Removal and degradation of phenol in a saturated flow by in-situ electrokinetic remediation and Fenton-like process.

In this laboratory study, a sandy loam soil saturated with phenol solution was treated by in-situ electrokinetics-Fenton process incorporated with a permeable reactive wall of scrap iron powder (SIP). The soil was contaminated and saturated with aqueous phenol solution of 90-115 mg/kg in concentration. It was then placed in a soil cell. The soil cell was assembled with an anode reservoir and a cathode reservoir at its ends. A bed of SIP (1.05-32.69 g) was inserted in the soil cell at a distance of 5 cm from the anode reservoir compartment. For the test runs, 0.3% H(2)O(2) was used as the anode reservoir fluid, whereas de-ionized water was used as the cathode reservoir fluid. An electric gradient of 1 V/cm was applied to enhance the saturated flow in the soil cell for a period of 10 days. Experimental results have shown that the electroosmotic (EO) flow quantity decreased as the amount of SIP increased. This phenomenon was in good agreement with the results showing the value of EO permeability increased with a decreasing amount of SIP. Results also showed that throughout the test period the cumulative, consumed mass of H(2)O(2) in the anode reservoir increased as the amount of SIP decreased. On the other hand, the cumulative, increased mass of phenol in the cathode reservoir was found to increase with a decreasing amount of SIP. Meanwhile, the residual phenol concentration in the soil cell was found to decrease with a decreasing amount of SIP. When 1.05 g scrap iron powder was used, an overall removal and destruction efficiency of phenol of 99.7% was obtained. Therefore, it is evident that an in-situ combined technology of electrokinetic remediation and Fenton-like process is capable of simultaneously removing and degrading the phenol in a saturated flow.     

Preparation and application of granular ZnO/Al2O3 catalyst for the removal of hazardous trichloroethylene

Trichloroethylene (TCE) is a volatile and nerve-toxic liquid, which is widely used in many industries as an organic solvent. Without proper treatment, it will be volatilized into the atmosphere easily and hazardous to the human health and the environment. This study tries to prepare granular ZnO/Al(2)O(3) catalyst by a modified oil-drop sol-gel process incorporated the incipient wetness impregnation method and estimates its performance on the catalytic decomposition of TCE. The effects of different preparation and operation conditions are also investigated. Experimental results show that the granular ZnO/Al(2)O(3) catalyst has good catalytic performance on TCE decomposition and the conversion of TCE is 98%. ZnO/Al(2)O(3)(N) catalyst has better performance than ZnO/Al(2)O(3)(O) at high temperature. Five percent of active metal concentration and 550 degrees C calcination temperature are the better and economic preparation conditions, and the optimum operation temperature and space velocity are 450 degrees C and 18,000 h(-1), respectively. The conversions of TCE are similar and all higher than 90% as the oxygen concentration in feed gas is higher than 5%. By Fourier transform infrared spectrography (FT-IR) analyses, the major reaction products in the catalytic decomposition of TCE are HCl and CO(2). The Brunauer-Emmett-Teller (BET) surface areas of catalysts are significantly decreased as the calcination temperature is higher than 550 degrees C due to the sintering of catalyst materials, as well as the reaction temperature is higher than 150 degrees C due to the accumulations of reaction residues on the surfaces of catalysts. These results are also demonstrated by the results of scanning electron micrography (SEM) and energy disperse spectrography (EDS).     

Synthesis of granular activated carbon/zero valent iron composites for simultaneous adsorption/dechlorination of trichloroethylene

The coupling adsorption and degradation of trichloroethylene (TCE) through dechlorination using synthetic granular activated carbon and zerovalent iron (GAC-ZVI) composites was studied. The GAC-ZVI composites were prepared from aqueous Fe²⁺ solutions by impregnation with and without the use of a PEG dispersant and then heated at 105 °C or 700 °C under a stream of N₂. Pseudo-first-order rate constant data on the removal of TCE demonstrates that the adsorption kinetics of GAC is similar to those of GAC-ZVI composites. However, the usage of GAC-ZVI composites liberated a greater amount of Cl than when ZVI was used alone. The highest degree of reductive dechlorination of TCE was achieved using a GAC-ZVI700P composite (synthesized using PEG under 700 °C). A modified Langmuir-Hinshelwood rate law was employed to depict the behavior of Cl liberation. As a result, a zero-order Cl liberation reaction was observed and the desorption limited TCE degradation rate constant decreased as the composite dosage was increased. The GAC-ZVI composites can be employed as a reactive GAC that is not subject to the limitations of using GAC and ZVI separately.     

