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Decomposition of dyes in the textile wastewater with ozone
Abstract
Ozone treatment of textile wastewater and recycling of this treated water as process water have been investigated. Effects of pH, temperature,dye concentration and UV radiotion on the treatment of some azo dyes such as N‐ROT‐GRE, N‐ORANGE and INDISOL‐RUBINOL with ozone were investigated. Temperature was found not to effect the decomposition rates of these dyes. The ozone treatment was found to be more ecomomical with the diluted dye solution than with concentrated solutions. No positive effect of U V radiotion on decomposition of dyes were observed. When the flow rate of ozone was 0.2 mg / sec. chemical oxygen demand ( COD ) decreases of 44 mg and 36.6 mg per minute were found for the wastewaters of cotton dying and wool dying respectively.
... 17 Numerous research workers have reported that the ozonation process is most effective for the decolorization of textile effluent to achieve high color removal and improved biodegradability. [18][19][20][21][22][23] A number of studies have been carried out to optimize the process conditions, which are mainly pH, applied ozone dose, dye concentration and temperature. [23][24][25][26][27] Ozone has also been successfully used for reduction clearing of polyester fibers. ...
... 45 The copper number was determined using the standard procedure. 20 A 3 -g sample of bleached fabric was boiled in a mixture of 100 ml of Fehling's solution and 200 ml of distilled water for 15 minutes in a reflux condenser. The supernatant was then filtered and quantitatively transferred to a beaker. ...
This paper discusses the effect of ozone bleaching on the quality of cotton fabric in terms of whiteness, dye pick-up, copper number and degree of polymerization (DP). The process parameters (pH, ozone dose and treatment time) were optimized, and the best whiteness (60-62) and quality of bleached fabric was obtained at pH 5, 45 min treatment time and room temperature. A strongly acidic environment and longer ozonation time decreased the quality of fabric by producing a higher copper number (0.18) and DP loss (51.5%). Statistical analysis of the experimental data using analysis of variance confirmed that process parameters significantly affected the bleaching efficiency. The process was then applied to bleach 20 different samples of cotton fabric re-using the same water bath, and the whiteness of ozone-bleached samples did not decrease, even after the 20th reuse of the water bath.
... 28−32 Morin is a textile dye with a flavonoid backbone, which was found to break down under the oxidation of ambient oxygen with catalysis of visible light. 28 Grosjean et al. 29 reported the fading 20 Mineralization of Acid Orange 6 was also realized in a Co 2+ /peroxymonosulfate system. 35 Some of the degradation products from mineralization are small molecules and do not contain benzene rings. ...
... 17,30,33,34 Natural light or ambient nitric acid and ambient ozone were found to be oxidative enough to degrade colorants into smaller molecules. 29,30,33,34,40 However, carbonyl compounds were not found as colorant degradation products in previous studies. Generation of chemicals with low molecular weight in this study might be caused by the high oxidative potential of ozone at high concentration when introduced into the sample solution. ...
Commercial manufacture of fruit leathers (FL) usually results in a portion of the product that is out of specification. The disposition of this material poses special challenges in the food industry. Because the material remains edible and contains valuable ingredients (fruit pulp, sugars, acidulates, etc.), an ideal solution would be to recover this material for product rework. A key practical obstacle to such recovery is that compositing of differently-colored wastes results in an unsalable grey product. Therefore, a safe and scalable method for decolorization of FL prior to product rework is needed. This research introduces a novel approach utilizing ozonation for color removal. To explore the use of ozonation as a decolorization step, we first applied it to simple solutions of the commonly used food colorants 2-naphthalenesulfonic acid (Red 40), tartrazine (Yellow 5), and erioglaucine (Blue 1). Decolorization was measured by UV/Vis spectrometry at visible wavelengths, and with a Hunter colorimeter. Volatile and semi-volatile byproducts from ozone-based colorant decomposition were identified and quantified with SPME-GC-MS. Removal of Yellow 5, Red 40 and Blue 1 of about 65%, 80% and 90%, respectively, was accomplished with 70 g ozone applied per 1 kg redissolved and resuspended FL. Carbonyl compounds were identified as major byproducts from ozone-induced decomposition of the food colorants. A conservative risk assessment based on quantification results and published toxicity information of potentially toxic byproducts, determined that ozone-based decolorization of FL before recycling is acceptable from a safety standpoint. A preliminary cost estimate based on recycling of 1,000 tons of FL annually suggests a potential of $275,000 annual profit from this practice at one production facility alone.
... AOPs are treatment technologies that allow oxidizing the organic compounds present in wastewater by exploiting the reactivity of active species [7]. The literature has widely studied Fenton, Photo-Fenton, and ozonation processes [8][9][10] and shows the dye removal capabilities from wastewater. However, to optimize and enhance the performance of these processes, special attention to the process variables, such as pH, reagent dose, pollutant concentration, temperature, UV source, etc., is needed [11]. ...
... Several removal or decolorization methods based on physical, chemical, physico-chemical, and biological processes were previously examined independently or in combination to resolve this problem and decolorize the azo dyes [10][11][12][13]. Photocatalytic degradation [14], Ozonation [15], Advanced Oxidation Processes [16], and a combined photocatalytic and electrochemical oxidation process [17] are among the most widely applied chemical methods used in recent years. For instance, Montanaro et al. [18] reported the efficient coumarin degradation using UV-assisted electrochemical oxidation on boron doped diamond anodes. ...
