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1.
Novel hydrogel nanocomposites were synthesized by solution polymerization of acrylamide in the presence of carrageenan biopolymer and laponite RD clay. Laponite was used as an inorganic cross-linker. Ammonium persulfate was applied as an initiator. The structure and morphology of the nanocomposites were investigated using XRD, scanning electron microscopy, and transition electron microscopy techniques. The influence of both laponite nanoclay and the carrageenan content on the swelling degree of nanocomposites was studied and it was found that all nanocomposites containing carrageenan component have a high swelling degree compared to a nanocomposite without carrageenan. The obtained nanocomposites were examined to remove a cationic crystal violet (CV) dye from water. The effect of carrageenan and clay contents on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content, it was depressed as the carrageenan content increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominant in adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results indicated that the experimental data fit the Langmuir isotherm best. Maximum adsorption capacity was obtained for carrageenan-free nanocomposite with 79.8?mg?g?1 of adsorbed CV onto nanocomposite.  相似文献   

2.
Nanocomposite superabsorbents were synthesized by simultaneously solution copolymerization of acrylamide (AAm) and sodium acrylate (Na-AA) in the presence of carrageenan biopolymer and sodium montmorillonite (Na-MMt) nanoclay. Potassium persulfate (KPS) and methylenebisacrylamide (MBA) were used as initiator and crosslinker, respectively. The structure and morphology of the nanocomposites were investigated using XRD, FTIR, scanning electron microscopy (SEM), and TEM techniques. The influence of nanoclay and carrageenan contents as well as monomer weight ratios on the degree of swelling of nanocomposites was studied. The optimum water absorbency was obtained at 10 wt% of clay, 10 wt% of carrageenan, and 1:1 of monomers weight ratio. The obtained nanocomposites were examined to remove of crystal violet (CV) cationic dye from water. The effect of carrageenan and clay content on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content up to 14 wt% of clay, it was decreased as the carrageenan increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Freundlich isotherm the best.  相似文献   

3.
Adsorption studies of aqueous basic dye solutions using sepiolite   总被引:2,自引:0,他引:2  
Sepiolite, low cost, locally available and natural mineral was studied as an adsorbent for the removal of Basic Astrazon yellow 7GL from aqueous solutions and batch contact tests. The kinetics of the adsorption process was tested for the pseudo-first order, pseudo-second order reaction and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. Good correlation coefficients were obtained for the pseudo-second order kinetic model. Langmuir, Freundlich and Dubinin-Radushkevich isotherm models were applied to the experimental equilibrium data by changing temperature. The isotherm constants were determined by using the linear regression of these models. The monolayer coverage capacities of sepiolite for basic dye were found to be in the range of 62.5-88.5 mg/g at different temperatures. Thermodynamic studies showed that the reaction for dye uptake by sepiolite is endothermic in nature. Based on the optimum parameters sepiolite was also used as adsorbent for raw wastewater treatment and found as efficient as dye color removal.  相似文献   

4.
In this study, Acrylic acid (AA)/2‐acrylamido‐2‐methlypropane sulfonic acid (AMPS) hydrogels were prepared by free radical polymerization in aqueous solutions of AA, AMPS, and N,N‐methylenebisacrylamide (NMBA) as crosslinker. Potassium persulfate (PPS)/potassium bisulfide (PBS) were used as initiator and accelerator pair. The water absorption capacities and dye adsorption properties of the hydrogels were investigated. Adsorption properties of the hydrogels were evaluated by depending on different adsorption conditions such as different initial dye concentration and contact time. The concentrations of the dyes were determined using UV/Vis Spectrophotometer at wavelength 530 nm for safranine T (ST) and 622 nm for brilliant cresyl blue (BCB). Adsorption kinetic studies showed that pseudo‐first order kinetic model is suitable to explain the adsorption kinetic data of the hydrogels. Langmuir and Freundlich isotherm models were used to describe adsorption data. The result revealed that the adsorption of basic dyes onto hydrogels fit very well both Langmuir and Freundlich isotherms. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