Photocatalytic treatment of black table olive processing wastewater

The photocatalytic treatment of an effluent from black table olive processing over TiO2 suspensions was investigated. The study focused on the effect of various operating parameters on the treatment efficiency including initial organic load, catalyst type, concentration and reuse, and addition of hydrogen peroxide. Initial organic load, expressed in terms of chemical oxygen demand (COD), was studied in the range 1-8 g/L, anatase TiO2 concentrations in the range 0.25-2 g/L and H2O2 concentrations in the range 0.025-0.15 g/L. Treatment efficiency, which was assessed in terms of COD, total phenols, aromatics and color reduction, generally increased with decreasing initial COD and increasing contact time, catalyst and H2O2 concentrations; however, for H2O2 there was a maximum dosage above which performance deteriorated. Depending on the conditions employed, nearly complete decoloration (>90%) could be achieved, while mineralization never exceeded 50%. Shake-flask tests with non-acclimated activated sludge showed that both the original and photocatalyzed effluents were degradable aerobically with the biodegradation rate of the original effluent being three times greater than the oxidized one. On the other hand, photocatalytic oxidation of the original effluent was at least two orders of magnitude faster than its biological oxidation to achieve comparable levels of degradation.     

Use of an integrated photocatalysis/hollow fiber microfiltration system for the removal of trichloroethylene in water

This work focused on the degradation of toxic organic compounds such as trichloroethylene (TCE) in water, using a combined photocatalysis/microfiltration (MF) system. The performances of the hybrid system were investigated in terms of the removal efficiency of TCE and membrane permeability, in the presence or absence of background species, such as alkalinity and humic acids. The mass balancing of the fate of TCE during photocatalytic reactions was performed in order to evaluate the feasibility of the photocatalytic membrane reactor (PMR). Greater TCE degradation (>60%) was achieved with an increase in the TiO2 dosage (up to 1.5g/L) in PMR, but a substantially large TiO2 dosage brought about a decrease in TCE degradation efficiency. The photocatalytic decomposition of TCE appeared to be more effective in acidic pH conditions than with a neutral or alkaline pH. The addition of alkalinity and humic acid into the feedwater did not have a significant effect on TCE degradation, while humic acids (whose dose was 1mg/L as TOC) in the feedwater played a part in a decline of permeability by 60%. Membrane permeability in the PMR was also affected by tangential velocities. An improvement of 60% in flux was achieved when the tangential velocity increased from 0.19 to 1.45m/s. This is because flow regimes can govern the deposition of TiO2 particles on the membrane surface.     

二氧化碳和环氧乙烷共聚及共聚物的体外降解

文中利用双金属催化剂(DMC)催化二氧化碳和环氧乙烷共聚,催化效率最高达到1139g/g催化剂,远远高于以前报道,其中碳酸酯键含量最高可达50%。实验发现,催化剂浓度是影响催化效率的重要因素,而温度的高低基本决定了碳酸酯键含量的多少。文中还研究了聚碳酸亚乙酯的体外降解性能,在降解液中经历大约70 d后,共聚物几乎全部降解为二氧化碳和低分子量聚乙二醇。     

Pilot-scale treatment of a trichloethylene rich synthetic wastewater in anaerobic hybrid reactor,with morphological study of the sludge granules

A pilot-scale research was conducted to study the biodegradation of trichloroethylene (TCE) in anaerobic hybrid reactor (AHR). At an influent TCE and COD concentrations of 50 and 2,000 mg/l, respectively, the AHR showed a maximum 99.93 ± 0.13 and 97.81 ± 0.42 % of TCE and COD removals, respectively, at 24 h of hydraulic retention time. The flocculent sludge (<0.5 mm diameter in size) was gradually converted to compact granular sludge (>2 mm diameter in size) after the completion of the acclimatization study. The biomass growth yield, the maximum substrate (COD), and the maximum co-substrate (TCE) utilization rates were found to be 0.05 mg VSS/mg COD/day, 0.526 mg COD/mg VSS/day, and 0.0125 mg TCE/mg VSS/day, respectively. The AHR has the high potentiality for the treatment of high concentration of TCE present in some industrial wastewater.     