This study used a novel integrated technology of ceramic supported carbon membrane (CSCM) to degrade azo dyes through an anaerobic mixed culture. The CSCM worked simultaneously as biofilm support, redox mediator, and nano-filter to enhance the dye decolorization efficiency. The decolorization of Acid Orange 7 (AO7) was initially investigated with and without microorganisms in both ceramic support (CS) and CSCM reactors. The CSCM bioreactor (B-CSCM), operated with microorganisms, gave a maximum decolorization of 98% using a CSCM evolved from 10% weight (wt.) of Matrimid 5218 solution. To know the influence of permeate flow, feed concentration, and dye structure on the decolorization process, different B-CSCMs for dye removal experiments were studied over monoazo AO7, diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71). The highest color removal, operated with 50 mg·L⁻¹ feed solution and 0.05 L·m⁻²·h⁻¹ of permeate flux, was 98%, 82%, and 72%, respectively, for AO7, RB5, and DB71. By increasing these parameters to 100 mg·L⁻¹ and 0.1 L·m⁻²·h⁻¹, the decolorization rate of dye solution still achieved 37% for AO7, 30% for RB5, and 26% for DB71. In addition, the system was run for weeks without apparent loss of activity. These findings make evident that the combined phenomena taking place in CSCM bioreactor result in an efficient, cost-effective, and ecofriendly azo dye decolorization method.
... Ozonation is one of the most effective means of decolorization of dye-laden wastewater and has demonstrated to be able to achieve high color and residual COD removal (Church-ley 1994; Strickland & Perkins 1995; Koyuncu & Afsar 1996;Liakou et al. 1997) with improved biodegradability (Tzitzi 1994). One major advantage is that ozone can be applied in its gaseous state and therefore does not increase the volume of wastewater and sludge. ...
Textile industry discharges large amounts of highly colored wastewater, using chemicals reagents within its industrial processes. Discharge of these effluents in open water bodies represents an environmental and aesthetic problem and it may also limit photosynthesis in aquatic plants. Many treatment alternatives have been reported in laboratory as well as full scale, including physical, chemical, biological, Advanced Oxidation Process (AOP) and a combination of them. This abstract of literature review aims to put together extensive information about dyes and the best available technologies (BAT) for their removal from textile effluents.
... The decomposition rate was considerably higher at acidic pH. However, the influence of temperature and UV irradiation on the decomposition rate was negligible (Koyuncu and Afsar, 1996). The negligible influence of UV irradiation on the decomposition rate of azo dyes by ozone has been supported by other authors. ...
The more recent methods for the removal of synthetic dyes from waters and wastewater are compiled. The various methods of removal such as adsorption on various sorbents, chemical decomposition by oxidation, photodegradation, and microbiological decoloration, employing activated sludge, pure cultures and microbe consortiums are described. The advantages and disadvantages of the various methods are discussed and their efficacies are compared.
... 뛰어나다고 보고되어 있다 [9]. 또한 대전 효과가 높아 안정화된 나노 버블은 기포 특성이 장시간 유지되기에 생명공학 분야와 의학적인 응 용이 가능하다 [10]. 나노 (Figure 1(A)), C. vulgaris 균주 또한 N. oculata와 비슷한 경향을 보임을 확인하였다 (Figure 1(B) (Figure 2). ...
Microalgae Nannochloropsis oculata (N. oculta) and Chlorella vulgaris (C. vulgaris) are important sources for biodisel because of the high content of neutral lipids. Stable nano bubble is maintained for a long time and therefore it is possible for use in biotechnology. In this study, effects of nano bubble oxygen or hydrogen water on the microalgae growth were characterized. The cell growth in nano bubble water was similar to that of control, and the total lipid content was rather low. But, chlorophyll content of N. oculata grown in nanno bubble oxygen and hydrogen water increased 54% and 30%, and increased 59%, 39% in C. vulgaris. Carotenoid content also increased 21%, 25% in N. oculata and 49%, 29% in C. vulgaris grown in nano bubble oxygen and hydrogen water. From these results, nano bubble water seems to enhance the photosynthetic capacity of microalgae. © 2014 The Korean Society of Industrial and Engineering Chemistry. All rights reserved.
... The chemical damage to fabric cellulose in terms of copper number (Fehling test), was computed in accordance with a standard procedure (Koyuncu and Afsar 1996). Accordingly, a 3-g bleached fabric sample was boiled for 15 min in 100 mL of Fehling's solution mixed with 200 mL of distilled water in a reflux condenser. ...
The influence of various additives on the efficiency of optimized ozone bleaching process at pilot scale has been discussed in this study. The results reveal that the best whiteness (63.79) and strength of bleached fabric is achieved with the addition of surfactant (2 g/L) at an ozone dose of 50 g/h, pH 5, and ozone treatment time of 45 min at room temperature. The dyeing quality of ozone-bleached and hydrogen peroxide-bleached fabric samples is almost identical. The analysis of variance of the experimental data validates that the process parameters have significantly affected the efficiency of ozone bleaching process.
... The decomposition rate was considerably higher at acidic pH. However, the influence of temperature and UV irradiation on the decomposition rate was negligible (Koyuncu and Afsar, 1996). The negligible influence of UV irradiation on the decomposition rate of azo dyes by ozone has been supported by other authors. ...
