Treatment of TCE-Contaminated Groundwater Using Fenton-Like Oxidation Activated with Basic Oxygen Furnace Slag

The industrial solvent trichloroethylene (TCE) is among the ubiquitous chlorinated organic compounds found in groundwater contamination. The objective of this study was to evaluate the potential of applying basic oxygen furnace (BOF) slag as the catalyst to enhance the Fenton-like oxidation to remediate TCE-contaminated groundwater. Results indicate that TCE oxidation via the Fenton-like process can be enhanced with the addition of BOF slag. Results from the X-ray powder diffraction analysis reveal that the major iron type of BOF slag/quartz sand media was iron oxyhydroxide (α-Fe2O3). Approximately 81% of TCE removal was observed (with initial TCE concentration of approximately 5?mg?L?1), with the addition of 1,000?mg?L?1 of H2O2 and 10?g?L?1 of BOF slag. Results also show that TCE concentrations dropped from 5 to 1.1?mg?L?1, and chloride concentrations increased from 0 to 2.7?mg?L?1 after 60 min of reaction with the presence of H2O2 and BOF slag. This indicates that the depletion of TCE corresponded with the oxidation reactions and release of chloride ions very well in this study. Results demonstrate that the BOF slag can be used to supply catalysts continuously, and it can be installed in a permeable barrier system to enhance the Fenton-like process in situ.     

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).     

Enhanced Bioremediation of Fuel-Oil Contaminated Soils: Laboratory Feasibility Study

In this study, microcosm experiments were conducted to evaluate the effectiveness of (1) nutrients, hydrogen peroxide (H2O2), and cane molasses addition; (2) soil washing by biodegradable surfactant [Simple Green (SG)]; and (3) soil pretreatment by Fenton-like oxidation on the bioremediation of fuel-oil contaminated soils. The dominant native microorganisms in the fuel-oil contaminated soils after each treatment process were determined via polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis. Results show that approximately 32 and 56% of total petroleum hydrocarbon (TPH) removal (initial concentration of 5,000?mg?kg?1) were observed in microcosms with the addition of nutrient and cane molasses (1,000?mg?L?1), respectively, compared to only 9% of TPH removal in live control microcosms under intrinsic conditions (without amendment) after 120 days of incubation. Addition of cane molasses would cause the increase in microbial population and thus enhance the TPH degradation rate. Results also show that approximately 61% of TPH removal was observed in microcosms with the addition of H2O2(100?mg?L?1) and nutrient after 120 days of incubation. This indicates that the addition of low concentration of H2O2(100?mg?L?1) would cause the desorption of TPH from soil particles and increase the dissolved oxygen and subsequent bioremediation efficiency in microcosms. Approximately 95 and 69% of TPH removal were observed in microcosms with SG (100?mg?L?1) and higher dose of H2O2(900?mg?L?1) addition, respectively. Moreover, significant increases in microbial populations were observed and two TPH biodegraders (Pseudomonas sp. and Shewanella sp.) might exist in microcosms with SG or H2O2 addition. This indicates that the commonly used soil remedial techniques, biodegradable surfactant flushing, and Fenton-like oxidation would improve the TPH removal efficiency and would not cause adverse effects on the following bioremediation process.     

Fenton and Electro-Fenton Methods for Oxidation of H-Acid and Reactive Black 5

Oxidative treatment of H-acid (HA) and Reactive Black 5 (RB5) using Fenton reagent (Fe2+/H2O2) and the electro-Fenton (EF) method is reported. Optimization of doses of ferrous iron and hydrogen peroxide was carried out in each case using HA; and the oxidation of RB5 was also carried out under the optimized conditions. Approximately 71% chemical oxygen demand (COD) was removed in 2 h using the conventional Fenton method at optimized doses: Fe2+ = 0.3?g/L (5.37 mM), H2O2 = 6?mL/L (53.0 mM), H2O2/Fe2+ = 10. In contrast, more than 92% COD was removed in 15 min using the EF method with an optimized Fe2+ dose of 0.130?g/L (2.34 mM) and 8?ml/L (70.6 mM) of H2O2. The pseudo-first-order rate constants (k) for the Fenton reagent and EF method were 0.054 and 0.38?min?1. The COD removal through the EF method was seven times faster. The calculated energy requirement of the EF method was 0.82?kg?COD/kW?h at the minimum applied current (0.25 A) when approximately 92.5% COD was removed. In the case of RB5, about 67 and 87% COD was removed under optimized Fenton and electro-Fenton conditions, respectively. The higher efficiency of the EF method was attributed to incremental addition of Fe2+ and accompanying higher H2O2/Fe2+ molar ratio. The results are discussed in the light of the mechanism for Fenton’s oxidation.     