Home Region Focus and Technical Efficiency of Multinational Enterprise

• The transaction costs economics (TCE) perspective on regionalization suggests that multinational enterprises (MNEs) would experience advantages from regionalization and, hence, greater technical efficiency from a high home region focus (HRF). We extend this TCE perspective by proposing that whether a regional (i.e., higher HRF) or global (i.e., lower HRF) strategy leads to greater technical efficiency depends on the degree of regional integration (i.e., economic and policy) of the MNEs?? home regions.
• This is the first study in the regional/global strategies literature to analyze the effects of HRF and regional integration (economic and policy) on firms?? technical efficiency performance. We suggest that advantages from regionalization arise when firms align their HRF strategy with the degree of regional integration; disadvantages from regionalization can arise when the two are misaligned.
• Our empirical analysis on a sample of 645 manufacturing Triad MNEs during 2000?C2006 provides overall support for our conceptual framework.

     

Kinetic study of trichloroethylene combustion on exchanged zeolites catalysts

In this paper is presented a kinetic study of the catalytic combustion of trichloroethylene (TCE) over Y-zeolites exchanged with several cations. The catalysts, based on zeolite, were prepared by ion exchange and characterized by means of physico-chemical techniques and then tested under kinetic conditions. The kinetic results obtained were interpreted using kinetic models of power-law type and Eley-Rideal. The results obtained indicate that catalyst Y-Cr is more active than Y-Co catalyst. The greater activity of catalyst exchanged with Cr can be attributed to the higher acidity that presented these catalysts.     

Degradation of phenol and TCE using suspended and chitosan-bead immobilized Pseudomonas putida

The degradability of phenol and trichloroethene (TCE) by Pseudomonas putida BCRC 14349 in both suspended culture and immobilized culture systems are investigated. Chitosan beads at a size of about 1-2mm were employed to encapsulate the P. putida cells, becoming an immobilized culture system. The phenol concentration was controlled at 100 mg/L, and that of TCE was studied from 0.2 to 20 mg/L. The pH, between 6.7 and 10, did not affect the degradation of either phenol or TCE in the suspended culture system. However, it was found to be an important factor in the immobilized culture system in which the only significant degradation was observed at pH >8. This may be linked to the surface properties of the chitosan beads and its influence on the activity of the bacteria. The transfer yield of TCE on a phenol basis was almost the same for the suspended and immobilized cultures (0.032 mg TCE/mg phenol), except that these yields occurred at different TCE concentrations. The transfer yield at a higher TCE concentration for the immobilized system suggested that the cells immobilized in carriers can be protected from harsh environmental conditions. For kinetic rate interpretation, the Monod equation was employed to describe the degradation rates of phenol, while the Haldane's equation was used for TCE degradation. Based on the kinetic parameters obtained from the two equations, the rate for the immobilized culture systems was only about 1/6 to that of the suspended culture system for phenol degradation, and was about 1/2 for TCE degradation. The slower kinetics observed for the immobilized culture systems was probably due to the slow diffusion of substrate molecules into the beads. However, compared with the suspended cultures, the immobilized cultures may tolerate a higher TCE concentration as much less inhibition was observed and the transfer yield occurred at a higher TCE concentration.     

Use of carbon stable isotope to investigate chloromethane formation in the electrolytic dechlorination of trichloroethylene

Carbon stable isotope trichloroethylene ((13)C TCE) was used to investigate the formation of chloromethane (CM) during the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite packed cathode. A method was developed to use a conventional GC/MS to analyze and quantify regular and (13)C TCE and their dechlorination products. The concentration of a (13)C compound can be calculated, based on the concentration of its regular counterpart, from the response ratio of two fragments of different mass per charge values from the compounds in a sample and two characteristic MS spectrum ratios: one is the response ratio of the two fragments of the regular compound, and the other is the response ratio of the corresponding fragments of the regular and (13)C compounds at the same concentrations. The method was used to analyze the regular and (13)C compounds observed in an experiment of dechlorination in an ammonium acetate solution that contained both regular TCE and (13)C TCE. Results of analysis confirmed that CM was not a direct product of TCE dechlorination at the granular graphite cathode that cis-DCE was an intermediate product of TCE dechlorination, and that 1,1-DCE was not a dechlorination product.     

