**3. Results**

*Textile Industry and Environment*

*2.4.2 UV-Vis spectroscopy*

*2.4.3 FTIR spectroscopy*

*2.4.4 Atomic absorption spectroscopy*

*2.4.5 Reflectance spectrophotocolorimetry*

measured, in order to indirectly determine the formation of ionic species. The latter was used as a criterion to verify the separation of the groups capable of forming

Preliminary information about the discoloration and decomposition of textile dyes in water was obtained from the variation of absorbance in the UV-Vis range, between 190 and 700 nm, with a Cary 50 (Varian) spectrophotometer. The discoloration of RR141 was analyzed at 544 nm and discoloration of RB160 at 615 nm. Similarly, the degradation of RR141 was analyzed at 288 nm, and the degradation of RB160 at 280 nm. These wavelengths correspond to the absorbance maxima of the

An FTIR analysis was carried out to obtain information about the functional groups that are formed and disappear in the course of ozonation. For this purpose, a PerkinElmer Series 200 equipment was used. The samples of dye subjected to ozonation at intervals of 4 h, up to a maximum of 12 h, were dried and prepared in

Sodium ion monitoring was carried out through the ozonation cycles of the samples prepared for dyeing, using an AA3300 spectrophotometer (PerkinElmer). The purpose of this analysis was to directly verify that ozonation did not have any adverse effect on the inorganic salt content necessary for subsequent dyeing.

With the series of samples of model solutions of 50 mg/L of concentration at which the cycles of contamination with dye and subsequent ozonation were carried out up to five times, dyeing tests were made with reactive and direct dyes applied on samples of cotton, for determining the feasibility of reusing water pretreated with ozone in dyeing processes of cellulosic materials. The dyes were made on cloth prepared for this purpose. A dyeing was made with each water sample, and the difference in color kept by the samples of cloth dyed with the pretreated water was determined in relation to a reference standard, that is, a sample of the same type dyed using distilled water and maintaining the other constant conditions. The test was carried out according to the AATCC method 173-2005 of the American Association of Textile Chemists and Colorists (AATCC) called Calculation of Small Color Differences for Acceptability, which is of extended application in the textile

A Color Eye 7000-A spectrophotometer (Gretag-Macbeth) with color integration sphere and colorimetry software was used. This equipment simulates the color appreciation by the human eye and translates it into a value or coefficient of color difference (ΔE) that, according to the method used, should not be greater than unity, that is, ΔE < 1.0. This value less than 1.0 represents a color difference that a common observer could not perceive, while ΔE > 1.0 is a color difference that any person can detect and, therefore, implies that the result of a dye is not

ions, located in the molecules of the dyes, during the ozonation process.

compounds studied within the visible and UV ranges, respectively.

the form of a tablet mixed with KBr, to effect the measurements.

**40**

industry [9].

acceptable [9].

In all cases, the discoloration was carried out during the first hour, despite the low concentration of ozone used. The addition of inorganic auxiliaries accelerates the reaction of ozone with textile dyes. **Figure 4** presents the variation of the UV-Vis spectra for the RR141 during 60 min of ozonation. From the variation of the spectra of the RR141 dye during ozonation, it can be concluded that this compound is rapidly destroyed under the action of ozone. The tendency to discoloration during the ozonation process is very similar for both dyes. The studied compounds are rapidly destroyed under the action of ozone. **Figure 5** shows the discoloration of RB160 for three different concentrations at 615 nm.

The influence of the by-products of the degradation of the dyes on the dyes made with the treated water depends not only on the accumulation of these through the cycles of ozonation contamination but also of the dyeing class of the dye used in the dyeing with the treated water, as well as the chemical constitution of the latter. The results obtained in this study showed that for both dyes studied, analyzed at 50 mg/L, the color disappears after 30 min of ozonation.

**Figure 6** shows the discoloration for the studied dyes at 50 ppm. Based on the preliminary analysis, it can be stated that the discoloration of the RR141 and RB160 is almost identical.

**Figure 4.** *Variation of the UV-Vis spectrum of RR141 during ozonation.*

RR141 has four amino groups and seven sulfonic groups, while RB160 has five amino groups and five sulfonic groups. Thus, taking into account the proportion between sulfonic groups and amino groups in the dye molecules, their reactivity and molecular weight, the observed discoloration rates are consistent. **Figure 7** shows the degradation of the dyes studied, during 60 min of ozonation and with an initial concentration of 50 mg/L.