5.
Films of chitosan/polyvinyl alcohol (PVA)/sepiolite nanocomposite were prepared by a simple and “green” route through solution mixing; followed by freezing–thawing cycles. The structures of nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis, X-ray diffractometry, and Fourier transform infrared spectroscopy. The SEM and TEM micrographs confirmed a needle-type dispersion of sepiolite nanoclay in the hydrogel nanocomposites. The effects of sepiolite and chitosan/PVA weight ratio on the swelling of nanocomposites were investigated. The water absorbency of nanocomposites was decreased by introducing sepiolite nanoclay. The nanocomposites with high content of chitosan showed high swelling capacity. The nanocomposite films showed pH-dependent swelling behavior with a maximum water absorbency under acidic pH. The cefazolin with a broad-spectrum activity toward gram-positive and gram-negative bacteria was loaded in hydrogels. The release of cefazolin from nanocomposites was evaluated at pH 7.4. The content of released drug was affected by both sepiolite amount and chitosan/PVA weight ratio. The nanocomposites films released more cefazolin than the neat hydrogel film. Cefazolin-loaded nanocomposites showed the antibacterial activity with a large zone of inhibition against gram-positive Bacillus cereus bacterium.  相似文献   

6.
In this study, N-isopropylacrylamide/itaconic acid (NIPAAm/IA) hydrogels prepared by irradiating with γ radiation were used in experiments on cesium ion adsorption. The cesium ion adsorption capacity of the hydrogels was investigated as a function of Cs+ concentration, pH and temperature. The adsorption behavior of cesium was evaluated by using the radiotracer method. The adsorption isotherm models were applied to the experimental data, and it was seen that Freundlich isotherm explained the adsorption better than Langmuir isotherm. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The Cs+ adsorption could be best described by the pseudo-first-order equation. The thermodynamic parameters including ΔG°, ΔH° and ΔS° for adsorption processes of Cs+ on the hydrogel were also calculated, and the negative ΔH° and ΔG° confirmed that the adsorption process was exothermic and spontaneous.  相似文献   

7.
Biopolymer-based magnetic beads, composed of kappa-carrageenan (κ-Car) and Fe3O4 nanoparticles, were synthesized. The magnetic beads were prepared through in situ precipitation of Fe2+/Fe3+ ions in the presence of carrageenan and subsequently treating with K+ solution. The structure of magnetic kappa-carrageenan beads (mκ-Carb) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and thermal gravimetric analysis techniques. According to SEM micrographs, an undulant and coarse structure with cubic-shaped sections was obtained when the magnetic nanoparticles were incorporated in composition of beads. The TEM image confirmed the formation of magnetic nanoparticles with an average size of 3–7 nm. The synthesized beads were examined as adsorbent to remove crystal violet dye from aqueous solutions. It was found that due to coarse surface, the rate of dye adsorption on magnetic beads can be improved slightly. The experimental adsorption kinetics was analyzed according to pseudo-first-order and pseudo-second-order kinetic models and the adsorption kinetics followed well the pseudo-second-order model. Isotherm adsorption data of dye on beads were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data have the best fit to Langmuir isotherm model, and maximum adsorption capacity of beads for dye obtained was 84.7 mg/g. The influence of pH on the variation of adsorption capacity of beads for crystal violet was not considerable. The thermodynamic parameters indicated that the adsorption of CV dye on beads is spontaneous.  相似文献   

8.
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.  相似文献   

9.
In this article, surface modification of feldspar using hexadecyltrimethyl ammonium bromide (HDTMA) and its dye removal ability in single and binary systems was studied. Acid Black 1 (AB1) and Acid Red 14 (AR14) were used as model dyes. The monocomponent Langmuir isotherm model was applied to experimental data and the isotherm constants were calculated for both dyes. The monolayer coverage capacities of surfactant‐modified feldspar (HDTMA‐feldspar) for AB1 and AR14 dyes in single solution system were found as 6.369 mg/g and 3.984 mg/g, respectively. It was observed that the equilibrium uptake amounts of AB1 and AR14 dye in binary mixture onto sorbent decreased with increasing concentrations of the other dye resulting in their antagonistic effect. Equilibrium adsorption for binary systems was analyzed by using the Extended Langmuir and Jain and Snoeyink Modified Extended Langmuir models. The rate of kinetic processes of single and binary dye systems onto adsorbent was described by using two kinetics adsorption models. The pseudo‐second‐order model was the best choice among the kinetic models to describe the adsorption behavior of single and binary dyes onto HDTMA‐feldspar. Thermodynamic parameters showed that dye adsorption on HDTMA‐feldspar were exothermic and unspontaneous in nature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

