X-ray studies of regenerated cellulose fibers wet spun from cotton linter pulp in NaOH/thiourea aqueous solutions

Regenerated cellulose fibers were fabricated by dissolution of cotton linter pulp in NaOH (9.5 wt%) and thiourea (4.5 wt%) aqueous solution followed by wet-spinning and multi-roller drawing. The multi-roller drawing process involved three stages: coagulation (I), coagulation (II) and post-treatment (III). The crystalline structure and morphology of regenerated cellulose fiber was investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Results indicated that only the cellulose II crystal structure was found in regenerated cellulose fibers, proving that the cellulose crystals were completely transformed from cellulose I to II structure during spinning from NaOH/thiourea aqueous solution. The crystallinity, orientation and crystal size at each stage were determined from the WAXD analysis. Drawing of cellulose fibers in the coagulation (II) bath (H₂SO₄/H₂O) was found to generate higher orientation and crystallinity than drawing in the post-treatment (III). Although the post-treatment process also increased crystal orientation, it led to a decrease in crystallinity with notable reduction in the anisotropic fraction. Compared with commercial rayon fibers fabricated by the viscose process, the regenerated cellulose fibers exhibited higher crystallinity but lower crystal orientation. SAXS results revealed a clear scattering maximum along the meridian direction in all regenerated cellulose fibers, indicating the formation of lamellar structure during spinning.     

Applications of Ozone Decomposition Models

Simulated ozone decomposition profiles in “pure” water were made using two analytical kinetic ozone decomposition models and contrasted with experimental and literature data. Fundamental and applied applications of ozone consumption models are presented, demonstrating the importance of both direct and indirect oxidation of inorganic and organic species. A novel approach to simulating ozone decomposition in the presence of natural organic matter (NOM) is presented, concluding that NOM predominantly behaves as a direct consumer of ozone and promoter of ozone decomposition.     

An Investigation in the Use of Ozone Gas in the Bleaching of Cotton Fabrics

Ozone, composed of three atoms of oxygen, can be used to oxidize many inorganic and organic impurities. Because of its high oxidizing capacity, the opportunities and parameters of ozone gas use in bleaching of cotton fabrics were researched in this study. It was found that in a very short time cotton fabrics can be bleached if the water content of cotton-woven fabric was 60% and the pH of the water impregnated was 7. Moreover, ozonation at room temperature was shown to be more efficient than ozonation at high to medium temperatures.     

The use of ozone to decolorize residual direct paper dyes in kraft paper machine whitewater

Production of colored kraft papers results in strongly colored paper machine spent Whitewaters (ww). The residual dyes prevent efficient recycle of the ww and necessitate periodic system cleanings. Many of the dyes are not adsorbed or degraded by biological effluent treatment and therefore discolor receiving waters. Ozone was tested as a bleaching agent for 15 direct paper dyes added at typical residual levels to kraft mill ww. These dyes included azo, polyazo, stilbene, benzothiazole and phthalocyanine direct dyes commonly used in Canadian dyed paper production. Ozone charges of 15 ‐100 mg/L rapidly bleached most of the dyes, although a few of the yellow stilbene and azo dyes were quite resistant. The efficiency of ozone‐mediated residual dye bleaching was altered substantially by the pH, the ww concentration, and the target dye's chemical structure. Preozonation of residual dye‐containing ww greatly decreased the color conferred to bleached kraft pulp fibers added to the ww. Thus, ozonation should permit much more ww recycle (less effluent) when changing colors on the paper machine. Depending on the availability of oxygen or ozone in a mill, and local ozone economics, ozone may be the most efficient, cost‐effective way to improve ww quality, increase ww recycle and minimize effluent color problems and environmental impact.     

Dyes Color Removal by Ozone and Hydrogen Peroxide: Some Aspects and Problems

Application of oxidation processes with the use of strong oxidizing agents, ozone and hydrogen peroxide, is limited because of high costs and some problems with parameters of discoloration reactions. This paper presents findings concerning the use of ozone itself and hydrogen peroxide in combination with Fe²⁺ catalyst for discoloration of dye solutions of concentration 100 mg/L and wastewaters from production of dyestuffs Reactive Orange 20, Reactive Blue 13, Direct Blue 74, and Acid Violet 1. Both agents discolored both the dye solutions and wastewaters successfully. The paper presents a discussion about some aspects and problems occurring in the use of those oxidative agents for discoloration processes in laboratories. There is also a presentation of the effects that such parameters as consumption of oxidants and the doses applied, pH and temperature, had on the time required for discoloration reactions.     

