Pre-oxidation Step Research Articles

Solar photo-Fenton as a pre-oxidation step for biological treatment of landfill leachate in a pilot plant with CPCs

A solar photo-Fenton process, without iron addition, is proposed for the decontamination of a landfill leachate in a pilot plant with CPCs, after a preliminary pre-treatment in aerated and non-aerated lagoons. The solar photo-Fenton reaction leads to 60% mineralization (DOC final = 1200 mg L −1) and 90% reduction of aromatic content of the leachate after 5 sunny clear days (165 kJ UV L −1), consuming 275 mM of H 2O 2. Photo-Fenton kinetics comprises a “lag period” after the acidification until approximately 68.7 kJ UV L −1 in which less oxidized compounds are converted into more oxidized ones but without significant CO 2 release, followed by a first-order kinetic behaviour ( k = 0.007 L kJ UV −1, r 0 = 20.2 mg kJ UV −1) until 136 kJ UV L −1, with a H 2O 2 consumption rate in both periods of k H 2 O 2 = 2.1 mmol H 2 O 2 k J UV − 1 . According to activated sludge respirometry and Zahn–Wellens biodegradability tests, BOD 5/COD ratio, polyphenols concentration and COS (carbon oxidation state), the biodegradability of the leachate was enhanced during the photo-Fenton treatment. From the kinetic results, the optimal amount of UV solar energy required for photo-treatment to reach a biodegradable effluent is 100 kJ UV L −1 (10.5 h of photo-Fenton at a constant solar UV power of 30 W m −2), consuming 180 mM of H 2O 2 when used in excess, which means almost 40% mineralization of the leachate, 82% reduction of polyphenols concentration and 83% reduction of aromatic content.

Removal of arsenic from contaminated groundwater by membrane-integrated hybrid treatment system

Experimental investigations were carried out to separate arsenic from contaminated groundwater by using three different types of nanofiltration membranes in a flat sheet cross flow membrane module with a pre-oxidation step for conversion of trivalent arsenic to pentavalent form. KMnO 4 was used as an oxidising agent in the pre-oxidation step. Effects of pressure, iron concentration in groundwater, pH, and pre-oxidation on the performance of the membranes in terms of flux as well as percentage rejection of arsenic were studied. While transmembrane pressure was found to have strong impact on flux and retention of arsenic, pH and pre-oxidation exhibited strong influence on percentage removal of arsenic. Introduction of pre-oxidation step remarkably enhanced arsenic separation in a largely fouling-free membrane module. Overall arsenic removal increased from 50–63% to 97–100% for all the three types of membranes over a transmembrane pressure range of 5–12 kgf/cm 2 on pre-oxidation of trivalent arsenic. With increase in pH from 3 to 10, arsenic rejection increased by 23% for NF-1, 33% for NF-2 and 26% for NF-20 membranes. Polyamide composite nanofiltration membrane fitted in a cross flow membrane module could successfully remove arsenic from contaminated groundwater with a pre-oxidation step.

The Effects of Pre-Oxidation and Alloy Chemistry of Austenitic Stainless Steels on Glass/Metal Sealing

An oxidation treatment is often performed on austenitic stainless steel prior to joining to alkali barium silicate glass to produce hermetic seals. The thin oxide formed during this pre-oxidation step acts as a transitional layer and a source of Cr and other elements that diffuse into the glass during the subsequent bonding process. Pre-oxidation is performed in a low pO2 atmosphere to avoid iron oxide formation; the final oxide is composed of Cr2O3, MnCr2O4 spinel, and SiO2. Significant heat-to-heat variations in the oxidation behavior of austenitic stainless steel were observed in this work, resulting in inconsistent glass/metal seal behavior. Twenty-five (25) stainless steel heats were examined including 304L, 316L, and experimental high sulfur alloys similar to 303SS. The objectives were to characterize the oxidation kinetics, the oxide morphologies, and compositions that affect glass/metal adhesion. It was found that poor glass sealing is associated with a more continuous layer of SiO2 at the metal/oxide interface. The effects of alloy chemistry, in particular Mn and Si concentrations, on glass/metal sealing behavior were empirically determined. A criterion based on the Mn/Si ratio was developed for use in selecting heats with good glass/metal bonding characteristics. To test this criterion, four other austenitic stainless steels were evaluated: 21-6-9 (also known by original Armco Steel Co. trade name Nitronic® 40), 22-13-5 (Nitronic® 50), Nitronic® 60, and Gall-Tough® (Carpenter Technology Corp.). These alloys have compositions significantly different from 300-series alloys, but they were still found to comply with the compositional guidelines developed for predicting glass/metal adhesion.