Treatment of Fuel-Oil Contaminated Soils by Biodegradable Surfactant Washing Followed by Fenton-Like Oxidation

Among petroleum-hydrocarbon pollutants, fuel-oil is more difficult to treat compared to gasoline and diesel fuel. The objectives of this bench-scale study were to: (1) develop a two-stage remedial system consisting of surfactant washing followed by Fenton-like oxidation process to remediate fuel-oil contaminated soils; (2) evaluate the effects of residual surfactant and soil organic matter (SOM) on the efficiency of Fenton-like oxidation; (3) evaluate the effect of potassium dihydrogen phosphate (KH2PO4) addition on the stability of H2O2 and oxidation efficiency; and (4) evaluate the possible oxidation products after the oxidation process. In the surfactant washing stage, biodegradable surfactant, Simple Green (SG) (50?g?L?1), was applied to flush fuel-oil contaminated soils with initial total petroleum-hydrocarbons (TPHs) concentration of 50,000?mg?kg?1. Results show that approximately 90% of TPH could be removed after washing with 45 pore volumes (PVs) of SG followed by 25 PVs of deionized water, while the soil TPH concentration dropped from 50,000 to 4,950?mg?kg?1. In the Fenton-like oxidation stage with initial soil TPH concentration was approximately 4,950?mg?kg?1, TPH removal efficiency can be significantly increased with increased H2O2 concentrations. Results also reveal that residual SG and SOM would compete with TPH for oxidants and cause the decrease in oxidation efficiency. An “oxidation-sorption-desorption-oxidation” scheme for soil TPH was observed in this experiment due to the initial sorption of TPH on SOM. Results show that an addition of 2.2 mM of KH2PO4 could increase the stability and half-life of H2O2, but caused the decrease in TPH removal efficiency. The oxidation potential of Fenton-like process was not capable of completely oxidizing fuel-oil to nontoxic end products. The observed by-products after oxidation process contained carboxyl groups with molecular weights similar to their parent compounds. Results from this study indicate that the two-stage remedial system is a promising technology for fuel-oil contaminated soil treatment.     

M5640+P204+P507萃取净化镍电解液

对硫酸镍电解液的萃取净化除杂进行了系统研究。采用M5640对铜离子进行除杂的条件为:pH3.0,相比1∶1,萃取剂体积浓度15%,振荡时间5min,在此条件下铜离子的萃取率大于99.83%,萃余液含铜已达到5N镍电解液标准要求。去除铜离子之后,采用P204对电解液进行除杂,试验条件:pH4.0,相比2∶1,萃取剂体积浓度25%,振荡时间7min,温度20℃。萃余液再用P507萃取除杂,试验条件:用氢氧化钠溶液均相制皂75%,提高待萃液当中钴离子的含量至4.19g/L,即Co/Ni为1/10,4级萃取,控制水相pH4～5。最终萃余液中各杂质离子的含量均达到生产5N镍的电解液标准。     

TXIB对Mextral973H从铜氨溶液中萃取铜及氨的影响研究

以Cu-NH_3-NH_4Cl-H_2O体系为研究对象,TXIB(2,2,4-三甲基-1,3-戊二醇双异丁酸酯)为改质剂,考察TXIB用量、萃取剂浓度、萃取相比、水相铜浓度、氨浓度等对萃取剂Mextral973H从铜氨溶液中萃取铜及氨的影响。结果表明,TXIB的使用可以显著降低氨的共萃而不影响铜的萃取。在萃取相比O/A=1/1、有机相浓度20%、铜浓度18.0g/L、氨浓度84.0g/L的条件下,向有机相中添加10%的TXIB后,铜萃取率由60.44%变化为60.20%,有机相共萃氨量从410.2mg/L降至154.8mg/L。     

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.     

