Swelling equilibria and dye adsorption studies of chemically crosslinked superabsorbent acrylamide/maleic acid hydrogels

Superswelling acrylamide (AAm)/maleic acid (MA) hydrogels were prepared by free radical polymerization in aqueous solution of AAm with MA as comonomer with some multifunctional crosslinkers such as trimethylolpropane triacrylate and 1,4-butanediol dimethacrylate. AAm/MA hydrogels were used in experiments on swelling and adsorption of a water-soluble monovalent cationic dye such as Basic Blue 17 (Toluidin Blue). As a result of dynamic swelling tests, the influence of relative content of MA on the swelling properties of the hydrogel systems was examined. AAm/MA hydrogels were swollen in the range 1660-6050% in water, while AAm hydrogels swelled in the range 780-1360%. Equilibrium water content of AAm/MA hydrogels were calculated in the range 0.8873-0.9837. Water intake of hydrogels followed a non-Fickian type diffusion. The uptake of the cationic dye, BB-17 to AAm/MA hydrogels is studied by batch adsorption technique at 25 °C. In the experiments of the adsorption equilibrium, S-type adsorption in Giles's classification system was found. The binding ratio of hydrogel/dye systems was gradually increased with the increase of MA content in the AAm/MA hydrogels.     

A new fast swelling poly[DAPB-co-DMAAm-co-AASS] superabsorbent hydrogel for removal of anionic dyes from water

The objective of this research is to utilize a new poly[N,N-diallyl pyrrolidinium bromide-co-N,Ndimethyl acrylamide-co-acrylic acid sodium salt]superabsorbent hydrogel（SAH）for the removal of two anionic dyes,e.g.,Reactive Red 5B（RR5B）and Reactive Orange M2R（ROM2R）,from water.The SAH was characterized by swelling in water,FTIR,TGA and SEM.The SAH DDA6showed good swelling property and thermal stability.We have also investigated the parameters affecting dye adsorption such as pH,adsorbent dose,adsorption rate and initial dye concentration.The experimental data were also analyzed by applying the well known Langmuir and Freundlich isotherm models.     

Synthesis of poly (acrylamide-co-aconitic acid) adsorbents by gamma-irradiation,characterization, adsorption studies and application for cationic dyes removal

In this study, acrylamide (AAm)/aconitic acid (ACA) copolymers were prepared with two different mol% of aconitic acid 4%, 17% and were irradiated with gamma irradiation at different irradiation doses (4 - 25kGy). The percent yield was assigned by gravimetrical method. The effect of irradiation dose, pH and involved amounts of monomers (AAm/ACA) in hydrogels on swelling properties were investigated. The conversion of monomers to hydrogels was 100% at 25kGy. Poly(acrylamide-co-aconitic acid) P(AAm/ACA) hydrogels have been used for the adsorption of some aqueous solutions of dyes such as Methylene Blue (MB) and Safranine-O (S). The hydrogels were swollen in distilled water at pH 3, 5, 7, 8 and in aqueous solutions of dyes. The initial swelling rates of hydrogels are increased by increasing of pH. The effects of concentration of the aqueous solutions of dye and hydrogel composition on the adsorption were investigated. The adsorption is increased and changed depending on the structure of dye and composition of hydrogel.     

Adsorption of Uranyl Ions into Poly(Acrylamide‐co‐Acrylic Acid) Hydrogels Prepared by Gamma Irradiation