Persulfate regeneration of trichloroethylene spent activated carbon

The objective of this study was to demonstrate the regeneration of trichloroethylene (TCE) spent activated carbon using persulfate oxidation and iron activated persulfate (IAP) oxidation. Both processes resulted in decreases in the adsorbability of regenerated activated carbons. IAP was shown to rapidly degrade the aqueous TCE and causes a significant mineralization of the TCE. The release of chloride ions provided evidence of this. Persulfate oxidation mainly resulted in desorption of TCE from the activated carbon and only partial mineralization of the TCE through a carbon activated persulfate reaction mechanism. Concerning destruction of the TCE, in the regeneration test using persulfate, 30% of the original TCE was present in the solution and 9% remained on the activated carbon after the first regeneration cycle. In contrast, in the test that used IAP, it was observed that no TCE was present in the solution and only approximately 5% of the original TCE remained on the activated carbon after the first regeneration. Following the regeneration cycles, elemental analysis was carried out on the samples. BET surface area and EDS analysis showed some effects on the physico-chemical properties of the activated carbon such as a slight decrease in the surface area and the presence of iron precipitates on the carbon.     

Optically enhanced sensitivity of external electro-optic polymer probing system

We propose an optical-sensitivity-enhanced external electro-optic (EO) measurement system using a poled polymer as an EO sensor. A pumping laser is used to induce the photoisomerization effect in a prepoled EO polymer to both enhance and maintain the noncentrosymmetric molecular orientation. This approach increases the EO coefficient and, hence, enhances the EO measurement sensitivity. Experimental results of an EO sensor made of DR1/PMMA show that this method can improve the sensitivity by at least a factor of 2.     

Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene

Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al(2)O(3) support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE.     

Semicontinuous microcosm study of aerobic cometabolism of trichloroethylene using toluene

A semicontinuous slurry-microcosm method was applied to mimic trichloroethylene (TCE) cometabolic biodegradation field results at the Que-Jen in-situ pilot study. The microcosm study confirmed the process of aerobic cometabolism of TCE using toluene as the primary substrate. Based on the nucleotide sequence of 16S rRNA genes, the toluene-oxidizing bacteria in microcosms were identified, i.e. Ralstonia sp. P-10 and Pseudomonasputida. The first-order constant of TCE-degradation rate was 0.5 day(-1) for both Ralstonia sp. P-10 and P.putida. The TCE cometabolic-biodegradation efficiency measured from the slurry microcosms was 46%, which appeared pessimistic compared to over 90% observed from the in-situ pilot study. The difference in the TCE cometabolic-biodegradation efficiency was likely due to the reactor configurations and the effective time duration of toluene presence in laboratory microcosms (1 days) versus in-situ pilot study (3 days). The results of microcosm experiments using different toluene-injection schedules supported the hypothesis. With a given amount of toluene injection, it is recommended to maximize the effective time duration of toluene presence in reactor design for TCE cometabolic degradation.     

Preparation of activated carbon@ZnO composite and its application as a novel catalyst in catalytic ozonation process for metronidazole degradation

The present study aimed to investigate the efficiency of granular activated carbon modified with ZnO nanoparticles (GAC@ZnO composite) as a catalyst for metronidazole degradation using catalytic ozonation process. The catalytical properties of GAC@ZnO composite were measured by using FESEM, FT-IR, XRD, EDX, and BET advanced techniques. Also, the effects of pH factor (3, 5, 7, 9, and 11), initial concentration of contaminant (10–30 mg/L), reaction time (5–90 min), catalyst dosage (0.2–2.5 g/L), on the catalytic ozonation process, were studied. In addition, the effects of the interfering factors on the work of ozone degradation agent and hydroxyl radicals are tested. The results of characterisation study showed a successful formation of GAC@ZnO composite with favorable catalytic properties. In addition, the GAC surface properties were enhanced by the modification with ZnO nanoparticles, where more efficient reaction sites for metronidazole degradation were created onto GAC. The degradation performance of the GAC@ZnO composite was high in which 83% of metronidazole removal was achieved in optimum conditions (pH = 11, catalyst dosage = 2 g/L, and reaction time = 30 min). In addition, the degradation rate was noticeably found to be higher in case of using catalytic ozonation process than using ozonation process alone. The kinetic degradation reactions of metronidazole followed the pseudo-first-order equation. According to the results of this model’s parameters, the degradation process is occurred on or near GAC@ZnO composite surface depending on the concentration of the pollutant. From the results obtained, it can be concluded that the GAC@ZnO composite in the catalytic ozonation treatment process was efficacious catalyst as it has excellent performance toward eradication of metronidazole wastewater.     