Investigation of Ozone Reaction in River Waters Causing Instantaneous Ozone Demand

Ozone consumption by water can be characterized by the instantaneous ozone demand (IOD) and a pseudo first order decay constant. Utilizing the flow injection analytical system for measuring IOD, the instantaneous ozone demand characteristics of two river waters (Korea) were investigated, utilizing a ?OH probe compound and ?OH scavenger, and were compared with those of two commercial humic acids (the Suwannee River humic acid and Aldrich humic acid). The major findings were as follows; (1) The IOD in river waters was found to be mainly due to the reaction of the ozone with natural organic matter (NOM), which constituted approximately 0.26–0.29?mg/mg DOC, and was responsible for the consumption of more than 40% of the applied ozone. Whereas, the IOD of the two commercial humic acids were three times more than those of the river waters. (2) The IOD in the river waters was mainly caused by the direct ozone reaction with dissolved organics, not from the ?OH mediated ozone reaction. However, for the two commercial humic acids, more than 40% of the IOD came from the ?OH mediated ozone reaction. (3) The hydrophobic fractions of the dissolved organics in the river waters were mainly responsible for the IOD. The IOD of the hydrophobic organics was approximately ten times larger than that of the hydrophilic organics. Although the exact magnitude of the IOD, and the relative importance of the direct/indirect ozone reaction with river water may vary greatly depending upon the source of the NOM, the characteristics of the IOD compromise a significant fraction of the ozone dose need (especially in achieving good ozone disinfection) in water treatment plants.     

Effect of Mn Dispersion on Gas Phase Ozone Decomposition at Room Temperature Using Natural Manganese Oxides

In this study, various analyses were performed to evaluate the ozone removal characteristics using natural manganese ore (NMO) at room temperature. NMO exists primarily in the form of MnO₂, and the specific forms of manganese oxide are formed as the calcination temperature increases. The activity tests, XRD, BET, and XPS analyses confirmed that the dispersion of manganese site exposed to the surface was a critical factor for ozone removal using NMO. To evaluate the actual application of NMO as a catalyst for ozone decomposition, NMO was also made as a form of monolith; as a result, the catalyst showed an excellent conversion rate (over 80%) even at space velocity 30,000 h^?1.     

Degradation of Cellulose Models During an Ozone Treatment. Ozonation of Glucose and Cellobiose With Oxygen or Nitrogen as Carrier Gas at Different pH

Many parameters can influence the kinetics of cellulose models ozonation. In this work the effect of pH and oxygen as gas carrier on the evolution of the reaction was studied. The involvement of free radical species seemed to be unimportant in high ozone concentration available in water, even at high pH with regard to the reaction rate and by-product formation. Conversely, in basic pH conditions better reaction selectivity with formation in a higher yield of gluconic acid and cellobionic acid was found during the glucose and the cellobiose ozonation. The participation of the solvent and the partial ionization of the hydroxyl group at the Cl position explain this enhanced selectivity. Furthermore, the formation of compounds with a low molecular weight has been proved to be due to a hydrotrioxide fragmentation mechanism involving oxygen.     

The Kinetics of Ozonolysis of Synthetic Dyes

Synthetic organic dyes were decomposed rapidly by ozone. The dyes all adhered well to first order kinetics with the exception of the Direct Yellow 12 which showed an initial zero order phase at pH 5. This has been tentatively ascribed to attack by unhydrolyzed ozone on the ethylenlc double bond. From one to four millimoles per liter of ozone was sufficient to attain a 5O% reduction in the concentration of all dyes during the first order ozonations.     

Ozone Consumption in Natural Waters: Effects of Background Organic Matter,pH and Carbonate Species

It was demonstrated that, in natural waters, the overall kineticsof dissolved ozone consumption can be characterized by the “specific ozone utilization rate”, w[time ^?1]. The dependency of w on the chemical quality of the raw water was analyzed. And, the variation of w values measured in different water samples was explained in terms of the pH, alkalinity, and total organic carbon content of the solution matrix.     

The effect of denim color fading ozonation on yarns

Denim color fading ozonation is dissimilar from other ozone applications as it is employed with distinctive parameters and on special products. In this study, yarns of cotton, lyocell and PET treated by denim color fading ozonation were investigated in terms of the effects of time, pH and water content on their physical properties, which included chemical and crystalline structures, surface microstructure, yarns strength and elongation. It is found that, the cellulose in cotton and lyocell yarns has a loss of strength and elongation, while only slight impacts on their crystalline structures are observed. An aggregation and compact crystalline structure of PET prevents it from the decomposition of ozone, whose prevention may also benefit from its poor ability of moisture regain. As a result, synthetic materials, such as PET is recommended more than cellulose fibers to be used in ozone fading process. Meanwhile, such process should neither be employed on cotton, lyocell and other cellulose yarns at pH < 7 nor without paying attention to select a proper water content.     