The by-products of the two dyes require for their destruction of ozonation times greater than the 30 min necessary for the discoloration. Both curves are almost identical.

These results agree with the conclusions obtained by other researchers, who associate the presence of amino groups in the molecules of the dyes to a very fast reaction with ozone, while the presence of sulfonic groups increases the resistance

**43**

**Figure 7.**

**Figure 6.**

and formic acids [11, 12].

*Degradation of the dyes studied at 50 mg/L.*

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation…*

of the dye toward the attack with ozone [7, 11]. The composition of the intermediates and final ozonation products depends on the chemical structures of the dyes. Phenols, quinones, hydroquinones, and acids such as phthalic, muconic, fumaric, maleic, etc. have been identified among ozone intermediates. The final products that have been identified are sulfate and nitrate ions, elemental nitrogen, and oxalic

If one takes as a starting point the mechanisms proposed in the literature for the degradation of organic compounds, the formation of maleic acid precedes the formation of oxalic acid and is carried out from the first minutes of ozonation. **Figure 8** shows the variation of the pH during ozonation of the dyes [7].

*DOI: http://dx.doi.org/10.5772/intechopen.81468*

*Discoloration of the compounds studied at 50 mg/L.*

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation… DOI: http://dx.doi.org/10.5772/intechopen.81468*

**Figure 6.** *Discoloration of the compounds studied at 50 mg/L.*

*Textile Industry and Environment*

**42**

identical.

**Figure 5.**

**Figure 4.**

*Variation of the UV-Vis spectrum of RR141 during ozonation.*

initial concentration of 50 mg/L.

*Influence of concentration on discoloration of RB160 during ozonation.*

RR141 has four amino groups and seven sulfonic groups, while RB160 has five amino groups and five sulfonic groups. Thus, taking into account the proportion between sulfonic groups and amino groups in the dye molecules, their reactivity and molecular weight, the observed discoloration rates are consistent. **Figure 7** shows the degradation of the dyes studied, during 60 min of ozonation and with an

The by-products of the two dyes require for their destruction of ozonation times

greater than the 30 min necessary for the discoloration. Both curves are almost

These results agree with the conclusions obtained by other researchers, who associate the presence of amino groups in the molecules of the dyes to a very fast reaction with ozone, while the presence of sulfonic groups increases the resistance

**Figure 7.** *Degradation of the dyes studied at 50 mg/L.*

of the dye toward the attack with ozone [7, 11]. The composition of the intermediates and final ozonation products depends on the chemical structures of the dyes. Phenols, quinones, hydroquinones, and acids such as phthalic, muconic, fumaric, maleic, etc. have been identified among ozone intermediates. The final products that have been identified are sulfate and nitrate ions, elemental nitrogen, and oxalic and formic acids [11, 12].

If one takes as a starting point the mechanisms proposed in the literature for the degradation of organic compounds, the formation of maleic acid precedes the formation of oxalic acid and is carried out from the first minutes of ozonation. **Figure 8** shows the variation of the pH during ozonation of the dyes [7].

#### **Figure 8.** *pH variation during ozonation for RR141 at 50 mg/L.*

The decrease of the pH in the ozonation of the dyes contributes to verify, in an indirect way, the formation of organic acids during the ozonation process. It is known that during the first minutes of ozonation, the formation of maleic acid is observed, the concentration of which then decreases markedly. However, the pH continues to decrease due to the subsequent formation of oxalic acid, which continues to form and accumulate throughout the ozonation process, although at a slower rate. It has been found that ozonation induces the denaturation and desulfurization of sulfo- and nitrophenols in the first stage of the reaction [13]. The increase in the conductivity of the dye solutions in ozonation serves as an indirect confirmation of the formation and accumulation of sulfate and nitrate ions, which in turn confirm the denitration and desulphurization of the dyes in the first step of the reaction. **Figure 9** shows the variation of conductivity for RR141 during ozonation [7].

During the process of dyeing textile materials with reactive dyes, the addition of large amounts of salt is necessary to promote the incorporation of the dye into the fiber. **Figure 10** shows the effect of salt addition on the ozonation of RR141 at 50 mg/L.

Once the dye is inside the fiber, it is necessary to add alkali, in order to promote the formation of the covalent bonds characteristic of this class of compounds. **Figure 11** shows the effect of adding sodium carbonate during ozonation for RR141 and **Figure 12** shows the effect of sodium hydroxide.