Water resources are of critical importance to both natural ecosystem and human developments. Increasing environmental pollution from industrial wastewater particularly in developing countries is of major concern. Heavy metal contamination exists in aqueous waste streams of many industries, such as metal plating facilities, mining operations, tanneries, etc. Some metals associated with these activities are cadmium, chromium, iron, nickel, lead and mercury. Heavy metals are not biodegradable and tend to accumulate in living organisms causing diseases and disorders. Many industries like dye industries, textile, paper and plastics use dyes in order to colour their products and also consume substantial volumes of water. As a result they generate a considerable amount of coloured wastewater. The presence of small amount of dyes (less than 1 ppm) is highly visible and undesirable. Many of these dyes are also toxic and even carcinogenic and pose a serious threat to living organisms. Hence, there is a need to treat the wastewaters containing toxic dyes and metals before they are discharged into the waterbodies. Many physico-chemical methods like coagulation, flocculation, ion exchange, membrane separation, oxidation, etc are available for the treatment of heavy metals and dyes. Major drawbacks of these methods are high sludge production, handling and disposal problems, high cost, technical constraints, etc. This necessitates cost effective and environmentally sound techniques for treatment of watsewaters containing dyes and metals. During the 1970s, the increasing awareness and concern about the environment motivated research for new efficient technologies that would be capable of treating inexpensively, waste waters polluted by metals and dyes. This search brought biosorption/adsorption to the foreground of scientific interest as a potential basis for the design of novel wastewater treatment processes. Several adsorbents are currently used which are by-products from agriculture and industries, which include seaweeds, molds, yeast, bacteria, crabshells, agricultural products such as wool, rice, straw, coconut husks, peat moss, exhausted coffee waste tea leaves, walnut skin, coconut fibre, etc. Adsorption/Biosorption using low cost adsorbents could be technically feasible and economically viable sustainable technology for the treatment of wastewater streams. Low cost adsorbents are nothing but materials that require little processing, are abundant in nature or is a byproduct or waste material from another industry.
... Common treatment methods for color in wastewater include coagulation/flocculation, chlorination, carbon adsorption, advanced oxidation, and ozonation ͑Waters 1979 ;Cooper 1993;Lin and Lin 1993͒. Ozonation is one of the most effective means of decolorizing dye-laden wastewaters and has been shown to: ͑1͒ achieve high color and effluent chemical oxygen demand ͑COD͒ removal ͑Horning 1977; Matsui et al. 1981;Saunders et al. 1983;Green and Sokol 1985;Gould and Groff 1987;Shaban and Bader 1988;Churchley 1994;Gaehr et al. 1994;Huang et al. 1994;Namoodri et al. 1994;Strickland and Perkins 1995;Koyuncu 1996͒; ͑2͒ allow recovery of heavy metals from premetalized dyes ͑Adams et al. 1995;Kanzelmeyer and Adams 1996;Adams et al. 1996͒;and ͑3͒ improve biodegradability ͑Netzer and Miyamoto 1975͒. Ozone (O 3 ) is strong oxidant (E 0 ϭ2.07 V) that selectively oxidizes unsaturated bonds ͑e.g., -CvC-or -NvN-͒ and aromatic structures ͑Langlais et al. 1991͒, which may absorb light in the visible spectrum thus imparting color to the dye and dyed fabric ͑Waring and Hallas 1990; Shore 1990͒. ...
This paper presents the results of a laboratory study on the effect of pH (2, 5, and 9) and gas-phase ozone concentration (1, 7, and 11 wt %) on the decolorization efficiency via ozonation for seven common textile dyes. Higher gas-phase ozone concentrations resulted in higher decolorization rates due to more rapid ozone transfer. Higher gas-phase ozone concentration, however, was also observed to have a positive, neutral, or negative effect on ozone dose requirements for different dyes. In general, greater ozone utilization efficiency was achieved at lower pH levels where direct ozone reactions predominate. It was observed that because ozonation can cause significant resolubilization of precipitated dyes, complete removal of dye precipitate should be accomplished prior to polishing via ozonation. The results point to the need for laboratory and/or pilot testing for dye-laden wastestreams to allow process optimization.
... At higher pH, indirect reactions of ozone may lead to a less efficient process by the indiscriminant oxidation of all parts of dye molecule in addition to other scavengers in solution (Adams & Gorg 2002). Ozonation is one of the most effective means of decolourizing dye-laden wastewater and has been shown to achieve high colour and effluent COD removal (Churchley 1994;Strickland & Perkins 1995;Koyuncu & Afsar 1996;Liakou et al. 1997) with improved biodegradability (Tzitzi 1994). The dosage applied to the dye-containing effluent is dependent on the total colour and residual COD to be removed. ...
Water pollution control is presently one of the major thrust areas of scientific research. While coloured organic compounds
generally impart only a minor fraction of the organic load to wastewaters, their colour renders them aesthetically unacceptable.
Stringent regulating measures are coaxing industries to treat their waste effluents to increasingly high standards. Colour
removal, in particular, has recently become an area of major scientific interest as indicated by the multitude of related
research reports. During the past two decades, several decolourization techniques have been reported, few of which have been
accepted by some industries. There is a need to find alternative treatments that are effective in removing dyes and colourants
from large volume of effluents, which are cost-effective, like the biological or integrated systems. This article reviews
some of the widely used and most promising industrial wastewater decolourization methods. Data on decolourizing efficiencies
of different causative agents, obtained by means of different physical, chemical and biological methods are discussed. Further
a critical review is made on the various treatment methodologies and emerging technologies with a note on their advantages
and disadvantages.
... ozonation ± are promising techniques to reduce these recalcitrant wastewater loads. Ozonation has been applied to many ®elds in water and wastewater treatment (Schulz et al., 1992;Tzitzi et al., 1994;Koyuncu and Afsar, 1996;Lopez et al., 1998). High color removal eciency, enhanced biodegradability, destruction of phenolic compounds as well as considerable reduction in chemical oxygen demand (COD) can be attained by ozonation for textile mill euents (G ahr et al., 1994). ...
The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for textile mill effluents ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the chemical oxygen demand (COD). However, little is known about the reaction intermediates and products formed during ozonation. This work deals with the degradation of hydrolyzed Reactive Yellow 84 (Color Index), a widely used azo dye in textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the hydrolyzed dye in ultra pure water was performed in a laboratory scale cylindric batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (400 nm), was almost complete after 60 and 90 min with an ozone concentration of 18.5 and 9.1 mg/l, respectively. The TOC/TOC0 ratio after ozonation was about 30%, the COD was diminished to 50% of the initial value. The BOD5/COD ratio increased from 0.01 to about 0.8. Oxidation and cleavage of the azo group yield nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused increases in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.