Effect of organic matter on arsenic removal during coagulation/flocculation treatment

The aim of this study is to evaluate the influence of organic matter on arsenic removal by coagulation/flocculation on both a model water with low mineral content and a natural water sample. Ferric chloride was used as coagulant at concentrations avoiding the preoxidation step usually required to oxidize As(III) and increase its removal. Arsenic removal was accomplished by combining evaluation of arsenic residual concentrations and speciation analysis with zeta potential measurements. A preliminary study evaluated the influence of coagulant dose, coagulation pH, and organic matter on As(III) and As(V) removal. The main conclusions were: (i) As(III) removal depended on coagulant dose and on the number of sites available on hydroxide surfaces rather than on coagulation pH; (ii) As(V) removal depended on the zeta potential of colloidal suspension and was more influenced than As(III) by coagulation pH and the presence of organic matter; (iii) organic matter removal followed As(V) removal. This allowed determination of adsorption as the main mechanism occurring during As(V) and organic matter removal and supposing precipitation/coprecipitation as an important As(III) removal mechanism. Adsorption on preformed ferric hydroxide flocs experiments allowed then confirmation of these hypotheses.

Sorption of As(V) from waters using chitosan and chitosan-immobilized sodium silicate prior to atomic spectrometric determination

A natural biosorbent containing amine functional groups, chitosan, and a novel sorbent, chitosan-immobilized sodium silicate, were prepared and utilized for the selective sorption of As(V) from waters prior to its determination by atomic spectrometric techniques, namely, hydride generation atomic absorption spectrometry (HGAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Chitosan was synthesized from chitin and sodium silicate was used as the immobilization matrix due to its straightforward synthesis. Through sequential sorption studies, it was shown that chitosan-immobilized sodium silicate has exhibited a better chemical stability than the chitosan itself which demonstrates the advantage of immobilization method. Both chitosan and chitosan-immobilized sodium silicate were shown to selectively adsorb As(V), arsenate, from waters at pH 3.0 at which neither chitin nor sodium silicate displayed any sorption towards As(V). The sorption of arsenate by chitosan is supposed to have electrostatic nature since pH of 3.0 is both the point at which the amino groups in chitosan are protonated and also the predominant form of As(V) is H 2AsO 4 −. A pre-oxidation step is required if both As(III) and As(V) are to be determined. Desorption from the sorbents was realized with 1.0% (w/v) l-cysteine prepared in a pH 3.0 solution adjusted with HCl. Among the possible interfering species tested, only Te(IV) and Sb(III) were shown to cause a decrease in the sorption capacity especially at high interferant concentrations. High concentrations of Sb(III) also resulted in gas phase interference during hydride generation. The validity of the method was checked both via spike recovery experiments and also through the analysis of a standard reference material. Spike recovery tests were carried out with four different types of water; namely, ultra-pure, bottled drinking, tap, and sea water; and percent recovery values were found to be 114 (±4), 112 (±2), 43 (±4), and 0 (±1), respectively. It was concluded that the proposed methodology can be applied efficiently to low-to-medium ionic strength solutions, such as most drinking waters. The accuracy of the method was additionally investigated through the analysis of a standard reference material and a good correlation was found between the determined (26.6 ± 2.4 μg L −1) and the certified (26.67 μg L −1) value.

