Residual Dyebath Research Articles

Using nano clay and graphite as low-cost, sustainable adsorbents to remove dye toxins from waste water

Purpose This study aims to observe the coloring efficacy of graphite (G) and nano bentonite clay (BCNPs) on the adsorption of Basic Blue 5 dye from residual dye bath solution. Design/methodology/approach Some factors that affected the adsorption processes were examined and found to have significant impacts on the adsorption capacity such as the initial concentration of G and/or BCNPs (Co: 40–2,320 mg/L), adsorbent bath pH (4–9), shaking time (30–150 min.) and initial dye concentration (40–200 mg/L). The adsorption mechanism of dye by using G and/or BCNPs was studied using two different models (first-pseudo order and second-pseudo order diffusion models). The equilibrium adsorption data for the dye understudy was analyzed by using four different models (Langmuir, Freundlich, Temkin modle and Dubinin–Radushkevich) models. Findings It has been found that the adsorption kinetics follow rather a pseudo-first-order kinetic model with a determination coefficient (R2) of 0.99117 for G and 0.98665 for BCNPs. The results indicate that the Freundlich model provides the best correlation for G with capacities q_max = 2.33116535 mg/g and R2 = 0.99588, while the Langmuir model provides the best correlation for BCNPs with R2 = 0.99074. The adsorbent elaborated from BCNPs was found to be efficient and suitable for removing basic dyes rather than G from aqueous solutions due to its availability, good adsorption capability, as well as low-cost preparation. Research limitations/implications There is no research limitation for this work. Basic Blue 5 dye graphite (G) and nano bentonite clay (BCNPs) were used. Practical implications This work has practical applications for the textile industry. It is concluded that using graphite and nano bentonite clay can be a possible alternative to adsorb residual dye from dye bath solution and can make the process greener. Social implications Socially, it has a good impact on the ecosystem and global community because the residual dye does not contain any carcinogenic materials. Originality/value The work is original and contains value-added products for the textile industry and other confederate fields.

Novel colored polyurethane nanoparticle for recyclable dyeing polyester fabric

Colored wastewater has to be treated before its discharge, which is a great challenge for the protection of the ecological environment. A novel polymeric dye with nanoparticle morphology has been handily designed to dye polyester fabrics and can be fully recycled to avoid a large number of dyes discharge. It solves the colored wastewater pollution problem in the dyeing process from the source. The colored polyurethane nanoparticles with an average size of 500 nm are prepared via emulsion polymerization. The average content of the colorant monomer on nanoparticle is 2.77%. The colored nanoparticle demonstrates no thermal degradation at 110 °C and no damage under 20 MPa, which means good adaptability for the high-temperature dyeing process. The color depth of dyed polyester fabric can be easily adjusted by changing the concentration of colored nanoparticles in dyebath. The colored nanoparticles in the residual dyebath can be collected by extraction filtration leading to the concentration decreases from 11 mg mL−1 to 0.000025 mg mL−1 after filtered. Both the colored polyurethane nanoparticles and filtered water are fully reused for the next dyeing process to achieve the purpose of avoiding water consumption and residue dyes discharged. This work can promote the development of green and clean dyeing processes in the textile industry.

Application of phenolic compounds as natural dye extracted from date-pits: dyeing studies of modified acrylic fibres

This research work involves the dyeing of acrylic fabric with natural dye extracted from date pits powders using Soxhlet extraction process. The effect of dye bath pH, salt concentration, dyeing time and temperature were studied. The optimal dyeing conditions where pH 4, 0 g/L salt, 60 min, and 80 °C. The COD and the BOD5 of the residual dye bath were measured and it was shown from the registered values that the residual dye bath presents an acceptable rate of organic discharge.

The role of auxiliaries in the immersion dyeing of textile fibres: Part 11 residual inorganic electrolyte levels present during the wash-off of commercial grade reactive dyes

When both 2% omf and 5% omf dyeings on cotton were produced using three commercial grade reactive dyes in the complete absence of added inorganic electrolyte, a substantially modified wash-off process could be used in which both the number of wash-off baths and the liquor ratio utilised for each wash-off bath could be reduced. Measurements of the chloride ion concentration of residual dyebath, wash-off bath and final rinse bath liquors revealed that the reason why such a modified wash-off process could be utilised is due to the inherently very low dye-fibre substantivity that exists within the dyed substrate that results from the absence of added NaCl or Na2SO4 in dyeing.