Acrylamide (AAm)/Acrylic Acid (AAc) copolymers have been prepared by gamma irradiation of binary mixtures at three different compositions where the acrylamide/acrylic acid mole ratios varied around 15, 20, and 30%. Threshold dose for 100% conversion of monomers into hydrogels was found to be 8.0 kGy. Poly(Acrylamide‐co‐Acrylic Acid) (poly(AAm‐co‐AAc)) hydrogels have been considered for the removal of uranyl ions from aqueous solutions. Swelling behavior of these hydrogels was determined in distilled water at different pH values and in aqueous solutions of uranyl ions. The results of swelling tests at pH 8.0 indicated that poly(AAm‐co‐AAc) hydrogel, containing 15% acrylamide showed maximum % swelling. Diffusion of water and aqueous solutions of uranyl ion into hydrogels was found to be non‐Fickian in character and their diffusion coefficients were calculated. The effect of pH, composition of hydrogel, and concentration of uranyl ions on the adsorption process were studied at room temperature. It was found that one gram of dry poly(AAm‐co‐AAc) hydrogel adsorbed 70–320 mg and 70–400 mg uranyl ions from aqueous solutions of uranyl nitrate and uranyl acetate in the initial concentration range of 50–1500 mg UO₂ ²⁺L^?, depending on the amount of AAc in the hydrogels, respectively. Adsorption isotherms were constructed for poly(AAm‐co‐AAc)–uranyl ion system indicating an S type of adsorption in the Giles classification system. It is concluded that crosslinked poly(AAm‐co‐AAc) hydrogels can be successfully used for the removal of uranyl ions from their aqueous solutions.     

Dye removal by a novel hydrogel‐clay nanocomposite with enhanced swelling properties

Acrylamide (AAm)‐2‐acrylamide‐2‐methylpropanesulfonic acid sodium salt (AMPSNa) hydrogel and AAm‐AMPSNa/clay hydrogel nanocomposite having 10 w% clay was prepared by in situ copolymerization in aqueous solution in the presence of a crosslinking agent (N,N′‐methylenebisacrylamide (NMBA)). Swelling properties and kinetics of the hydrogel samples were investigated in water and aqueous solutions of the Safranine‐T (ST) and Brilliant Cresyl Blue (BCB) dyes. The swelling and diffusion parameters were also calculated in water and dye solutions. It was observed that the AAm‐AMPSNa/clay hydrogel nanocomposite exhibits improved swelling capacity compared with the AAm‐AMPSNa hydrogel. It was also found that the diffusion mechanisms show non‐Fickian character. Adsorption properties of the hydrogel samples in the aqueous solution of ST and BCB dyes were also investigated. Clay incorporation into the hydrogel structure increased not only the adsorption capacity but also the adsorption rate. Adsorption capacity values of the hydrogel nanocomposite were found to be 484.2 and 494.2 mg g^?1 for the ST and BCB dyes, respectively. It was seen that the adsorption of dyes by the hydrogel nanocomposite completed in 10 min while the AAm‐AMPSNa hydrogel adsorbed dyes approximately in 90 min. Adsorption data of the samples were modelled by the pseudo‐first‐order and pseudo‐second‐order kinetic equations in order to investigate dye adsorption mechanism. It was found that the adsorption kinetics of hydrogel nanocomposite followed a pseudo‐second‐order model. Equilibrium isotherms were analyzed using the Langmuir and Freundlich isotherms. It was seen that the Langmuir model fits the adsorption data better than the Freundlich model. Copyright © 2008 John Wiley & Sons, Ltd.     

Cationic dye adsorption by acrylamide/itaconic acid hydrogels in aqueous solutions

Acrylamide/itaconic acid (AAm/IA) hydrogels containing different quantities of itaconic acid have been irradiated with γ radiation. The hydrogels were used in an experiment concerning the adsorption of cationic dyes such as Basic Blue 9, Basic Violet 1 and Basic Blue 12. In the experiments of the adsorption of dyes from their synthetic aqueous solutions, type S adsorption isotherms were found. One mole of monomeric unit of AAm/IA hydrogels adsorbed 78.5–513.1 μmole of Basic Blue 9, 60.2–641.1 μmole of Basic Violet 1 and, 28.8–593.3 μmole of Basic Blue 12, while acrylamide hydrogel did not adsorb any cationic dye. As a result, it was shown that the AAm/IA hydrogels could be used as an adsorbent for water pollutants such as dyes, and immobilization of these organic contaminants in the hydrogels from waste water can solve one of the most important environmental problems of the textile industry. © 1997 John Wiley & Sons, Ltd.     