Oxidation by Fenton's reagent combined with biological treatment applied to a creosote-comtaminated soil

In this study, we investigated the feasibility of using Fenton oxidation to remove sorbed polycyclic aromatic hydrocarbons (PAHs) in aged soil samples with creosote oil from a wood preserving site. The optimal dosage of reagents was determined by a statistical method, the central composite rotatable experimental design. The maximum PAH removal was 80% with a molar ratio of oxidant/catalyst equal to 90:1. In general low molecular weight PAHs (3 rings) were degraded more efficiently than higher molecular weight PAHs (4 and 5 rings). The hydrogen peroxide decomposition kinetic was studied in the presence of KH 2PO 4 as stabilizer. The kinetic data were fitted to a simple model, the pseudo-first-order which describes the hydrogen peroxide decomposition. The PAH kinetic degradation was also studied, and demonstrated that non-stabilized hydrogen peroxide was consumed in less than 30 min, whilst PAH removal continued for up to 24 h. In a second part of the work, a combined chemical and biological treatment of the soil was carried out and shown to be dependent on the pre-oxidation step. Different reagent doses (H 2O 2:Fe) were used (10, 20, 40, 60:1) in the pre-treatment step. An excess of hydrogen peroxide resulted in a poor biological removal, thus the optimal molar ratio of H 2O 2:Fe for the combined process was 20:1. The combined treatment resulted in a maximum total PAH removal of 75% with a 30% increase in removal due to the biodegradation step. The sample with highest PAH removal in the pre-oxidation step led to no further increase in removal by biological treatment. This suggests that the more aggressive chemical pre-oxidation does not favour biological treatment. The physico-chemical properties of the pollutants were an important factor in the PAH removal as they influenced chemical, biological and combined treatments.

Cutinase Inhibition by Means of Insecticidal Organophosphates and Carbamates. 3. Oxidation of Phosphorothionates by Chloroperoxidase from Caldariomyces fumago

Chloroperoxidase (CPO) from Caldariomyces fumago combined with hydrogen peroxide and chloride proved to be most efficient for the transformation of organophosphorothionate pesticides, i.e., chlorpyrifos, chlorpyrifos-methyl, parathion, and parathion-methyl, into their more potent serine esterase inhibiting oxon analogues. Following CPO pre-oxidation steps, the detection limit of a recently described spectrophotometric cutinase assay could be increased by about 2 orders of magnitude as a consequence of increased inhibition rates of the organophosphates. This type of enzymatic oxidation is easier to perform and more efficient, as compared to bromine or N-bromosuccinimide, used for acetylcholine esterase (AChE) assay in water analyses, but is insufficient for complex matrices such as plant sample extracts. The performance of a complete assay, including sample preparation, oxidation, and inhibition, takes about 3 h. Performing oxidations of organophosphorus compounds, two significant anomalies were observed. Upon CPO oxidation, chlorpyrifos-methyl showed a very strong cutinase inhibition as compared to the corresponding oxon standard, and oxidized malathion, contrarily to malaoxon, revealed cutinase inhibition, which however obeyed a reversible reaction mechanism in contrast to the usually irreversible reactions of organophosphates. Except for methomyl, no significant effects of CPO oxidation on the inhibition strength of insecticidal carbamates could be detected. The applicability of the assay was tested with fruit samples spiked with chlorpyrifos at 0.2-0.5 mg/kg, thereby regarding the role of the latter as the pesticide detected most often in fruits. Mean recoveries ranged between 30-50%. An enhanced recovery of 84% was obtained for an apple juice sample spiked with parathion-methyl (0.5 mg/L).

Effect of Ozonation on Biodegradability Characteristics of Surplus Activated Sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O3/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.

Process study and optimization for fabrication of poly-Si thin-film transistors on plastic substrates

— A complete poly-Si thin-film transistor (TFT) on plastic process has been optimized to produce TFT arrays for active-matrix displays. We present a detailed study of the poly-Si crystallization process, a mechanism for protecting the plastic substrate from the pulsed laser used to crystallize the silicon, and a high-performance low-temperature gate dielectric film. Poly-Si grain sizes and the corresponding TFT performance have been measured for a range of excimer-laser crystallization fluences near the full-melt threshold, allowing optimization of the laser-crystallization process. A Bragg reflector stack has been embedded in the plastic coating layers; its effectiveness in protecting the plastic from the excimer-laser pulse is described. Finally, we describe a plasma pre-oxidation step, which has been added to a low-temperature (<100°C) gate dielectric film deposition process to dramatically improve the electrical properties of the gate dielectric. These processes have been integrated into a complete poly-Si TFT on plastic fabrication process, which produces PMOS TFTs with mobilities of 66 cm2 /V-sec, threshold voltages of −3.5 V, and off currents of approximately 1 pA per micron of gate width.

