PhotoCatalytic Degradation of Methyl Blue Dye and Enhanced Antibacterial Properties of Treated Wool with ZrCL₄ and Dyeing with Madder

Introduction

Natural dyes or colorants derived from flora and fauna are believed to be safe because of their non-toxic, non-carcinogenic and biodegradable nature. The present trend throughout the world is shifting towards the use of ecofriendly and biodegradable commodities. This leads to increasing demand for natural dyes [1]. Madder is widely distributed in southern and southeastern Europe, the Mediterranean area and in Asia. It is a main source of natural dye producing a variety of anthraquinone pigments in its roots and rhizomes [2–4]. Natural dye madder is not able to create a strong bond with the wool fiber. Therefore, it should be used as a substance for helping create a strong bond between dye and fiber. Mordant is the substance of helping, which the two reasons are important: 1. creates a link with the dye and affect on the color fastness, however, the mordant should be optimized; 2. the mordant effect on the shade therefore wide range of mordant can be achieved wide shads. Nearly all previous research is focused on the enzyme treated and inorganic mordants (AL,Cu, Zn, Ne…) on the wool.

Extracts obtained from many plants have recently gained popularity and scientific interest. Many plants have been used for different purposes, such as food, drugs and perfumery [5]. Researchers have been interested in biologically active compounds isolated from plant species for the elimination of pathogenic microorganisms because of the resistance that microorganisms have built against antibiotics [6].

The genus Rubiais represented in the Turkish flora by five species, one of which is endemic. R. tinctorumgrows in the west, south and south east parts of Europe[7]. Some members of this genus are of economicimportance. Common Madder (R. tinctorumL.)produces anthraquinone pigments in its roots, one of them being alizarin (1,2dihydroxyanthraquinone)which has been used for dyeing textiles since 2000 BC[8]. The underground parts of R.tinctorumhave been used as a natural dye in Turkey[9].

This study was aimed to determine the antimicrobial activity of madder against various microorganisms and the self-cleaning properties of the wool fabrics.

The wool fabric with the weight 1688.55 g/m², width 140 cm was used from Iran Merinos Co. The anionic detergent was used for scouring the wool. The mordant used was zirconium chloride (IV) (ZrCl₄). It was produced by Merck. Also, formic acid from Merck was applied for dyeing process. Powder of Iranian madder roots was used for dyeing of wool fabrics.

Method

The mordanting treatments were carried out before, simultaneously and after the dyeing. Zirconium salt concentrations of %1, %3, %6 and 9% o.w.f. were used and the liquor ratio was 50:1. Following the mordanting treatment, the fabrics were maintained for 1h at a temperature of 85^◦C. Dye solutions were prepared 24 h prior to dyeing by adding madder powder to water (50%o.w.f., liquor ratio 50:1). The dyeing process was started at 40 ^◦C and the temperature was increased to 85 ^◦C over 20 min and then held at that temperature for 1 h; finally, the fabrics were rinsed. The acidic pH was maintained using formic acid.

The chemical compositions of the fabrics were examined by the FTIR spectroscopy [Bomem-MB 100 Series (Hartmann and Broun)rsqb].

Photo Catalytic Degradationof Methyl Blue on Wool Samples

A 5 μl of 5% MB was introduced onto the wool sample and the fabric was irradiated under UV lamp at ambient temperature for 24 and 48h. The distance between the fabric sample and the lamp was 40 cm. The fabrics’ photo catalytic degradation were determined using a Gretagmacbeth COLOREYE 7000A spectrophotometer integrated with an IBM-PC. CIELAB color coordinates (L*, a*, b*, C*, h˚) and color differences (ΔE) of sample were calculated for 10˚ observer and D₆₅ illuminant according to equation 1.

ΔE=[(Δ a*)²+(Δ b*)²+( Δ L*)²]^1/2   (1)

Evaluation of antibacterial efficiency

The antibacterial activity of the treated wool fabric was tested against two bacteria, Staphylococcus aureus (S. aureus), American Type Culture Collection No.6538, as a gram positive bacterium and Escherichia coli, American Type Culture Collection No.11303, as a gram negative bacterium. To this end, some colonies of each bacterium were suspended in a physiologic saline solution (NaCl 0.9% in distilled water at pH 6.5) with concentration of 0.5 Mc Farland. The vials of bacterial suspensions were then incubated with agitation at 37ºC ± 2ºC, 220 rpm for 2 hours. A homogenous suspension of bacteria was prepared and serial dilution was then done in 5 Steps (dilution of 1:100000). A concentration of about 1.5-2Í10³ CFU/ml was applied for the antibacterial testing. The bacteriological culture tubes (ie, 125 Í17 mm glass tubes), containing one piece of the treated wool fabric (10 mmÍ10mm) were sterilized by an autoclave device in moisturized heat (121º C, 15 Ib) for 15-20 minutes. An aliquot of 1cc bacterial suspension and 2^cc of TSB (Tryptic Soy Broth) was then added to every tube and 3 ml was detected in each tube. To ensure that any decrease in bacterial count was due to the exposure to the wool fabrics, one control of the saline solution with TSB, and one control of aliquot with the untreated fabrics including the tubes containing the treated wool fabrics with the bacterial suspensions and the control tubes were incubated at 37ºC for 24h. The samples of 10 µl from each tube were then taken and counted according to the pour plate method. Thus, samples were mixed with melted agar (that decreases the temperature down to 45ºC) and poured. The plates incubated at 37ºC for 24h and the colonies of each plate were counted by a colony counted device to determine the bacteria reduction of the suspensions. The results of the numbers before and after the treatment with the wool fabrics were used to determine the bactericidal effect and the percentage of reduction of bacteria was calculated using the following equation:

Reduction rate (%) = 100 (A-B)/A           (2)

Where R is the bacterial reduction ratio, A is the number of bacterial colonies from the untreated fabrics and B is the number of the bacterial colonies from the treated fabrics.

The infrared spectra of untreated wool as well as the sample mordanted with zirconium salt are shown in Figure 1. The N-H stretching and bending vibrations in wool are usually appeared at 3100-3500 cm^-1 and 1550-1640 cm^-1 respectively, depending on the type of amide (primary and secondary), chemical environment (solid and liquid) and intra- or inter-molecular hydrogen bonds. The C=O stretching vibration band appears in the normal region between 1630 and 1670 cm^-1which usually overlaps with N-H bending [10, 11].

Figure 1a present N-H stretching of a secondary amide at 3251 cm^-1 as expected for wool. The bands at 1634 cm^-1 are also characteristic of N-H stretching vibration which overlaps with C=O vibration. The weak C-H stretching, CH₂ out of plane bending, C-O-C asymmetric stretching and S-O-S (cystine monoxide) vibrations in wool appear at 2919, 835, 1232 and 1072 cm^-1, respectively. Other weak bands appeared at 3759 and 3682 cm^-1 are attributable to O-H stretching vibrations in free primary and secondary alcohols [11].

Figure 1b indicates formic acid treated wool / 9% zirconium salt, the intensity of bands at 3811 and 3852 cm^-1were increased and new band at 1701 cm^-1was appeared. These changes are due to interaction OH groups of wool and interaction between carboxylic wool and formic acid cations. The band at 1391 cm^-‏‎1 was disappeared due to CH stretching and bending vibration after mordanted. The intensity of the bands at 1065 and 502 cm^-1 were increased, that are due to interaction between formic acid anions and amino groups of wool and change of OCN conformation in amide groups, respectively.

As can be seen in the Figure 1c, dyeing wool structure was the same as untreated wool. The intensity of band at 3851 cm^-1was increased. Its change is due to dye absorbent and increment of OH bands of anthraquinone in wool.

As can be seen in the Figure 1d, decrement in the intensity of band at 3516 cm^-1 can be expressed interaction between OH anthraquinone of madder on one hand and wool and mordant cations on the other hand was decreased free OH groups in wool.

Figure1: FTIR spectra a) untreated wool, b) 9% zirconium salt treated wool, c) madder dyeing wool, d) 9% zirconium salt / madder wool   Click here to View figure

 

Microscopic Characterization

The SEM images of untreated wool fiber and the samples treated with formic acid and different concentrations of zirconium salt are shown in Figures 2a-g. It can be observed that the scales have damaged in dyeing with madder and formic acid treated fiber. The zirconia particles can be observed on samples of formic acid treated. It is evident that increment in zirconium salt concentration increased the aggregated particles on the surface of the fiber. In the sample of formic acid in Figure (a) can be observed presence of particles which the tip of the scales is probably isolated by formic acid.

Figure2: SEM images (a) dyeing with madder wool fiber, (b) wool fibers dyeing with madder and  1%zirconium salt in before mordant method (c) wool fibers dyeing with madder and  9%zirconium salt in before mordant method (d) wool fibers dyeing with madder and  1%zirconium salt in simultaneously mordant method (e) wool fibers dyeing with madder and 9%zirconium salt in simultaneously mordant method (f) wool fibers dyeing with madder and  1%zirconium salt in after mordant method (g) wool fibers dyeing with madder and  9%zirconium salt in after mordant method.   Click here to View figure

 

Figure 3a-g and Table 1 show the presence of chemical elements on the surface of untreated fiber as well as on the surface of wool dyeing with madder and zirconium salt as investigated by EDX analysis. In these patterns, Au peaks clearly show that gold is successfully coated on surfaces of all fibers; and there is no Zr present on untreated wool. EDX analysis of cross-linked wool illustrates more efficient interactions between wool surface and zirconium salt leading to presence of Zr at this sample´s surface. The increment of zirconium salt concentration increased presence of Zr and in after mordant method be seen Zr more due to zirconium salt is a after- treatment method.

Table 1: Energy dispersive X-ray analysis 

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