Ozone,Hydrogen Peroxide/Ozone And UV/Ozone Treatment Of Chromium- And Copper-Complex Dyes: Decolorization And Metal Release

Metal-complex azo dyes constitute a significant fraction of the dyes used in the textile industry and exhibit properties such as superior light- and wash-fastness. While effluent color is not always regulated, the textile finishing industry often decolorizes wastewater using processes including chemical oxidation. In this study, the use of ozone, hydrogen peroxide/ozone and UV/ozone oxidant systems was examined for treatment of two common metal-complex (premetalized) dyes, Acid Black 52 (chromium) and Direct Blue 80 (copper). Oxidant dosages required for decolorization of these dyes were determined. The effect of bicarbonate alkalinity on the ozonation and the hydrogen peroxide/ozone processes also was examined.     

Studies on the Effect of Hydroxy Benzene Diazonium Salts on Physico-Mechanical Properties of Jute Fiber

Jute fiber was treated with three different hydroxy benzene diazonium salts in acidic and basic media. The formation of coupling with lignin in the polymer system was observed by the infrared spectra and nitrogen content estimation. The physico-mechanical properties, viz., tensile strength, tenacity, elongation at break, moisture regain, shrinkage, and loss in weight of jute fiber were studied. The tensile strength, tenacity, and moisture regain properties of the treated fiber were found lower in comparison to those of raw (control) fiber. However, higher tensile strength and tenacity of the fiber treated with ortho hydroxy benzene diazonium salts in comparison to fiber treated with meta hydroxy benzene diazonium salts were observed. The tensile strength and tenacity of the fiber treated with meta hydroxy benzene diazonium salts were higher than those of the fiber treated with para hydroxy benzene diazonium salts. The elongation at break of the treated fiber is found greater than that of the raw fiber. The fiber treated in basic media shows higher tensile strength than that treated in acidic media. The formation of metallated azo complex compound on jute fiber was observed by infrared spectra. The nature of the shades developed on jute fiber was also reported.     

Influence of Ozonation Conditions on Aldehyde and Carboxylic Acid Formation.

The influence of ozonation conditions (i.e. ozone dose and contact time) on the aldehyde and carboxylic acids formation was studied on a pilot scale. The data derived from changes in the molecular weight distribution of natural organic matter (NOM) and the concentration of residual ozone can be applied to a selection of the optimum ozonation conditions. The results confirm the relative ease with which ozone reacts with the organic matter. The short contact time (4–6?min) appeared to be sufficient for the reaction. The higher molecular weight (1600?D) fraction of NOM seems to be slightly more reactive to ozone than the lower molecular weight fraction (500?D). It was also observed that carboxylic acids had been formed at much higher quantities than aldehydes. Two differently acting groups of aldehydes were identified. The concentration of the first one (i.e. formaldehyde, acetaldehyde) strongly depends on ozone dose, while the concentration of the second group of aldehydes (i.e. glyoxal, methylglyoxal) seems to be relatively independent of the ozone dose.     

Azo Dye Ozonation Film Theory Utilization for Kinetic Studies

The ozonation kinetics of three azo dyes (Direct Yellow 27, Direct Blue 1 and Acid Black 52) in aqueous solution has been studied. Two types of reactors have been used, an agitated tank for studying the influence of variables and the stoichiometry, and an agitated cell for kinetic measurements. Both the film theory and the modes of ozone action on organic matter have been considered for obtaining the kinetic rate constants. A model of ozone absorption in the fast pseudo–m–th ozone order kinetic regime with two parallel reactions fits satisfactorily the experimental results. From it, the kinetic constants of both reactions have been evaluated.     

Reaction Mechanisms for DBPS Reduction in Humic Acid Ozonation

In this study, XAD-8 resins were used to extract the natural organic matter (NOM) from samples collected at the intake of Feng Yuan Water Treatment Plant (in central Taiwan) into five groups: humic acids, fulvic acids, hydrophobic neutrals, hydrophobic bases, and hydrophilic fractions. Quantitative results show that hydrophobic and hydrophilic fractions contribute 44.2% and 55.5% of NOM, individually. Ozonation processes will significantly reduce both disinfection by-products formation potential (DBPFP) and average molecular weight of the humic acid sample. Additionally, double carbon bonds are broken up so that hydrophobic fractions were converted to hydrophilic fractions by ozonation leading to the reduction of DBPFP.