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This work studied the destruction of various M-EDTA complexes and trace organic pollutants in treated reusable wastewater under advanced oxidation using UV irradiation and ozonation. Effect of dosage of hydrogen peroxide and acidity of reaction matrices on oxidation efficiencies were investigated. The rate constant of mineralization presents a decreasing trend as Fe(III)-EDTA > Fe(II)-EDTA > Al(III)-EDTA > Pb(II)-EDTA > Na(I)-EDTA > Zn(II)-EDTA > Cu(II)-EDTA. The mineralization efficiencies using ozone alone are 15%, 40% and 15% for the water samples after reverse osmosis (RO), microfiltration (MF) and superfiltration (SF) processes, respectively. The presence of hydrogen peroxide in photochemical reaction matrixes can effectively enhance the mineralization of organic carbon species. When 150 mg l(-1) of H2O2 was added in the effluents, the mineralization markedly increased to 80%, 92% and 89%, respectively.
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PMID:Destruction of organic pollutants in reusable wastewater using advanced oxidation technology. 1576 97

The catalytic activity of water-washed manganese nodule leached residue (WMNLR) samples improved by treating with acetic acid. The effects of acetic acid treatment on the physicochemical properties and catalytic activity of manganese nodule leached residue have been studied. The surface area, surface oxygen, surface hydroxyl groups, surface acidity, electron donating properties, etc., increase gradually with acid treatment up to 0.5 M and thereafter show a decreasing trend. The rate constant of H2O2 decomposition, catalytic activity of CO oxidation, and esterification of acetic acid also show a similar trend to that of surface properties.
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PMID:Studies on manganese nodule leached residue 4. Physicochemical characterization and catalytic activity of acetic acid treated manganese nodule leached residue. 1608 22

The epoxidation of cyclooctene catalyzed by iron(III) [tetrakis(pentafluorophenyl)] porphyrin chloride [(F20TPP)FeCl] was investigated in alcohol/acetonitrile solutions in order to determine the effects of the alcohol composition on the reaction kinetics. It was observed that alcohol composition affects both the observed rate of hydrogen peroxide consumption (the limiting reagent) and the selectivity of hydrogen peroxide utilization to form cyclooctene epoxide. The catalytically active species are formed only in alcohol-containing solvents as a consequence of (F(20)TPP)FeCl dissociation into [(F20TPP)Fe(ROH)]+ cations and Cl- anions. The observed reaction kinetics are analyzed in terms of a proposed mechanism for the epoxidation of the olefin and the decomposition of H2O2. The first step in this scheme is the reversible coordination of H2O2 to [(F20TPP)Fe(ROH)]+. The O-O bond of the coordinated H2O2 then undergoes either homolytic or heterolytic cleavage. The rate of homolytic cleavage is found to be independent of alcohol composition, whereas the rate of heterolytic cleavage increases with alcohol acidity. Heterolytic cleavage is envisioned to form iron(IV) pi-radical cations, whereas homolytic cleavage forms iron(IV) hydroxo cations. The iron(IV) radical cations are active for olefin epoxidation, whereas the iron(IV) cations catalyze the decomposition of H2O2. Reaction of iron(IV) pi-radical cations with H2O2 to form iron(IV) hydroxo cations is also included in the mechanism, a process that is favored by alcohols with a high charge density on the O atoms. The proposed mechanism describes successfully the effects of H2O2, cyclooctene, and porphyrin concentrations, as well as the effects of alcohol concentration.
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PMID:Influence of solvent composition on the kinetics of cyclooctene epoxidation by hydrogen peroxide catalyzed by iron(III) [tetrakis(pentafluorophenyl)] porphyrin chloride [(F20TPP)FeCl]. 1652 1

We report the preparation of mesoporous aluminosilicate materials that exhibit molecular-scale ordering in their pore wall framework. The materials were derived from mesoporous aluminosilica-surfactant mesophases via benign template removal methods, which allowed the retention of molecular ordering in surfactant-free materials. The molecularly ordered aluminosilica-surfactant mesophases were obtained from hydrothermal crystallization of cetyltrimethylammonium hydroxide/Al,Si/H2O systems at 135 degrees C for 12 days. Benign template removal via H2O2-mediated oxidation of the surfactant at room temperature was found to be the most effective method in generating surfactant-free materials with molecular ordering, high textural properties (depending on Al content), and high acidity. The Al in the resulting aluminosilicates was entirely incorporated in framework (tetrahedrally coordinated) sites. Template extraction in acidified ethanol also generated molecularly ordered materials but compromised the Al content and acidity. Template removal via conventional calcination generated porous materials with high textural properties but which exhibited only limited molecular ordering and had relatively low acidity and significant amounts of nonframework Al. This work demonstrates that molecular ordering in mesoporous silicate-surfactant mesophases is due to crystallographic ordering within inorganic frameworks rather than the arrangement/packing of surfactant molecules.
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PMID:Crystalline-like molecularly ordered mesoporous aluminosilicates derived from aluminosilica-surfactant mesophases via benign template removal. 1667 24

