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.     

Decolorization of dyes using immobilized laccase enzyme on zinc ferrite nanoparticle from single and binary systems

In this paper, laccase enzyme was immobilized onto zinc ferrite nanoparticle and the characteristics of enzyme immobilized nanoparticle (EIN) were evaluated by Fourier transform infrared (FTIR) and scanning electronic microscope (SEM). Enzymatic decolorization of dyes using EIN from single and binary systems was studied. Direct red 31 (DR31) and Acid blue 92 (AB92) were used as model dyes. The effects of several parameters such as EIN dosage, pH, and dye concentration on decolorization of dyes from single and binary systems were evaluated. The optimized amount of EIN, reaction time, and pH for decolorization of dyes from single and binary systems were 0.2 g (for DR31) and 0.3 g (for AB92), 40 min, and 3 in single systems and 0.2 g (for DR31 and AB92), 40 min, and 3 in binary systems, respectively. Dye decolorization kinetics followed Michaelis-Menten model. The results showed that enzymatic process using EIN was effective method to decolorize dyes from single and binary systems.     

Magnetically modified spent grain for dye removal

Spent grain, the major by-product of the brewing industry, was magnetically modified by contact with water-based magnetic fluid. The prepared material has been used as a new inexpensive magnetic adsorbent for the removal of water-soluble dyes. The dye adsorption could be described both with the Langmuir and Freundlich isotherms. The maximum adsorption capacities reached the value up to 72.4 mg of dye (Bismarck brown Y) per g of dried magnetically modified spent grain.     

Kinetic, equilibrium and thermodynamic studies of ternary system dye removal using a biopolymer

In this paper, dye removal ability of sodium alginate (SA) as a biopolymer from ternary systems was investigated. Physical characteristics of SA were studied using Fourier transform infra-red (FTIR) and scanning electron microscopy (SEM). Three textile basic dyes were used as model compounds. The adsorption kinetics, isotherms and thermodynamics were studied. The effect of SA dosage, initial dye concentration and pH on dye removal was elucidated. It was found that adsorption kinetics of dyes followed with pseudo-second order kinetics. In addition, dyes followed with Langmuir, and extended Langmuir isotherm in single and ternary systems, respectively. The thermodynamic data showed that the dye adsorption onto SA was a spontaneous, endothermic and physisorption reaction. Based on the data of present investigation, one could conclude that the alginate being a biocompatible, eco-friendly and low-cost adsorbent might be a suitable alternative for elimination of dyes from colored aqueous solutions.     

Morphological structures of the cellulose hybrids containing polyhedral oligomeric silsesquioxane and their application for removing C.I. Reactive Red 250

Cellulose hybrids containing polyhedral oligomeric silsesquioxane (POSS) were synthesized by crosslinking reaction. The chemical and morphological structures of the hybrids were characterized by elemental analysis, infrared spectrum, scanning electron microscope and atomic force microscope. The hybrids were used for adsorbing C.I. Reactive Red 250 in aqueous solution. Adsorption kinetic and equilibrium isotherm of the cellulose hybrids for the dye were investigated. The hybrids formed new adsorptive positions for dyes because of a nanometer-sized cubic core and numerous organic functional groups (-C-N-). The adsorption capacity of the hybrid materials was significantly higher than that of the control cellulose. The adsorption of the dye on the hybrids was good fit with Langmuir isotherm equation and the second-order model. The apparent activation energy of the dye on the hybrid was 14.87 kJ/mol.     

Synthesis of urethane polycarboxylate as a novel adsorbent and its binary system dye removal ability from aqueous solution

In this paper, urethane polycarboxylate (UPC) as a novel adsorbent was synthesized and characterized. Dye removal ability of UPC from aqueous solution of single and binary systems was studied. Fourier transform infrared (FTIR) was used to characterize UPC. Basic Blue 41 (BB41), Basic Red 18 (BR18), and Basic Violet 16 (BV16) were used as cationic dyes. Dye removal isotherm and kinetic were evaluated. The effect of UPC dosage, initial dye concentration, and inorganic anions on dye removal was investigated. The capacity of UPC to remove BB41, BR18, and BV16 were 333 mg/g, 278 mg/g, and 222 mg/g, respectively. Dye removal kinetics and isotherm using UPC were fitted with the pseudo-second order and Langmuir model, respectively. The results showed the UPC might be used as a dye adsorbent to treat multicomponent systems containing cationic dyes.     