Copper and Nickel Removal from Aqueous Solutions Using New Chelating Poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid] Hydrogels

New poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid], poly [AAm/NVP/HECA], chelating hydrogels with different composition of HECA monomer have been prepared via free radical solution polymerization using N,N‐methylene bisacrylamide as a crosslinker. The hydrogels obtained were loaded with metal ions and characterized by FT‐IR spectroscopy, Scanning Electron Microscope (SEM) and Thermogravimatric analysis (TGA). The removal of Cu²⁺ and Ni²⁺ from aqueous solutions by the hydrogel was examined by a batch equilibrium method. The influence of treatment time, pH, initial concentration of the metal ions and HECA content in the feed compositions on the amount of adsorbed metal ions was studied. Swelling of the hydrogel was also carried out in distilled water and metal ion solutions. The removal of the metal ions followed the following order: Ni²⁺>Cu²⁺. The amount of metal ions removed increased with increasing HECA content in the feed composition, treatment time, pH of the medium and initial concentration of metal ions. The desorption of metal ions were carried out using 1 N HCl and 0.5 N H₂SO₄. The poly[AAm/NVP/HECA] hydrogels could be used many times without significantly decreasing their adsorption capacity.     

(Sodium Alginate/Acrylamide) Semi‐Interpenetrating Polymer Networks and their Usability on Removal of Lead,Cadmium, Nickel Ions

In this study, (sodium alginate (NaAlg)/acrylamide (AAm)) interpenetrating polymer networks (IPN) have been prepared at three different compositions, where the sodium alginate composition varies 1, 2, and 3% (w/v) in 50% (w/v) acrylamide solutions. These solutions have been irradiated with a ⁶⁰Co‐γ source at different doses. The percent conversion was determined gravimetrically and 100% gelation was achieved at the 10.0 kGy dose. The swelling results at pH 7.0 and 9.0 indicated that (NaAlg/AAm)3IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water, with swelling increasing in the order of Ni²⁺>Cd²⁺>Pb²⁺. Diffusion in aqueous solutions of metal ions within (NaAlg/AAm)IPN hydrogels was found to be Fickian character. Diffusion coefficients of (NaAlg/AAm)IPN hydrogels in water and aqueous solutions of metal ions were calculated. The maximum weight loss temperature and half life temperature for NaAlg, PAAm, (NaAlg/AAm)IPN and (NaAlg/AAm)IPN‐metal ion systems were found from thermal analysis studies. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb nickel, cadmium and lead ions from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of metal ion at pH 7.0. Adsorption isotherms were constructed for the (NaAlg/AAm)IPN‐metal ion systems. S type adsorption in the Giles classification system was found.     

Aam/Aac水凝胶对碱性藏花红染料的吸附特性研究

以丙烯酰胺(AAm)、丙烯酸(AAc)合成了单体配比分别为1，2、1／1、2，1的AAm/AAcc水凝胶，采用分光光度计法研究了此水凝胶对水溶性单价阳离子染料碱性藏花红的吸附特性，测定了它们的吸附动力学曲线和吸附等温线：探讨了水凝胶单体组成对该染料吸附性能的影响：并且用静电场理论解释了解吸后水凝胶更优的再吸附特性，研究表明，AAm，AAc水凝胶可作为染料污水处理中一种良好的吸附剂。     

Water uptake and dye sorption studies of chemically crosslinked highly swollen novel ternary acrylamide‐based hydrogels including citraconic acid and sodium acrylate

