Model Cationic Dye Research Articles

Novel Fe3O4@lignosulfonate/phenolic core-shell microspheres for highly efficient removal of cationic dyes from aqueous solution

The application of green adsorbents from renewable biomass for dye wastewater treatment has received wide attention in recent years. In this work, novel lignin-based Fe3O4@lignosulfonate/phenolic core-shell microspheres were fabricated for the first time to remove cationic dyes from aqueous solutions. The emulsion polymerization using p-toluenesulfonic acid as a curing agent was employed to synthesize the microspheres at a moderate temperature. Detailed characterizations were conducted to provide a broad evaluation of the microspheres followed by batch experiments to analyze the methylene blue (as a model cationic dye) adsorption performance. Results showed that lignosulfonate/phenolic shell coated uniformly on the Fe3O4 core to form a well-defined core-shell microsphere. Due to cross-linking by phenolic resin, the lignosulfonate coated on the microspheres is highly insoluble in aqueous solutions at a wide pH range, which is prerequisite for an effective dye adsorption from wastewater. The adsorption study showed that the endothermic adsorption process was completed in 40 min and the adsorption kinetics followed a pseudo-second-order model. The equilibrium data were consistent with the Langmuir equation and the maximum monolayer capacity was 283.6 mg/g, which was much higher than those of most lignins and lignin-rich biomass. After adsorption, the microspheres were recycled and a fast regeneration (<10 min) was achieved using ethanol as a methylene blue extraction solvent. Overall, these results indicate that the novel Fe3O4@lignosulfonate/phenolic microspheres offer a great potential for removing cationic dyes from wastewater in practical applications.

Characterization and utilization of industrial microbial waste as novel adsorbent to remove single and mixed dyes from water

Industrial microbial waste (IMW) from amylase production using Aspergillus niger was characterized and utilized as novel adsorbent to remove two model cationic dyes (crystal violet, CV; methylene blue, MB) in their single and binary system. IMW was composed of organic Aspergillus niger biomass and inorganic perlite and diatomite, and thereby was regarded as a composite sorbent which was also characterized using FTIR, SEM, and XPS. The sorptive properties of IMW were studied in batch experiments by varying initial dye concentration, contact time, temperature, sorbent dosage, and NaCl concentration. The adsorption of CV and MB exhibited very similar trends in both single and binary dye solutions. Isotherms, kinetics, and thermodynamics were used to describe the sorption processes. The Langmuir model provided a good fit of the experimental data with the maximum monolayer adsorption (qm) of 175.4 mg/g and 92.6 mg/g for CVs and MBs, respectively in the single dye system. In the mixed dye solutions, the qm for CVm and MBm was reduced to 74.6 mg/g and 52.9 mg/g, respectively. Second-order kinetic model (R2 > 0.999) better explained the adsorption for the two dyes in single or mixed forms, suggesting chemical sorption nature of the process. The adsorption was dominated primarily by membrane diffusion and found to be endothermic and spontaneous. The IMW can thus be repurposed as a novel and promising cleaning agent for removal of organic pollutants from miscellaneous wastewaters.

Swelling and auramine-O adsorption of carboxymethyl cellulose grafted poly(methyl methacrylate)/Cloisite 30B nanocomposite hydrogels