Due to this, the effluents of the dyeing with reactive dyes present considerable quantities of both salts and alkalis [7]. To study the influence of these inorganic substances, solutions of 50 mg/L of each of the dyes were prepared, and variable amounts of Na2SO4, Na2CO3, and NaOH were added to them before they were subjected to ozonation. The presence of inorganic auxiliaries in the dye solution has influence on the kinetics of discoloration. However, the concentration of these salts has no important influence on the kinetics. As an example, for RR141 and firstorder reaction, rate constant is 0.0264 min<sup>−</sup><sup>1</sup> without addition of sodium sulfate, 0.0299 min<sup>−</sup><sup>1</sup> with addition of 10 g/L of salt, and 0.0303 min<sup>−</sup><sup>1</sup> with 20 g/L.

During the process of partial oxidation of the dyes with ozone, intermediate products are formed. These products accumulate through the recirculation cycles of the treated water and can influence the quality of the dyes made. **Figure 13** shows the accumulation of partial oxidation products through the consecutive recirculations for RR141.

**45**

**Figure 9.**

**Figure 10.**

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation…*

The water recycled up to five times by the procedure described in the methodology was used to make dyes on cotton cloth with direct dyes (AD80, AD50, and RD23) and with reactive dyes (AR84, RR141, and NR5). The determination of the quality of the coloration of these dyes was carried out by means of the AATCC method Test Method 173-2005 Calculation of Small Color Differences for Acceptability [9]. **Figure 14** illustrates the behavior of dyes made with direct dyes and reagents, in terms of the color difference coefficient (ΔE), when using RR141 solutions treated with ozone with up to five recirculation cycles of the pretreated water. A value of ΔE less than one means that the quality of the dye is acceptable. **Figure 14** shows that water contaminated with RR141 and pretreated can be used for dyeing processes with direct dyes during four cycles tested without significantly affecting the quality of the dye. The dye that best behaves in this case is Direct Blue 80 (AD80), which belongs to group B of the SDC classification, while Direct Yellow 50 (AD50) and Direct Red 23 (RD23), belonging to groups A and C, respectively, are very similar in their behavior. Regarding the reactive dyes, it is observed that it can be dyed with them without the coloration being affected for

*DOI: http://dx.doi.org/10.5772/intechopen.81468*

*Conductivity variation during ozonation for RR141 at 50 mg/L.*

*Effect of salt addition during ozonation for RR141.*

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation… DOI: http://dx.doi.org/10.5772/intechopen.81468*

#### **Figure 9.** *Conductivity variation during ozonation for RR141 at 50 mg/L.*

*Textile Industry and Environment*

*pH variation during ozonation for RR141 at 50 mg/L.*

The decrease of the pH in the ozonation of the dyes contributes to verify, in an indirect way, the formation of organic acids during the ozonation process. It is known that during the first minutes of ozonation, the formation of maleic acid is observed, the concentration of which then decreases markedly. However, the pH continues to decrease due to the subsequent formation of oxalic acid, which continues to form and accumulate throughout the ozonation process, although at a slower rate. It has been found that ozonation induces the denaturation and desulfurization of sulfo- and nitrophenols in the first stage of the reaction [13]. The increase in the conductivity of the dye solutions in ozonation serves as an indirect confirmation of the formation and accumulation of sulfate and nitrate ions, which in turn confirm the denitration and desulphurization of the dyes in the first step of the reaction. **Figure 9** shows the variation of conductivity for RR141 during ozonation [7].

During the process of dyeing textile materials with reactive dyes, the addition of large amounts of salt is necessary to promote the incorporation of the dye into the fiber. **Figure 10** shows the effect of salt addition on the ozonation of RR141 at

Once the dye is inside the fiber, it is necessary to add alkali, in order to promote

Due to this, the effluents of the dyeing with reactive dyes present considerable quantities of both salts and alkalis [7]. To study the influence of these inorganic substances, solutions of 50 mg/L of each of the dyes were prepared, and variable amounts of Na2SO4, Na2CO3, and NaOH were added to them before they were subjected to ozonation. The presence of inorganic auxiliaries in the dye solution has influence on the kinetics of discoloration. However, the concentration of these salts has no important influence on the kinetics. As an example, for RR141 and first-

without addition of sodium sulfate,

with 20 g/L.

the formation of the covalent bonds characteristic of this class of compounds. **Figure 11** shows the effect of adding sodium carbonate during ozonation for RR141

with addition of 10 g/L of salt, and 0.0303 min<sup>−</sup><sup>1</sup>

During the process of partial oxidation of the dyes with ozone, intermediate products are formed. These products accumulate through the recirculation cycles of the treated water and can influence the quality of the dyes made. **Figure 13** shows the accumulation of partial oxidation products through the consecutive recircula-

and **Figure 12** shows the effect of sodium hydroxide.

order reaction, rate constant is 0.0264 min<sup>−</sup><sup>1</sup>

**44**

50 mg/L.

