Utilization of polyampholyte hydrogels for simultaneous removal of textile dyes from aqueous solutions

The study aimed to create hydrogel structures with greater functionality, otherwise known as polyampholytes (PAHs), and to use these in simultaneous removal studies for remazol-type dyes found in environmental waste waters. Adsorption studies were accomplished at 20°C and 35°C, indicated that adsorption process was exothermic in nature. The Q_m values for the PAH-dye systems were in the interval 111–122 mg dye/g PAH with Ads% from 94% to 98%. The ability of PAH hydrogels to adsorb two different species of dye molecules at the same time is an advantage of PAH adsorbents compared to other hydrogel adsorbents prepared in this area.     

New sorbent hydrogels for removal of acidic dyes and metal ions from aqueous solutions

Summary Poly(N-hydroxymethylacrylamide), PHMA, hydrogels were prepared by using N-hydroxymethylacrylamide, HMA, monomer and polyethyleneglycol(400)diacrylate as a crosslinking agent in aqueous medium and then amine groups were incorporated onto PHMA hydrogels by amination reaction with different diamines. The obtained hydrogels were characterized by determination of amine value, hydroxymethyl group content and FTIR spectra. The amine value of hydrogels changed from 2.23 to 4.64 mmol/g by depending on the amine compounds used in amination reaction. Their swelling degree increased at acidic pH values and they showed pH dependent swelling behaviour. They were used as sorbent for removal of indigo carmine and Cu(II) ion, as a model dye molecule and metal ion, respectively, from aqueous solutions. The adsorption properties of the hydrogels were investigated by depending on pH, time and initial indigo carmine or Cu(II) ion concentration. It was seen that the amine group incorporated hydrogels have quite high adsorption rate and adsorption capacity, and their adsorption capacities changed with pH of the solution. Langmuir isotherm model was the best fit for adsorption of both indigo carmine and Cu (II) ion.     

Utilization of paper mill sludge for removal of cationic textile dyes from aqueous solutions

ABSTRACT

The present study is concerned usage of paper mill sludge (PMS) as an effective adsorbent to remove the two cationic character dyes (Basic Blue 3 [BB3] and Basic Yellow 28 [BY28]) from aqueous solutions. The surface morphology and some characteristics of PMS were determined by Fouirer Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET). The parameters affecting the process – temperature (10–55°C), adsorbent dose (0.5–10 g/l), initial pH (2–10 pH), initial concentration (50–250 mg/l) and contact time (0–24 h) – were examined in the batch adsorption experiments. Maximum adsorption capacities (q_max) of two dyes at 1 g/l dose and pH value of 7 were also calculated as 89.35 and 79.81, respectively. Adsorption phenomena of BB3 and BY28 cationic dyes onto PMS is controlled by pseudo-second-order model. Thereafter, equilibrium experimental data were applied to Langmuir, Freundlich and Dubinin–Redushkevich (D-R) isotherms, and Langmuir isotherm is the best represent the equilibrium adsorption process for both dyes. The processes occurred by physical adsorption because of calculated activation values (E_a) of BB3 and BY28 dyes were 19.43 and 9.35 kJ/mol, respectively. In addition, based on thermodynamic calculations such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), the results clearly demonstrated that the adsorption process were of exothermic and spontaneous nature for both dyes. At the light of obtained findings, it can be stated that PMS can be used effectively in removal of cationic dyes from textile wastewaters and is an alternative to commercial adsorbents due to its low-cost and abundance in the paper industries.     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

The removal of cationic dyes from aqueous solutions by adsorption onto pistachio hull waste