Effects of preoxidation on the nucleation and growth behavior of chemically vapor-deposited α-Al2O3 on a single-crystal Ni-based superalloy

A chemical vapor deposition (CVD) procedure was developed for preparing a high-quality α-Al2O3 coating layer on the surface of a single-crystal Ni-based superalloy using AlCl3, CO2 and H2 as precursors. A critical part of this procedure was a short-time preoxidation step (1 min) with CO2 and H2 in the CVD chamber, prior to introducing the AlCl3 precursor. Without this preoxidation step, extensive whisker formation was observed on the alloy surface. Characterization results showed that the preoxidation step resulted in the formation of a continuous oxide layer (∼50 nm) on the alloy surface. The outer part of this layer (∼20 nm) appeared to contain mixed oxides, whereas the inner part (∼30 nm) mainly consisted of α-Al2O3 grains with θ-Al2O3 as a minor phase. We observed that the nucleation of α-Al2O3 in the preoxidized layer was promoted by (1) rapid heating (10 seconds) of the alloy surface to the temperature region where α-Al2O3 was expected to nucleate; (2) the low oxygen pressure environment of the preoxidation step, which kept the rate of oxidation low; and (3) contamination of the reactor chamber with HfCl4. The preoxidized layer served as an effective diffusion barrier for mitigating the interaction with some of the alloying elements such as Co and Cr with the CVD precursors and eliminating whisker formation on the alloy surface.

Stabilized leachates: ozone-activated carbon treatment and kinetics

Ozone has been used as a pre-oxidation step for the treatment of stabilized leachates. Given the refractory nature of this type of effluents, the conversion of some wastewater quality parameters has been moderate after 1 h of ozonation (i.e. 30% chemical oxygen demand (COD) depletion). Ozone uptake was calculated in the interval 1.3– 1.5 g of ozone per gram of COD degraded. An optimum dose of ozone has been experienced in terms of biodegradability of the processed effluent ( 60 min of treatment, 1×10 −3 mol L −1 ozone inlet feeding concentration and 50 L h −1 gas flow-rate). pH and other typical hydroxyl radical generator systems exerted no influence on the efficiency of the process, suggesting the negligible role played by the indirect route of oxidation (generation of hydroxyl radicals). The ozonated effluent was thereafter treated in a second adsorption stage by using a commercial activated carbon. Removal levels up to 90% of COD in approximately 120 h were experienced for adsorbent dosages of 30 g L −1 . Both steps, the single ozonation and the adsorption stage have been modelled by using different pseudoempirical models.

Combined advanced oxidation and biodegradation of industrial effluents from the production of stilbene-based fluorescent whitening agents

Three different industrial wastewaters from the production of stilbene-based fluorescent whitening agents were investigated with regard to the applicability of advanced oxidation processes combined with biodegradation. Oxidation processes included the application of ozone, hydrogen peroxide, UV-radiation and Fenton's reagent (Fe 2+/H 2O 2). Characterization of the combined chemical–biological treatment was done by sum parameters and HPLC analysis. In addition, toxicity was determined using the luminescence inhibition test. Results showed that processes producing OH-radicals without the need of UV-irradiation proved to be suited for the oxidation of all three wastewaters. H 2O 2/UV processes were ineffective due to the high inner filter effect of the effluents. Comparing the combined oxidative-biological process with biological treatment, the applied pre-oxidation steps did not always lead to a significant improvement of the biological degradation. In one case, an inverted treatment starting with biodegradation followed by oxidation turned out to be the preferable procedure. After oxidation with ozone or ozone combined with UV-irradiation, an increase in toxicity was partly observed indicating the formation of toxic intermediate products. In some cases samples had to be diluted before the biodegradation step to achieve a better biodegradability.