... The decomposition rate was considerably higher at acidic pH. However, the influence of temperature and UV irradiation on the decomposition rate was negligible (Koyuncu and Afsar, 1996). The negligible influence of UV irradiation on the decomposition rate of azo dyes by ozone has been supported by other authors. ...
The more recent methods for the removal of synthetic dyes from waters and wastewater are complied. The various methods of removal such as adsorption on various sorbents, chemical decomposition by oxidation, photodegradation, and microbiological decoloration, employing activated sludge, pure cultures and microbe consortiums are described. The advantages and disadvantages of the various methods are discussed and their efficacies are compared. Keywords: Synthetic dyes, Wastewater, Adsorption, Oxidation, Biodegradation
In the present study, the effect of advanced oxidation processes such as ozone/UV, ozone/H2O2 and ozone/UV/H2O2 on decolouration of Acid Red 88, Acid Orange 7, Acid Orange 10 and Acid Red 73 dye effluents in the presence of sodium sulphate salt were considered. Studies were carried out to analyse and compare the effect of aromatic, azo and sulphonic acid groups on decolouration of acid dye effluents. Among the advanced oxidation processes, ozone/UV/H2O2 treatment is more efficient for decolouration than other treatments in all the dye effluents except in Acid Red 88, where ozone/UV treatment shows better decolouration than the other processes. Acid dyes possessing only naphthalene rings in its structure undergo faster decolouration than the dyes with the combination of benzene and naphthalene rings. Among the dyes studied, those with higher number of sulphonic acid groups in its structure are easier to decolour. But on increasing the azo groups in its structure, increasing decolouration time was observed. It was also found that acidic pH and lower salt concentration in the effluents are more efficient for decolouration in all the treatment processes.
Advanced oxidation processes (AOPs), namely the Fenton oxidation, ozonation, electrochemical oxidation, and photocatalysis, are potential alternative techniques for dye removal from textile effluents. Their inherent ability to completely mineralize pollutants including those recalcitrant to biodegradation and to be compatibly integrated in conventional technologies present grounds for consideration of AOPs as alternative wastewater treatment options. Advanced oxidation involves the generation and subsequent reaction of various radicals and reacting species with the target compounds. This chapter discusses the fundamentals and chemistry and efficiencies of the Fenton process, ozonation, electrochemical oxidation, and photocatalysis processes for complete dye removal from wastewater. The reaction mechanisms, performance, and factors affecting efficiency are discussed.
Chlorine was first introduced as a large-scale drinking water disinfectant in Boston, USA, in 1908. Its use, initially in the form of sodium hypochlorite, brought dramatic reductions in the prevalence of water-borne diseases (Bullet al.1990). Elemental chlorine rapidly became the most widely used disinfectant. Currently, water treatment accounts for 6% of chlorine production, or 2.9 million tonnes of 1996’s total global consumption of 48.8 million tonnes (Chemical Week 1998).
Ozonation is a promising technology for the treatment of biorefractory compounds. Parabens belong to a chemical family of apparently innocuous preservatives that have been used in the food and cosmetic industries for several years. Oxidation of different parabens, such as methylparaben (MP), ethylparaben (EP), propylparaben (PP), and butylparaben (BP), was carried out using O3 in ultrapure water. A design of experiments procedure has been carried out in order to optimize the ozonation process as well as to study the interaction between the studied variables: pH and temperature (T). In addition to the application of the single ozonation, ozone-combined processes were studied under the optimal conditions obtained for O3 (namely, pH 8 and T = 20 °C). The tested processes were O3/Fenton, O3/H2O2, O3/UV, O3/UV/H2O2, O3/photo-Fenton, O3/UV/TiO2, and O3/UV/TiO2/H2O2. According to the experimental results, single ozonation is a more effective treatment than O3/H2O2 and O3/Fenton processes. In addition, the introduction of ultraviolet (UV) irradiation results, in all cases, in a faster and more efficient removal of the parabens, because of the contribution of ozone photolysis to the radical-mediated pathway. The most efficient method for the degradation of these emerging pollutants was O3/UV/TiO2/H2O2. The influence of different aqueous matrices (namely, ultrapure water, river water, wastewater treatment plant (WWTP) effluent, and reservoir water) on the removal of the target pollutants has been analyzed. The direct ozonation pathway is the predominant degradation mechanism and a remarkable synergistic effect of bicarbonate ions has been demonstrated.
A polymeric adsorbent with high adsorption capacity was prepared, based on chemical modification of polystyrene, and was used for removal of reactive dye (Remazol Blue 3R) from its aqueous solution. The adsorption capacity was found to be 784 mg g-1 by batch method and 1095 mg g-1 by column method. The effect of pH, contact time, salinity, and concentration of anionic surfactant on the adsorption capacity were also investigated. The experiments reported in this article provide some insights into ways of removing dyes from effluents generated in textile processing. Cost of effluent treatment has become a major concern for the textile industry as disposal of untreated, or under-treated effluent, is no more an option.
An attempt was made to study the effect of presence of inorganic salts namely, sodium carbonate, sodium chloride and sodium sulphate, and their concentrations on decolouration of acid dye effluent by ozonation. Studies have been conducted at different salt concentrations and at alkaline pH on Acid Black 1 dye effluent, having a concentration of 500 μM. It has been found that salt content in the effluent increases the decolouration time of the acid dye effluent. Higher the salt content more is the decolouration time and among the salts, sodium carbonate requires more time for complete decolouration than the sodium chloride and sodium sulphate. Chemical oxygen demand (COD) reduces by 52, 58 and 62% whereas total organic carbon (TOC) reduces by 28, 32 and 33% for the salt present in the effluent, namely sodium carbonate, sodium chloride and sodium sulphate respectively. IR spectra study confirms the formation of acidic by-products during ozonation.