The efficacy of pistachio hull powder (PHP) prepared from agricultural waste was investigated in this study as a novel adsorbent for the elimination of dye molecules from contaminated streams. Removal of methylene blue (MB) as a cationic model dye by PHP from aqueous solution was studied under different experimental conditions. The selected parameters were solution pH (2–10), PHP dosage (0.5–3 g/L), MB concentrations (100–400 mg/L), contact time (1–70), and solution temperature (20–50 °C). The experimental results indicated that the maximum MB removal could be attained at a solution pH of 8. The dosage of PHP was also found to be an important variable influencing the MB removal percentage. The removal efficiency of MB improved from 94.6 to 99.7% at 70 min contact time when the MB concentration was decreased from 300 to 100 mg/L at a pH and PHP dosage of 8 and 1.5 g/L, respectively. The kinetic analysis showed that the pseudo-second-order model had the best fit to the experimental data. The Langmuir equation provided the best fit for the experimental data of the equilibrium adsorption of MB onto PHP at different temperatures. In addition, the maximum adsorption capacity increased from 389 to 602 mg/g when the temperature was increased from 20 to 50 °C. The thermodynamic evaluation of MB adsorption on PHP revealed that the adsorption phenomenon under the selected conditions was a spontaneous physical process. Accordingly, pistachio hull waste was shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewaters.     

Highly selective removal of organic dyes from aqueous solutions with chitin beads entrapping rectorite

By blending chitin with rectorite and organic rectorite in an 8 wt % NaOH/4 wt % urea aqueous solution, we successfully fabricated millimeter‐scale chitin/rectorite composite beads (BCRs) and chitin/organic rectorite beads (BCO), respectively, via an optimal dropping technology. The adsorption of the organic dyes on the BCRs and BCOs were investigated to evaluate the selective removal of methylene blue (MB) and methyl orange (MO) of different charges. Adsorption kinetics experiments were carried out, and the data fit a pseudo‐second‐order equation well. The results reveal that the BCR and BCO sorbents efficiently and selectively adsorbed MO and MB, respectively, from wastewater. The adsorption capacity (Q_e) and removed percentage of MB by BCR were 0.1978 mg/g and 98.90%. The Q_e and R values of MO by BCO were 0.3988 mg/g and 99.70%. Therefore, in this study, we dealt with the development of a clean and safe process for water pollution remediation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40905.     

Efficient removal of cationic dyes from aqueous solutions using a modified poly(ethylene terephthalate) fibers adsorbent

ABSTRACT

A novel adsorbent was synthesized through functionalization of glycidyl methacrylate-g-poly(ethylene terephthalate) (GMA-g-PET) fibers with iminodiacetic acid (IDA) to give IDA-GMA-g-PET fibers. This adsorbent was then exploited for the removal of Malachite Green (MG) and Rhodamine B (RB) dyes. MG has shown faster adsorption kinetics and equilibrium was attained in 15 mins. and 90 mins. for MG and RB, respectively. IDA-GMA-g-PET fibers showed 100% removal efficiency for MG and RB dyes from the solutions having initial concentrations of 300 mg L^?1and 200 mg L^?1, respectively. Desorption conditions of dyes and reusability of the fibers were also investigated.     

Evaluation of polystyrene anion exchange resin for removal of reactive dyes from aqueous solutions

The Amberlite IRA-900 resin was tested to remove C.I. Reactive Black 5, C.I. Reactive Red 2 and C.I. Reactive Red 120 dyes from solutions. Batch adsorption studies concerning effects of the phase contact time, pH, temperature, the presence of salts and surfactants were run. A pseudo second-order kinetic model was used to evaluate the rate constants. The Langmuir equation provided good fit for the experimental data of the equilibrium adsorption. The studies of dyes uptake using the dynamic method were run. The treatment efficiency of Amberlite IRA-900 to model wastewaters was tested. Desorption experiments by the batch method were performed.     

Adsorption of phenazine dyes using poly(hydroxamic acid) hydrogels from aqueous solutions