Catalytic hydrotreating of 2,4'-DDT and 4,4'-DDT

The results of catalytic hydrotreating of a commercial mixture of 2,4'-DDT and 4,4'-DDT are reported. Experimental runs were carried out in a batch reactor (300 cm3) at constant hydrogen pressure (PH2 = 20 bar) and temperature. Temperature levels 150, 180, 200 and 230 degrees C were tested. A commercial sulphide Ni-Mo catalyst was adopted. The reacting medium was hexadecane. The kinetic constant and reaction order of the destruction reaction of 2,4'-DDT and 4,4'-DDT have been evaluated at temperature of 180, 200 and 230 degrees C. Destruction and removal efficiency (DRE) at T = 230 degrees C has been calculated.     

Artificial neural networks for the automated detection of trichloroethylene by passive Fourier transform infrared spectrometry

Artificial neural networks are applied to the automated classification of trichloroethylene (TCE) signatures from passive Fourier transform infrared remote sensing interferogram data. Through the use of three data collection methods, a combination of laboratory and field data is acquired that allows the methodology to be evaluated under a variety of infrared background conditions and in the presence of potentially interfering compounds such as sulfur hexafluoride, methyl ethyl ketone, acetone, carbon tetrachloride, and ammonia. To maximize the computational efficiency of the network optimization, experimental design techniques are employed to develop a training protocol for the network that takes into account the relationships among five variables that are related either to the network architecture or to the training process. This protocol is implemented for the case of a back-propagation neural network (BNN) and is used to develop an optimized network for the detection of TCE. The classification performance of the network is assessed by comparing both TCE detection capabilities and false detection rates to similar classification results obtained with the technique of piecewise linear discriminant analysis (PLDA). When applied to prediction data withheld from the optimization of both the BNN and PLDA algorithms, the BNN method is observed to outperform PLDA overall, with TCE detection rates in excess of 99% and false detection rates less than 0.5%.     

Photodegradation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans: direct photolysis and photocatalysis processes

This study employed direct photolysis to treat mixed polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) solutions. The solutions included a synthetic standard 17 2, 3, 7, 8-substituted congeners solution and a practical liquid extracted from the bag filter ash of an electric arc furnace. Additionally, this work utilized a coupled catalyst (ZnO/SnO2) under UV irradiation for photocatalytic degradation of 1, 2, 3, 6, 7, 8-HxCDD and OCDD. The direct photolysis rate of PCDFs was faster than that of PCDDs. The degradation rate of international toxicity equivalency quantity (I-TEQ) for PCDDs and PCDFs in the synthetic standard solution was 1.369 and 1.472 h(-1), respectively, and that in the ash-extracted solution was 0.061 and 0.117 h(-1), respectively. The rate of photocatalytic degradation declined as the number of chlorine atoms increased. No 2, 3, 7, 8-substituted congeners were identified during photocatalytic degradation; additionally, the photolytic rate of the UV/coupled catalyst was higher than that of UV/single catalyst system. Experimental results suggested that the primary degradation pathway for direct photolysis and photocatalysis of PCDD/Fs was the CCl cleavage and CO cleavage, respectively.     

Mechanism and kinetics of reductive dehalogenation of PBB (polybrominated biphenyl) in the sonolytic and ketyl radical system

The kinetics and mechanism of reductive destruction of aqueous polybrominated biphenyl (PBB) were studied. Complete degradation was achieved within 30 min of ultrasound-assisted chemical process (UACP), which involved sonication, ketyl radical and its anion, and metal catalyst (ferrous ion). Reductive dehalogenation of PBB is a first-order reaction between PBB concentration and UACP reaction time. The kinetic condition of PBB degradation was optimized in terms of temperature, dosage of radical initiator, and metal catalyst. Mechanism of reductive debromination was also proposed to explain the function of ketyl and aryl radicals on the debromination of bromobiphenyl. Two kinetic models were studied to elucidate the debromination mechanism pathway. Laboratory observed data were found to fit model predicted values obtained from equilibrium and differential equations.