Synthesis, characterization and application of quinazolinone based reactive dyes for various fibers

Seven hot brand heterocyclic mono azo reactive dyes (7a–g) have been synthesized by coupling diazotized 2-phenyl-3{4′-[(4″-aminophenyl)sulphonyl]phenyl}-quinazoline-4(3H)-one-6-sulphonic acid (4) with various 2-chloro-4-nitro anilino cyanurated coupling components (6a–g) and their dyeing performance on silk, wool, and cotton has been assessed. The purity of dyes was checked by thin layer chromatography. These dyes were identified by recording IR and ¹H-NMR spectra. The λ _max, R _f value, %exhaustion, %fixation, light fastness, wash fastness, rubbing fastness, reflectance (%R) value, and K/S value have also been studied.     

Exploration of biosorption potential of forest industry by-product for removal of reactive dye from aqueous solution

Natural sawdust of Calabrian pine was explored as low-cost industrial by-product for a hetero-bireactive dye removal from aqueous solution in this study. Batch experiments were carried out to investigate the effects of contact time and dye concentration on biosorption efficiency. Maximum biosorption amounts were achieved almost in the 20-30 min of contact for the studied dye range (50-200 mg l ^-1). An increase in the dye concentration resulted in decrease in the percent dye removal and increase in the biosorption capacity of biosorbent. Different kinetic and isotherm models were used to examine the biosorption experimental data for elucidating the dye removal mechanism. The equilibrium data were best represented by Freundlich isotherm model confirming multilayer coverage. The kinetics of dye biosorption best obeyed the pseudo-secondorder equation. The negative value of standard Gibbs free energy change (-3.61 kJ mol^-1) indicated that physical forces were involved in the spontaneous dye biosorption. Thus, the sawdust as a possible non-conventional biosorbent presented an interesting option for bioremediation of contaminated environments by such unsafe dyes.     

Study of analytical methods for quantifying unfixed form of bifunctional reactive dyes used in dyeing cellulosic fibers (cotton)

The objective of the present study was to examine the reliability and compatibility of three methods for quantifying the unfixed form of heterobifunctional reactive dye type monochlorotriazine/β-sulfatoethylsulfone used in dyeing cellulosic fibers (cotton). The first method is based on spectrophotometric analysis by measuring the absorbance of residual dyebath (after dyeing process) and residual soaping bath (after washing-off phase), the second one is based on colorimetric analysis by measuring the reflectance of dyed fabric, and the third on high-performance liquid chromatography (HPLC) technique. The purpose of the latter is to identify and quantify the hydrolyzed and inactive forms of dye in residual soaping bath. The calculated unfixed dye rates unequivocally prove the reliability and compatibility of these methods. According to the availability of the required laboratory instruments, we can select the most suitable method in every case, though the tests proved that the HPLC technique is most efficient.     

Preparation and use of amine-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fibers for removal of chromium(VI) from aqueous solution

Poly(ethylene terephthalate) (PET) fibers were grafted with glycidyl methacrylate (GMA) using benzoyl peroxide as initiator. 1,6-diaminohexane (HMDA) was then covalently attached to this GMA grafted PET fibers. Variations of time, temperature, initiator and monomer concentrations were investigated. HMDA-GMA-g-PET fibers were used as a new sorbent for removal of Cr(VI) ions from aqueous solutions through batch adsorption method. Effects of various parameters such as pH, treatment time, and initial ions concentration on the adsorption amount of ions onto reactive fibers were investigated. The adsorption rates of Cr(VI) ions were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. Within 60 min, at pH 3, Cr(VI) was removed by 98 % while the initial concentration of ions was at 25 mg/l and by 94 % at 400 mg/l. The Cr(VI) ions adsorbed were easily desorbed by treating with 1M KOH within 10 min.     

Colorimetric studies of benzoquinoline based hot brand monoazo reactive dyes and their dyeing performance on various fibers

A series of hot brand monoazo reactive dyes (9a-l) were obtained by the coupling of diazotized 1Hbenzo[ g]pyrazolo[3,4-b]quinoline-3-ylamine (5) with various cyanurated coupling components (8a-l) in good yield. Synthesized dyes were characterized by various spectroscopic techniques. Their dyeing performances as reactive dyes have been assessed on silk, wool, and cotton fabrics. The percentage dye bath exhaustion and fixation on different fibers were found to be very good. The dyed fabric showed moderate to very good light fastness and good to excellent washing and rubbing fastness properties. Spectral properties and colorimetric data of synthesized dyes have also been studied in detail.     