Arsenite Oxidation by Alcaligenes faecalis Strain O1201

Batch experiments were conducted to examine the oxidation of arsenite (As (III)) to arsenate (As (V)) by Alcaligenes faecalis strain O1201 isolated from soils. Pure cultures of O1201 completely oxidized As (III) to As (V) in the exponential growth phase at As (III) concentrations ranging from 10 to 1,000?mg/L in less than 12 h. The growth of O1201 requires an organic substrate as the carbon and energy source, and the oxidation of As (III) was mainly observed in the exponential growth phase. As (III) concentration at 500?mg/L inhibited the growth of O1201, whereas its oxidation product As (V) did not show any inhibition effects even at concentration as high as 1,000?mg/L. Kinetics studies of As (III) oxidation were performed under the optimal conditions for O1201 at pH 7 and 30°C in a chemical defined medium with citrate as the sole carbon source. The Monod expression coupled with a logistic growth model was used to analyze the kinetics of As (III) oxidation. The best fit parameters of half-velocity coefficient Kc of 15?mg/L, maximum reaction rate coefficient kmc of 0.47 mg As (III)/mg dry weight/h, and logistic growth rate coefficient r of 0.22–0.34?h?1 were obtained using a nonlinear regression analysis.     

高含砷冶炼污酸单级硫化脱砷试验

硫化法是目前冶炼污酸除砷应用最广泛的方法。常规硫化法采用阶梯式硫化、多级硫化、高效硫化反应器等工艺,或产出大量危废渣且后液不能回用只能排放,或成本高、流程长,或对高含砷污酸处理效果不理想。对含砷16 060 mg/L、铜28.04 mg/L、铅9.80 mg/L的高含砷污酸的除杂工艺进行研究,考察了硫化钠（Na2S?9H2O）加入量、加入方式及时间、反应温度等因素对除杂效果的影响,确定了“硫化+絮凝”的工艺,通过优化药剂加入方式从而减少药剂加入量,探索出了最佳工艺控制条件,达到“流程短、加药精准、污染小”的目的。结果表明,污酸中的砷可降至0.23 mg/L甚至<0.1 mg/L,铅、铜分别降至<0.1 mg/L,远低于工业硫酸一级品的限值。     

Organic Removal of Anaerobically Treated Leachate by Fenton Coagulation

The leachate from a Hong Kong landfill, containing 15,700 mg∕L of chemical oxygen demand (COD) and 2,260 mg∕L of ammonia nitrogen (NH3–N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37°C. The process on average removed 90.4% of COD with 6.6 days of hydraulic retention at an organic loading rate of 2.37 g of COD∕L?day. The UASB effluent was further treated by the Fenton coagulation process using H2O2 and Fe2+. Under the optimal condition of 200 mg of H2O2∕L and 300 mg of Fe2+∕L and an initial pH of 6.0, 70% of residual COD in the UASB effluent was removed, of which 56% was removed by coagulation∕precipitation and only 14% by free radical oxidation. It is obvious that H2O2 and Fe2+ had a strong synergistic effect on coagulation. The average COD in the final effluent was 447 mg∕L. Removing each gram of COD required 0.28 g of Fe2+ and 0.18 g of H2O2.     

Arsenite Oxidation by Batch Cultures of Thiomonas Arsenivorans Strain b6

Arsenite [As(III)] oxidation by Thiomonas arsenivorans Strain b6 was investigated in batch reactors at pH 6 and 30°C over As(III) concentrations ranging from 10 to 1,000 mg/L in the absence of added organic carbon. Strain b6 completely oxidized As(III) to arsenate [As(V)] during exponential growth phase for lower levels of As(III) concentrations ( ≤ 100?mg/L). At higher levels of 500 and 1,000 mg/L, As(III) oxidation was observed mostly in the exponential phase but continued into the stationary phase of growth. The Haldane substrate inhibition model was used to estimate biokinetic parameters for As(III) oxidation. The best fit parameters of half saturation constant Ks = 33.2±1.87?mg/L, maximum specific substrate utilization rate k = (0.85±0.18)-mg As(III)/mg dry cell weight/h, substrate inhibition coefficient Ki = 602.4±33.6?mg/L, yield coefficient Y = (0.088±0.0048)-mg cell dry weight/mg As(III), and endogenous decay coefficient kd = 0.006±0.002?h?1 were obtained using the Adams-Bashforth-Moulton algorithm and nonlinear regression technique. Sensitivity analysis revealed that Y and Ki are the most sensitive to model predictions, while kd is the least sensitive to model simulation at both low and high concentrations of As(III).     