10.
Summary Super swelling acrylamide (Am)/N-vinylpyrrolidone (NVP)/3-(2-hydroxyethyl carbamoyl) acrylic acid (HECA) hydrogels were prepared by free radical polymerization of quaternary mixtures of Am, NVP, HECA and water. The hydrogels were used in experiments on swelling, diffusion and adsorption of some water-soluble monovalent cationic dyes such as Crystal Violet (CV), Malachite Green (MG) and Methylene Blue (MB). In the experiment of the adsorption of dyes from their aqueous solutions type-S adsorption isotherm were found. The diffusion of water within the hydrogel was found to have non Fickian character. The uptake of dyes within the hydrogel increased in the following order: MG > MB > CV. The binding ratio of the hydrogel/dye systems was gradually increased with the increase of HECA content in the AAm/NVP/HECA hydrogel.  相似文献   

11.
《分离科学与技术》2012,47(6):1005-1016
Arsenic contamination in drinking water resources is a global problem; therefore, its removal from drinking water has become an important sustainable matter. The adsorption process can be more cost-effective and applicable, especially, if the absorbents used in the process are low-cost natural geo-materials. Beidellite, zeolite, and sepiolite are inexpensive and natural minerals available locally, modified, and used as adsorbents for the removal of arsenic ions from aqueous solutions in batch experiments. The kinetics of the adsorption process was separately tested for the pseudo-first order and pseudo-second order reactions and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. The comparison among the models showed that the pseudo second-order model best described the adsorption kinetics. Applied to the experimental equilibrium, at different temperatures were the Langmuir and Freundlich isotherm models. The Langmuir isotherm was used to calculate the adsorption capacities (Q°) of minerals for arsenic ions. The adsorption capacities of these three modified minerals, at different temperatures, ranged from 476 to 841 µg/g. Thermodynamic studies showed that the arsenic uptake reactions by minerals were endothermic and spontaneous in nature. Bottled spring water containing arsenic, sold in markets, was used to conduct the arsenic adsorption study beidellite, zeolite, and sepiolite, minerals which efficiently removed the arsenate ions from the bottled drinking water. The use of modified beidellite, zeolite, and sepiolite as adsorbents in the arsenic ion removal processes is possible, based on the optimum parameters found.  相似文献   

12.
Environment‐friendly carboxymethyl cellulose (CMC) hydrogel beads were successfully prepared using epichlorohydrin (ECH) as a crosslinking agent in the suspension of fluid wax. There was an ether linkage formed between ECH and CMC, which was identified from bands in FTIR spectra of the prepared hydrogel. The prepared hydrogel beads with diameters about 4 mm were apparently spherical and fully transparent. The X‐ray diffraction (XRD) spectra indicated that the adsorption of metal ion onto the oxygen atom of carboxyl group led to change in crystallinity patterns of hydrogels. The scanning electron microscope (SEM) images clearly showed that the hydrogels had an internal porous structure. The adsorption capacity increased as initial concentrations of metal ions and the pH value of metal ion solution increased. Freundlich and Langmuir isotherm models were employed to analyze the data from batch adsorption experiments. There are vey good correlation coefficients of linearized equations for Langmuir model, which indicated that the sorption isotherm of the hydrogel beads for metal ions can be fitted to the Langmuir model. The maximum adsorption amount of hydrogel beads for metal ions is 6.49, 4.06, and 5.15 mmol/g for Cu(II), Ni(II), and Pb(II), respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

