Decomposition of Aqueous 2,2,3,3-Tetra-Fluoro-Propanol by UV/O3 Process

2,2,3,3-Tetra-fluoro-propanol (TFP) has been extensively used in compact disk-recordable and digital versatile disk-recordable manufacture and a large amount of wastewater containing the chemical is being discharged. This investigation evaluates the feasibility and effectiveness of the use of UV, O3, and UV/O3 to degrade aqueous TFP. TFP oxidation tests were performed with initial TFP concentrations of 772–887?mg/L with various solution pH values (acidic, alkaline, uncontrolled), solution temperatures (26, 37, 48, and 60°C), and UV wavelengths (254 and 185?nm). Experimental results demonstrated that alkaline conditions favor the TFP degradation and increase the mass of TFP decomposition per unit mass of ozone consumption, in both UV254?nm/O3 and UV185?nm/O3 processes. There was no significant difference in the rate of TFP degradation when using either UV254?nm or UV185?nm. TFP exhibited zero-order degradation kinetics when sufficient ozone was supplied. A higher oxidation temperature was found to be no help for the UV/O3 oxidation of TFP in the tested concentration and temperature ranges. The cost of the UV254?nm/O3 or UV185?nm/O3 per unit volume of wastewater with an initial TFP concentration of 3,387?mg/L is comparable to that of the Fered–Fenton process as described in the literature.     

Numerical Simulation of Bromate Formation during Ozonation of Bromide

The purpose of this study is to develop a kinetic model that links O3 decomposition reactions from the TFG ozone decay model with recognized Br? oxidation reactions, secondary ?OH reactions, and H2O2 reactions in order to improve O3 decay and bromate formation prediction capabilities under multiple water quality conditions. The model was compared with experimentally measured ozone decomposition and final bromate concentration data sets provided by two researchers. The data sets included varying pH (6.5–8.5), initial hydrogen peroxide (0–1 mM), and initial bromide concentration (0.1–1 mM). Model verification was carried out by sensitivity analysis of the rate constants and then optimization of the most sensitive rate constants using the method of least squares. Model predicted ozone decay data was analyzed and compared with measured ozone decay data using R-squared statistic for linear regression model. The model predicted final bromate concentration is analyzed by comparing it with the residual Δ(%) between experimental and model results. The TFG model was effectively tested for multiple data sets and it was found that model prediction was a success both for ozone decay (regression coefficients >0.95 for all experimental conditions but one) and bromate prediction with residual of less than 100% for all experimental conditions except low peroxide dose (<20 μm).     

Degradation and Mineralization of Simazine in Aqueous Solution by Ozone/Hydrogen Peroxide Advanced Oxidation

Advanced oxidation of simazine in aqueous solution by the peroxone (hydrogen peroxide/ozone) treatment was investigated using Box-Behnken statistical experiment design and response surface methodology. Effects of pH, simazine and H2O2 concentrations on percent simazine and total organic carbon (TOC) removals were investigated. Ozone concentration was kept constant at 45?mg?L?1. The optimum conditions yielding the highest simazine and TOC removals were also determined. Both simazine and peroxide doses affected simazine removal while pH and pesticide dose had more pronounced effect on mineralization (TOC removal) of simazine. Nearly 95% removal of simazine was achieved within 5 min for simazine and peroxide concentrations of 2.0 and 75?mg?L?1, respectively at pH = 7. However, mineralization of simazine was not completed even after 60 min at simazine doses above 2?mg?L?1 indicating formation of some intermediate compounds. The optimum H2O2/pH/Simazine ratio resulting in maximum pesticide (94%) and TOC removal (82%) was found to be 75/11/0.5(mg?L?1).     