Thiazole based disperse dyes for nylon and polyester fibers

Nine disperse dyes have been synthesized by diazotization of 2-amino-4-(p-nitrophenyl)-5-nitrothiazole and coupled to substituted N-alkylanilines. Spectral properties in the IR and visible range of the dyes obtained were investigated. The dyeing performance of these dyes was assessed on nylon and polyester fibers. These dyes were found to give reddish brown to bluish violet shades on dyeing with very good depth, brightness and levelness on nylon and polyester fibers. The dyed fibers showed fairly good light fastness, very good to excellent fastness to wash, rubbing, perspiration and excellent fastness to sublimation. The dyebath exhaustion and fixation on the fiber were found to be very good.     

Selective removal of Pb(II) ions from aqueous solutions by acrylic acid/acrylamide comonomer grafted polypropylene fibers

Polypropylene-based chelating fibers grafted with acrylic acid and acrylamide side chains were simply synthesized, and subsequently employed as adsorbents for Pb(II) removal selectively from aqueous solutions. The assynthesized fibers were characterized by elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. The adsorption results revealed that kinetics data were fitted by a pseudo-second order model (semi-saturation time 6.2 min), thereby suggesting chelating interaction to be the main mechanism during the adsorption process. The adsorption isotherm data fitted well with a Langmuir model. The thermodynamic study revealed the adsorption of Pb(II) as an exothermic spontaneous chemisorptive process. Coexisting Na(I), Mg(II), and Al(III) in solution showed negligible effects in the adsorption process. As confirmed by carboxyl amination, the carboxylate oxygen preferentially chelates coexisting Ca(II) over Pb(II), thereby leading to lower extents of Pb(II)-O chelate interaction. The spent fibers were effectively and repetitively (five cycles) regenerated while maintaining high performance upon treatment with 1 M hydrochloric acid solutions.     

Study on differences of reaction behavior of phenolic hydroxyl groups with vinyl sulfone reactive dyes and monochlorotriazine reactive dyes

Using p-methylphenol as a model compound for phenolic hydroxyl groups on silk fibroin, the reaction kinetics of two typical of reactive dyes including vinyl sulfone reactive dyes and monochlorotriazine reactive dyes with phenolic hydroxyl groups were studied by reverse phase ion-pair high-performance liquid chromatography. The results showed that, the reaction rates of monochlorotriazine reactive dyes with phenolic hydroxyl groups were by far faster than those of vinyl sulfone reactive dyes, attributed to the stability of resultants from the former. The optimum reaction conditions for phenolic hydroxyl groups with vinyl sulfone reactive dyes and monochlorotriazine reactive dyes were at 50–70 °C and pH=8–9 for the former, and at 85–95 °C and pH=8–9 for the latter. The methods and results in this paper would help to deeply study the reaction mechanisms of reactive dyes with silk fibroin.     

Sorption potential of modified nanocrystals for the removal of aromatic organic pollutant from aqueous solution

Chemically modified starch nanocrystals were used as adsorbents for the removal of aromatic organic compounds from water. The nanocrystals were chemically modified by grafting with stearate moieties which enhanced the adsorption capacity of the nanometric substrate. Their adsorption capacity ranged between 150 and 900 μmol g⁻¹ of modified nanoparticles and the adsorption isotherms could be described accurately by the Langmuir model. The adsorption kinetics followed a two-step process with first pure adsorption of the aromatic compounds onto the surface of the nanoparticles followed by a diffusion of the compounds into the layer of surface chains grafted onto the nanoparticles. Furthermore, the feasibility of using these nanoparticles in continuous flow mode processes was confirmed using a fixed bed column setup. The fixed bed column could also be regenerated by washing with ethanol and was found not to exhibit any loss in adsorption capacity over multiples adsorption-desorption cycles.     