**Figure 8.**

0.0299 min<sup>−</sup><sup>1</sup>

tions for RR141.

#### **Figure 10.** *Effect of salt addition during ozonation for RR141.*

The water recycled up to five times by the procedure described in the methodology was used to make dyes on cotton cloth with direct dyes (AD80, AD50, and RD23) and with reactive dyes (AR84, RR141, and NR5). The determination of the quality of the coloration of these dyes was carried out by means of the AATCC method Test Method 173-2005 Calculation of Small Color Differences for Acceptability [9]. **Figure 14** illustrates the behavior of dyes made with direct dyes and reagents, in terms of the color difference coefficient (ΔE), when using RR141 solutions treated with ozone with up to five recirculation cycles of the pretreated water. A value of ΔE less than one means that the quality of the dye is acceptable.

**Figure 14** shows that water contaminated with RR141 and pretreated can be used for dyeing processes with direct dyes during four cycles tested without significantly affecting the quality of the dye. The dye that best behaves in this case is Direct Blue 80 (AD80), which belongs to group B of the SDC classification, while Direct Yellow 50 (AD50) and Direct Red 23 (RD23), belonging to groups A and C, respectively, are very similar in their behavior. Regarding the reactive dyes, it is observed that it can be dyed with them without the coloration being affected for

**Figure 11.**

*Effect of sodium carbonate addition during ozonation for RR141.*

**Figure 12.** *Effect of sodium hydroxide addition during ozonation for RR141.*

up to four cycles. Even though the NR5 presents differences of ΔE > 1.0 from the second cycle, the results can be considered acceptable, since this dye is generally used at concentrations above 5% of the weight of the textile material, which makes it possible to hide the differences of coloration.

During the dyeing processes with reactive dyes, important quantities of sodium salts, mainly sodium sulfate, are added. The function of this salt is to neutralize the negative charge that the fiber acquires when impregnated with water. This function is performed by the sodium ion [11]. To verify that the sodium ion is not affected by the ozonation process, solutions were prepared as in the case of dye recirculations, with initial concentrations of 50 mg/L, both dye and sodium. The sodium ion content was analyzed by atomic absorption spectroscopy at 303.2 nm. **Figure 15** illustrates the result of the analysis for RR141 [14].

It can be observed that the content of sodium ion does not decrease during ozonation, which is the condition for the process to have an economic attraction

**47**

**Figure 14.**

**Figure 13.**

at commercial concentration.

only one band at 3450 cm<sup>−</sup><sup>1</sup>

another one at 1140 cm<sup>−</sup><sup>1</sup>

amines. **Figure 16** shows that region for RR141. In the region between 600 and 2000 cm<sup>−</sup><sup>1</sup>

absorption bands. One of them at 620 cm<sup>−</sup><sup>1</sup>

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation…*

due to the recovery of the salt contained in the exhausted dyeing bath. In fact, the sodium ion content increases slightly, due to the presence of ions of this type in the structure of the dyes and in the salts used in their manufacture to standardize them

A preliminary analysis by FTIR of the changes in the structures of the dyes dur-

; which corresponds to stretches of phenols or aromatic

, of bending of SO3

, of stretching of bond S─O, confirms the desulfonation

, the dyes have several common

, appears

═, together with

ing ozonation was carried out. In the area between 2000 and 4000 cm<sup>−</sup><sup>1</sup>

*Color differences obtained by dyeing cotton by reusing ozonated RR141 solutions.*

*DOI: http://dx.doi.org/10.5772/intechopen.81468*

*Accumulation of products in the ozonation of RR141 with water recirculation.*

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation… DOI: http://dx.doi.org/10.5772/intechopen.81468*

**Figure 13.** *Accumulation of products in the ozonation of RR141 with water recirculation.*

#### **Figure 14.**

*Textile Industry and Environment*

**Figure 11.**

**Figure 12.**

**46**

up to four cycles. Even though the NR5 presents differences of ΔE > 1.0 from the second cycle, the results can be considered acceptable, since this dye is generally used at concentrations above 5% of the weight of the textile material, which makes

It can be observed that the content of sodium ion does not decrease during ozonation, which is the condition for the process to have an economic attraction

During the dyeing processes with reactive dyes, important quantities of sodium salts, mainly sodium sulfate, are added. The function of this salt is to neutralize the negative charge that the fiber acquires when impregnated with water. This function is performed by the sodium ion [11]. To verify that the sodium ion is not affected by the ozonation process, solutions were prepared as in the case of dye recirculations, with initial concentrations of 50 mg/L, both dye and sodium. The sodium ion content was analyzed by atomic absorption spectroscopy at 303.2 nm. **Figure 15**

it possible to hide the differences of coloration.