Ozone Degradation of Iodinated Pharmaceutical Compounds

This study investigates the aqueous degradation of four iodinated x-ray contrast media (ICM) compounds (diatrizoate, iomeprol, iopromide, and iopamidol) by ozone and combined ozone and hydrogen peroxide. In laboratory scale experiments, second-order kinetic rate constants for the reactions of the ICM compounds with molecular ozone and hydroxyl radicals, and overall at pH 7.5, were determined. For the four ICM compounds the degradation rate constants with molecular ozone were low and in the range of 1–20?M?1?s?1, whereas the rate constants with hydroxyl radicals were in the range of 1×109–3×109?M?1?s?1. Diatrizoate had the lowest rate constant of the four compounds with respect to molecular ozone reactions. At pH 7.5, the extent of compound degradation was proportional to the applied ozone dose and inversely related to the initial compound concentration at a given ozone dose. At this pH approximately 90% of the degradation could be attributed to hydroxyl radical reactions. Enhancement of the radical mechanism by the addition of hydrogen peroxide during ozonation led to complete removal of the nonionic compounds, and >80% removal of diatrizoate, at relatively low oxidant mass ratios (H2O2/O3<0.25). A similar enhancement in compound degradation was evident with the presence of small concentrations of humic substances ( ～ 4–5?mg?L?1). Ozone oxidation led to major cleavage of the ICM compounds and the release of inorganic iodine; the proportion of iodine release was similar among the nonionic ICM compounds but much greater for diatrizoate.     

Oxidation of Methyl Tert-Butyl Ether in Aqueous Solution by an Ozone/UV Process

In this paper, the oxidation of methyl tert-butyl ether (MTBE) in aqueous solution by an ozone/ultraviolet (UV) process was described. The oxidation process was investigated experimentally in a semibatch reactor under various operational conditions, i.e., ozone gas dosage, UV light intensity, and water quality in terms of varying bicarbonate concentration. The ozone/UV process was very successful in oxidizing MTBE. The rate of removal of MTBE increased when the incident UV light intensity increased for the same concentration of influent ozone gas. Similarly, an increase in influent ozone gas concentration resulted in faster removal of MTBE for the same incident UV light intensity. However, bicarbonate in the range of 2–8?mM showed no significant effect on MTBE removal for MTBE concentration ( ～ 1.0?mM) used in this study. Moreover, it was observed that the reaction intermediates could react well in the ozone/UV process, and complete mineralization could be achieved by the ozone/UV process, if desired.     

Ozonation of Spent Reactive Dye-Baths: Effect of HCO3?/CO32? Alkalinity

The effect of carbonate and bicarbonate alkalinity (soda ash buffer as 5,180 mg/L HCO3? alkalinity at pH 7 and as 5,100 mg/L CO32? alkalinity at pH 12) on the ozonation of reactive vinylsulphone dyestuffs in a simulated spent dye-bath has been studied at varying pHs. Adsorbable organic halogen (AOX) formation due to the high chloride content of the effluent and detoxification, which was evaluated in terms of the relative toxicity index Itox determined from the ED50 values for the marine photobacteria Vibrio fischeri, were also evaluated. Highest total organic carbon (56%), chemical oxygen demand (44%), and UV254 (77%) removals were achieved at pH 7 in the presence of HCO3? alkalinity. The fastest decolorization was observed for the case pH 2, the first order decolorization rate constant found as k620 = 0.16?min?1, closely followed by the pH 12 case with soda ash (k620 = 0.12?min?1) case. No positive correlation was evident between AOX, whose maximum value (=1.3 mg/L) appeared after 40 min ozonation at pH 7 and decreased to 0.54 mg/L after 120 min treatment, and Itox, which decreased to 0.16 at t = 50?min and increased rapidly thereafter. The Itox values were more related to color abatement kinetics. The maximum relative toxicity index of Itox = 0.83 occurred after 120 min. It was also established that the presence of alkalinity in the spent reactive dye-bath had no negative impact on the oxidation rates. In contrast, its absence seriously inhibited treatment efficiency. It is speculated that, with added soda ash, the carbonate radicals HCO3? and CO3??, which are more stable and selective than OH?, were produced and promoted the oxidation process.     

Low Temperature Luminescence Properties of Tm3+ Doped Aluminate Phosphor

(Ba0.66Sr0.33)Mg0.8Al11.47O19:Tm0.013 (BSMA:Tm3 ) phosphor was synthesized by solid-state reactions. The sample was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), vacuum ultraviolet (VUV) spectra, ultraviolet (UV) spectra and FT-IR spectrum. XRD pattern reveals that BSMA:Tm3 has the same structure as BaAl12O19 phase. SEM image illustrates that the phosphor has the hexagonal shape and deep slice structure. VUV and UV emission spectra at 20, 50 and 100 K show that the low temperature luminescence intensities become weak gradually with the increasing of the temperature under 147 and 254 nm excitation. The strong broadband peaks at around 357 and 397 nm and the peak at 516 nm under 147 nm excitation all correspond to the characteristic transitions of Tm3 ions. However, under UV (254 nm) excitation, the main peak becomes 530 nm which has very high line intensity, and the peaks at about 362 and 403 nm are very weak. The excitation spectrum at 20 K shows that there are three absorption peaks at around 153, 186 and 193 nm when 516 nm emission is monitored. The absorption peaks of [AlO4], [AlO6] and Al-O can be observed in FT-IR spectrum.     