Synthesis and application of alkyl-substituted red dyes for unmodified polypropylene fibers

Following the previous studies regarding blue and yellow dyes, a series of new red dyes having different length of alkyl substituents on the same chromophore were synthesized in order to dye unmodified polypropylene fiber. The affinity of the dyes onto unmodified polypropylene fiber was increased with the increase of the length of alkyl substituents. Therefore, the longest hexyl-substituted dye showed very deep shade of dyeing with K/S value of around 30 at maximum absorption wavelength. Within the range below 2 % o.w.f., the exhaustion (%) showed more than 80 %. The color fastnesses to washing, rubbing, and light of the dyeings were also improved greater for the dyes having longer alkyl substituents than the shorter ones. Since color hue of the dyes exhibited very strong red, they could be considered to be used as the primary red color dyes for unmodified polypropylene fibers.     

Dye removal using polymeric adsorbent from wastewater containing mixture of two dyes

In this paper, poly(amido primary-secondary amine) (PAPSA) as a high capacity polymeric adsorbent was synthesized. Dye removal ability of PAPSA from single and binary systems was investigated. The functional groups of PAPSA were studied using Fourier transform infrared (FTIR). Acid Blue 92 (AB92), Direct Red 23 (DR23), and Direct Red 81 (DR81) were used as model compounds. The kinetic and isotherm of dye adsorption were studied. The effect of operational parameter such as adsorbent dosage, dye concentration, and pH on dye removal was evaluated. It was found that adsorption of dyes onto PAPSA showed Langmuir isotherm. The maximum dye adsorption capacity (Q ₀) of PAPSA was 10000 mg/g, 12500 mg/g, and 10000 mg/g for AB92, DR23, and DR81, respectively. Adsorption kinetic of dyes followed pseudo-second order kinetics. Dye desorption tests showed that the dye release of 85 % for AB92, 91 % for DR23 and 89 % for DR81 were achieved in aqueous solution at pH 12. The results showed that the PAPSA as a polymeric adsorbent with high dye removal ability might be a suitable alternative to remove dyes from colored wastewater.     

pH control for dyebath reuse in dyeing of polyamide with binary mixtures of acid dyes

Hydrolyzable organic esters were compared with ammonium sulphate as an acid donor for the pH control in dye-bath-reuse system of acid dyes mixtures. The ability of pH control, levelness, dyeing properties and reproducibility in dye-bath-reuse system were investigated comparatively. Hydrolyzable organic esters showed higher exhaustion and color yield than ammonium sulphate. In addition, hydrolyzable organic ester exhibited very low conductivity less than 0.5 mS, while ammonium sulphate give high conductivity. However, we could not observe any difference in levelness of dyed samples between two kinds of acid donors in laboratory scale dyeing. Over 10 cycles of reuse, hydrolyzable organic esters showed higher reproducibility than ammonium sulphate. No deterioration of the color fastness and levelness occurs over 10 cycles of reuse.     

Preparation of adsorbent based on cotton fiber for removal of dyes

Synthetic dyes are used extensively in modern industries, which are toxic and harmful to environment and human. Cotton fiber is a kind of abundant, renewable and eco-friendly cellulose fiber in nature, however, the adsorption capacity of raw cellulose for pollutants was often low. Therefore, an efficient adsorbent for removal of dyes was successfully prepared by grafting beta-cyclodextrin (β-CD) and amino-terminated hyperbranched polymer (NH₂-HBP) onto cotton fibers in this study, which was effective to anionic dyes and cationic dyes. The adsorbent were characterized using FTIR, SEM and XPS analysis. The results of adsorption experiments showed that the adsorbent based on cotton fiber exhibited better adsorption performance for Congo red(CR) and methylene blue(MB). The experimental results revealed that the pH value had a great influence on the adsorption capacity.     

The effects of texturing induced microstructural changes on the relaxation behaviour of polyamide 66 multifilament yarns

Polyamide 66 multifilament yarns are textured in order to be endowed the properties of natural staple fibre yarns for textile applications. Texturing changes crystallinity, orientation and promotes the formation of stable secondary links between the macromolecular chains. Two polyamide yarns with the same linear density but composed of filaments of different fineness were textured by the air-jet and the false-twist procedures. The microstructural changes induced by texturing modify the relaxation behaviour of yarns. By the application of the Nutting’s power law which relates stress, strain and time, the influence of texturing and filament fineness on the relaxation behaviour of the yarns stretched form 15% to 25% was studied. Relationships between Nutting’s model parameters and crystallinity, orientation and stability of secondary crosslinks formed during texturing were also studied.     