Kinetics of Arsenite Oxidation by Chemoautotrophic Thiomonas arsenivorans Strain b6 in a Continuous Stirred Tank Reactor

As(III) oxidation by a chemoautotrophic bacterium, Thiomonas arsenivorans strain b6, was evaluated in a continuous stirred tank reactor (CSTR) under a range of influent As(III) concentrations (2,000–4,000 mg/L) and hydraulic retention times (HRTs) (21.7–74.9 h). Five steady states were obtained after the CSTR was continuously operated for 115 days with over 99% As(III) oxidized under the optimal growth conditions for strain b6 at pH 6 and 30°C. The culture exhibited strong resilience by recovering from an As(III) overloading of 4,847.4±290.9?mg/day/L operated at a HRT of 21.7 h. Arsenic mass balance analysis revealed that As(III) was mainly oxidized to As(V), with unaccounted arsenic well within the analytical error of measurement. The best estimates of biokinetic parameters for As(III) oxidation were obtained using the steady-state data and the Monod expression based model [k = 5?mg As(III)/mg dry cell weight/h; Ks = 20.1?mg/L; kd = 0.008?h?1; and Y = 0.011?mg cell dry weight/mg As(III)]. The Monod model and the reactor mass balance successfully simulated both the steady-state and transient phases of CSTR operation. Sensitivity analyses defined Y and k to be the most sensitive to model predictions, whereas kd and Ks were least sensitive to model simulations of As(III) oxidation under steady-state conditions.     

Arsenite Oxidation by Alcaligenes Faecalis Strain O1201 in a Continuous-Flow Bioreactor

As(III) oxidation by a pure bacterial culture, Alcaligenes faecalis strain O1201, was evaluated using a continuous stirred tank reactor. The bioreactor system was operated for 204 days under a wide range of influent As(III) concentrations (500–8,000?mg/L) and hydraulic retention times (25.6–90.7?h) with citrate as the sole carbon and energy source at pH 7 and 30°C. Nine steady-state conditions were obtained with As(III) oxidation efficiency exceeding 95%. The system quickly recovered from an As(III) overloading at 15,000?mg/day/L while it operated at a HRT of 12.8?h. A material balance analysis revealed that nearly all the As(III) removed in the continuous stirred tank reactor (CSTR) was oxidized to As(V) and only 3.2% of the As(III) fed to the CSTR was unaccounted for. Biokinetic parameters, kmc = 0.86?mg/mg cell dry weight/h and Kc = 70?mg/L, for As(III) oxidation were obtained using the Monod expression and data obtained at steady-state conditions.     

Advanced Oxidation of Diuron by Photo-Fenton Treatment as a Function of Operating Parameters

Advanced oxidation of diuron in aqueous solution by photo-Fenton treatment was investigated by batch experiments. Effects of operating parameters, namely, the concentrations of pesticide (diuron), hydrogen peroxide (H2O2), and ferrous ion [Fe (II)] on oxidation of diuron were investigated by using Box-Behnken statistical experiment design and the response surface methodology. Diuron oxidation by photo-Fenton treatment was evaluated by determining the total organic carbon (TOC), diuron, and adsorbable organic halogen (AOX) removals. Concentration ranges of the reagents resulting in the highest level of diuron oxidation were determined. Diuron removal increased with increasing H2O2 and Fe (II) concentrations, up to a certain level. H2O2 concentration had a more profound effect than diuron and Fe (II) on removal of diuron, TOC, and AOX from the aqueous solution. Complete (100%) disappearance of diuron was achieved after a 15?min reaction period. However, 85% of diuron was mineralized after 240?min, indicating a low level of intermediate formation. Optimal H2O2/Fe (II)/diuron ratio resulting in maximum diuron (100%), TOC (85%), and AOX (100%) removals was found to be 267/36/25?(mg?L?1).     

Predicting Fenton-Driven Degradation Using Contaminant Analog

The reaction of hydrogen peroxide (H2O2) and Fe(II) (Fenton's reaction) generates hydroxyl radicals (?OH) that can be used to oxidize contaminants in soils and aquifers. In such environments, several factors can limit the effectiveness of chemical oxidation, including reactions involving H2O2 that do not yield ?OH, ?OH reactions with nontargeted chemicals, and insufficient iron in the soil or aquifer. Consequently, site-specific studies may be necessary to evaluate the feasibility of chemical oxidation using H2O2. Here, the degradation of a contaminant analog, α-(4-pyridyl-1-oxide) N-tert-butylnitrone (4POBN), was used to estimate ?OH concentration and simplify testing procedures. A kinetic model was developed, calibrated using 4POBN degradation kinetics, and used to predict the disappearance of 2-chlorophenol (2CP), a representative target. Good agreement between predicted (Y) and measured (X) values for 2CP (Y = 0.95X) suggests that the kinetics of analog degradation can be used to predict the degradation rate of compounds for which the rate constant for reaction with ?OH is known.     