Evaluating Ozone as a Remedial Treatment for Removing RDX from Unsaturated Soils

Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27?mg?L?1; 150?mL?min?1) was effective in mineralizing 80% of the RDX (30?mg?RDX?L?1) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and >80% within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus <0.3% cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility.     

Effect of pH and Gas-Phase Ozone Concentration on the Decolorization of Common Textile Dyes

This paper presents the results of a laboratory study on the effect of pH (2, 5, and 9) and gas-phase ozone concentration (1, 7, and 11 wt?%) on the decolorization efficiency via ozonation for seven common textile dyes. Higher gas-phase ozone concentrations resulted in higher decolorization rates due to more rapid ozone transfer. Higher gas-phase ozone concentration, however, was also observed to have a positive, neutral, or negative effect on ozone dose requirements for different dyes. In general, greater ozone utilization efficiency was achieved at lower pH levels where direct ozone reactions predominate. It was observed that because ozonation can cause significant resolubilization of precipitated dyes, complete removal of dye precipitate should be accomplished prior to polishing via ozonation. The results point to the need for laboratory and/or pilot testing for dye-laden wastestreams to allow process optimization.     

Photocatalytic Degradation of Orange II in Aqueous Iron-Rich Montmorillonite Solutions

In this work the photodegradation of orange II was carried out in the presence of iron-rich montmorillonite (MMt) (2.24% Fe2O3) using a 15-W low-pressure ultraviolet lamp (λ = 254?nm,?I = 48.4?μW/cm2). The effects of pH, MMt dose, and dye concentration were studied. A low pH value is favorable for the decolorization of orange II. The hydroxyl radical (?OH) concentration increased with increasing concentration of MMt in aqueous solutions in the range of 0–1.5 g/L. Concentrations higher than 5.0 g/L MMt inhibited the ?OH production. There was no significant decrease in photocatalytic activity when the catalyst was reused. Hydroxyl radicals were detected by tert-butyl alcohol in aqueous MMt suspensions under ultraviolet irradiation and were responsible for the degradation of orange II. Free iron ions dissolved in MMt suspensions, structural iron in the MMt structural and the charged surface of nanoclay are responsible for the hydroxyl radical (?OH) production. Free iron ions dissolved in solution plays a predominant role in the degradation of orange II. This study shows that iron-rich MMt is a potential photocatalyst for dye wastewater treatment.     

Mass Transfer of Ozone in a Novel In Situ Ozone Generator and Reactor

A porous tubular reactor that also served as an electrode for ozone generation was studied in this research to determine the effects of in situ ozone generation on mass transfer and reaction rates. Experimental data over a range of gas flow rates and ozone generation rates gave KLa values in the range 0.77–1.14?min?1. These values are more than double the values typically reported for bubble columns, and about 30% higher than that for packed beds. The specific power requirement for the laboratory-scale in situ reactor is an order of magnitude lower than that for bubble columns and stirred tank reactors that are used for ozone dissolution. A compartments-in-series fluid flow model was developed to describe the reactor system, and this model provides a good comparison to the experimental data for dissolved ozone and off-gas concentrations in the reactor. Sensitivity analyses indicate that the dissolved and off-gas ozone profiles are most sensitive to the gas–liquid partition coefficient and the overall mass transfer coefficient.     