Central composite design experiment is used to study the effect of ozone treatment for acid dye effluents and to optimise the variables such as salt concentration, pH and time, which influence the efficiency of colour and COD removal of dye effluents. Acid Red 88 dye is used for this study and the salt additive sodium sulphate is varied between 5 and 15 g/l, pH is between 3 and 11 and the treatment time is varied between 30 and 360 s. It is observed from the results that the treatment time plays a major role in decolouration and COD removal of the dye effluent. The increasing decolouration efficiency is obtained with increasing treatment time. At neutral pH, the efficiency of ozone is low in terms of decolouration when compared with that at acidic and alkaline pH. Lower salt concentration gives faster decolouration of the effluent while increasing the salt concentration interferes with the decolouration efficiency. Maximum COD removal of 64% is obtained at lower salt concentration in about 195 s at alkaline pH.
In this study, chemical oxygen demand (COD) was removed using different processes containing O3, H2O2, HCO3−, and powder activated carbon (PAC) from the synthetic dye solutions. The effects of the experimental parameters such as temperature, ozone dose, dye concentration, pH, and time on the removal of COD were investigated. The Taguchi method was applied to determine the optimum conditions. An orthogonal array L18 (21 * 37) experimental design plan was selected to define the optimum conditions. In addition, the mechanism of the COD removal was explained on the basis of the results of Fourier transform infrared (FTIR) spectroscopy. To gain information about COD removal mechanism at various pHs, electrophoretic mobilities of particles were measured. The chosen experimental parameters and their ranges are: (0–39 mM); temperature (18–70 °C); ozone dose (164–492 mg/min); dye concentration (200–600 ppm); PAC (0–1.5 g); H2O2 (0–0.056 mM); pH (3–12); and time (10–30 min). Under these optimum conditions, it was found that the COD removal efficiency from the synthetic dye solutions was 98%.
The main objectives of this research are to investigate characteristics of ozone solubility due to low solubility of conventional bubbles-ozone generators, evaluate the treatment characteristics of reclaiming textile wastewater for industrial water by means of micro/nano bubbles-dissolved ozone flotation(MNB-DOF) process. The textile wastewater used in this research was obtained from final effluent of the textile wastewater in B city. There is a 400L reactor which consists of a micro-nano bubble system and a ozone generator for experiments. As a result of generating micro-nano bubbles (below ) by using of MNB-DOF process, it improved ozone solubility due to higher ozone transfer rates. Consequently, the shorter ozonation time clearly indicates the lower power costs. The reported results clearly indicated that MNB-DOF process can be effectively and inexpensively. Results of the experiments through MNB-DOF process in this study satisfy all reclaiming standards as industrial water: pH 6.5~8.5, SS 10 mg/L or below, ) 6 mg/L or below, turbidity 10 NTU or below, Coliforms 1,000/100 mL or below. Therefore there is a possibility of the reclaiming of the textile wastewater as industrial water.
Rosolic acid has been used as model compound to check the efficiency of different advanced oxidation processes in the abatement of dyestuffs having triphenylmethane structure. Ozone is very effective; even at low flows (17 × 10−3 min−1 for an ozone flow of 0.2 g h−1) important degradation rates have been obtained. This effect is not enhanced by UV irradiation. On the other hand, different solar photocatalysts have been employed, namely Fe(III), Cr(III), Cr(VI) and TiO2. The best results are obtained using Fe(III), as under this experimental conditions, nearly complete elimination of the dye could be accomplished; however, TiO2 has also shown a good performance. The reaction has been scaled-up using a solar plant for water detoxification with rather promising results.
Investigations carried out to study the feasibility of application of ozone technology for decolouration, toxicity and towards recycling of acid dye effluents for dyeing of silk fabric are reported in this paper. The dyes Acid Red 88, Acid Red 18, Acid Orange 7, Acid Orange 10 and Acid Red 73 were used in this study. The used dye baths were treated with ozone till complete colour removal and reused. For all the dyes two successive recycling processes were carried out. Characteristics of effluents and ozone treated effluents were assessed in terms of total dissolved solids (TDS) and chemical oxygen demand (COD). Gambusia affinis was used for the bioassay tests to find the LC50 value of the treated effluents. The effect of recycling on quality of dyeing was determined using colour difference (ΔE*) and relative unlevelness index (RUI). This study reveals that treatment of acid dye effluents with ozone does not have an effect on TDS reduction. But it reduces the COD of effluents including the effluents obtained in recycling processes. The toxicity of the ozone treated effluents increases with increasing time. A dye having a greater number of sulphonic acid groups in its structure reveals higher toxicity. Resulting effluents from the application of Acid Red 88 and Acid Red 73 on silk fabric can be recycled twice and those from Acid Red 18 and Acid Orange 10 can be recycled once with acceptable ΔE* values. Acid Orange 7 effluent is found to be unsuitable for recycling because of its higher colour difference values. The levelness of the shade determined on the basis of RUI, produced on the silk fabric in the recycling processes, is either excellent or good in all the cases, which include those producing higher colour difference.
It is necessary to study the effect of dyebath additives on decolorization efficiency in order to optimize ozone-based decolorization processes as the consumption of ozone can be reduced through selecting ozone favorable additives. The effect of 5 dyebath additives viz. electrolytes (sodium chloride and sodium sulfate), chelating agent (ethylene diamine tetra acetic acid or EDTA), reducing agent (sodium dithionite), optical brightener (Uvitex BHT), and dispersing agent (Zetex DNVL) was investigated. All of the additives showed synergistic effect as addition of sodium chloride, sodium dithionite and Zetex DN-VL markedly improved decolorization efficiency, but EDTA and optical brightener showed negative effect. Sodium sulfate did not show any positive or negative effect on decolorization efficiency.