*Effect of sodium hydroxide addition during ozonation for RR141.*

*Effect of sodium carbonate addition during ozonation for RR141.*

illustrates the result of the analysis for RR141 [14].

*Color differences obtained by dyeing cotton by reusing ozonated RR141 solutions.*

due to the recovery of the salt contained in the exhausted dyeing bath. In fact, the sodium ion content increases slightly, due to the presence of ions of this type in the structure of the dyes and in the salts used in their manufacture to standardize them at commercial concentration.

A preliminary analysis by FTIR of the changes in the structures of the dyes during ozonation was carried out. In the area between 2000 and 4000 cm<sup>−</sup><sup>1</sup> , appears only one band at 3450 cm<sup>−</sup><sup>1</sup> ; which corresponds to stretches of phenols or aromatic amines. **Figure 16** shows that region for RR141.

In the region between 600 and 2000 cm<sup>−</sup><sup>1</sup> , the dyes have several common absorption bands. One of them at 620 cm<sup>−</sup><sup>1</sup> , of bending of SO3 ═, together with another one at 1140 cm<sup>−</sup><sup>1</sup> , of stretching of bond S─O, confirms the desulfonation

#### **Figure 15.**

*Analysis by means of atomic absorption of the presence of sodium ion during the recirculation of water contaminated with RR141.*

**Figure 16.** *Variation of the FTIR spectrum of RR141 during ozonation, between 2000 and 4000 cm<sup>−</sup><sup>1</sup> .*

of the compounds during ozonation. Also, a band at 1050 cm<sup>−</sup><sup>1</sup> , of stretching of C─O bond, and a band located at 1400 cm<sup>−</sup><sup>1</sup> , of COO─ ion stretching, confirm the formation of organic acids. Additionally, the dyes have absorption at 1500 cm<sup>−</sup><sup>1</sup> , corresponding to NO2 formation, and at 1620 cm<sup>−</sup><sup>1</sup> , which indicates the formation of secondary amines.

RR141 show absorption at 760 and 1720 cm<sup>−</sup><sup>1</sup> . The first one corresponds to vibrations of the aromatic ring, while that of 1720 corresponds to the vibration of the -COOH group and indicates the formation of carboxylic acids. **Figure 17** shows region between 600 and 2000 cm<sup>−</sup><sup>1</sup> for RR141 [15].

**49**

**4. Conclusions**

**Figure 17.**

According to the results, we can conclude the following:

*Variation of the FTIR spectrum of RR141 during ozonation, between 600 and 2000 cm<sup>−</sup><sup>1</sup>*

tion is carried out during the first 30 min of treatment.

such as organic acids, if the ozonation time is prolonged.

other factors, such as the dyeing auxiliaries.

tion times (>120 min).

the quality of the dyeing result.

1.The discoloration of the model solutions of RB160 and RR141 dyes by ozona-

*.*

2.The rate of the ozonation reaction for the dyes is different and depends mainly on the chemical structure of the dye used, the initial concentration of this, and

3.In addition to the discoloration, it is possible to decompose the intermediates present in the water, until obtaining biodegradable and nontoxic compounds

4.During the cycles of recirculation of the water, an accumulation of ozonation products is observed. However, these products allow water to be reused for several cycles, depending on the type of dyes used in dyeing with treated water. In addition, such ozonation products can be degraded by longer ozona-

5.A water recirculation scheme was proposed in dyeing processes of textile materials, both with reactive dyes and with direct dyes, which does not affect

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation…*

*DOI: http://dx.doi.org/10.5772/intechopen.81468*

*Chemical and Tinctorial Aspects Related to the Reuse of Effluents Treated by Ozonation… DOI: http://dx.doi.org/10.5772/intechopen.81468*

**Figure 17.** *Variation of the FTIR spectrum of RR141 during ozonation, between 600 and 2000 cm<sup>−</sup><sup>1</sup> .*
