Bleaching of Knitted Cotton Fabric Applying Ozone

Several samples of knitted cotton fabric in raw state were impregnated with a solution of industrial wetting detergent and treated directly with ozone gas in a closed chamber. Working conditions for the variables: time, pH of the impregnation solution, residual pickup and feed flow rate of oxygen (for ozone generation) were investigated to identify the effects on whiteness degree and fabric strength. The application of ozone proved to be an efficient and promising technology with low water usage.     

Application of an Experimental Design to Modeling of Ozone Bleaching Stage in TCF Processes

An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50 mg/L ozone inlet concentration, 80–220 LN h ozone flow, and 0.25–0.65% o.d.p. ozone dose. The influence of these variables on several pulp properties after the Z and P stages of the XZP sequence was examined. The models defined from the results obtained predicted, in the Z stage, variations in ISO brightness, viscosity, and kappa number of 74.6–85.6%, 496–876 mL/g, and 0.44–2.27, respectively. For the P stage, the models predicted variations in ISO brightness and viscosity of 84.2–92.7% and 568–857 mL/g respectively. It is possible to obtain bleached eucalyptus pulp of brightness over 89% ISO and viscosities over 800 mL/g. The variable most strongly influencing the pulp properties was found to be the ozone dose.     

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.     

Developments in Ozone-Based Bleaching of Pulps

ABSTRACT

This paper summarizes the review of developments in the area of ozone-based elemental chlorine free (ECF) and total chlorine free (TCF) bleaching of wood and non-wood pulps. Focused areas of review are reaction mechanism of ozone with carbohydrates and lignin, effect of process conditions maintained during ozone bleaching on pulp properties, effect of using different cellulose protectors, effect of alkaline extraction after ozone bleaching of pulps, effect of ozone bleaching on final bleached pulp properties, ECF and TCF bleaching sequences used along with ozone for of wood and non-wood pulps, and commercial scale utilization of ozone for pulp bleaching.     

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.     

Dissolved Ozone Decomposition in Presence of Activated Carbon at Low pH: How Experimental Parameters Affect Observed Kinetics of the Process

Plenty of controversies have recently surrounded the mechanism and kinetics of ozone decomposition process in presence of activated carbon. We have decided to study and explain the source of these controversies, or at least identify it correctly. Several series of experiments were conducted and various parameters (activated carbon amount and grain size, initial ozone concentration, agitation speed) were modified over their course. It was found that widely accepted (pseudo)first-order kinetics cannot explain some observations, and the best fitting was found for half-order kinetics. Ozone decomposition mechanism explaining these results was proposed.     

The Use of Ozone or Oxygen in The First Bleaching Stage

An ODED or a ZEDED sequence bleached kraft hardwood and softwood pulps to 87 — 89‰ ISO brightness. The bleached yields were similar for a given pulp, whether oxygen or ozone was used in the first stage. The strength properties of the fully bleached pulps were essentially the same as those of the unbleached pulps. The COD and colour values of the effluents after ozone delignification and subsequent extraction were 25‰ and 60‰ lower, respectively, than those of the effluents after an oxygen treatment.     

Use of Ozone in the Decolorization of Sugar Industry Liquors

A method that uses ozone for the decolorization step in cane sugar refining is presented. It concerns an important and new application of ozone in the field in the cane sugar industry. Very efficient decolorization of clarified liquors was obtained at different scales. To obtain satisfactory decolorization, suitable treatment operation conditions were established. In the pilot plant study, refined sugar of high purity was obtained, which fulfilled the international quality requirements. At the laboratory scale, a kinetic study for the process has been developed in a continuous system with the use of Danckwert's model. The effective kinetic coefficient (βO₃) values were between 10⁵ and 10⁶ L/mol·s.     

Application of Ozone and Advanced Oxidation Processes to the Treatment of Lye-Wastewaters from the Table Olives Industry

An important fraction of wastewaters generated in the black table olives industry results from the treatment of the olives with sodium hydroxide for debittering and darkening of the fruit. These lye-wastewaters are characterized by a high presence of organic compounds, mainly phenols and polyphenols. The decomposition of that organic content was studied by means of several chemical treatments: ozonation alone and combined with hydrogen peroxide or UV radiation, as well as UV radiation alone and combined with hydrogen peroxide. The degradation levels and the effect of the additional presence of H₂O₂ and UV radiation on the organic matter removal were established for these processes. An approximate kinetic study was conducted, which led to the evaluation of the rate constants for the organic matter reduction. In a second phase, non-pretreated lye-wastewaters and preozonated wastewaters were degraded biologically by means of aerobic microorganisms. The evolution of the organic matter and the biomass were followed. It was demonstrated that the pretreatment with ozone significantly enhances the efficiency of the aerobic process, increasing both the substrate removal level and the degradation rate. This enhancement is probably due to the elimination of most of the toxic phenolic compounds and the increase of the biodegradability in the ozonation pretreatment.     

Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Ozone in the United States of America -- State-Of-The-Art

Applications for ozone in the United States have evolved through a lengthy maturation process, which began with drinking water treatment (taste/odor/color removal) in the early 1900s, and grew slowly until acceleration began in the mid-1980s. Although deodorization became a stable market in the 1960s-1970s, these applications were small, for the most part. One of the largest uses for ozone is oxidation of process chemicals in the chemical industry, which began in the USA about the 1940s, and subsequently has spread worldwide. Today, thanks primarily to environmental regulatory pressures which began to impact ozone in the mid-1980s, ozone now is used increasingly in the USA for drinking water treatment and for some municipal and industrial wastewater applications. The U.S. Environmental Protection Agency (EPA) has recognized the growing importance of ozone (> 200 drinking water plants use ozone today), and has appointed IOA representatives to two of its regulatory development committees as stakeholders. Several U.S. cities have installed or are installing wastewater treatment processes for potable reuse purposes, which include the use of ozone. Three full-scale U.S. pulp bleaching plants use tons/day quantities of ozone. Smaller applications for ozone include water treatment for cooling tower waters (biofouling control), swimming pools and spas, marine aquaria, bottled water disinfection and maintenance of high purity waters in the pharmaceuticals and electronics industries. A new application for ozone is in commercial laundries to reduce energy costs and replace chemicals. In mid-1997, a public declaration was made by an expert panel that ozone is Generally Recognized As Safe (GRAS) for contact with foods. This declaration opens the door for ozone to be used in U.S. food processing industries. U.S. research scientists and engineers are at the forefront in studies which define the technical aspects of ozone technologies in a variety of applications employing advanced oxidation, including the treatment of hazardous wastes, groundwater remediation, and process water recovery and reuse in the semi-conductor industry.     

Hydroxyl Radical/Ozone Ratios During Ozonation Processes. II. The Effect of Temperature,pH, Alkalinity,and DOM Properties

The influence of temperature, pH, alkalinity, and type and concentration of the dissolved organic matter (DOM) on the rate of ozone (O₃) decomposition, O₃-exposure, ?OH-exposure and the ratio R_ct of the concentrations of ?OH and O₃ has been studied. For a standardized single ozone dose of 1 mg/L in all experiments, considerable variations in O₃-exposure and ?OH-exposure were found. This has important implications for water treatment plants regarding the efficiency of oxidation and disinfection by O₃. In oligotrophic surface waters and groundwaters, minimal calibration experiments are needed to model and control the ozonation process, whereas in eutrophic surface waters more frequent measurements of O₃ kinetics and R_ct values are required to evaluate seasonal variations.