Swelling and adsorption properties of poly(hydroxamic acid), (PHA) hydrogels in aqueous solutions of some phenazine dyes such as Neutral Red, Safranin T, and Janus Green have been investigated. PHA hydrogels containing N,N′ methylenebisacrylamide or ethyleneglycoldimethacrylate were used in experiments on swelling, diffusion and adsorption of the dyes. The equilibrium swelling (S_eq) values of PHA hydrogels in aqueous solutions of the phenazine dyes were calculated as 2.16–33.25 g g^?1. Swelling kinetic parameters such as initial swelling rate, swelling rate constant, and maximum swelling were found. Dye diffusion into hydrogels was found to be non‐Fickian in character. Diffusion coefficients are ranged 1.32 × 10^?6 cm² s^?1 ? 44.70 × 10^?6 cm² s^?1. Adsorption of the phenazine dyes onto PHA hydrogels was studied by batch technique. PHA hydrogels in the phenazine dye solutions showed the dark coloration. The data was found that Freundlich isotherm model fits. According the Freundlich constants, the adsorption isotherms are of S‐type in Giles classification. All swelling and binding parameters for PHA‐EGDMA were found to be higher than those for PHA‐NNMBA. The type of crosslinker influenced the swelling, binding, and sorption more than the type of dye. Finally, it can be said that PHA hydrogels may be used a sorbent for removal of dyes. POLYM. ENG. SCI., 58:310–318, 2018. © 2017 Society of Plastics Engineers     

Functionalized galactoglucomannan‐based hydrogels for the removal of metal cations from aqueous solutions

New types of hydrogels derived from O‐acetyl galactoglucomannan (AcGGM) hemicellulose have been synthesized and characterized. The objective of this work was to analyze the sorption capacity (S) of three types of hydrogels containing AcGGM derivatives incorporated into the carboxylic groups of the polymer chain in the AA hydrogel, sulfonic groups in the APA hydrogel, and amide groups in the acrylamide (Aam) hydrogel. These hydrogels are capable of interacting and removing ions such as cadmium [Cd(II)], copper [Cu(II)], lead [Pb(II)], nickel [Ni(II)], and zinc [Zn(II)]. The results show that AA and Aam hydrogels had a lower sorption capacity of ions compared to the APA hydrogel, which had a high sorption capacity. The maximal sorption capacity was determined by the successive enrichment method, obtaining Pb(II) amount of 48.3 mg/g of AA hydrogel, 65.8 mg/g of APA hydrogel, and 40.8 mg/g of Aam hydrogel. Hence, Pb(II) ions are greatly retained by the three hydrogels. These results are promising for the development of new materials with potential applications in metal ion removal. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44093.     

Removal of cationic dyes from aqueous solutions by kaolin: Kinetic and equilibrium studies

Experimental investigations were carried out using commercially available kaolin to adsorb two different toxic cationic dyes namely crystal violet and brilliant green from aqueous medium. Kaolin was characterized by performing particle size distribution, BET surface area measurement and XRD analysis. The effects of initial dye concentration, contact time, adsorbent dose, stirring speed, pH, salt concentration and temperature were studied in batch mode. The extent of adsorption was strongly dependent on pH of solution. Free energy of adsorption (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) changes were calculated. Adsorption kinetic was verified by pseudo-first-order, pseudo-second-order and intra-particle-diffusion models. The rate of adsorption of both crystal violet and brilliant green followed the pseudo-second-order model for the dye concentrations studied in the present case. The dye adsorption process was found to be external mass transfer controlled at earlier stage and intra-particle diffusion controlled at later stage. Calculated external mass transfer coefficient showed that crystal violet dye adsorbed faster than brilliant green on kaolin. Adsorption of crystal violet and brilliant green on kaolin followed the Langmuir adsorption isotherm.     

Removal and recovery of cationic dyes from aqueous solutions using spherical sulfonic lignin adsorbent

A novel spherical sulfonic lignin adsorbent, denoted as SSLA, was adopted to removal and recover the cationic dyes from aqueous solutions, e.g., Cationic Red GTL, Cationic Turquoise GB, and Cationic Yellow X‐5GL, and various affecting factors were optimized. It was found that the adsorption of cationic dyes on the adsorbent was initially concentration‐ and temperature‐dependent, and followed both the Freundlich and Langmuir isothermal adsorption. The positives values for ΔH indicated that the process was endothermic. The breakthrough adsorption capacities for GTL, GB, and X‐5GL were 536.0, 550.0, and 582.0 mg/g, respectively, which prevailed over the commercial powdered activated carbon and strongly acidic cation‐exchange resin R732 evidently. Additionally, the maximum recovery percentage could reach 93.2, 97.1, and 96.5% separately for GTL, GB, and X‐5GL, when a mixture of 3.0 mol/L HCl and alcohol with the volume ratio of 1 : 4 was adopted as eluant. Moreover, the results of the mobile desorption and recovery tests indicated that the maximum concentrations of GTL, GB, and X‐5GL in the eluants could reach 13,108, 13,980, and 13,520 mg/L, respectively. Only 6.3, 5.0, and 4.6% of adsorption capacities for GTL, GB, and X‐5GL decreases individually after 20 replicates of adsorption and desorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2284–2291, 2006     

