yielded birnessite-type manganese oxide.

The kinetics of oxidation of perchloroethylene (PCE), trichloroethylene (TCE), three isomers of dichloroethylene (DCE) and vinyl chloride (VC) by potassium permanganate (KMnO(4)) were studied in phosphate-buffered solutions of pH 7 and ionic strength approximately 0.05 M and under isothermal, completely mixed and zero headspace conditions. Experimental results have shown that the reaction appears to be second order overall and first order individually with respect to both KMnO(4) and all chlorinated ethenes (CEs), except VC. The degradation of VC by KMnO(4) is a two-consecutive-step process. The second step, being the rate-limiting step, is of first order in VC and has an activation energy (E(a)) of 7.9+/-1 kcal mol(-1). The second order rate constants at 20 degrees C are 0.035+/-0.004 M(-1) s(-1) (PCE), 0.80+/-0.12 M(-1) s(-1) (TCE), 1.52+/-0.05 M(-1) s(-1) (cis-DCE), 2.1+/-0.2 M(-1) s(-1) (1,1-DCE) and 48.6+/-0.9 M(-1) s(-1) (trans-DCE). The E(a) and entropy (DeltaS(*)) of the reaction between KMnO(4) and CEs (except VC) are in the range of 5.8-9.3 kcal mol(-1) and -33 to -36 kcal mol(-1) K(-1), respectively. Moreover, KMnO(4) is able to completely dechlorinate CEs, and the increase in acidity of the solution due to CE oxidation by KMnO(4) is directly proportional to the number of chlorine atoms in CEs.

The kinetics of oxidation of chlorinated ethenes (CE) with KMnO4 was studied in phosphate-buffered solutions under pseudo-order, isothermal and zero headspace conditions. The results indicate that the reaction is first order in both the reductant and oxidant, The second order rate constants for the reactions between KMnO4 and CE at 20 degrees C are 0.035+/-0.004 M(-1)s(-1) (PCE) 0.80+/-0.12 M(-1)s(-1) (TCE), 1.52+/-0.05 M(-1)s(-1) (cis-DCE), 2.1+/-0.2 M(-1)s(-1) (1, 1-DCE) and 48.6+/-0.9 M(-1)s(-1) (trans-DCE), respectively. The activation energy (E-a) for the reaction between KMnO4 and CE (except vinyl chloride) ranges from 5.8 +/- 0.1 kcal/mol to 9.3 +/- 0.9 kcal/mol.

This study indicates that the dissolved-phase TCE was rapidly oxidized by permanganate while the destruction of source free phase TCE appeared to be controlled by the rate of mass transfer of both permanganate and TCE toward their interface. The oxidation of dissolved-phase TCE by permanganate had caused a significant decrease in pH [e.g., from 6.5 (background) to 3.5 (at similar to 1 pore volume)] and an increase in chloride [e.g., from 83 mg/L (background) to 380 mg/L (at similar to 1 pore volume] in the extracted water in the beginning of the test. The downward migration of permanganate fronts near the aquitard provides evidences for the destruction of source free phase TCE. Two sets of soil cores collected near the aquitard at different times reveal that MnO2 layers were formed above the source TCE zones and increased as the test proceeded.

The kinetics of oxidation of trichloroethylene (TCE) by potassium permanganate (KMnO4) was investigated in a phosphate buffer solution of pH 7 and ionic strength (I) of 0.05 M at three different temperatures (10, 15, and 20 degrees C), The results indicate that the oxidation of TCE by KMnO4 at a constant pH and temperature may be modeled as an irreversible second-order (first-order individually with respect to KMnO4 and TCE) reaction. The second-order rate constant and the activation energy, determined using the initial rate method for the reaction between TCE and KMnO4, were 0.89 +/- 0.03 M(-1)s(-1) and 35 +/- 2.9 kJ/mol, respectively. The results of this study also confirmed the assumed reaction stoichiometry, i.e., 2 mol of KMnO4 are required for the mineralization of 1 mol of TCE.