Copper oxide-carbon nanotube (CuO/CNT) nanocomposite: Synthesis and photocatalytic dye degradation from colored textile wastewater

In this paper, CuO/CNT nanocomposite was synthesized and its photocatalytic dye degradation ability for colored textile wastewater was studied. The characteristics of the nanocomposite were investigated by XRD, SEM and FTIR. The photodegradation of Direct Red 31 (DR31) and Reactive Red 120 (RR120) by CuO/CNT in presence of H₂O₂ was investigated. Photocatalytic dye degradation was determined by UV-vis spectrophotometer. Effects of catalyst dosage, initial dye concentration and salt on photodegradation performance were studied. The photocatalytic dye degradation ability of pure CuO and CuO/CNT nanocomposite is 78 % and 89 % for DR31 and 70 % and 87 % for RR120, respectively. The results showed that CNT increased the photocatalytic activity of CuO. The presence of salt decreases dye degradation efficiency. The dye degradation kinetics by nanocomposite followed first-order kinetic model. The reaction rate at 0.005 g catalyst was 0.0137 and 0.0105 min^-1 for DR31 and RR120, respectively. It was found that the CuO/CNT nanocomposite as a photocatalyst could be used to degrade dyes from colored wastewater.     

Eco-friendly biopolymer/clay/conducting polymer nanocomposite: Characterization and its application in reactive dye removal

In this study starch-montmorillonite/polyaniline (St-MMT/PANI) nanocomposite was synthesized by chemical oxidative polymerization of aniline in the presence of starch-montmorillonite nanocomposite dispersion. The prepared ternary nanocomposite was characterized using FT-IR, XRD, SEM, TGA and TEM techniques. XRD patterns combined with TEM results confirmed the intercalation of MMT in the starch matrix. SEM micrographs revealed the growth of polyaniline over the surface of the St-MMT nanocomposite. The St-MMT/PANI nanocomposite was used for the adsorption of a reactive dye. Batch removal experiment results showed complete removal of dye in a very short contact time. Further investigations indicated that the removal mechanism was based on both the adsorption and electrostatic attraction between nanocomposite and dye molecules. The experimental data were well fitted to the Langmuir isotherm and pseudo-second-order kinetic model. The adsorption capacity of reactive dye on St-MMT/PANI nanocomposite was 91.74 mg g^?1. All these results demonstrated the effectiveness of the hybrid system as an efficient adsorbent for removal of reactive dyes from textile effluents.     

Functionalization of the aquatic weed water hyacinth <Emphasis Type="Italic">Eichhornia crassipes</Emphasis> by using zinc oxide nanoparticles for removal of organic dyes effluent

In this study, purified Eichhornia crassipes dead biomass, coated biomass with ZnO nanoparticles (NPs) and one coated with both ZnO NPs and polyethylenimine (PEI) were successfully fabricated as a bioadsorbent and biodegradent of organic dyes from the textile dye effluent. These ZnO NPs are capable of enhancing the dispersability and adsorption capacity of PEI and the anionic dyes. The surface analyses of Eichhornia crassipes, Eichhornia crassipes/ZnO NPs and Eichhornia crassipes/ZnO NPs/ PEI were characterized by SEM, specific surface area and micropore volume. The effect of three parameters including Eichhornia crassipes concentration, dye concentration and contact time on the color removal percent and degradation percent were evaluated. The results showed that the bleached Eichhornia crassipes was an efficient adsorbent for cationic dyes. Also, the effectiveness of Eichhornia crassipes/ZnO NPs was employed as photocatalytic agent for the degradation of C.I. Direct Red 23 in the presence and absence of UV irradiation. Moreover, Eichhornia crassipes/ZnO NPs/PEI shows a high adsorption capacity toward the anionic dyes C.I. Acid Red 40 and C.I. Reactive Orange 91. It was found that, Eichhornia crassipes/ZnO NPs was completely degraded C.I. Direct Red 23 by >90 % within 90 min of UV irradiation time, whereas in the absence of UV irradiation it required a substantially longer time (120 min) to achieve a similar degradation percent. In addition, Eichhornia crassipes/ZnO NPs/PEI was most effective and show the maximum adsorption capacity for C.I. Reactive Orange 91 and C.I. Acid Red 40 and its efficiency for the color removal percent was 100 % for C.I. Reactive Orange 91 and 95 % for C.I. Acid Red 40 in less than 60 min processing time.     

