OKRA (HIBISCUS ESCULENTUS) AND FENUGREEK (TRIGONELLA FOENUM GRACEUM) MUCILAGE: CHARACTERIZATION AND APPLICATION AS FLOCCULANTS FOR TEXTILE EFFLUENT TREATMENTS

The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum,commonly called Okra and Fenugreek,respectively,as flocculants was described.These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes.Influences of varying polysaccharide concentration,contact time and pH on removal of pollutant from the text...     

OKRA(HIBISCUS ESCULENTUS)AND FENUGREEK(TRIGONELLA FOENUM GRACEUM)MUCILAGE:CHARACTERIZATION AND APPLICATION AS FLOCCULANTS FOR TEXTILE EFFLUENT TAEATMENTS

The use of new food grade polysaccharides (mucilage) obtained from Hibiscus esculentus and Trigonella foenum graceum,commonly called Okra and Fenugreek,respectively,as flocculants was described.These polysaccharides were used for removal of solids (suspended solids (SS) and total dissolved solids (TDS)) and dyes from real textile effluents and aqueous solutions of different class of synthetic dyes.Influences of varying polysaccharide concentration,contact time and pH on removal of pollutant from the textile wastewater were investigated.Results showed that polysaccharides (mucilage) obtained from Okra and Fenugreek were capable of removing 90%-94% of SS,30%-44% of TDS and 30%-35% of dye using a very low concentration of polysaccharide.X-ray diffraction (XRD) patterns of solid waste material obtained before and after the treatment with polysaccharides were used as a supportive evidence to explain the mechanism of flocculation.     

A Novel Kinetic Approach for Photocatalytic Degradation of Azo Dye with CdS and Ag/CdS Nanoparticles Fixed on a Cement Bed in a Continuous‐Flow Photoreactor

Azo dyes are one of the synthetic dyes that have been used in many textile industries. Azo dye and their intermediate products are toxic, carcinogenic, and mutagenic to aquatic life. Removal of azo dyes is one of the main challenges before releasing the wastes discharged by textile industries. Photocatalytic degradation of azo dyes by nanoparticles is one of the environment‐friendly methods used for the removal of dyes from textile effluents. Therefore, this study focused on degradation of azo dye, Direct Red 264. Photocatalytic degradation of DR 264 azo dye was investigated using CdS and Ag/CdS nanoparticles immobilized on a cement bed in a continuous‐flow photoreactor under UV‐C exposure. The effect of the parameters of type and mass of catalyst, temperature, flow rate, dye concentration, and light intensity were evaluated for azo dye removal. Under optimal conditions, photocatalytic degradation of DR 264 azo dye using Ag/CdS nanoparticles immobilized on a cement bed in a continuous‐flow photoreactor obtained an efficiency of 99.99%. A developed kinetic model was proposed based on the intrinsic elementary reactions. The proposed model is in a good agreement with the Langmuir–Hinshelwood (L–H) equation. The pseudo–steady‐state approximation has considered for the concentration of hydroxyl radicals associated with the L–H model under certain conditions and explains consistently the dependence of the apparent kinetic parameter, k_obs (the reaction rate constant), and K_R (the adsorption equilibrium constant) with the light intensity. Based on the model, k_obs for Ag/CdS was greater than the CdS nanoparticles.     

Decolorization of Some Azo Dyes by Immobilized <Emphasis Type="Italic">Geotrichum</Emphasis> sp. Biomass in Fluidized Bed Bioreactor

Geotrichum sp. strain, which is able to decolorize azo dyes enzymatically, was used in this study for decolorization of synthetics solutions contaminated by toxic azo dyes orange G, trypan blue, azorubine, and methyl red. The biomass of Geotrichum sp. was immobilized in calcium alginate and polyacrylamide gels and used for the decolorization of tested azo dyes in fluidized bed bioreactor. The highest specific decolorization rate was obtained when the fungal biomass was entrapped in calcium alginate beads. Immobilized biomass in calcium alginate continuously decolorized azo dyes after eight repeated batch decolorization experiments without significant loss of activity whereas polyacrylamide immobilized biomass retained only 10% of its activity after 4 days of incubation. The effects of some physicochemical parameters such as temperature, pH, and dyes concentration on decolorization performance of isolated fungal strain were also investigated.     