Imidazole modified acrylate-containing photocured hydrogels for the efficient removal of malachite green dye from aqueous solutions

In this work, we aimed to prepare a simple and an efficient adsorbent for the removal of toxic, cationic dye; malachite green (MG). We reviewed many previous studies and designed our adsorbent based on the rationale that (1) acidic groups containing monomers which are capable of making hydrogen bonds (or electrostatic interactions) with MG are very effective in adsorption and (2) π-π stacking enhances the adsorption capacity. We first synthesized an imidazole-acrylate adduct and used it for the preparation of photocured hydrogels. The imidazole-acrylate adduct was characterized by H NMR and FTIR spectroscopy. The effect of experimental conditions on the MG adsorption properties of the hydrogels such as the effect of pH, time and MG concentration were also investigated. Under the optimum conditions (pH = 6 and 220 min contact time) at room temperature, the maximum adsorption capacity was found as high as 714.28 mg/g. The results showed that the adsorption process of the optimum hydrogel, which can be used 4 times without a significant loss in its adsorption capacity, fits the Langmuir isotherm model. The hydrogel adsorbent displayed good selectivity and reusability.     

Ag+ ions imprinted cryogels for selective removal of silver ions from aqueous solutions

ABSTRACT

The removal of heavy metal ions from aquatic media or any conditions is crucial. Silver ions turn out to be the important example of this problem on earth when these are released to the environment. In the present study, silver ions (Ag⁺) imprinted poly(hydroxyethyl methacrylate) (PHEMA)-based cryogels were prepared using N-methacryloyl-L-cysteine as functional monomer, to be chelated with Ag⁺ ions. The maximum adsorption capacity of Ag⁺-imprinted polymeric cryogel was found to be 49.27 mg/g from aqueous solutions. To investigate the affinity of Ag⁺-imprinted PHEMAC cryogel column, photographic film material from the natural silver ion source was used. The recovery results were 72.8% for the Ag⁺-imprinted PHEMAC cryogel and 0.62% for the non-imprinted PHEMAC cryogels. These values clearly showed the selectivity of the Ag⁺-imprinted PHEMAC cryogel column. The adsorption–desorption cycle was performed more 10 times with use of the same Ag⁺-imprinted PHEMAC cryogel for the determination of reuse. These molecularly imprinted cryogels were used in adsorption process for a long time with no significant loss.     

La-doped WO3@gCN Nanocomposite for Efficient degradation of cationic dyes

In present investigation, gCN supported carbon coated Lanthanum doped tungsten oxide (C@LWO/gCN) composite were synthesized via hydrothermal approach. The photodegradation of different cationic dyes like malachite green (MG), crystal violet (CV) and methylene blue (MB) has been carried out under prepared C@LWO/gCN composite. Furthermore, the comparative photodegradation was also performed using pristine LWO and C@LWO nanowires. The synthesized samples were characterized via physiochemical techniques such as XRD, FESEM, EDX, FTIR, BET and UV/Vis spectroscopy. The results proved incorporation of La ions into WO₃ lattice and reduced band gap of doped sample which significantly boost up the capability of the material towards photodegradation. The maximum degradation was found out at pH = 6, 5 mg catalyst dose, 5 ppm dye concentration and 35 °C temperature. The achieved results proved that the trapping agents compete with prepared composite specie for the h⁺, e⁻, HO^● and O₂^●- radicals. The obtained experimental records of photodegradation of cationic dyes using C@LWO/gCN composite has correlation with pseudo first order kinetics, Langmuir-Hinshelwood model and t_1/2. The simplest facile synthetic approach, remarkable photodegradation performance against colored and colorless effluents suggest that C@LWO/gCN composite exhibit great potential for large-scale wastewater treatment.     