Dye Adsorption from Aqueous Solution by Cellulose/Chitosan Composite: Equilibrium,Kinetics, and Thermodynamics

A novel eco-friendly porous adsorbent of cellulose (CE)/chitosan (CS) aerogel was prepared through sol-gel process and freeze-drying to remove Congo Red (CR). A series of aerogels were prepared by adjusting the mass ratios of CE and CS. Composite aerogels were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). SEM images showed that it was possible to change the structure of the aerogel by adjusting the amount of chitosan. The effects of dosage of chitosan, initial pH, temperature, adsorbent dosage, contact time, and initial dye concentration on adsorption capacities for CR were studied in detail. Batch adsorption studies showed that aerogel exhibited maximum removal efficiency to CR at a composite ratio of 1:3 and dosage of 2.5 g/l. CE/CS aerogel had excellent adsorption capacities for CR at a pH range of 3-11, which indicated stability of the aerogel in both acidic and alkaline conditions. CR adsorption on the composite aerogel fitted pseudo-second-order kinetics and Langmuir isotherm. The Langmuir isotherm model revealed that the maximum theoretical adsorption capacity of this material for CR was 381.7 mg/g at pH 7.0 at 303 K for 24 h. The adsorption mechanism included electrostatic and chemical interactions. The results indicated that the adsorption capacity of CE/CS aerogels was higher than the other chitosan composites adsorbents.     

Preparation and acid dye adsorption behavior of polyurethane/chitosan composite foams

We prepared a series of polyurethane(PU)/chitosan composite foams with different chitosan content of 5∼20 wt% and investigated their adsorption performance of acid dye (Acid Violet 48) in aqueous solutions with various dye concentrations and pH values. It was observed that PU/chitosan composite foams exhibited well-developed open cell structures. Dye adsorption capacities of the composite foams increased with the increment of chitosan content in composite foams, because amine groups of chitosan serve as the binding sites for sulfonic ions of acid dyes in aqueous solutions. In addition, dye adsorption capacities of composite foams were found to increase with decreasing the pH value, which stems from the fact that the enhanced chemisorption between protonated amine groups of chitosan and sulfonic ions of acid dye is available in acidic solutions. The dye adsoption kinetics and equilibrium isotherm of the composite foams were well described with the pseudo-second order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacity (q _max) for the PU/chitosan composite foams with 20 wt% chitosan content is evaluated to be ca. 30 mg/g.     

Cellulose-based porous adsorbents with high capacity for methylene blue adsorption from aqueous solutions

A novel cellulose-based porous adsorbent with high adsorption capacity for methylene blue (MB) was prepared by free radical polymerization methods. The obtained polymer grafting rate and dye removal efficiency are as high as 338.64 % and 97.74 %, respectively, when the dosage of monomer is 4.5 g, the polymerization condition is 3 h at 70 °C. The cellulose-based adsorbent showed high mechanical properties and good flexibility. The Langmuir isotherm model revealed that the maximum theoretical adsorption capacity of this material for methylene blue was 1734.816 mg g-1 at pH 9.0 at 313 K, which is higher than the values observed for other adsorbents. Scanning electron microscopy (SEM) showed that the cellulose-based adsorbent exhibits a typical well-defined porous and interconnected three-dimensional framework structure, which is benefits to dye adsorption. The adsorption kinetics (pseudo first-order, pseudo-second-order, and intraparticle diffusion models) was also studied, and the pseudo-second-order model fitted MB adsorption better than the pseudo-first-order and intraparticle diffusion models at different initial dye concentrations (500-3000 mg l ^-1). The novel polyacrylic acid-grafted quaternized cellulose (PAA-g-QC) adsorbent is thus potentially useful for the treatment of dye-contaminated wastewater.     