Use of polyacrylamide-grafted<Emphasis Type="Italic"> Plantago psyllium</Emphasis> mucilage as a flocculant for treatment of textile wastewater

The chemical modification of Plantago psyllium mucilage (Psy), an anionic polysaccharide, was done by grafting polyacrylamide (PAM) chains to prepare a graft-copolymer (Psy-g-PAM). It was synthesized in the presence of nitrogen using ceric ammonium nitrate–nitric acid redox initiator and characterized by IR spectroscopy, scanning electron microscopy and viscosity measurements. This grafted copolymer was tested for its flocculation efficiency in textile wastewater by the standard Jar test method. The effects of polymer concentration, pH and contact time on the percentage removal of solid wastes [total dissolved solids (TDS) and suspended solids (SS)] and color from textile effluent are reported. The optimum dose was found to be 1.6 mg l^–1, at which maximum solid removal (SS and TDS) was seen. The most suitable pH for TDS and color removal was neutral (7.0) and for SS removal alkaline pH (9.2) was found to be most suitable. The optimum treatment duration for solid waste removal was 5 h. The X-ray diffraction analysis of Psy-g-PAM and solid waste before and after treatment suggests the interaction of the solid waste and Psy-g-PAM copolymer.     

Surface modification of inorganic oxide particles with silane coupling agent and organic dyes

The silane coupling agent 3‐glycidoxypropyl trimethoxylsilane (GPS) was grafted onto the surface of silica gel, P ₂ glass beads and TiO ₂ oxide particles. FT‐IR, thermogravimetric and elemental analysis were used to characterize the modified particles. The effects of various factors on the GPS grafting efficiency such as catalyst, GPS concentration, reaction temperature and time were studied. After modification with GPS, the xanthene dye rhodamine B and azo dyes 4‐phenylazophenol and 4‐phenylazoaniline, respectively, were grafted on to the particles, which were then used as pigment fillers. The colors of the pigments were adjusted by changing the kind of dyes, the concentration, the pH and the reaction solvents. Copyright © 2001 John Wiley & Sons, Ltd.     

PLANTAGO PSYLLIUM-GRAFTED-POLYACRYLONITRILE： SYNTHESIS,CHARACTERIZATION AND ITS USE FOR SOLID REMOVAL FROM SEWAGE WASTEWATER

Plantago psyllium mucilage (PSY), an anionic natural polysaccharide consisting of pentosan and uronic acid obtained from the seeds of Plantago psyllium (Plantago family), was grafted with acrylonitrile (AN). Graft copolymers were prepared by ceric ion initiated solution polymerization technique and were characterized by FT-IR spectroscopy, scanning electron microscopy and differential scanning calorimetry. These copolymers are good flocculating agents for removal of suspended (SS) and total dissolved solid (TDS) in sewage wastewater treatment. The effects of copolymer dose, pH and contact time on flocculation capacity of one selected copolymer sample were studied by jar test method. The suitable pH range for maximum solid removal was 7.0 to 9.2 and the optimum copolymer dose was 1.2mg/L. The overall process for solid removal took 4h. X-ray diffraction (XRD) patterns of grafted copolymer, PSY grafted polyacrylonitrile (PSY-g-PAN) and solid waste, before and after treatment are used to suggest the interaction of the solid waste with PSY-g-PAN copolymer.     