Carboxymethyl cellulose (CMC) grafted poly(methyl methacrylate)/Cloisite 30B nanocomposite hydrogels were prepared for adsorptive removal of auramine-O (as a cationic dye model) from wastewater. For the synthesis of nanocomposite hydrogel by free radical polymerization method, potassium persulfate (KPS), methyl methacrylate (MMA), N,N′-methylene bisacrylamide (MBA) and Cloisite 30B were used as initiator, monomer, cross-linker and nano-filler, respectively. The nanocomposite hydrogels were characterized by FTIR, TGA, SEM and XRD techniques. The FTIR results showed that the monomer was grafted onto carboxymethyl cellulose chains successfully. Swelling behavior of nanocomposite hydrogel as a function of KPS, MBA, MMA concentration and CMC/Cloisite 30B weight ratio was studied by Taguchi method using Minitab 16 software. According to ANOVA results, the most effective factor of equilibrium swelling of nanocomposite hydrogel was CMC/Cloisite 30B weight ratio. Addition of Cloisite 30B to hydrogel up to a certain amount improved swelling, though its high amount decreased swelling. The effects of pH and ionic strength on swelling of optimum hydrogels were investigated. Maximum swelling of nanocomposite hydrogel occurred at pH 7.0. The kinetic data of adsorption fitted well to pseudo-second-order model. The best isotherm for investigation of adsorption mechanism was Langmuir model suggesting the formation of a monolayer on the adsorbent surface. FTIR results, before and after auramine-O adsorption, showed that complexation is the main mechanism of adsorption. High adsorption capacity of nanocomposite hydrogels made them more efficient in wastewater treatment application.

Ytterbium tungstate nanoparticles as a novel sorbent for basic dyes from aqueous solutions

Ytterbium tungstate nanoparticles (YTNPs) were used as a sorbent for removing methylene blue (MB), as a model cationic dye, from water solutions. YTNPs were characterized through scanning electron microscopy. The factors influencing the efficiency of the sorbent in a batch adsorption procedure (i.e., initial pH, amount of YTNPs, and contact time) were evaluated at a constant concentration of MB, and central composite design was used to determine their efficacies. The results indicated the best conditions in the case of a 200-ppm MB solutions to be 3 mg mL−1 (as the amount of YTNPs used), pH = 10, and contact time = 30 min. The adsorption kinetics, isotherm and desorption properties of YTNPs were also fully investigated. The Langmuir model was used for fitting the adsorption isotherm and the results indicated a high adsorption capacity for the model dye. The adsorption kinetics was found to comply with a pseudo-second-order behavior, which means that adsorption constitutes the rate-determining step. Furthermore, YTNPs were successfully used to remove MB from water and wastewater samples.

Removal of anionic and cationic dyes with bioadsorbent oxidized chitosans

Different oxidized chitosans were prepared following various approaches, by thermo-acid oxidation or by using KMnO4/NaHSO3, (NH4)2S2O8/NaHSO3 and K2Cr2O7/NaHSO3 redox pairs added sequentially or simultaneously. All these reactions pursue the formation of carboxylic groups which enhance their capability to remove model cationic and anionic dyes such as methylene blue and methyl orange, respectively. The resulting oxidized chitosans were structurally and thermally characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy and thermogravimetry. The swelling capacity of these hydrogels was also determined as well as the remediation ability of dyes in different conditions. The results showed that the adsorption of methylene blue followed a pseudo second-order kinetics model, while the adsorption behavior was in agreement with the Langmuir isotherm model. Remarkably, the oxidized chitosans showed removal ability for both dyes cationic and anionic, which of great importance for application of these materials as versatile bioadsorbents.

Synthesis and application of 3D graphene nanocomposite for the removal of cationic dyes from aqueous solutions: Response surface methodology design

Abstract In this study, functionalized 3D graphene (magnetic citric acid-functionalized 3D graphene nanocomposite (MCF3DG)) was designed and synthesized via a One-Step hydrothermal process and it was used as a novel adsorbent for the removal of crystal violet (CV) dye from aqueous solution as a cationic dye model. The products have been characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and UV/Vis diffuse reflectance spectroscopy. Response surface methodology (RSM) has been applied in order to study the influence of experimental factors (initial pH, initial dye concentration, contact time and adsorbent dosage) on the removal efficiency of CV dye with MCF3DG as an adsorbent. The results from RSM indicated that the efficiency of CV removal is 100% under the optimum conditions of experimental factors (pH = 7.5, amount of adsorbent = 28 mg, CV concentration = 18 mg/L and contact time = 12 min). The obtained experimental results suggest that the MCF3DG is a very good candidate for the rapid removal of crystal violet (CV) as a cationic dye model from aqueous solutions.