Modified polyamide 66 fibers for the removal of reactive dyes from aqueous suspension

In this paper, we report the modification of polyamide sample (PA) with different contents of chitosan (CS) using citric acid (CA) as a cross-linker [PA-CA-CS]. New materials were confirmed to be formed in PA using FT-IR spectrum. It is also checked in terms of the change in thermal stability event and decomposition behavior in thermogravimetry through TG-DTA instruments. Then, the ability of unmodified and modified supports was tested for the adsorption of two reactive dyes i.e. Cibacron Brilliant Yellow 3G-P and Cibacron Blue P-3R. Sorption experiments were performed under varying several experimental conditions such as pH, contact time, initial dye concentration, and temperature. The isotherm and kinetic models were undertaken to assess the dye removal mechanism. The applicability of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin equations was checked and data were fitted using Langmuir model. The second-order equation was shown to fit the adsorption kinetics. Data gleaned from both thermodynamic results and modeling data indicate that the adsorption follows a chemical and exothermic process.     

Adsorption Kinetics of Acid Red on Activated Carbon Web Prepared from Acrylic Fibrous Waste

In this work, activated carbon (AC) web was prepared using physical activation under the layer of charcoal in high temperature furnace. The carbonization of acrylic fibrous waste was performed at different temperatures (800 °C, 1000 °C, and 1200 °C) with heating rate of 300 °C/h and at different holding time. At 1200 °C, the heating rate of 300 °C/h and no holding time provided better results of surface area as compared to carbonization at 800 °C and 1000 °C. The activated carbon web (AC) prepared at 1200 °C was used for removal of Acid Red 27 dye from aqueous media by varying different parameters like initial concentration of dye, stirring speed, adsorbent dosage, and pH. The results were evaluated using non-linear forms of Langmuir and Freundlich isotherms. The Freundlich isotherm was found to describe the results more effectively because of non-homogenous surface of activated carbon web. Further, the kinetics of adsorption was examined using linear and nonlinear forms of pseudo 1st order and pseudo 2nd order.     

Coloration and Decoloration of Textiles Using a TiO<Subscript>2</Subscript> Composite Pigment

A colorable pigment was prepared by dye adsorption onto titanium dioxide and subsequent silane coating. The effects of pH value, dye concentration, and adsorption times on dye adsorption were discussed. Large adsorption capacity of an anionic dye was obtained at pH value of 2 and the adsorption process was well described by the Langmuir isotherm model. Good dyeability and color fastness of pigment dyed fabric were achieved in the normal life cycle under sunlight. The decoloration of pigment was realized through photocatalytic degradation of dye molecules by titanium dioxide under ultraviolet irradiation when reusing the pigment dyed textiles after disposal. The new absorption peaks in the FTIR spectrum at 2924.95 cm^-1, 1714.91 cm^-1, 1461.17 cm^-1, and 1289 cm^-1 verified silane modification. Silane modification improved fixation of dyes onto the pigment and immobilization of pigments onto substrates. The close attachment of silane coating layer to titanium dioxide was conducive to photodegradation of dye molecules in the pigment.     

Removal of some cationic dyes from aqueous solution by acrylamide- or 2-hydroxyethyl methacrylate-based copolymeric hydrogels

In this study, anionic hydrogels were prepared using a crosslinker (N,N′-methylenebisacrylamide) through a free radical addition reaction in aqueous solutions of neutral acrylamide or 2-hydroxyethyl methacrylate monomer and anionic monomers, mesaconic acid or aconitic acid. Cationic dyes along with safranine (azine-), nile blue (oxazine-) and methylene blue (thiazine-) were selected as models of pollutants, and adsorption of these dyes onto the hydrogels was investigated. To examine the effect of concentration on adsorption, dye solutions prepared with a concentration range of 5–50 mg l^?1 and 0.1 g hydrogel at 25 °C were exposed to the hydrogels until equilibrium was established. Dye adsorption onto the hydrogels was found to be an L type Giles adsorption isotherm. Monolayer sorption capacity and adsorption constant values were calculated from the Langmuir plots. To calculate R_L values, a non-dimensional analysis was used and they were always found to be 0<R<1. In other words, the hydrogels were favorable for adsorption of these dyes. Aqueous solutions of dyes were observed to interact with hydrogels in the following order: oxazine > azine > thiazine. Furthermore, the higher the number of carboxyl groups in the hydrogel composition, the higher the adsorbed amount of substance.     