Application of Fenton‐Based Reactions for Treating Dye Wastewaters: Stability of Sulfonated Azo Dyes in the Presence of Iron(III)

Fenton‐ and photo‐assisted Fenton advanced oxidation processes generate reactive oxygen species from hydrogen peroxide and are candidates for the remediation of dye wastewaters. The purpose of this study was to investigate interactions of iron (III) with hydroxyazo dyes. The o‐hydroxyazo dyes Acid Orange 7 (AO7; 4‐[(2‐hydroxynaphthalen‐1‐yl)azo]benzenesulfonic acid sodium salt) and Acid Orange 10 (AO10; 7‐hydroxy‐8‐(phenylazo)naphthalene‐1,3‐disulfonic acid disodium salt) represent dyes allegedly able to chelate Fe^III through the chromophore. The p‐hydroxyazo dye Acid Orange 20 (AO20; 4‐[(4‐hydroxynaphthalen‐1‐yl)azo]benzenesulfonic acid sodium salt) represents an analogous structure that is unable to chelate Fe^III due to the position of the OH group. Reactions were carried out at pH 2 – 3 in perchlorate or chloride media in the absence of peroxide. No evidence was found by UV/VIS spectroscopy for complexation of Fe^III by the o‐hydroxyazo chromophore. Instead, Fe^III apparently coordinated or formed an ion pair with the sulfonate group, and, when only one sulfonate group was present (i.e., AO7), the dye formed a co‐precipitate with iron(III) hydrous oxides and perchlorate ion. Dye precipitation was seeded by colloidal iron hydrolysis product nuclei. By contrast, the p‐hydroxyazo dye (AO20) was rapidly oxidized by iron(III). The net Fe²⁺/oxidized AO20 ratio was 2 : 1, and a minor yield of 1,4‐naphthoquinone was obtained. The major initial oxidation product, which was not identified, formed a reversible complex with Fe²⁺. Results of this study indicate that the effectiveness of Fenton‐based methods for treating certain azo dyes that form insoluble ferric salts may be compromised by removal of the catalyst from solution. However, the degradation of certain other azo dyes might be assisted by direct thermal oxidation by iron(III).     

Adsorption of reactive dye on chitosan in air-lift reactor

This study was undertaken to identify factors exerting the strongest influence on the adsorption of dye. The maximum adsorption capacity (at the adopted operating conditions) was the main parameter used to evaluate the process. In addition, the feasible adsorption capacity of chitosan was evaluated. Breakthrough experiments were carried out in a circulating air-lift reactor at a constant concentration of reactive dye Black 8 (100 mg/dm³). The tests studied different chitosan concentrations in the reactor and a range of flow intensities. The results of the breakthrough tests were compared by means of apparent mass transfer coefficients, determined by slopes at C/C ₀=1/2. The adsorption capacity of chitosan was affected to the greatest extent by the flow rate of the medium to the reactor. In turn, the utilization of the maximum adsorption capacity of chitosan, at the assumed efficiency of dye removal, was determined by chitosan concentration in the reactor.     

Gliding Arc Discharge for Decolorization and Biodegradability of Azo Dyes and Printing and Dyeing Wastewater

Gliding arc discharge process was used for the pretreatment of four azo dye solutions, which are classified to acidic, reactive and chemical indicator, as well as printing and dyeing wastewater with the objective of improving their overall biodegradability. The percentage color removal of all samples were found to be over 92% after 40?min treatment, and the color disappearance of four azo dyes followed the first-order kinetics completely. The biochemical oxygen demand (BOD₅)/chemical oxygen demand (COD) ratio increased from 0.02 to 0.46 for acid orange II (AO7), 0.173 to 0.55 for methyl orange, 0.019 to 0.4 for direct fast black, 0 to 0.65 for reactive red K-2BP. The decolorization of printing and dyeing wastewater achieved 97.5% and the COD removal efficiency was 76.6%. The BOD₅/COD ratio increased to 0.55 after 20?min treatment. The experimental results indicates it is possible to combine gliding arc discharge with conventional biological treatment for the remedy of wastewater containing generally non-biodegradable dye.     