Synthesis and Photoluminescence of BaMgAl10O17 ：Eu^2＋ Phosphor by Oxalate Co-precipitation Process

Single phase of Ba1-x MgAl10O17 ： x Eu^2＋ （0.02≤ x ≤ 0. 14） phosphors was first successfully prepared by coprecipitation in aqueous medium with a “reverse strike” method, using oxalic acid and ammonia together as precipitants. Completely crystallized phosphors were obtained at 1300 ℃, which is 300 ℃ lower than the temperature of solid-state reaction. Their photoluminescence was investigated under UV and VUV region, respectively. The emission spectra of Ba1-x MgAl10O17：xEu^2＋ samples excited by 254 or 147 nm showed a characteristic wide band with the peak centred at about 450 454 nm. Optimum emission intensity reached at x = 0.1 and then concentration quenching occurred. The synthesized phosphor shows 10% higher emission intensity than that prepared by solid-state reaction.     

活性炭催化臭氧化处理含氰废水的试验研究

研究了活性炭催化臭氧化降解低质量浓度含氰废水,考察了臭氧投加量、活性炭用量、pH值等因素对处理效果的影响.试验结果表明:活性炭对臭氧有明显的催化作用,并可以提高臭氧的利用率;在CN-初始质量浓度150 mg/L、臭氧投加量30 mg/min、活性炭14 g/L、反应30 min条件下,CN-去除率为99.8%,相对于单...     

金矿含氰废水的臭氧氧化处理

采用臭氧氧化法处理金矿含氰废水 ,对臭氧投加量、p H值、催化剂等对除氰效果的影响进行了实验研究 .研究结果表明 ,臭氧能够有效地去除金矿废水中的氰化物 ,臭氧投加量、p H值、Cu2 对处理效果有一定影响     

Molecular Ozone and Radical Pathways of Bromate Formation during Ozonation

An understanding of bromate formation mechanisms is critical for minimization and control of bromate formation during ozonation. Bromate formation observed in different natural source waters in the presence of a hydroxyl radical scavenger indicated that bromate formed predominantly through the free radical pathway. Carbonate radicals formed in the presence of alkalinity act as secondary oxidants of bromine species leading to enhanced bromate formation. The effects of adding hydrogen peroxide and ammonia during ozonation were also evaluated.     

Preparation and Luminescent Properties of BAM Blue Phosphor forPDP and CCFL

The Bax-0.05MgAl10O16 x :Eu0.05^2 (0.88≤ x≤ 1.02) phosphors with different Ba^2 content and the Ba0.85MgAl10O16.94:Eu0.05^2 phosphors with different fluxes (BaF2, MgF2, AlF3, BaCl2, MgCl2, AlCl3, H3BO3)were prepared by high temperature solid-state reaction method and their luminescence characteristics were studied under 254 nm excitation and vacuum ultraviolet (VUV) excitation. With the increase of the Ba^2 content, there is an increase in the emission intensity, and when x = 0.94, it reaches a maximum. Then, as the Ba^2 content increases, the emission intensity slowly falls. The fluorides have better flux-effects than chlorides and H3BO3. The possible mechanism in the process of particle growth was discussed when fluorides were used as fluxes. The effect of the activator concentration on this system was also investigated. The quenching concentration is 0.13 mol in per mole host.     

Effects of Bromide Ion and Natural Organic Matter Fractions on the Formation and Speciation of Chlorination By-Products

The impacts of bromide concentration and natural organic matter (NOM) characteristics on the formation and speciation of disinfection by-products (DBPs) in chlorinated NOM fractions were investigated. A total of 20 bulk water NOM fractions with a wide range of specific ultraviolet (UV) absorbance (SUVA254) values were obtained from a source water employing XAD-8 or XAD-4 resin adsorption in completely mixed batch reactors. SUVA was not a good predictor of DBP [trihalomethanes (THMs), haloacetic acids (HAAs), and adsorbable organic halogens (AOX)] formation and speciation. The destruction in the UV254 absorbance from chlorination did not correlate with DBP formation at any bromide level. NOM moieties which do not absorb UV light at 254?nm significantly contributed to DBP formation. Mass balance calculations on halogens using THMs, HAAs, and AOX data indicated that significant amounts of DBPs (>54% of AOX) other than THMs and HAAs were formed in NOM fractions with 60–110?μg/L bromide concentration. The relative occurrence of such other halogenated by-products decreased with increasing bromide concentrations up to 500?μg/L level. NOM in the studied water was more susceptible to the formation of brominated THM species as opposed to brominated HAAs. At constant dissolved organic carbon concentration, chlorine dose and pH, increasing bromide concentrations in NOM fractions increased the total concentrations of DBPs and resulted in a shift toward the formation of brominated species. Further, increasing bromide concentrations increased the spectrum of detected species (i.e., occurrence of all nine HAAs) and provided a competitive advantage to THM and HAA precursors in NOM over precursors of other DBPs.     