A System for the Direct Determination of the Nonvolatile Organic Carbon, Dissolved Organic Carbon, and Inorganic Carbon in Water Samples through Inductively Coupled Plasma Atomic Emission Spectrometry

A new system has been developed for the determination of total organic carbon (TOC) and inorganic carbon (IC) or total inorganic carbon (TIC) in waters. Only nonvolatile organic compounds can be detected through the present method. The system presented in this work is based on the measurement of the carbon atomic emission intensity in inductively coupled plasma atomic emission spectrometry (ICP-AES). This way, the organic matter does not undergo any preoxidation step. A semiautomatic accessory connected to the spectrometer separates the different carbon fractions (i.e., organic and inorganic). Because most of the solutions used in the present work did not contain suspended solid particles, the actual parameter that was determined was the dissolved organic carbon (DOC). The present system exhibits good sensitivities compared to those provided by conventional TOC and IC determination methods. The limits of detection obtained in the present work have been 0.07 and 0.0007 mg/L C in terms of TOC and IC, respectively. Furthermore, the system is able to handle high-salt-content solutions. This fact suggests that it would be possible to analyze seawater samples, avoiding some of the problems encountered with conventional methods, such as system blocking or interferences. The TOC and IC values found for natural samples are very close to those measured using conventional methods. The ICP-AES method has been successfully used in two interesting applications: (i) monitoring the efficiency of a water treatment plant and (ii) determining the contents of dissolved carbon dioxide, on one hand, and that of carbonate and bicarbonate, on the other, in the same sample.

Basic examinations on chemical pre-oxidation by ozone for enhancing bioremediation of phenanthrene contaminated soils

Biological treatment of polycyclic aromatic hydrocarbons (PAH) has been demonstrated to be a feasible and common remediation technology which has been successfully applied to the clean-up of contaminated soils. Because bioavailability of the contaminants is of great importance for a successful bioremediation, a chemical pre-oxidation step by ozone was tested to enhance the subsequent biodegradation steps. Oxidation of PAH by ozone should result in reaction products that have a better solubility in water and thus a better bioavailability. A major part of this work was done by examinations of the model substance phenanthrene as a typical compound of PAH. After initial ozonation of phenanthrene, analysis by GC-MS showed at least seven identified conversion-products of phenanthrene. In comparison with phenanthrene these conversion products were more efficiently biodegraded by Sphingomonas yanoikuyae or mixed cultures when the ozonation process resulted in monoaromatic compounds. Primary ozonation products with biphenylic structures were found not to be biodegradable. Investigations into the toxicity of contaminated and ozonated soils were carried out by well-established toxicity assays using Bacillus subtilis and garden cress. The ozonated soils surprisingly showed higher toxic or inhibitory effects towards different organisms than the phenanthrene or PAH itself. The microbial degradation of phenanthrene in slurry reactors by S. yanoikuyae was not enhanced significantly by preozonation of the contaminated soil.

Chemical-Biological Treatment of Table Olive Manufacturing Wastewater

Wastewater generated in the table olive processing industries has been treated by means of an integrated wet air oxidation–aerobic biodegradation process. Chemical oxygen demand (COD) conversion in the range of 30–60% (6 h of treatment) has been achieved by using relatively mild conditions (443–483 K and 3.0–7.0 MPa of total pressure using air). Use of the homogeneous catalysts [copper (II)] or radical promoters (hydrogen peroxide) resulted in a higher efficiency of the process (roughly between 16 and 33% COD removal improvement depending on operating conditions). Biodegradability tests, conducted after the oxidation pretreatment, showed a negative effect with the addition of copper to the reaction media. Promoted experiments resulted in the highest values of biodegradability (measured as the ratio of biological oxygen demand to COD). The rate of the COD biodegradation was compared to the kinetics of the aerobic process without a previous chemical preoxidation. The calculated kinetic parameters showed the positive effect of the pretreatment (maximum growth rate of 0.03 ± 0.006 h−1 and 0.014 ± 0.00014 h−1). Acclimation of microorganisms to oxygenated species formed in a chemical preoxidation step enhanced the efficacy of the biodegradation (maximum growth rate of 0.04 ± 0.007 h−1).

Yttrium silicate formation on silicon: Effect of silicon preoxidation and nitridation on interface reaction kinetics

The effects of oxygen and nitrogen pretreatments on interface reaction kinetics during yttrium silicate formation on silicon are described. X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) are used to determine chemical bonding and composition of films formed by oxidation of yttrium deposited on silicon. Capacitance–voltage testing is used to determine the quality of the dielectric and the electrical thickness. The effect of ultrathin silicon oxide, nitrided oxide, and nitrided silicon interfaces on metal oxidation kinetics is also described. When yttrium is deposited on clean silicon and oxidized, XPS and MEIS indicate significant mixing of the metal and the silicon, resulting in a film with Y–O–Si bonding and composition close to yttrium orthosilicate (Y2O3⋅SiO2). A thin (∼10 Å) in situ preoxidation step is not sufficient to impede the metal/silicon reaction, whereas a nitrided silicon interface significantly reduces the silicon consumption rate, and the resulting film is close to Y2O3. The mechanisms described for yttrium are expected to occur in a variety of oxide and silicate deposition processes of interest for high-k dielectrics. Therefore, in addition to thermodynamic stability, understanding the relative rates of elementary reaction steps in film formation is critical to control composition and structure at the dielectric/Si interface.