Highly swollen hydrogels made by the polymerization of acrylamide (AAm) with some anionic monomers such as citraconic acid (CITA) and sodium acrylate (SA) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen AAm/CITA/SA or AAm/SA/CITA hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with CITA and SA as co‐monomers and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4‐butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. Chemically crosslinked AAm/CITA/SA or AAm/SA/CITA hydrogels were used in experiments on sorption of water‐soluble monovalent cationic dye such as “Nil blue” (Basic Blue 12; BB 12). Equilibrium percentage swelling values of AAm/CITA/SA or AAm/SA/CITA hydrogels were calculated in the range of 1797–22,098%. Some swelling kinetic parameters were found. Diffusion behavior of water was investigated. Water diffusion into the hydrogels was found to be non‐Fickian in character. For sorption of cationic dye, BB 12 into the hydrogels was studied by batch sorption technique at 25°C. AAm/CITA/SA or AAm/SA/CITA hydrogels in the dye solutions showed coloration, whereas AAm hydrogel did not show sorption of any dye from the solution. The sorption capacity of AAm/CITA/SA or AAm/SA/CITA hydrogels was investigated. At the end of the experiments, 21.70–78.91% BB 12 adsorptions were determined. Copyright © 2007 John Wiley & Sons, Ltd.     

Cyclodextrin-Cross-Linked Hydrogels for Adsorption and Photodegradation of Cationic Dyes in Aqueous Solution

Possessing three-dimensional porous structures and tunable mechanical strengths, cyclodextrin-containing polymeric hydrogels are one of the most promising water-based adsorbent materials due to their easy availability, simple chemical modification and environmental friendliness. In this work, two kinds of hydrogels were prepared via the copolymerization with acrylic acid and vinyl-derivatized β-cyclodextrins in water. These two gels have showed good adsorption performance towards cationic dyes through the noncovalent interactions with their anionic backbones and porous network. Meanwhile, pseudo-second-order model was selected to clarify the adsorption kinetics process. Moreover, nano-scaled TiO₂ was doped into these resultant cyclodextrins-based hydrogels to achieve efficient degradation of dyes upon light irradiation. The obtained TiO₂-loaded hydrogels could exhibit improved adsorption performance and make the adsorbed dyes photo-degraded with the decolorization rates above 95%. It can be envisioned that such cyclodextrin-based soft materials may find applications in dye clearance and water treatment.     

Adsorption of acid red 114 and reactive black 5 in aqueous solutions on dendrimer‐conjugated magnetic nanoparticles

The adsorption of the dyes Acid Red 114 and Reactive Black 5 in aqueous solutions on polyhydroxyl dendrimer magnetic nanoparticles (Fe₃O₄@SiO₂‐TRIS) was studied in a batch system. The Fe₃O₄@SiO₂‐TRIS NPs were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, and transmission electron microscopy. Experiments were performed under different conditions such as the initial dye concentration, adsorbent dose, and pH. The pseudo‐second‐order model provided a very good fit for the two anionic dyes. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherms at different temperatures, and the former agreed very well with the experimental data. However, the adsorption capacity of Fe₃O₄@SiO₂‐TRIS NPs was reduced during surface modification, which could be due to the dye occupying the binding sites of the dendrimer. Thermodynamic parameters, namely the change in free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰), were also determined.     

Super Absorbent Hydrogel Based on Poly[acrylamide/maleic acid/2-methacryloxy ethyl trimethylammonium chloride]: Synthesis,Characterization and their Application in the Removal of Chromium (VI) from Aqueous Solution

New poly[acrylamide/maleic acid/2-methacryloxy ethyl trimethylammonium chloride], poly[AAm/MA/METAC], super absorbent hydrogels (M1-M4) were prepared via microwave irradiated free radical solution polymerization using different compositions. According to swelling experiments, hydrogel M1 with higher METAC content gave relatively higher swelling percentage compared to other hydrogels. The hydrogel M1 was characterized by FT-IR, TGA, and SEM analysis. The influence of the uptake conditions such as pH, time, adsorbent dose and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. Furthermore, the Langmuir and Freundlich adsorption isotherms were applied and they showed a good fit to the experimental data.     