Adsorption and dyeing characteristics of reactive dyes onto cotton fiber in nonionic Triton X-100 reverse micelles

The nonionic reverse micelles used for dyeing cotton fiber were prepared with a non-ionic surfactant Triton X-100 (TX-100) by injecting small amount of reactive dye aqueous solution. The adsorption capacity of three water-soluble anionic azo dyes including Reactive Blue 222, Reactive Red 195 and Reactive Yellow 145 onto cotton fiber was investigated. The Langmuir and Freundlich isothermals were employed to model the adsorption data. In addition, the color strength and fixation rate of cotton fabrics dyed in the reverse micelles and bulk water were examined and compared. The salt and alkali as influencing factors were also discussed. The FT-IR spectra were employed to study the polarity of water added in reverse micelles. The results indicated that the adsorption of the dyes onto cotton showed better agreement with Langmuir model. The adsorption process was monolayer adsorption. Reactive Yellow 145 with lower negative charge and higher hydrophilicity exhibited the higher adsorption capacity. The fixation percentage and color strength of the cotton fiber dyed in TX-100 reverse micelles was higher than those in bulk water. The polarity of water in TX-100 reverse micelles was lower than that in bulk water.     

The antimicrobial characteristic study of acrylic fiber treated with metal salts and direct dyes

Acrylic fabric was treated with direct dyes in combination with copper and zinc sulfates as mordanting agents and then tested for their antimicrobial activity against Gram-positive and Gram-negative bacteria. The metal salts used were also studied for their likely effects on the antimicrobial property of fabrics dyed with C.I. Direct Yellow 12, C.I. Direct Red 23, C.I. Direct Red 31, and C.I. Direct Black 38. Untreated (control) acrylic fabric exhibited no antibacterial behavior whilst dyed and mordanted fabrics revealed considerable antimicrobial properties. It was found that the fabric treated with C.I. Direct Yellow 12 and copper sulfate as mordant achieved the highest antimicrobial activity with good washing fastness. Finally, FT-IR analysis, light, and washing fastnesses of the treated samples were evaluated.     

Direct dye removal by using UV/hydrogen peroxide/multiwalled carbon nanotubes

In this study, decoloration of Direct Blue 71 (DB71) and Direct Red 23 (DR23) has been discussed by using Multiwalled Carbon Nanotubes (MWCNTs) and Hydrogen peroxide under UV radiation. The purpose of this study is removal of organic compounds by using carbon nanotubes that are effective adsorbents for different types of pollutants, due to their porous nature and large surface area. It also causes catalytic decomposition of hydrogen peroxide. Adsorption rate was investigated under various parameters (initial dye concentration, salt, temperature and pH). The main objective of this study is to appraise the synergic effect between H₂O₂ and MWCNTs under UV radiation. The dye adsorption results of spectrophotometer, showed that by decreasing the dye concentration from 0.2 g/l to 0.05 g/l with the optimal value of MWCNTs 0.2 g/l and hydrogen peroxide 2 g/l at pH=4 and 6 cm distance from the UV lamp, the dye removal increased.     

Acrylamide-assisted Photografting of Bisacrylamide Dyes onto Cotton

Dibromopropionamide groups of C.I. Reactive Red 136 were dehydrobrominated to obtain bisbromoacrylamide groups. Photografting yield of the modified dyes onto cotton increased with the addition of acrylamide comonomer, presumably reducing the steric hindrance between the dyes with bulky chromophores. The acrylamide-assisted grafting was more prominent with increasing degree of the functionality. The optimum grafting was obtained with 2.5 molar ratio AAm and 7 % photoinitiator with respect to 0.03 mol/l dye under a UV energy of 25 J/cm². The grafting yield and K/S of the grafted cotton with C.I. Reactive Red 83 was lower than that with the modified Red 136 at the same degree of functionality 2.0, probably because the relatively larger chromophore of the Red 83. In addition, the washing, rubbing and light fastness of the grafted cotton fabrics with the modified Red 136 were higher than the adsorption-based conventional dyeing, which was more pronounced as the degree of functionality increased.