Biohydrogen Production by Mesophilic Anaerobic Fermentation of Glucose in the Presence of Linoleic Acid

In this work, linoleic acid (LA), a long chain fatty acid bearing 18 carbons and two double bonds, inhibited hydrogen consumption in a mixed anaerobic culture acclimated to glucose. At pH = 7.6, a metabolic shift from methane to hydrogen formation was observed in cultures maintained at 37°C and fed 5,000?mg?L?1 glucose in the presence of 500–2,000?mg?L?1 LA. The hydrogen yield increased with increasing LA levels while the quantity of methane decreased. The major volatile fatty acids produced were acetate and butyrate with greater levels observed in cultures fed with LA. Acetate, butyrate, and hydrogen accumulation suggests inhibition of aceticlastic methanogens, hydrogenotrophic methanogens, and butyrate degrading microorganisms, respectively, in the presence of LA. A maximum hydrogen yield of 1.71±0.22?mole?mole?1 glucose was observed only when glucose was reinjected into cultures receiving 2,000?mg?L?1 LA plus 5,000?mg?L?1 glucose.     

Adiabatic water suppression using frequency selective excitation

We tested the hypothesis that hypoxic newborn piglets can be successfully resuscitated with lower O2 concentrations than 21%. Severely hypoxic, 2-4-d-old, anesthetized piglets were randomly divided into five resuscitation groups: 21% O2 (n = 10), 18% O2 (n = 9), 15% O2 (n = 9), 12% O2 (n = 8), all normoventilated, and a hypoventilated 21% O2 group (PaCO2; 7.0-8.0 kPa, n = 9). Base excess (BE) reached -20 +/- 1 mmol/L at the end of hypoxia. After 3 h of resuscitation, BE had risen to -4 +/- 1 mmol/L in the 21% O2, 18% O2, and hypoventilated groups, but was -10 +/- 2 mmol/L in the 15% O2 group (p < 0.05 versus 21% O2 group) and -22 +/- 2 mmol/L in the 12% O2 group (p < 0.05 versus 21% O2 group). Four animals died during resuscitation, all allocated to the 12% O2 group (p < 0.05 versus 21% O2 group). Somatosensory evoked potentials (SEPs) recovered in 39 of 45 piglets, and remained present during resuscitation in all except the 12% O2 group. SEP recovered initially even in six of eight animals in the 12% O2 group, but disappeared again in all later during resuscitation. The SEP amplitude recovered to levels not significantly different from the 21% O2 group in all groups except the 12% O2 group. Plasma hypoxanthine concentrations and extracellular hypoxanthine concentrations in the striatum decreased during resuscitation to levels not significantly different from the 21% O2 group in all but the 12% O2 group (p < 0.05 versus 21% O2 group). In conclusion, severely hypoxic newborn piglets were resuscitated as efficiently with both hypoventilation and 18% O2 as with 21% O2.     

Effect of Cd(II) on Different Bacterial Species Present in a Single Sludge Activated Sludge Process for Carbon and Nutrient Removal

Heavy metal cadmium(II) was added stepwise into an A2O pilot plant to investigate the toxic effects of Cd(II) on the removal efficiencies, kinetic parameters (yield coefficients and maximum specific growth rates) and reaction rates of carbon, nitrogen and phosphate for the acclimatized heterotrophic and autotrophic bacteria. Results showed that 2?mg/L Cd(II) initially affected the biological reaction of phosphate removal. At Cd(II) 5?mg/L, the efficiencies of total nitrogen removal and nitrification were substantially dropped. At the same time, the yield coefficient and maximum specific growth rate of heterotrophs were significantly decreased from 0.8?g?COD/g?COD and 6.44?day?1 to 0.54?g?COD/g?COD and 4.67?day?1, respectively. And, the denitrification rate was inhibited by about 61%. The inhibition percentages of anaerobic release, anoxic and aerobic uptake rates of phosphate were about 76, 64, and 90%, respectively. When Cd(II) concentration was continually increased up to 35?mg/L, removal efficiency of chemical oxygen demand (COD) was significantly dropped. However, there was no obvious inhibition on the biological reactions of anaerobic ammonification.