The decolourisation of aqueous solutions of dyes by ozonation in the presence of hydrogen peroxide, potassium permanganate or Ferral using a bubble column reactor was investigated. Addition of hydrogen peroxide in the ozonation reaction of dyes did not affect its decolourisation efficiency. The addition of potassium permanganate considerably increased the decolourisation efficiency during ozonation of all of the dyes studied. Ferral showed excellent catalytic activity under acidic conditions but in alkaline conditions its catalytic activity diminished. The effect of the ozonation on COD was also monitored and was found to be highly effective in reducing the COD of aqueous dye solutions. In addition to studying the effect of addition of hydrogen peroxide, potassium permanganate or Ferral on the ozonation of aqueous solutions of individual dyes, tests were carried out on effluent from a commercial dyeing unit. Copyright © 2005 Society of Chemical Industry
The decolorization of aqueous solutions of textile dyes by Ferral-catalyzed ozonation using a bubble-column reactor was investigated. The optimum catalyst concentration and pH for decolorization was determined. Experimental results show that Ferral-catalyzed ozonation can be an effective method for decolorization of various aqueous dyes. Ferral showed their catalytic activity at highly acidic conditions with considerable reduction of chemical oxygen demand (COD).
Various processes including O3, powder activated carbon (PAC) adsorption, , O3/H2O2 and O3/PAC were used in order to remove dye and chemical oxygen demand (COD) from synthetic wastewater containing Bomaplex Red CR-L dye in a semi-batch reactor. These processes rapidly removed the dye and COD from dye solution. The dye removal efficiency was over 99% for a reaction period of 30 min for all the processes. It was observed that PAC adsorption and O3/PAC processes were considerably more effective than ozonation process for the removal of COD from dye solution. The COD removal efficiency of O3/PAC was higher than PAC adsorption process. O3/PAC process was considerably effective to remove COD from dye solutions despite using less amount of PAC (approximately four times less than one used for PAC adsorption) for the same amount of COD removal with a higher efficiency. process positively affected the COD removal efficiency, whereas O3/H2O2 process negatively affected the COD removal efficiency as compared to the ozonation process alone. In addition, the yield and mechanisms of dye removal were also explained on the basis of the results of Fourier transform infrared spectroscopy (FTIR). It was concluded that the O3/PAC process is a highly efficient process to remove dye and COD from synthetic textile wastewaters as compared to the other processes.
Ozonation in batch experiments were conducted at elevated temperatures to study the influence of temperature on the efficiency of ozonation. The effect of temperature on ozonation was determined by measuring the extent of colour removal and the reduction of chemical oxygen demand (COD) and total organic carbon (TOC) of a textile waste effluent. It was found that increasing the temperature causes a decrease in the levels of colour, COD and TOC. Complete mineralisation of the dye molecule, however, did not occur to an appreciable extent. The efficiency of colour removal was 71.3%, whilst the COD and TOC reduction efficiency was 20.3 and 19.3%, respectively, at the highest temperature studied (50 °C). The removal efficiency of COD, however, did not improve significantly when the temperature was increased from 40 to 50 °C.
In this study, the possibility of recycling of reactive dye bath for dyeing of cotton fabric after decolouration using oxidation technique was assessed. Cold brand reactive dyes namely Red 5MR and Golden Yellow MR were used and the oxidation was carried out by ozone. The dyed effluents were reused five times. Time required for decolouring the dye effluent and the effect of decoloured dye effluent on tonal variation of the cotton fabric were analysed. Ozone was found to be more effective on decolouring the dye effluent. The samples produced from the decoloured dye effluents were examined by comparing the spectral reflectance values of the samples with control using colour difference (ΔE∗) and relative unlevelness index values. Based on the colour reproduction ability, it has been found that effluents produced in Red 5MR and Golden Yellow MR can be recycled thrice. The levelness of the shade produced in the recycling of effluents is either excellent or good in all the cases, which includes the samples that produce higher colour difference.
We have studied the decomposition and decoloration of 4-(2-Hydroxynaphthylazo) benzenesulfonic acid sodium salt (AO7, acid dye) as a model for textile wastes by using a flow-type subcritical water system. The operating temperature was ranged from 180 to 374 °C at 10–25 MPa at a wide range of residence time. The pressure (up to 25 MPa) did not affect the decomposition reactions. AO7 completely decomposed at higher temperatures and or longer residence times. The main products from decomposition of AO7 were found to be 2-naphthalenol, phenol, 1,1′-Binaphthalene-2,2′-diol, and N-(phenylmethylene)benzenamine. In order to identify the decomposition pathways, the products were also individually treated under a batch type subcritical water conditions. We found that 2-naphthalenol underwent to further decomposition to 1,1′-Binaphthalene-2,2′-diol during the subcritical water reaction. Other decomposition products resulted from the decomposition of directly AO7. Kinetic model of the subcritical water reaction was developed by considering major products. The kinetic constants obtained from the proposed reaction pathway showed good agreement with experimental results.
Central composite design experiment is used to study the effect of ozone treatment for acid dye effluents and to optimise the variables such as salt concentration, pH and time, which influence the efficiency of colour and COD removal of dye effluents. Acid Red 88 dye is used for this study and the salt additive sodium sulphate is varied between 5 and 15 g/l, pH is between 3 and 11 and the treatment time is varied between 30 and 360 s. It is observed from the results that the treatment time plays a major role in decolouration and COD removal of the dye effluent. The increasing decolouration efficiency is obtained with increasing treatment time. At neutral pH, the efficiency of ozone is low in terms of decolouration when compared with that at acidic and alkaline pH. Lower salt concentration gives faster decolouration of the effluent while increasing the salt concentration interferes with the decolouration efficiency. Maximum COD removal of 64% is obtained at lower salt concentration in about 195 s at alkaline pH.