Graphene Oxide/Alginate Quasi-Cryogels for Removal of Methylene Blue

Quasi-cryogelation technique is a simple yet effective technique for improving the adsorptive efficiency of biopolymer-based adsorbent materials. In this work, a biopolymer-based adsorbent material, graphene oxide alginate quasi-cryogel beads are reported. Alginate biopolymer was crosslinked and frozen at − 21 °C in order to obtain a gel with cryogel-like microstructure. Graphene oxide was included in the bead formulation in order to enhance the adsorptive characteristics. Beads were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and swelling experiments. Removal of the model cationic dye, methylene blue, was studied by batch adsorption method. It is found that the adsorption follows the Freundlich isotherm model and pseudo-first order kinetics with reaching an adsorption capacity of 122.26 mg/g in 60 min. Results indicate that the physisorption might be due to the π–π interactions between graphene oxide and methylene blue, in addition to electrostatic interactions. Moreover, quasi-cryogelation technique significantly improved the dye removal properties.

Graphene oxide-wrapped magnetite nanoclusters: A recyclable functional hybrid for fast and highly efficient removal of organic dyes from wastewater

We report the facile and cost-effective fabrication of a novel functional hybrid composed of graphene oxide (GO)-wrapped magnetite (Fe3O4) nanoclusters (Fe3O4@GO) by electrostatically driven co-assembly. In comparison with previously reported Fe3O4-GO composites that were prepared through one-pot, in situ deposition of smaller-sized Fe3O4 nanoparticles, the Fe3O4@GO hybrid composite reported in the present study are obtained by weak electrostatic interaction between negatively charged GO nanosheets and positively charged Fe3O4 nanoclusters (size ∼500 nm). The as-prepared Fe3O4@GO hybrid has a core-shell structure where thin and flexible GO shells efficiently infold the Fe3O4 nanocluster core. The adsorptive characteristics of Fe3O4@GO hybrid was evaluated using two model cationic dyes; methylene blue (MB) and rhodamine B (RhB) and one model anionic dye; methyl orange (MO). The adsorption of dyes onto Fe3O4@GO hybrid composite was investigated as a function of solution pH, adsorbent dosage, ionic strength, contact time and temperature. The adsorption kinetics, isotherms, thermodynamics, stability, and reusability of the adsorbent were also studied in detail. The results showed that the adsorption kinetics and the equilibrium adsorptions are well-fitted with pseudo-second order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacities for MB, RhB and MO are 131.10, 34.50 and 39.95 mg/g respectively at 303 K. The Fe3O4@GO adsorbent exhibited rapid magnetic separation, easy regeneration, excellent stability, and good sustainability in removal efficiency even after continued recycling. The results demonstrated that Fe3O4@GO composite possesses great potential as an efficient and recyclable adsorbent for the removal of both cationic and anionic dye pollutants in environmental remediation.

Advanced desalination of dye/NaCl mixtures by a loose nanofiltration membrane for digital ink-jet printing

Abstract In digital printing, a high salt content in dye solutions is detrimental, which calls for effective strategy for dye/salt fractionation. In this study, a loose nanofiltration (NF) membrane Sepro 2A was employed to desalinate diverse dye species (2 reactive dyes and 4 cationic dyes). This membrane, with a molecular weight cutoff of 490 Da, showed consistently high rejections to all the reactive and cationic dyes (>97.7%). Operational conditions such as dye concentrations and applied pressures have limited effects on the rejection of the membrane. An integrated NF-diafiltration process, involving a pre-concentration and a diafiltration step, was specifically designed for the fractionation of dye/NaCl mixtures. This loose NF membrane showed >99.7% rejection to reactive dyes (reactive blue 2 and reactive orange 16) and ca. 99.3% salt removal with ca. 2.0% dye loss after 5.0 diavolumes. However, the NF membrane experienced a 15.9% loss to methylene blue due to the lower rejection to this model cationic dye (97.2%). The current study provides important insights into dye/salt fractionation by loose NF membranes for digital ink-jet printing.