Through the use of the Active Thermochemical Tables approach, the best currently available enthalpy of formation of HO2 has been obtained as delta(f)H(o)298 (HO2) = 2.94 +/- 0.06 kcal mol(-1) (3.64 +/- 0.06 kcal mol(-1) at 0 K). The related enthalpy of formation of the positive ion, HO2+, within the stationary electron convention is delta(f)H(o)298 (HO2+) = 264.71 +/- 0.14 kcal mol(-1) (265.41 +/- 0.14 kcal mol(-1) at 0 K), while that for the negative ion, HO2- (within the same convention), is delta(f)H(o)298 (HO2-) = -21.86 +/- 0.11 kcal mol(-1) (-21.22 +/- 0.11 kcal mol(-1) at 0 K). The related proton affinity of molecular oxygen is PA298(O2) = 100.98 +/- 0.14 kcal mol(-1) (99.81 +/- 0.14 kcal mol(-1) at 0 K), while the gas-phase acidity of H2O2 is delta(acid)G(o)298 (H2O2) = 369.08 +/- 0.11 kcal mol(-1), with the corresponding enthalpy of deprotonation of H2O2 of delta(acid)H(o)298 (H2O2) = 376.27 +/- 0.11 kcal mol(-1) (375.02 +/- 0.11 kcal mol(-1) at 0 K). In addition, a further improved enthalpy of formation of OH is briefly outlined, delta(f)H(o)298 (OH) = 8.93 +/- 0.03 kcal mol(-1) (8.87 +/- 0.03 kcal mol(-1) at 0 K), together with new and more accurate enthalpies of formation of NO, delta(f)H(o)298 (NO) = 21.76 +/- 0.02 kcal mol(-1) (21.64 +/- 0.02 kcal mol(-1) at 0 K) and NO2, delta(f)H(o)298 (NO2) = 8.12 +/- 0.02 kcal mol(-1) (8.79 +/- 0.02 kcal mol(-1) at 0 K), as well as H(2)O(2) in the gas phase, delta(f)H(o)298 (H2O2) = -32.45 +/- 0.04 kcal mol(-1) (-31.01 +/- 0.04 kcal mol(-1) at 0 K). The new thermochemistry of HO2, together with other arguments given in the present work, suggests that the previous equilibrium constant for NO + HO2 --> OH + NO2 was underestimated by a factor of approximately 2, implicating that the OH + NO2 rate was overestimated by the same factor. This point is experimentally explored in the companion paper of Srinivasan et al. (next paper in this issue).
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PMID:Active Thermochemical Tables: accurate enthalpy of formation of hydroperoxyl radical, HO2. 1672 70

Ultrafine powder CuO/Cu2 (OH)3Cl photocatalysts were prepared by CuCl2 and NaOH reaction and heating method of microwave liquid phase. XRD and FTIR were used to investigate the properties of the CuO/Cu2 (OH)3 Cl powder, and photocatalytic degradation of dyes by the CuO/Cu2 (OH)3 Cl catalysts was investigated. The results show that the decoloration rate is related to the pH value of dyes solution, irradiation time, as well as the intensity of irradiation. After irradiation with sun light for 4 h, the decoloration rate was up to 90% when the concentration of dyes was 20 mg x L(-1), the amount of catalyst was 40 mg) and the acidity was pH 8 in 50 mL dye solution. Adding Fe3+, H2O2 and other catalyst can improve the decoloration rate greatly. So the decoloration of dyes was due to photocatalytic degradation by analyzing the IR spectrum and the ultraviolet spectrum, and the photocatalytic activity of CuO/Cuz (OH)3 Cl powder is good in photocatalytic decoloration of dyes, such as amido black, indigo carmine and so on. The stability of photocatalytic nature of powder CuO/Cu2 (OH)3Cl was studied, and CuO/ Cu2 (OH)3 Cl powder can be recycled.
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PMID:[Study on preparation of CuO/Cu2 (OH)3Cl powder and its spectrum behavior for photodegradation decoloration of dyes]. 1682 11

Fluoride in drinking water above permissible levels is responsible for human and skeletal fluorosis. In this study, activated carbons (AC) prepared by one-step steam pyrolysis of rice straw at 550, 650, 750 degrees C, respectively, were modified by liquid-phase oxidation using HNO3, H2O2 and KMnO4. Characterization of these 12 carbons was made by their surface area, porosity, acidity, basicity, pH(pzc), pH and ability to remove fluoride anion. Based on the data of the latter factor, the RS2/KMnO4 carbon was selected. Along with batch adsorption studies, which involve effect of pH, adsorbate concentration, adsorbent dosage, contact time, temperature, and Co-ions (SO4(2-), Cl-, Br-). The effects of natural organic matter (NOM) were also made to remove the fluoride from natural water. On the basis of kinetic studies, specific rate constants involved in the adsorption process using RS2/KMnO4 carbon was calculated and second-order adsorption kinetics was observed. Equation isotherms such as Langmuir (L), Freundlich (F), Langmuir-Freundlich (LF) and Dubinin-Radushkevich (DR) were successfully used to model the experimental data. From the DR isotherm parameters, it was considered that the uptake of F- by RS2/KMnO4 carbon proceeds by an ion-exchange mechanism (E=10.46 kJ mol(-1)). The thermodynamic parameters of fluoride sorption were calculated and the sorption process was chemical in nature. The ability of RS2/KMnO4 to remove F- from Egyptian crude phosphoric acid (P(2)O(5)=48.42%) was tested and the adsorption capacity of F- in H(3)PO(4) was greater than that in distilled water. This is may be due to fluoride adsorption enhanced at lower pH of crude acid.
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PMID:Adsorption of fluoride in aqueous solutions using KMnO4-modified activated carbon derived from steam pyrolysis of rice straw. 1731 6