The environmental problems associated with textile activities are represented mainly by the extensive use of organic dyes. A great number of these compounds are recalcitrant and shown carcinogenic or mutagenic character. In this work three processes were studied for degradation of an anthraquinone dye (C.I. reactive blue-19). The ozonation process leads to complete decolorization with a very short reaction time; however, effective mineralization of the dye was not observed. The enzymatic process promotes quick decolorization of the dye; nevertheless, maximum decolorization degrees of about 30% are insignificant in relation to the decolorization degree achieved by the other processes. The best results were found for the photocatalytical process. The use of ZnO or TiO2 as photocatalysts, permits total decolorization and mineralization of the dye with reaction times of about 60 min.
Emulsion Liquid Membrane (ELM) is one of the process that has very high potential for industrial wastewater treatment of dyes. In this research, Red 3BS dye was extracted from simulated wastewater using Tridodecylamine as the carrier agent, sodium hydroxide as the stripping agent, kerosene as the diluent and span 80 was used as emulsifier. The important parameters affecting the Emulsion Liquid Membrane (ELM) extraction process including external phase concentration, treat ratio (emulsion/ external phase), concentration of carrier and agitation speed were investigated. The results show that the Red 3BS dye can be extracted almost 70% from simulated wastewater. The highest Red 3BS dye extraction was obtained by using 0.07 M Tridodecylamine, 5% (w/v) Span 80, 250 rpm agitation speed, 0.5 M thiourea in 1.0 M sodium hydroxide as the stripping agent, 1:3 treat ratio and kerosene as the diluent. As a conclusion, the Emulsion Liquid Membrane has a high potential in the extraction of dye from wastewater.
Decomposition and decoloration of 4-(2-Hydroxynaphthylazo) benzenesulfonic acid sodium salt (acid orange 7) was studied as a model for textile wastes using a flow-type sub-critical water system. The experiments were performed in the temperature ranging from 180 to 374 °C at pressure range of 10-25 MPa. The main products from decomposition of acid orange 7 were found to be 1,1'-Binaphthalene-2,2'-diol, 2-naphthalenol, phenol, and N-(phenylmethylene)benzenamine. In order to identify the decomposition pathways, the products were also individually treated under a batch type sub-critical water condition. It was found that 2-naphthalenol underwent to further decomposition to 1,1'-Binaphthalene-2,2'-diol during the sub-critical water reaction. Other decomposition products were resulted from decomposition of directly acid orange 7.
Wastewaters from textile industry contain organic dyes, which cannot be easily treated by biological methods. Therefore, pretreatment by an advanced oxidation process (AOP) is needed in order to produce more readily biodegradable compounds and to remove color and chemical oxygen demand (COD) simultaneously. In this research, ozone (O3) is combined with hydrogen peroxide (H2O2) for the advanced oxidation of an azo dye solution, namely aqueous solution of Acid Red 151, which is called as Peroxone process. The aim of the study is to enhance the ozonation efficiency in treating the waste dye solution. The effects of pH, initial dye and initial ozone concentrations and the concentration ratio of initial H2O2 to initial O3 on color and COD removals were investigated. Also, the kinetics of O3-dye reaction in the presence of H2O2 was approximately determined. As a result of the experimental study, it was seen that an increase in the initial dye concentration at a constant pH and initial ozone concentration did not change the COD % removal significantly, from a statistical analysis of the data. The results obtained at pH values of 2.5 and 7 gave higher oxidation efficiencies in terms of color and COD removals compared to those at pH of 10. The best initial molar ratio of H2O2 to O3 was found to be 0.5, which yielded highest treatment efficiency for each pH value studied. The results of the excess dye experiments suggest that the ozonation of Acid Red 151 follows an average first order reaction with respect to ozone at pH=2.5 and pH=7 whereas it is around 0.56 at pH=10. By Initial Rate Method, the orders with respect to individual reactants of O3 and dye were determined as one, the total order of the reaction being two for all the studied pH. As a conclusion, a further study of the peroxone process at a pH of 10 can be recommended to determine the reaction kinetics and mechanism at this pH, where radicals play an important role.
Decolorization of a number of aqueous water-soluble acid and reactive dyes was investigated to cover a range of structural types. The effect of various parameters including pH, initial concentration of dyes, applied ozone dose and the influence of the substituent groups of the dye were investigated. Ozonation was found effective for decolorization of all types of dyes studied. The total ozone consumption for decolorization varied from dye to dye depending upon their chemical structure. Ozonation reduced COD of the dye solution to a small extent, which was affected by the number of azo groups in the dye. The pH had a mixed effect on decolorization efficiency as some dyes showed high decolorization efficiency with increasing pH and decolorization of some dyes was independent of pH. Substituent groups attached to the dye structure affected decolorization efficiency in the ozonation process.
The ozonation kinetics of an azo dye, namely, Acid Red-151 was investigated. Effects of pH, initial ozone, and initial dye concentrations on the ozonation of the dye were studied. The reaction orders were found to be one with respect to both ozone and dye concentrations for the studied pH range of 2.5-10. The reaction rate constants were obtained as 125.8, 95.4, 87.9, and 129.9 L mmol(-1) min(-1) at the pH values of 2.5, 5, 7, and 10, respectively. The initial ozonation rate decreased with the increasing pH from 2.5 to 7. A further increase of pH to 10, yielded higher initial rates compared to the rates at pH = 5 and 7. However, increasing the initial dye and ozone concentrations increased the initial ozonation rate of the dye. Depending upon the initial conditions, up to 99% decolorization was achieved by ozonation in the present system. Also, chemical oxygen demand (COD) was partially reduced by ozone; the highest COD reduction being 58%, occurred at pH = 2.5, initial ozone and dye concentrations being 0.0360 and 0.0440 mmol/L, respectively.