Swelling and methylene blue adsorption of poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate) hydrogel

Dyes from wastewater have a negative impact on health and environment, even at low concentrations. Several methods have been proposed for their removal, one of them is using hydrogels as adsorbents for wastewater treatment. In this work, we propose N,N-dimethylacrylamide and 2-hydroxyethyl methacrylate copolymer (p(HEMA-co-DMAa)) as an adsorbent alternative. Swelling behavior as function of pH and temperature was studied. Morphological characterization of crosslinked copolymer and its hydrogel structure were performed by SEM analysis and FTIR spectroscopy. Swelling measurements and sorption studies were made using methylene blue (as cationic dye model) under different medium pH. Results from confocal images of swollen p(HEMA-co-DMAa) in methylene blue solutions indicate a macroporous material formed. The dye diffuses homogeneously through the entire hydrogel during swelling. The p(HEMA-co-DMAa) hydrogels were able to uptake up to 3.6 times their weight of water depending on temperature; the lower the equilibrium temperature the higher the water uptake. P(HEMA-co-DMAa) hydrogels adsorption capacity is competitive compared with other adsorbents already reported. It was determined that the LCST of the hydrogel at 321K and the formation of a complex at pH=8. The optimal removal time was at 4h after the copolymer was added. The hydrogel was stable (as suggested by FTIR spectrum) and able to uptake methylene blue in a wide pH range. Therefore, it is suitable as adsorbent alternative; additionally, the p(HEMA-co-DMAa) hydrogels would be environmentally friendly due to their biocompatibility and non-cytotoxicity.

Environmentally Sustainable Fabrication of Cu1.94S-rGO Composite for Dual Environmental Application: Visible-Light-Active Photocatalyst and Room-Temperature Phenol Sensor

In the present study a novel Cu1.94S-rGO (rGO = reduced graphene oxide) composite is synthesized in an ecofriendly way and its application as photocatalyst and phenol sensor is explored. The extensive microscopic and spectroscopic characterization tools were used to confirm the structures and chemical vicinity of synthesized djurleite nanocomposite. This highly permeable mesoporous composite shows a direct band gap of 2.17 eV, which confers its semiconducting properties. Wet hydrogen peroxide catalytic oxidation method of photocatalysis was adopted here for the photodegradation of model cationic and anionic dyes, which result in 90.76% and 79.44% removal efficiencies, respectively, with the fixed catalyst dose and minimum additive of 0.55 mM hydrogen peroxide dose. The removal efficiency was improved significantly by the addition of a higher amount of hydrogen peroxide. Significant reusability is also observed here in both kinds of dye molecules and is contingent on its potential applicability. It also ex...

Surface transformations of TiO 2 anatase deactivated in methylene blue solution with Cl − ions in the colloid

Abstract In textile wastewater, ions such as Cl−, NO3−, SO42− added as salts (dye-enhancers), were reported to exacerbate the deactivation of TiO2 surface in aqueous media. The rate of degradation of a model cationic dye methylene blue (MB) with or without NaCl and nature of adsorbed species on pure anatase TiO2 were investigated, other factors considered were pH4 and pH10, ultraviolet light (UV). XPS analysis of samples T1–T8, shows varying values of percent atomic concentration (PAC) from fresh sample Tf. For Tf, Ti (25.88%) and O (68.07%) values were higher than in any other sample and has the least C (4.11%) with no traceable amount of N, S and Na. For the deactivated samples, in addition to basic elements Ti, O and C, there were traces of new elements, nitrogen (N) in T1 (N: 1.16%), no nitrogen or sulfur (S) in T2, in T3 (N: 3.34%, S: 0.84%), T4 (N: 3.17%, S: 1.72%), T5 (N: 1.46%), T6 (N: 1.16%), T7 (N: 3.21%, S: 0.97%) and T8 (N: 3.02%, S: 1.11%, Na: 3.02%), no Cl− was found in any sample. Shifts were observed in the XPS high resolution spectra (HRS) in C1s, O1s, Ti2p, N1s, S2p and Na1s regions. FTIR confirmed the new adsorbed species on deactivated samples (T1–T8).