Thiocyanate content and lactoperoxidase activity of individual cow's milk of different breeds were determined, and the effects of different lactoperoxidase system (LP-s) activation strategies were compared. Lactoperoxidase activity varied significantly between Friesian and both Ayrshire and Tanzania Short Horn Zebu (TSHZ), but differences between Ayrshire and TSHZ were not significant. There was no significant variation in SCN- content between breeds. The LP-s was activated using three strategies based on SCN-: namely; equal concentrations of SCN- and H2O2 (7:7, 10:10, 15:15 mg/l), excess SCN- concentrations (15:10, 20:10, 25:10 mg SCN-:H2O2/l), and excess H2O2 concentrations (10:15, 10:20, 10:25 mg SCN-:H2O2/l), plus a fourth strategy based on I- (15:15 mg I-:H2O2/l). The keeping quality (KQ) was assessed using pH, titratable acidity, clot on boiling and alcohol stability tests. All activation strategies enhanced the shelf life of milk (typically increasing KQ from around 10 to around 20 h), but it was clear that the effectiveness of the LP-s depends on the type and concentrations of the activators of the system. The LP-s activated using I- as an electron donor was more effective than the LP-s activated using SCN- as an electron donor, increasing the KQ by a further 6-8 h compared with SCN-.
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PMID:Alternative strategies for activation of the natural lactoperoxidase system in cows' milk: trials in Tanzania. 1800 59

Heavy metal such as chromate compounds, together with unspent azo dyestuff, in effluent forms composite pollutants. The composite wastewater is persistent in color and nonbiodegradable. COD removal ratio and decolorization ratio of methyl orange solution were investigated by microwave -induced catalysis of H2O2 with chromium residue. Factors governing the degradation of methyl orange were experimentally studied including microwave power, microwave irradiation time, pH value, amount of chromium residue, and concentrations of H2O2 and methyl orange solution. Results indicated that some transition metal ions might be taken as catalysts for the purification of persistent organic pollutants in organic-heavy metal wastewater treatment, which can reduce the consumption of chemicals and lower the cost of wastewater purification. Chromium ions in residue and H2O2 could form Fenton-like reagent and produce hydroxyl to mineralize methyl orange. Microwave heating has both thermal and non-thermal effects, and can promote the mineralization rate of organic pollutants. Microwave can also enhance the utilization efficiency of H2O2 in the catalysis process and reduce the dosage of oxidant. The acidity is favorable for generation of hydroxyl for Fenton-like reagent. Employing chromate residue as catalyst in Fenton-like process, the decolorization ratio and COD removal ratio of aqueous MO at 1000 mg x L(-1) were 88% and 85%, respectively, under the following conditions: microwave frequency 2450 MHz, microwave power 700 W, microwave irradiation time 3 min, pH 3 and molar ratio of chromium to hydrogen peroxide 1:56.8.
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PMID:[Degradation of methyl orange solution by microwave-assisted catalysis of H2O2 with chromium residue]. 1897 29

The degradation of methyl red (MR), an azo dye, was carried out by the homogeneous photo-Fenton's process (HPFP) and the advanced photo-Fenton's process (APFP) using symmetrical peroxides such as hydrogen peroxide and ammonium persulfate (APS) as oxidants. The APFP showed higher efficiency than their homogeneous counterparts even at high dye concentrations due to the faster reduction of Fe3+ to Fe2+ ions on the iron surface. H2O2 proved to be a better oxidant for both the processes. However, APS efficiently inhibited the precipitation of iron oxy hydroxides at higher dosage of iron powder compared to H2O2 by providing excess acidity to the reaction medium. The rate constant for the kinetics of decolorisation by various oxidation processes is of the order: Fe0/H2O2/UV>Fe0/H2O2/dark>Fe0/APS/UV>Fe2+/H2O2/UV>Fe0/UV>Fe0/APS/dark>Fe0/dark approximately H2O2/UV>Fe2+/APS/UV>APS/UV>Fe2+/H2O2/dark>Fe2+/APS/dark approximately Fe2+/UV. The degradation reaction was followed by UV-visible and GC-MS spectroscopic techniques. Based on the intermediates obtained, probable degradation mechanisms have been proposed. It was found that the initial mechanism in the APFP involves the reduction of azo groups to amines while in the case of HPFP it leads to the formation of hydroxylated products due to the oxidation of azo groups.
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PMID:Photodegradation of methyl red by advanced and homogeneous photo-Fenton's processes: a comparative study and kinetic approach. 2044 30


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