Polyelectrolyte complexes. V. Solid‐state properties of some polycation/azo dye complexes controlled by the dye structure

The solid‐state properties of some polycation/azo dye complexes according to the dye structure were studied in this work. One polycation contained about 95 mol % N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride units in the backbone (PCA₅), and eight azo dyes, different in either the number of sulfonic groups or their distribution, were used as opposite components. The selected azo dyes were as Crystal Scarlet, Congo Red, Crocein Scarlet MOO, Ponceau SS, Amaranth, Ponceau S, Direct Blue 1, and Direct Red 80. Information on the compensation degree of the oppositely charges was obtained by the elemental analysis of the solid‐state polycation/dye complexes (the experimental contents of chlorine, nitrogen, and sulfur were compared with the calculated values). Differential scanning calorimetry was employed to probe the strength of the intermolecular interactions in the PCA₅/dye complexes. Wide‐angle X‐ray diffraction was used to assess the supramolecular order of the solid‐state complexes. The physical properties of the PCA₅/azo dye complexes (the complex stoichiometry, glass‐transition temperature, decomposition temperature, and degree of supramolecular order) were influenced mainly by the dye structure but also by the polycation concentration and the presence of NaCl. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 264–272, 2003     

Anthraquinone and Azo Dyes in Dyeing Processes of PET Films and PET Knitted Fabrics Using Supercritical CO2 Medium

Summary: Dyeing processes using supercritical fluid present advantages over the conventional dyeing process using aqueous medium. Previous works from our group on polymeric fibers such as N,N-dimethylacrylamide (DMAAm) modified poly(ethylene terephthalate), PET, showed higher sorption of disperse dyes in supercritical medium. Furthermore, recent studies showed that the association of UV radiation and DMAAm treatment leads to a better incorporation of dyes in modified PET soaked in aqueous medium. In this work, modified and non-modified PET knitted fabrics (KF) were dyed in supercritical CO₂ medium. Azo and anthraquinone dyes were used in order to compare the extent of incorporated dye in PET films and PET KF in supercritical CO₂. The dyeing process variables were studied by factorial design and by a response surface methodology (RSM) technique. The anthraquinone dye presented a better incorporation in PET than the azo dye. The UV light exposure and the dyeing times inputs showed positive main effects in the incorporation of dyes in PET films and PET KF. From the RSM data, DMAAm and UV light modified PET KF presented 7.43 mg of incorporated azo dye by g of PET if the optimized dyeing conditions, time: 135 min and pressure: 212 bar would be used. In the respective optimized dyeing conditions for the anthraquinone dye, time 150 min and pressure 229 bar, the incorporated dye would be 22.9 mg of dye by g of PET.     

Synthesis and evaluation of a series of symmetrical hot brand bis azo reactive dyes using 4,4′-methylene-bis-metanilic acid on various fibre

4,4′-Methylene-bis-metanilic acid (A) was synthesized by the reaction between metanilic acid and formaldehyde. The compound (A) was used as a bifunctional middle component in the preparation of several symmetrical hot brand bis azo reactive dyes. The compound (A) was tetrazotized and coupled with various m-nitro anilino cyanurated coupling component to give various hot brand bis azo reactive dyes. The entired compounds have been identified by IR, ¹H NMR spectra and elemental analysis. The dyes were applied on silk, wool and cotton fabrics and their fastness properties were evaluated. All the dyes give good fastness properties. The percentage dye bath exhaustion was also been studied.     