The wash-off of dyeings using interstitial water Part 5: Residual dyebath and wash-off liquor generated during the application of disperse dyes and reactive dyes to polyester/cotton fabric

Both 2% and 5% omf dyeings of polycotton fabric which had been produced using commercial grade disperse dyes and reactive dyes can be washed-off using two, novel processes that utilise polyamide beads. The bead wash-off processes provided dyeings that were of similar colour, depth of shade and fastness compared to those which had been subjected to a conventional reduction clearing process in the case of the disperse dyes and a conventional wash-off in the case of the reactive dyes. The wastewater obtained from the bead wash-off of disperse dyes contained considerably lower concentrations of chloride ion as well as lower TDS compared to that secured using a conventional reduction clearing process, which was attributed to the beads having adsorbed vagrant chloride ions. In contrast, bead wash-off of reactive dyes did not reduce either the chloride ion concentration nor TDS content of the wastewater produced, because of the swamping effect of the very high chloride ion concentration. Bead wash-off also enabled significant reductions in both heat energy and water consumption to be achieved.

Eco-Friendly Dyeing of Silk and Cotton Textiles Using Combination of Three Natural Colorants

abstractSilk and cotton fabrics were dyed with combination of three colorants extracted from Acacia catechu (AC), Alkanna tinctoria (AT), and Curcuma Longa (CL) in nine different formulations at 80°C by exhaustion method without mordanting. Dyed samples were evaluated for color value and washing fastness. The biodegradability of dye bath effluent was assessed by measuring the pH, TDS and COD of the residual dye bath liquor. It is inferred that the final color of dyed fabrics from each formulation is governed by the dominant natural dye in the dyeing combination. K/S values inferred that the exhaustion of natural dye is higher in silk fabric than cotton fabric in all formulations. It could be concluded that in the dyeing combination, colorant that have very good affinity towards the functional groups of fibers, itself acts as mordant for other natural colorants.

Using ecological reducing agents instead of sodium sulphide in dyeing with CI Sulphur Black 1

Although low‐cost sodium sulphide is used as a reducing agent in most sulphur dyeing processes, it is considered to be environmentally unfavourable because of the resultant contaminated wastewater and the toxic hydrogen sulphide generated during the dyeing process. In the present paper, hydrazine sulphate, glucose, and sodium borohydride in the presence of sodium hydroxide were used as ecologically safe reduction systems for the CI Sulphur Black 1 dyeing of cotton fabric, and results were compared with those obtained using sodium sulphide. Dyeing processes were carried out at 90 °C for 60 min, and the colour yield (the K/S value), dyeing fastness, and breaking strength of dyed fabrics after soaping were measured. Response surface methodology was employed for experimental design and optimisation of results. Mathematical model equations were derived and statistical analysis carried out by computer simulation programming using Minitab v.15. At a dosage of 0.8 g l−1 of CI Sulphur Black 1, the optimum sodium borohydride reduction system (sodium borohydride 0.47 g l−1, sodium hydroxide 0.65 g l−1) exhibited the highest colour yield and the lowest chemical oxygen demand of the residual dyebath.

One-Pot Synthesis of Disperse Dyes Under Microwave Irradiation: Dyebath Reuse in Dyeing of Polyester Fabrics

A series of 4-hydroxyphenylazopyrazolopyrimidine disperse dyes were prepared via one-pot reactions of p-hydroxyphenylhydrazone, hydrazine hydrate, and acetylacetone or enaminones using microwave irradiation as an energy source. Structural assignments of the dyes were confirmed by X-ray crystallographic structure determination. Instead of discharging the dyebath after each dyeing cycle, the residual dyebath was spectrophotometrically analyzed and then pH readjusted for a repeat dyeing with longer time. Fastness of the dyed samples was measured after each recycle. Most of the dyed fabrics tested displayed good light fastness and excellent fastness to washing and perspiration. Finally, the biological activity of the synthesized dyes against Gram positive bacteria, Gram negative bacteria and yeast were evaluated.

Study on analytical methods for quantifying the non‐adsorbed reactive dye forms in an exhausted dyebath

Reported herein are the results of an analysis of the compatibility of three methods for quantifying the non-adsorbed forms of reactive dyes, in an exhausted dyebath, of the type monochlorotriazine/β-sulphatoethylsulphone used in dyeing cellulosic fibres (cotton). The first method is based on spectrophotometric analysis and involves measuring the absorbance of the residual dyebath (after the dyeing process), the second is based on colorimetric analysis and involves measuring the reflectance of the dyed fabric and the third is based on high-performance liquid chromatography. The purpose of the latter is to identify and quantify the non-adsorbed dye forms in the residual dyebath. The calculated exhaustion values unequivocally prove the reliability and compatibility of these methods.