Enhanced swelling and adsorption properties of AAm‐AMPSNa/clay hydrogel nanocomposites for heavy metal ion removal

Novel type hydrogel‐clay nanocomposites based on the acrylamide (AAm)‐ 2‐acrylamido‐ 2‐methylpropane sulfonic acid (AMPS) sodium salt and clay were synthesized via in situ copolymerization in aqueous solution. Samples were characterized by determining total basic group (TGB) content and swelling degree, XRD analysis, and FTIR spectroscopy. Effects of monomer ratio and clay amount on the swelling properties of the samples were investigated. It was found that the hydrogel/clay nanocomposites exhibited improved swelling capacity compared with the hydrogels. Samples were used to remove heavy metal ions (Cu (II), Cd (II), and Pb (II)) from aqueous solution in competitive and non‐competitive conditions for the first time. The effects of time and pH of the initial metal ion solution on the adsorption capacity were investigated and selectivity properties of the samples were evaluated. It was found that incorporation of a low amount of clay (10% (wt)) into the polymer structure increased the heavy metal ion adsorption capacity of the sample. It was concluded that the AAm‐AMPS/clay nanocomposites could be used as novel type, fast‐responsive, and high capacity sorbent materials in heavy metal removing processes. Copyright © 2007 John Wiley & Sons, Ltd.     

Uptake of Basic Blue 17 from aqueous solutions by using chemically crosslinked polyelectrolyte AAm/AASS hydrogels

In this study, the removal of a cationic thiazin dye such as Basic Blue 17 (Toluidin Blue, BB 17) by chemically crosslinked acrylamide (AAm)/acrylic acid sodium salt (AASS) hydrogels was investigated. Super water retainer AAm/AASS hydrogels with various compositions were prepared from ternary mixtures of AAm, AASS and water by free radical polymerization in aqueous solution using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA), N,N′ methylenebisacrylamide (NMBA), 1,4 butanediol dimethacrylate (BDMA) and trimethylolpropane triacrylate (TMPTA). Adsorption of Basic Blue 17 from aqueous solutions was studied by batch sorption technique at 25^°C. The effect of Basic Blue 17 concentration and mass of adsorbent on the dye adsorption were examined. In the experiments of the sorption, C type and L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K _i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô) for AAm/AASS hydrogel-dye binding system were calculated by using Klotz linearization method. Finally, the amount of sorbed Basic Blue 17 per gram of dry hydrogel (q) was calculated to be 1.96–21.35 μ mol dye per gram for AAm/AASS hydrogels. Adsorption of Basic Blue 17 was changed range 39.17–96.63%. AAm/AASS hydrogels crosslinked by TMPTA, EGDMA, BDMA or NMBA can be used a sorbent in biotechnology, environment, sorption, separation, purification, immobilization and enrichment of some species.     

Transformation of textile dyes by white-rot fungus Trametes versicolor

We have investigated transformation of eight industrial dyes by a whiterot fungus, Trametes versicolor. The fungus was found to decolorize Reactive Golden Yellow R, Procion Red, Reactive Violet 5, Reactive Blue 28, and Ponceau Red 4R at an initial dye concentration of 80 ppm within 72 h of incubation, whereas it took 5 d to completely decolorize Reactive Black 5 (40 ppm). However, it did not significantly decolorize Reactive Red 152 and Novatic Blue BC S/D. During decolorization in liquid medium, laccase and manganese-independent peroxidase (MiP) activities were detected in culture filtrate of T. versicolor. Dye-decolorizing activity of the culture was found to be associated with H₂O₂-dependent activity of the culture filtrate. Furthermore, dye-decolorizing activity of the culture filtrate was not influenced by Mn²⁺ or veratryl alcohol, thus suggesting a role of extracellular MiP in decolorization of synthetic dyes by T. versicolor.     