Remote Plasma‐Assisted Deposition of Gate Quality Oxides Without the Use of a Preoxidation Step

This paper discusses the development of a low temperature gate oxide deposition process using remote plasma chemical vapor deposition which, unlike other plasma‐assisted gate oxide deposition processes, does not require a preoxidation step, a significant limitation of those processes. An important factor in the development of this process was the discovery that the background water concentration in the deposition chamber plays a crucial role in determining the electrical properties of the oxide films. A likely mechanism is proposed for this effect. It is shown that by carefully controlling the background water concentration, it is possible to develop a process which does not require preoxidation, while yielding films whose electrical properties are comparable to those reported for other processes and, in the case of some parameters, comparable to the properties of furnace‐grown oxides. The process has been verified to be scalable down to at least 30 Å. © 1999 The Electrochemical Society. All rights reserved.

Wastewater pretreatment with ultrasonic irradiation to reduce toxicity

In order to industrialize an ultrasonic process for wastewater treatment, several works were undertaken. The first one was the study of pentachlorophenol degradation [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Can. J. Chem. Eng. 75 (1997) 245]. Association of high-frequency ultrasound transducers was investigated [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Entropie 204 (1997) 21] and the mapping of ultrasonic fields in various reactors was studied [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Chem. Eng. Sci. 53 (1998) 523; V. Renaudin, N. Gondrexon, P. Boldo, C. Pétrier, A. Bernis and Y. Gonthier, Ultrasonics Sonochem. 1 (1994) S81]. The third step presented here consists of considering the ultrasonic process as a preoxidation treatment before a classical biological purification. During the ultrasonic irradiation of a sodium pentachlorophenate solution (NaPCP), the concentration of NaPCP, the acute toxicity effects on bacteria ( Vibrio fischeri) and on daphnids ( Daphnia magna) as well as the biodegradability of the pollutant solution were simultaneously monitored. Experimental results provide evidence that an ultrasonic treatment is an efficient preoxidation step.

Properties of gate quality silicon dioxide films deposited on Si–Ge using remote plasma-enhanced chemical vapor deposition with no preoxidation

SiO 2 films were deposited on Si–Ge using a low temperature (300 °C) remote plasma-assisted chemical vapor deposition (RPCVD) process. A novel feature of this process is that it does not require a preoxidation step prior to deposition. The electrical properties of the resulting oxide films were analyzed, indicating good interfacial (Dit∼3×1011 cm−2 eV−1) and excellent breakdown properties (Ebd∼10 MV/cm). Electron trapping was determined to be the dominant charge trapping mechanism. Interfacial properties and oxide reliability were seen to improve upon annealing at moderately high (550–650 °C) temperatures.

Coagulation of textile secondary effluents with Fenton's reagent

This study was designed to use both artificial and real textile secondary effluents to evaluate (1) the COD and color removal efficiencies for ferrous coagulation and Fenton's coagulation, and (2) the feasibility of using hydrogen peroxide to improve ferrous coagulation to meet more stringent effluent standards. The results indicate that the optimum pHs for both ferrous coagulation and Fenton's preoxidation processes range between 8.0–10 and 3.0–5.0, respectively. The rate for color removal is faster than that for COD removal in the Fenton's preoxidation process. The removals of COD and color are mainly accomplished during Fenton's preoxidation step. The ratio of COD removal for Fenton's coagulation versus ferrous coagulation, given the same ferrous dosage, ranges from 1.4 to 2.3, and it ranges from 1.1 to 1.9 for color removal, using two effluent samples. Therefore, using hydrogen peroxide can enhance the ferrous coagulation, and this ensures more stringent effluent standards of COD and color are met.