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.

Residual dyebath purification using a system of constructed wetland

A constructed wetland model, comprising two different substrate mixtures, was used to purify textile dyebath wastewater. Three laboratory prepared wastewaters containing three commercial dyes of different classes and chemical constitution (one vat and two reactive dyes), different chemicals (NaOH, NaCl) and auxiliaries (migration inhibitor, sequestering, defoaming and wetting agents) were employed. Purifying efficiency was verified by measuring pollution parameters, such as absorbance, pH, total organic carbon (TOC), chemical oxygen demand (COD) and electrical conductivity (EC). It was found that the constructed wetland model reduced dye concentration by up to 70%, lowered the TOC and COD values up to 88%, electrical conductivity up to 60% and pH from 12 to 7.6.

Efficiency of the coagulation/flocculation method for the treatment of dyebath effluents

Textile dyeing processes are among the most environmentally unfriendly industrial processes, because they produce coloured wastewaters that are heavily polluted with dyes, textile auxiliaries and chemicals. The coagulation/flocculation method was studied as a wastewater treatment technique for the decolourization of residual dyebath effluents after dyeing cotton/polyamide blends using reactive and acid dyes. It was discovered that a combination of aluminium sulphate and a cationic organic flocculant yields an effective treatment for residual dyebath wastewaters since almost complete decolourization was achieved, TOC, COD, AOX, BOD and the anionic surfactants were reduced and the biodegradability was increased.

Acid dyeing isotherms of cotton fabrics pretreated with mixtures of reactive cationic agents

Reactive cationic agents, phenylmonochlorotriazinyl and epoxypropyl, are used for cotton pretreatment using a pad–dry–curing technique. The dyeability of cationised cotton fabrics using CI Acid Red 1, determined spectrophotometrically for the residual dyebath, has been dependent on the cationic agent concentration and the appropriate mixture used. Comparative sorption isotherms, rate of dyeing at different temperatures, standard affinity, entropy and heat of dyeing for three different pretreated fabrics have been calculated and discussed. The equilibrium data obtained were fitted by the Langmuir isotherm model, allowing the corresponding sorption parameters to be determined.

PH control for dyeing polyamide in a reused acid dyebath

The pH control that can be achieved in a reused dyebath was investigated. The study involved a phosphate buffer system and four pH sliding systems, including ammonium sulphate and three hydrolysable organic esters. Instead of discharging the dyebath after each dyeing cycle, the residual dyebath was analysed using a UV‐Vis spectrophotometer and reconstituted to the required concentration of dyes, auxiliaries and acid donors. The dyebath was reused for 10 cycles and colour reproducibility, levelness and fastness of the dyed samples were measured after each recycling. In comparison with ammonium sulphate and sodium dihydrogen phosphate, hydrolysable organic esters gave a stable and effective pH shifting in the dyebath reuse system. In addition, hydrolysable organic esters resulted in a very low amount of salt in residual dyebath. No deterioration in colour fastness of the dyed fabrics over 10 cycles of dyebath reuse was evident.

Dyebath reuse in dyeing of nylon microfiber non-woven fabric with 1:2 metal complex dyes

Dyebath used for metal complex dyeing of nylon microfiber was recycled to reduce the overall amounts of metal complex dyeing effluents. Instead of discharging the dyebath after each dyeing cycle, the residual dyebath was analyzed spectrophotometrically and reconstituted to the required concentration of dyes and auxiliaries. Dyebaths were reused eight times and the CIELAB coordinates of dyed samples were measured after each recycling. Color difference (ΔE*) between the sample dyed in the fresh bath and that from reused dyebath was maintained below 1.5. The levelness and fastness of dyed fabrics from recycled dyebath were not impaired either. Chromium content of each recycled dyebath was similar to that of the first residual dyebath.

Chrome dyeing of cashmere with SCA‐Cr as the mordant

The recently developed mordant SCA-Cr has been employed in mill production for the afterchrome dyeing of cashmere for more than two years, and about 80 tonnes of the fibre has been dyed in this way. The mill results confirmed the value of the Cr(III)-containing mordant and the new technique has replaced the conventional chrome dyeing method, in which dichromate was employed as the mordant, in three biggest cashmere processing companies in China. The concentration of Cr(VI) in the residual dyebath was greatly decreased (to less than 0.01 mg/l). Because of the reduced oxidation damage to the cashmere during mordanting, the spinning properties, as well as other properties, of the loose cashmere stock were significantly improved and the quality of the final products was greatly enhanced.