Hydroxyapatite-supported Silver Nanoparticles and Preliminary Investigations of their Catalytic Potential

The hydroxyapatite-supported silver nanoparticles were synthesized and used as a new type of catalyst for the discoloration of a model cationic dye in a Fenton-like process. The structure and morphology of the catalyst were investigated by FTIR, TEM and SEM before and after reaction. The main factors that could influence the catalytic activity were summary investigated. The catalytic activity was monitored by evaluating the discoloration degree from the absorbance data recorded in the visible spectra. The results obtained during these preliminary investigations are very promising from applicative point of view.

Tannin-immobilized cellulose hydrogel fabricated by a homogeneous reaction as a potential adsorbent for removing cationic organic dye from aqueous solution

Tannin-immobilized cellulose (CT) hydrogels were successfully fabricated by homogeneous immobilization and crosslinking reaction via a simple method. The structures and properties of hydrogels were characterized by SEM and mechanical test. Methlyene Blue (MB) was selected as a cationic dye model, and the adsorption ability of CT hydrogel was evaluated. Tannins immobilized acted as adsorbent sites which combined MB by electrostatic attraction, resulting in the attractive adsorption ability of CT hydrogel. Adsorption kinetics could be better described by the pseudo-second-order model, and the absorption behaviors were in agreement with a Langmuir isotherm. The adsorption-desorption cycle of CT hydrogel was repeated six times without significant loss of adsorption capacity. In this work, both tannin immobilization and hydrogel formation were achieved simultaneously by a facile homogeneous reaction, providing a new pathway to fabricate tannin-immobilized materials for water treatment.

Physicochemical stability of calcium alginate beads immobilizing TiO2 nanoparticles for removal of cationic dye under UV irradiation

ABSTRACTRecently, there have been considerable interests to immobilize photocatalyst in alginate beads for removing pollutants from water sources. However, the feasibility of using alginate beads in industry largely depends on its long‐term stability during operation. This study investigated the physicochemical stability of alginate/titanium dioxide beads (Alg/TiO2) when exposed to UV irradiation in aqueous environment. The degradation of Alg/TiO2 beads was evident because the diameter and mass of the beads was reduced by 12% and 40%, respectively, after 120 h of irradiation. A substantial amount of TiO2 was leached into the external medium. Consequently, the removal efficiency of model cationic dye was found to reduce after every process cycle. Morphological analysis showed the formation of cavities on the surface of the Alg/TiO2 beads. Interestingly, the blank alginate beads degraded more rapidly than the Alg/TiO2 beads, confirming the UV‐shielding effect of TiO2. Nevertheless, this study reveals the need to improve the UV stability of alginate‐based beads before they can be considered for practical application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45002.

Optimization of cellulose and sugarcane bagasse oxidation: Application for adsorptive removal of crystal violet and auramine-O from aqueous solution

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H3PO4-NaNO2 mixture to obtain adsorbent materials with high contents of carboxylic groups. The oxidation reactions of Cel and SB were optimized using design of experiments (DOE) and response surface methodology (RSM). The optimized synthesis conditions yielded Cox and SBox with 4.8mmol/g and 4.5mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 13C NMR. The adsorption of the model cationic dyes crystal violet (CV) and auramine-O (AO) on Cox and SBox in aqueous solution was investigated as a function of the solution pH, the contact time and the initial dye concentration. The adsorption of CV and AO on Cox was described by the Elovich equation and the pseudo-first-order kinetic model respectively, while the adsorption of CV and AO on SBox was described by the pseudo-second-order kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities (Qmax) of 1117.8mg/g of CV and 1223.3mg/g of AO on Cox and 1018.2mg/g of CV and 682.8mg/g of AO on SBox. Desorption efficiencies were in the range of 50–52% and re-adsorption capacities varied from 65 to 81%, showing the possibility of reuse of both adsorbent materials.