Removal of cationic dyes by poly(acrylamide-co-acrylic acid) hydrogels in aqueous solutions

Poly(acrylamide-co-acrylic acid (poly(AAm-co-AAc)) hydrogels prepared by irradiating with γ-radiation were used in experiments on swelling, diffusion, and uptake of some cationic dyes such as Safranine-O (SO) and Magenta (M). Poly(AAm-co-AAc) hydrogels irradiated at 8.0 kGy have been used for swelling and diffusion studies in water and cationic dye solutions. The maximum swellings in water, and SO, and M solutions observed are 2700%, 3500%, and 4000%, respectively. Diffusions of water and cationic dyes within hydrogels have been found to be non-Fickian in character. Adsorption of the cationic dyes onto poly(AAm-co-AAc) hydrogels is studied by the batch adsorption technique. The adsorption type was found Langmuir type in the Giles classification system. The moles of adsorbed dye for SO and M per repeating unit in hydrogel (binding ratio, r) have been calculated as 3834×10⁻⁶ and 1323×10⁻⁶, respectively. These results show that poly(AAm-co-AAc) hydrogels can be used as adsorbent for water pollutants such as cationic dyes.     

RADIATION INDUCED ACRYLAMIDE/CITRIC ACID HYDROGELS AND THEIR SWELLING BEHAVIORS

Citric acid (CAc) moieties containing acrylamide (AAm) hydrogels were prepared by gamma irradiation of their aqueous solutions. A possible polymerization and crosslinking mechanism for acrylamide/citric acid (AAm/CAc) hydrogels is proposed. The effects of irradiation dose and citric acid content on swelling behavior were investigated. Swelling took place in water at 25°C and was followed gravimetrically. Incorporation of a relatively low amount of citric acid to acrylamide hydrogel increased its swelling up to 950% from 700%. The diffusion of water into AAm/CAc hydrogels was found to be a non-Fickian type. Diffusion coefficients of AAm/CAc hydrogels found as 5 × 10^?7? 10 × 10^?7 cm² sec^?1. It has also been found that the number average molar mass between crosslinks is increased with the CAc content and decreased with irradiation dose.     

Adsorption of Apollo reactive dyes on poly(N,N dimethylamino ethylmethacrylate) hydrogels

Poly(N,N-dimethylamino ethylmethacrylate) [P(DMAEMA)] hydrogels were prepared by irradiating the ternary mixtures of dimethylamino ethylmethacrylate (DMAEMA)/ethyleneglycol dimethacrylate (EGDMA)/water (H₂O) by γ-rays at ambient temperature. The swelling of four types of DMAEMA hydrogels in distilled water is higher than the swelling of these hydrogels in dye solutions. The value of equilibrium swelling of P(DMAEMA)1 hydrogel was 338% at pH 7.0 in distilled water, while it was 325% and 326% at pH 7.0 in Apollofix Red (AR) and Apollofix Yellow (AY) solutions, respectively. The adsorption capacity of P(DMAEMA)1 hydrogel was found to increase from 85 to 131 mg for AR g⁻¹ dry gel and from 58 to 111 mg for AY g⁻¹ dry gel with decreasing pH of the dye solutions.     

Magnetically assisted removal and separation of cationic dyes from aqueous solution by magnetic nanocomposite hydrogels

Magnetic poly(acrylic acid‐acrylamide‐butyl methacrylate) (P(AAB)) nanocomposite hydrogels were prepared and used as adsorbents for removal and separation of cationic dyes from aqueous solution. These magnetic P(AAB) nanocomposite hydrogels were characterized by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). It was found that these magnetic P(AAB) nanocomposite hydrogels had magnetic responsive characters. The dynamic swelling, removal, and separation of cationic dye, crystal violet (CV), and basic magenta (BM) by these magnetic nanocomposite hydrogels were studied. The adsorption capacity and isotherm studies of cationic dyes onto magnetic P(AAB) nanocomposite hydrogels have been evaluated. The magnetic P(AAB) nanocomposite hydrogels containing Fe₃O₄ particles can be easily manipulated in magnetic field for removal and separation of cationic dyes from aqueous solution. Adsorption process agreed very well with the Langmuir and Freundlich models. Copyright © 2010 John Wiley & Sons, Ltd.