The production of nitrocellulose (NC) creates large quantities of waste NC fines in wash water streams. Current processing techniques attempt to remove these fines by cross-flow microfiltration, air flotation, settling, centrifugation and lime precipitation. To date, no fundamental study investigating the interfacial thermodynamics of these fines has been reported. This work explored the stability of NC fines in water employing the DLVO model and the more recently developed extended DLVO (ExDLVO) model as described by van Oss and colleagues [van Oss C. J., Chaudhury M. K. and Good R. J. (1988) Chem. Rev. 88, 927–941]. Both models predicted that NC fines will become unstable and coagulate, with the addition of a 1:1 indifferent electrolyte at ionic strengths greater than approx. 5 mM. The ExDLVO theory, which accounts for Lewis acid-base (AB) interactions, predicted greater attractive potential energy availability. Experimental studies corroborated modeling predictions. Results indicate that NC fines may be easily destabilized allowing potential reuse.

The phenomenon of ozone-induced particle destabilization was studied employing a colloidal suspension of 150 mg/L sodium montmorillonite (Na-M) suspended in river water containing 3.1 mg/L natural organic matter(NOM). The suspension was treated with high (approximately 105 muM) and low (approximately 10 muM) ozone doses. Extended DLVO theory was utilized to investigate the surface thermodynamics of unozonated and ozonated Na-M coated with NOM (cNa-M). Ozonation decreased the surface charge and the Lewis base parameter, and increased the Lewis acid parameter and Lifshitz-van der Waals component of the surface energy. The overall result of these changes was a decrease in the change in the total free energy of interaction and hence a decrease in the stability of cNa-M with increasing ozonation. Modification in the surface thermodynamics responsible for destabilization could possibly be attributed to partial dealuminization of Na-M and associated NOM transformations, increasing the autophilicity of the colloids.

Pilot scale studies were conducted to investigate the effect of oxidation at various stages of water treatment process. Impact of pre- and postoxidation (before coagulation and after filtration, respectively), on the formation of disinfection by-products (DBPs) and assimilable organic carbon (AOC) was investigated. Based upon the oxidant (ozone or ozone + hydrogen peroxide) dosages evaluated, no consistently significant differences, in terms of DBP reduction and AOC formation, were observed in pre- vs. postoxidation scenarios. The ozone dosage required in postoxidation was found to be less than half of that required in preoxidation to achieve similar DBP reductions and AOC results. Addition of hydrogen peroxide along with ozone did not result in consistently improved treatment performance. Bench and pilot scale studies were conducted to investigate the effect of ozone oxidation pathway on the reduction of DBPs. It was found that, while ozone alone was not particularly effective for long term reduction of DBPs, ozonation in the presence of radical scavenging bicarbonate resulted in statistically significant higher reduction of DBP precursors.

A sodium montmorillonite (NaM) suspension (150 mg/liter) was treated with various ozone doses up to 97 μM (0.65 μmol O3/mg NaM). Suspension stability increased with increasing levels of ozonation as evidenced by increases in critical coagulation concentration (CCC) values of Na+, Ca2+, and La3+. The increase in induced stability of NaM was found to be most pronounced with Na+ as an indifferent electrolyte and least noticeable when La3+ was used. The enhanced stability of NaM can in large measure be attributed to an increase in the surface charge as a result of ozone-induced transformations. The conductivity of the suspending medium (water) was found to increase with ozonation indicating a leaching of ions from the crystal structure. DLVO theory was utilized to interpret the stability behavior of NaM suspensions; however, it underestimated CCC values. This discrepancy was attributed to an additional force resulting from hydrogen-bonding interactions. These interactions were found to be repulsive (hydration pressure) in nature. Hydration pressure increased with ozonation while Liftshitz—van der Waal forces remained largely unaffected. Electrostatic forces were found to be the major component responsible for increased stability of NaM as a result of ozonation, supporting a crystal dissolution hypothesis.