Synthesis and application of acrylamide/sodium vinylsulfonate/carboxymethylcellulose/zeolite hybrid hydrogels as highly swollen effective adsorbents for model cationic dye removal

Synthesis and application of acrylamide/sodium vinylsulfonate/carboxymethylcellulose/zeolite hybrid hydrogels as highly swollen effective adsorbents for model cationic dye removal

Highly efficient adsorption of cationic dye by biochar produced with Korean cabbage waste

Biochar was produced from Korean cabbage (KC), rice straw (RS) and wood chip (WC) and the use as alternative adsorbents to activated carbon (AC) in wastewater treatment was investigated. Congo red (CR) and crystal violet (CV) were used as a model anionic and cationic dye, respectively. Initial solution pH had little effect on CR and CV adsorption onto all biochars except for AC on CR. The isotherm models and kinetic data showed that adsorption of CR and CV onto all biochars were dominantly by chemisorption. All biochars had lower adsorption capacity for CR than AC. KC showed higher Langmuir maximum adsorption capacity (1304mg/g) than AC (271.0mg/g), RS (620.3mg/g) and WC (195.6mg/g) for CV. KC may be a good alternative to conventional AC as cheap, superb and industrially viable adsorbent for removal of cationic dyes in wastewater.

Tannin‐immobilized cellulose microspheres as effective adsorbents for removing cationic dye (Methylene Blue) from aqueous solution

AbstractBACKGROUNDTannin‐immobilized cellulose (T/C) microspheres were fabricated by a facile homogeneous reaction in a water/oil (W/O) emulsion for the removal of cationic dye from aqueous solution. The microspheres were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Zeta potentials test. Setting methylene blue (MB) as a cationic dye model, the adsorption isotherms, kinetics and effect factors of MB adsorption were investigated to evaluate the effectiveness for dye removal.RESULTSThe microspheres exhibited porous structure. Cellulose contributed to provide a support for the porous structure, and immobilized tannins acted as adsorbent sites which combined with MB by electrostatic attraction, resulting in the attractive adsorption ability of T/C microspheres. Microspheres exhibited rapid adsorption rate even when the initial MB concentration was 1500 mg L−1. The pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. Results indicated that the adsorption kinetic was more accurately described by the pseudo‐second‐order model. It has been demonstrated that the better agreement was with the Langmuir isotherm with correlation coefficient &gt;0.9996. Regeneration experiments showed that T/C microspheres can be reused at least three times without obvious loss of their original adsorption capacity.CONCLUSIONThe results revealed that the T/C microspheres can be considered as a stable and effective adsorbent for cationic dye removal from industrial effluents. Tannin immobilization and material forming were simultaneously implemented by a facile homogeneous reaction in W/O emulsion, providing a new pathway to fabricate tannin‐immobilized materials for water treatment. © 2016 Society of Chemical Industry

Functionalized hybrid materials assisted organic dyes removal from aqueous solutions

Carboxymethyl cellulose grafted polymethacrylic acid (CMC-g-PMAA) was investigated as a template for rod-like hydroxyapatite mineralization. CMC-g-PMAA/hydroxyapatite hybrid material exhibited high removal capacity toward methylene blue (MB), cationic dye model, from aqueous solutions. The adsorption behavior of MB using CMC-g-PMAA/hydroxyapatite hybrid was investigated in detail using batch adsorption technique. The hybrid material exhibited adsorption capacity up to 671mg/g. Pseudo-second-order and Langmuir isotherm models were found to describe the adsorption mechanism. This new adsorbent material has promising future for waste water purification.