Advanced Oxidation for Treatment of Aqueous Extracts from EDTA Extraction of Pb and Zn Contaminated Soil

The feasibility of using advanced oxidation processes (AOPs): ozone, ozone/sonification, and ozone/ultraviolet (UV) irradiation in treatment to remove heavy metals and ethylenediamine tetraacetate (EDTA) from aqueous extracts, obtained after soil extraction with EDTA, was examined. Extraction of soil contaminated with 1,243?mg?kg?1 Pb and 1,190?mg?kg?1 Zn with 40?mmol?kg?1 EDTA removed 41.8±0.9 and 7.2±.0.2% of Pb and Zn. Of the AOPs tested, only the use of ozone/UV enabled the decomposition of EDTA–heavy metals complexes in aqueous soil extracts, and recovery of released Pb and Zn by sorption on a commercial sorbent Slovakite. After treatment, the concentration of Pb, Zn, and EDTA in the extracts was fairly low (2.87±1.15?mg?L?1, 7.58±2.12?mg?L?1, and 0.012±0.002?mmol?L?1, respectively), and could presumably be reduced even further with a continuation of treatment. The treated extract was used for subsequent soil rinsing, which removed an additional 12.7±1.6 and 2.7±0.1% of soil Pb and Zn. The results of our study indicate that the use of ozone/UV is a feasible option for treatment of aqueous soil extracts from EDTA extraction. Treated extracts could be safely discharged or reused to lower requirements for process water.     

Enhancing effect of UV-light on the accumulation of carthamine in dyer's saffron florets

UV-C (254 nm)- and UV-B (280-320 nm)-light were irradiated onto bright-yellow capitula of dyer's saffron and their effects on carthamine accumulation compared. UV-C light promotes reddening of florets more prominently than UV-B light, yielding higher amounts of carthamine after the radiation process. The enhancement of carthamine synthesis by UV-C light was investigated on cellulose columns loaded with floret extracts under O2-sufficient or O2-deficient conditions. Externally charged O2 inhibits the UV-C- stimulated carthamine formation. The results are discussed in relation to light stimulation of carthamine synthesis in dyer's saffron florets.     

Ozone Inactivation Kinetics of CRYPTOSPORIDIUM in Phosphate Buffer

The rate of inactivation of Cryptosporidium parvum oocysts by ozone in 0.05 M phosphate buffer at pH 6, 7, and 8 was studied at 22 ± 1°C in batch reactors. Infectivity in neonatal CD-1 mice was used as the criterion for oocyst viability. Ozone inactivation data were fitted to the Incomplete gamma Hom (I.g.H.) and Chick-Watson (n = 1) model, both of which incorporate a first-order rate constant for the disappearance of aqueous ozone during the contact time. For a 0.05 M phosphate buffer ranging in pH from 6 to 8, a single I.g.H. model was found to adequately describe the kinetics of Cryptosporidium inactivation by ozone at 22°C. The I.g.H. model for pH 6–8 was found to provide a significantly better fit to the ozone inactivation data when compared with the Chick-Watson model. The effect of pH on ozone inactivation kinetics was associated with ozone residual stability over the pH range of 6–8. The sensitivity of Cryptosporidium to ozone at 22°C was therefore not statistically different at pH 6 when compared with pH 8. The inactivation behavior of Cryptosporidium by ozone was characterized by a tailing-off effect, with approximately equal importance of ozone concentration and contact time. The I.g.H. model for pH 6–8 can be used as an aid in the design of ozone disinfection systems, and this robust fitted model was used to formulate ozone design criteria—the initial oxone residual required for a given contact time for 1, 2, and 3 log units inactivation of Cryptosporidium at 22°C. Uncertainty associated with the ozone design criteria for 2 log units inactivation was quantified using inverse prediction intervals. An ozone design criterion was established that gives a 95% probability of achieving 2 log units inactivation of Cryptosporidium at 22°C, corresponding to an approximate safety factor of 0.7 log units.