Tubular structured ordered mesoporous carbon as an efficient sorbent for the removal of dyes from aqueous solutions

Tubular structured ordered mesoporous carbon CMK-5 was investigated for the adsorption of the industrial dyes reactive blue 19, acid red 57 and fuchsin basic in aqueous solutions at room temperature. It was found that CMK-5 exhibits an ultrahigh adsorption rate and superior adsorption capacities for these dyes. Its maximum adsorption capacities for reactive blue 19, acid red 57 and fuchsin basic were 733, 1131 and 1403 mg g⁻¹, respectively, and significantly greater than other literature reported results on porous carbons. Following adsorption of reactive blue 19, CMK-5 carbon could be regenerated by either ethanol extraction or thermal annealing at 600 °C, reaching ∼51% and ∼77%, respectively of the adsorption capacity of the original carbon. For comparison, ordered mesoporous carbon CMK-3 (rod structure), polymer based disordered mesoporous carbon, and steam and CO₂ activated commercial coconut carbons were investigated for the adsorption of reactive blue 19. The fast adsorption rate of CMK-5 carbon is due to its unique properties of tubular mesostructure, bimodal mesopore system and high surface area. In the case of requiring emergency removal of large amount of dyes in aqueous solution, CMK-5 would be an ideal choice.     

Polyelectrolyte CASA hydrogels for uptake of uranyl ions from aqueous solutions

In this study, uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked acrylamide/sodium acrylate (CASA) hydrogels. Adsorption studies were investigated by the spectroscopic method. CASA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), sodium acrylate (SA), and water by free radical polymerization in aqueous solution, using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA). Uranyl ion adsorption from aqueous solutions was studied by the batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In experiments of sorption, 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 the CASA hydrogel–uranyl ion binding system, were calculated using the Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 4.44 × 10^?4–14.86 × 10^?4 mol uranyl ion per gram for CASA hydrogels. Adsorption of uranyl ion (percentage) was changed within a range of 12.86–46.71%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 200–204, 2007     

Magnetic removal of crystal violet from aqueous solutions using polysaccharide‐based magnetic nanocomposite hydrogels

Magnetic Fe₃O₄@SiO₂ starch‐graft‐poly(acrylic acid) (SPAA) nanocomposite hydrogels were prepared and used as absorbents for removal of crystal violet from aqueous solutions. Dynamic swelling, effect of contact time, absorption kinetics and nanocomposite hydrogel mass for removal of crystal violet dyes from aqueous solutions were studied. Fourier transform infrared spectroscopy, scanning electron microscopy and vibrating sample magnetometer measurements were used for the characterization of the nanocomposite hydrogels. The nanocomposite hydrogels had high magnetic sensitivity under an external magnetic field, which allowed their magnetic separation from water, thus avoiding secondary pollution. The results obtained are very promising since: (i) high levels of colour removal (>85%) were achieved with low magnetic SPAA nanocomposite mass and (ii) the magnetic SPAA nanocomposites can be successfully used several times as absorbents of crystal violet in aqueous solution without needing filtration. © 2012 Society of Chemical Industry     

Polymer‐derived ceramic aerogels as sorbent materials for the removal of organic dyes from aqueous solutions

Polymer‐derived SiC and SiOC aerogels have been synthesized and characterized both from the microstructural point of view and as sorbent materials for removing organic dyes (Methylene Blue, MB, and Rhodamine B, RB) from water solutions. Their adsorbent behavior has been compared with a polymer‐derived SiC foam and a commercial mesoporous silica. The aerogels can efficiently remove MB and RB from water solution and their capacity is higher compared to the SiC foams due to the higher surface area. The SiOC aerogel remains monolithic after the water treatment (allowing for an easy removal without the need of a filtration step) and its maximum capacity for removing MB is 42.2 mg/g, which is higher compared to the studied mesoporous silica and many C‐based porous adsorbents reported in the literature. The reason for this high adsorption capacity has been related to the unique structure of the polymer‐derived SiOC, which consists of an amorphous silicon oxycarbide network and a free carbon phase.