Effect of hydrolysis degree of hydrolyzed polyacrylamide grafted carboxymethyl cellulose on dye removal efficiency

In this present work, a series of hydrolyzed polyacrylamide grafted carboxymethyl cellulose (CMC-g-HPAM) was prepared. The structure and solution properties of CMC-g-HPAM were characterized by FTIR, ¹H-NMR, elemental analysis and zeta potential measurements. The graft copolymers were applied as flocculants to remove methylene blue (MB), a cationic dye, from aqueous solutions. In comparison with its precursors, carboxymethyl cellulose (CMC) and polyacrylamide CMC-g-PAM, CMC-g-HPAM exhibited higher removal efficiencies. Furthermore, the flocculation performance of the copolymers was significantly improved with the increase of the hydrolysis degree, and the MB removal efficiency was more than 90 % when the hydrolysis degree of CMC-g-HPAM was higher than 80 %. More importantly, image analysis in combination with fractal theory demonstrated that the graft copolymers could produce notably denser and larger flocs, which was of great significance in practical water treatment. The improved flocculation performance was ascribed to both charge neutralization and bridging effects.     

Synthesis and polarized light‐induced birefringence of new polymethacrylates containing carbazolyl and azobenzene pendant groups

Low T_g copolymers of [11(N‐carbazolyl)undecylmethacrylate] and [2,5‐dimethylphenyl‐[(4‐nitrophenyl)azo]‐phenoxyalkylmethacrylate] have been synthesized and the polarized light‐induced birefringence of thick films (70 μm) has been investigated at a constant deducted temperature relative to T_g (T − T_g = 10 °C). The optical properties of these copolymers have been studied in relation to the azo‐dye content and the length of the alkyl spacer between the azo‐dye and the methacrylic backbone. They have been compared with the dispersion of (4‐methoxy‐2,5‐dimethylphenyl)‐(4‐nitrophenyl)diazene (DMNPAA) within a poly[11(N‐carbazolyl)undecyl‐methacrylate] and a poly[N‐vinylcarbazole] (PVK) matrix. The experimental curves have been fitted by biexponentials, so emphasizing the effects of the copolymer structure on the kinetics of the writing process. The photoinduced orientation is more than three orders of magnitude higher in a grafted material compared to the dispersion version. The azo‐dye concentration also has an important role in both the amplitude and the dynamics of the photo‐orientation. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 205–213, 2000     

Degradation of textile dyes mediated by plant peroxidases

The peroxidase enzyme from the plants Ipomea palmata (1.003 IU/g of leaf) and Saccharum spontaneum (3.6 IU/g of leaf) can be used as an alternative to the commercial source of horseradish and soybean peroxidase enzyme for the decolorization of textile dyes, mainly azo dyes. Eight textiles dyes currently used by the industry and seven other dyes were selected for decolorization studies at 25–200 mg/L levels using these plant enzymes. The enzymes were purified prior to use by ammonium sulfate precipitation, and ion exchange and gel permeation chromatographic techniques. Peroxidase of S. spontaneum leaf (specific activity of 0.23 IU/mg) could completely degrade Supranol Green and Procion Green HE-4BD (100%) dyes within 1 h, whereas Direct Blue, Procion Brilliant Blue H-7G and Chrysoidine were degraded >70% in 1 h. Peroxidase of Ipomea (I. palmata leaf; specific activity of 0.827 U/mg) degraded 50 mg/L of the dyes Methyl Orange (26%), Crystal Violet (36%), and Supranol Green (68%) in 2–4 h and Brilliant Green 54%), Direct Blue (15%), and Chrysoidine (44%) at the 25 mg/L level in 1 to 2 h of treatment. The Saccharum peroxidase was immobilized on a hydrophobic matrix. Four textile dyes, Procion Navy Blue HER, Procion Brilliant Blue H-7G, Procion Green HE-4BD, and Supranol Green, at an initial concentration of 50 mg/L were completely degraded within 8 h by the enzyme immobilized on the modified polyethylene matrix. The immobilized enzyme was used in a batch reactor for the degradation of Procion Green HE-4BD and the reusability was studied for 15 cycles, and the halflife was found to be 60 h.     