The electrochemical performance of pure Ti-Pt/beta-PbO2 electrodes, or doped with Fe and F (together or separately), in the oxidation of simulated wastewaters containing the Blue Reactive 19 dye (BR-19), using a filter-press reactor, was investigated and then compared with that of a boron-doped diamond electrode supported on a niobium substrate (Nb/BDD). The electrooxidation of the dye simulated wastewater (volume of 0.1 l, with a BR-19 initial concentration of 25 mg l(-1)) was carried out under the following conditions: current density of 50 mA cm(-2), volume flow rate of 2.4 l h(-1), temperature of 25 degrees C and electrode area of 5 cm2. The performances of the electrodes in the dye decolorization were quite similar, achieving 100% decolorization, and in some cases 90% decolorization was achieved by applying only ca. 0.3 A h l(-1) (8 min of electrolysis). The reduction of the simulated wastewater organic load, monitored by its total organic carbon content (TOC), was greater for the Ti-Pt/beta-PbO2-Fe,F electrode obtained from an electrodeposition bath containing 1 mM Fe3+ and 30 mM F-. In this case, after 2 h of electrolysis the obtained TOC reduction was 95%, while for the pure beta-PbO2 and the Nb/BDD electrodes the reductions were 84% and 82%, respectively.
Kinetic studies on the self-decomposition of ozone in water, the decomposition of CN- and CNO-, and the decolorization of several dyes by ozone were performed over a wide range of pH using a stopped-flow apparatus under homogeneous conditions at 298 K. The rate of selfdecomposition of ozone was measured in the pH range from 1 to 13.5, and it was found that in the pH range above 8 the rate was expressed by -d[03]/dt=314 [03] [OH-]0.88while in the acidic region the concentration dependence of the rate was complicated, and a simple rate expression could not be obtained. The rate of decomposition of CN- by ozone was expressed by -d[CN-]/dt=310 [O3]0.8 [CN-]0.55 (9.4<pH<11.6)and the rate of decomposition of CNO- was found to be much slower than that of CN-. The decolorization rates of naphthol yellow and methylene blue followed second-order kinetics. Rate constants are presented.
The photofading in aerated solution of 4-diethylaminoazobenzene (1) and of the corresponding 4′-methoxy (2) and 4′-nitro derivatives (3) under various conditions has been examined and compared with naphthol derivatives which are subject to azo–hydrazone tautomerism. Dyes (1)–(3) are efficient physical quenchers of singlet oxygen but show very little chemical reactivity with oxygen. Their ability to sensitize oxygen is low. More efficient photo-oxidative fading is observed upon short-wavelenght irradiation, which results from the reaction of oxygen with hydrazyl radicals, formed by initial hydrogen abstraction from the solvent.
4-Diethylaminoazobenzene (2) and 4-diethylamino-4′-methoxyazobenzene (3) undergo geometrical isomerization with a quantum yield of almost unity by irradiation in the visible region, and, with lower efficiency, by irradiation at a shorter wavelength or sensitization both with high and low energy hydrocarbons. These dyes are also photoreduced, this time however only by irradiation at λ 313 nm and with low quantum yield (10–4–4 × 10–2). Photoreduction also takes place by energy transfer from high energy sensitizers as well as by radical initiation by ketones. It is concluded that the lowest singlet and triplet states of these azobenzene derivatives, which are reasonable models for commercially useful monoazo-dyes, are only capable of geometrical isomerization, whereas hydrogen abstraction takes place from the high-lying triplet state of both the trans- and cis-configuration of these dyes.
Hydroxyl radicals are formed upon the hydroxide-ion catalyzed decomposition of ozone in water as is shown by the relative rates with which organic substrates compete with each other for consuming the oxidative intermediates. The yield of the decarboxylation of 14C-labelled benzoic acid indicates that up to 0.55 ± 0.08 mol of hydroxyl radicals may be produced from 1 mol ozone at pH 10.5. Published data on hydroxyl radical-reactions can now be applied to describe oxidations initiated by ozonation. Parameters influencing the prior ozone decomposition and protective effects of radical scavengers, such as carbonates, have to be accounted for when optimizing the processes. The solutes present in water influence appreciably the rate of the chain reaction leading to the decomposition of ozone.
An investigation of the effects of ozone on ammonia in municipal wastewaters is described and discussed relative to the application of ozone for advanced waste treatment. Ammonia is oxidized completely to nitrate, thereby eliminating the nitrogenous oxygen demand of the waste. In buffered solutions of ammonium chloride, the reaction is first-order with respect to the concentration of ammonia, and the rate increases with increasing pH over the range 7–9, and with increasing ozone partial pressure. In wastewater, the reaction is particularly sensitive to pH, with effective removal of ammonia occurring only if the pH of the wastewater can be maintained alkaline. Due to the elevated pH's required for effective ammonia oxidation, ozonation is especially attractive in conjunction with lime clarification and precipitation of phosphate. Application of ozone for disinfection purposes requires recognition of the ozone demand exerted by ammonia.
The oxygen uptake and the dissimilatory nitrate reduction by anaerobically grown cells of a denitrifying Alcaligenes strain, occurring in floc form or in suspension, were studied at different oxygen concentrations in the surrounding medium. When the oxygen concentration in the medium fell below 1·5 mg l−1, the nitrate reduction by the cells within flocs increased considerably. The cells in suspension showed an increased nitrate reduction when the oxygen concentration was below 0·1 mg l−1. When anaerobically grown cells had been aerated for 24 h in a nitrogen-free medium, the cells became sensitive to respiration inhibition by nitric oxide, resulting from nitrate reduction. This gave rise to an increased nitrate reduction below 2·5 mg oxygen l−1 when the cells were aggregated in flocs and below 0·1 mg oxygen per litre when the cells were in suspension. The nitrate reduction by the denitrifying, floc-forming pure culture was compared with that of activated sludge flocs.
The Societyse Dyers and Clourists. American Association of Textile Chemists and Clorists, 3rd
- Colour Index