Wicking properties of polyamide 66 twisted nanofiber yarn by tracing the color alteration in yarn structure

In view of the interest in wicking properties of these flexible structures, analysis of the wicking phenomena in nylon 6.6 nanofiber yarns is carried out by considering the twist rate effects. A novel method is used based on adding a pH-sensitive dye to yarn interstructure and the analysis of color alteration of nanofiber yarn structure, resulting from a shift in pH, during the capillary rise of distilled water. The results show that the addition of pH- sensitive dye has no influence on the average nanofiber diameter and the wicking behavior of yarns. This study shows that in short durations, the kinetic of the capillary rise follows the Lucas-Washburn equation. The Lambertw, a mathematical function, has been incorporated, which helps measure an equivalent structural factor of nanofiber yarns and vertical wicking height at any given time considering the gravitational effects. The statistical results show that the average of equilibrium wicking height and capillary rise rate coefficient tend to decrease with increasing the nanofiber yarn twist, due to the reduction of continuity and size of capillaries.     

Sorption properties of iron impregnated activated carbon web for removal of methylene blue from aqueous media

In this study, impregnation of iron chloride was carried out on needle punched web of waste acrylic fibers, which was subsequently carbonized under layer of charcoal by physical activation in high temperature furnace to produce iron impregnated activated carbon (FeAC). For comparison purpose, one more sample of activated carbon (AC) was prepared without impregnation of iron chloride. Both the webs were carbonized at 1200 °C with no holding time, and characterization of BET surface area, SEM morphology, EDX elemental analysis, XRD crystalline structure was performed. The FeAC web was used as adsorbent for the removal of methylene blue from aqueous solution. The dye removal percentage was investigated at different experimental parameters like different dye concentrations, adsorbent dosage, stirring speed and different pH. The obtained results were analyzed using linear and non-linear forms of Langmuir and Freundlich isotherms and adsorption kinetics (i.e. pseudo first order and pseudo second order model).     

Novel cationic softener containing MCT reactive dyes for cotton: Synthesis and characterization

Two novel cationic softener containing mono-s-chloro triazinyl reactive dyes together with their analogues were designed. The dyes were synthesized via reacting an N,N-dimethyldodecylamine with p-nitrobenzyl bromide. The resultant was reduced using stannous chloride and hydrochloric acid to produce the primary amine. The quaternary ammonium salt containing primary amine was then diazotized to produce diazonium salt part of azo dye. The diazonium salt was then coupled to H-acid/J-acid reacted with cyanuric chloride and sulfanilic acid. The analogue dyes were prepared via the same route without quaternary ammonium salt making stage. The chemical structures of the novel dyes were characterized by FTIR, ¹H-NMR, and elemental analysis. The spectroscopic properties of the dyes were determined in terms of λ _max and ? _max in aqueous solution.     

Novel fibers prepared from cellulose in NaOH/thiourea/urea aqueous solution

The regenerated cellulose fibers were prepared by wet-spinning from NaOH/thiourea/urea aqueous solvent system for the first time. The effects of coagulation and stretch conditions on the structure, morphology, and mechanical properties of the prepared fibers were investigated by wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM), and tensile tester, respectively. When the cellulose spinning dope was coagulated in 10% H₂SO₄/12.5% Na₂SO₄ aqueous solution at 15 °C, the prepared fibers had a typical crystalline structure of cellulose II and circular cross-sectional shapes with smooth surface and slightly high tensile properties to viscose fibers.     

Dyeing properties of nylon 66 nano fiber with high molecular mass acid dyes

Research and development of nano fiber products is very active over the world. Physical characteristics and dyeing properties of nylon 66 nano fiber were investigated in this study. X-ray diffraction, DSC, analysis of amino end group, and water absorption were performed to get information concerning physical properties of nano fiber. Nylon 66 nano fiber was dyed with high molecular mass acid dyes. Effects of dyeing temperature, pH of dyeing solution, and concentration of acid dyes on dyeing properties such as rate of dyeing and the extent of exhaustion, were examined and compared to those of regular fiber. It was found that nano fiber adsorbed acid dyes at lower temperature, got rapidly dyed, and its extents of exhaustion at specific dyeing temperature were higher than regular fiber. It was also observed that nano fiber could adsorb a large amount of acid dye without a significant loss in the extent of exhaustion. Washing fastness of the dyed nano fiber was lower by 1/2∼1 grade, light fastness by 1 grade than the dyed regular fiber.