Removal of sulphate and phosphate from aqueous solutions using a food grade polysaccharide as flocculant

The mucilage extracted from the seeds of Tamarindus indica pods, a food grade natural polysaccharide, is used as a flocculant for removal of sulphate and phosphate ions in aqueous medium. The maximum removal obtained was 73.71% for sulphate ions and 75.71% for phosphate ions after 30 min. The optimum mucilage dose was 50 mg/L for both sulphate and phosphate ions. The maximum removal was obtained at acidic pH for both the ions. A series of contact time experiments were conducted to assess the system variables such as concentrations of mucilage and ions and pH. The conductivity measurements were also done and correlated with the percent removal. This eco-friendly food grade polysaccharide was proved to be a very good flocculant for the removal of sulphate and phosphate ions.     

Synthesis,characterization, and dyeing performance of some azo thienopyridine and thienopyrimidine dyes based on wool and nylon

A string of novel heterocyclic mono azo dyes were synthesized and their utilization in dyeing different fabrics as wool and nylon were discussed. Thienopyridine azo dyes 4 and 6 were prepared by reaction of chloro acetamidederivative 2 with diamino compounds to yield 3 and 5 , followed by reaction with NaNO₂/HCl and coupling with nucleophilic reagent. One-pot reaction of chloro acetamide 2 with ammonium thiocyanat in solvent ethanol gave the unexpected thienopyrimidine derivative 7 , which contain two active sites, the former is primary amine that was able to form diazonium salt that coupled with N,N-dimethylaniline, resorcinol, and/or self-coupling to afford the azo dyes 8-10 , and the latter is active methylene group that underwent coupling with different diazonium salts to give the azo thienopyrimidine derivative dye 11-15 . The dyeing performance of these azo dyes had been investigated in terms of their dyeing behavior and fastness properties on different fabrics. Results showed that the color strength (K/S) values, as well as, washing, rubbing, and resistance to acid, alkali and light showed high efficiency of these heterocyclic mono azo dyes to dye wool rather than nylon fibers.     

Strategies for Enhancing Laccase Yield from <Emphasis Type="Italic">Streptomyces psammoticus</Emphasis> and Its Role in Mediator-based Decolorization of Azo Dyes

Enhanced production of laccases from Streptomyces psammoticus in solid-state fermentation was carried out using two different strategies: laccase inducers and scale-up process. Laccase yield was enhanced by a wide range of aromatic inducers. The best inducer was pyrogallol, which yielded 116 U/g as compared to the control (55.4 U/g). Scale-up studies in packed bed bioreactor was performed at different aeration rates. Aeration at 1.5 vvm was identified as the optimum condition for laccase production (75.4 U/g) in the column bioreactor. The enzyme yield was enhanced further by combining the best conditions from the first two experiments. Fermentation was carried out in bioreactors in the presence of 1 mM pyrogallol, which resulted in 3.9-fold increase in laccase yield (215.6 U/g). The role of laccase in azo dye decolorization was evaluated in the presence of four different laccase mediators, at different concentrations. 1-Hydroxybenzotriazole (HOBT) proved to be the best mediator for S. psammoticus laccase and decolorized the azo dyes efficiently. Acid orange, Methyl orange, and Bismarck brown were decolorized at the rates of 86%, 71%, and 75% respectively, by HOBT.     

A biosorption isotherm model for the removal of reactive azo dyes by inactivated mycelia of Cunninghamella elegans UCP542

The biosorption of three reactive azo dyes (red, black and orange II) found in textile effluents by inactive mycelium of Cunninghamella elegans has been investigated. It was found that after 120 hours of contact the adsorption led to 70%, 85%, 93% and 88% removal of reactive orange II, reactive black, reactive red and a mixture of them, respectively. The mycelium surface was found to be selective towards the azo dyes in the following order: reactive red > reactive black > orange II. Dye removal from a mixture solution resulted in 48.4 mg/g retention by mycelium and indicated a competition amongst the dyes for the cellular surface. A Freundlich adsorption isotherm model exhibited a better fit, thus suggesting the presence of heterogeneous binding sites. Electrondense deposits observed on the mycelium ultrastructure suggest that the dyes are mainly retained under the cellular surface of the inactive biomass of C. elegans.