13.
This work aimed to fabricate nanocomposites using low-cost and natural materials for fast and efficient dye adsorption from wastewater. To achieve this, fibrous sepiolite clay was incorporated into the gelatin (GE) biopolymer. The obtained nanocomposites were characterized by Fourier transform infrared spectroscopy and scanning electron microscope techniques. The effects of sepiolite/GE ratio, adsorbent dosage, solution pH, contact time, and initial dye concentration on the adsorption capacity of nanocomposites were well studied and optimized through batch adsorption study. Kinetics, isotherms, and thermodynamics analysis were also performed for methylene blue adsorption. The adsorption data were better fitted with the pseudo-second-order and Langmuir isotherm models. The prepared nanocomposites demonstrated a fast and efficient adsorption performance toward the MB dye with the maximum adsorption capacity as high as 684.8 mg g−1 within only an equilibrium time of 30 min, which revealed their promising potential in wastewater treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48266.  相似文献   

14.
The dye adsorption performance of four mesoporous silicas with different structure and textural properties, MCM-41, MCM-48, SBA-15 and mesocellular silica foam (MCF), was studied and compared by using toluidine blue O (TBO) as dye model in aqueous solution. These materials were characterized by X-ray diffraction (XRD), small-angle X-ray scattering, nitrogen adsorption-desorption analyses, and transmission electron microscopy (TEM). The effect of some parameters such as adsorbent dosage, contact time, temperature, and pH on the TBO removal in aqueous solution was studied. Results showed that adsorption capacity raised when adsorbent dosage, contact time and pH solution were increased while an increase in temperature decreased the adsorption of TBO. Langmuir, Freundlich and Temkin isotherm models were employed to elucidate the adsorption mechanism while the adsorption rate data were analyzed according to the pseudo-first and second-order kinetic models. Results showed that adsorption of TBO onto MCM-48, SBA-15, and MCF fitted well the Freundlich isotherm model while the kinetic studies showed that adsorption process could be better described by the pseudo-second-order model for all mesoporous silicas. Finally, some solvents were evaluated to carried out dye desorption from the TBO-loaded mesoporous silicas founding that acetic acid was the most efficient.  相似文献   

15.
Sepiolite clay was used as an adsorbent for the removal of iron ions from industrial methyldiethanolamine (MDEA) solvent. The raw sepiolite clay was modified by different chemical and thermal treatments, and was characterized by FTIR, XRD, SEM-EDX, and BET-specific surface area analysis. Treating sepiolite with nitric acid significantly improved the adsorption capacity of iron ions from lean MDEA. The experimental equilibrium data were represented by Henry, Freundlich, and Langmuir isotherm models. The thermodynamic parameters indicated that the adsorption of iron ions on sepiolite was spontaneous and endothermic process. The kinetic studies showed that the adsorption followed pseudo-second order model.  相似文献   

16.
The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG o) and enthalpy change (ΔH o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.  相似文献   

17.
《分离科学与技术》2012,47(13):1898-1905
Batch adsorption studies were carried out using H2SO4 modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibb's free energy change (ΔG0) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.  相似文献   

18.
In this study, poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO) hydrogels were synthesized and evaluated as adsorbent for dye removal from wastewater using methylene blue (MB) in aqueous solution as probe. PEO samples were photochemically prepared by varying irradiation time (1–16 h), while PVA samples were synthetized with different concentration of glutaraldehyde (GA) (0.03–0.48%). The obtained hydrogels were obtained through the analysis of a swelling test, scanning electron microscopy, and adsorption studies. PEO hydrogels adsorption capacity was dependent on the irradiation time, while the PVA hydrogel adsorption capacity reduces with GA concentration. Both hydrogels demonstrated a Langmuir isotherm adsorption model at the equilibrium and pseudo‐second order kinetic fits properly. pH studies showed that when pH reaches 12, the adsorbed MB amount is close to 8 and 2 times higher than pH = 2 both hydrogels. Photochemical preparation of hydrogels shows an easier way of tuning their properties in order to maximize dye removal. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45043.  相似文献   

19.
Hydrogel nanocomposites having high amount of functional group, enhanced swelling ability, and improved mechanical properties were prepared for removal of basic dyes from aqueous solutions. Acrylamide (AAM) and itaconic acid sodium salt (IANa) were polymerized using polyethyleneglycol (400) diacrylate as crosslinker in the presence of montmorillonite (MMT). The products were characterized by swelling degree, total basic group content, XRD analysis, and FTIR spectroscopy. It was observed that MMT addition increased the itaconic acid gelation. The incorporation of low amount of MMT into the hydrogel structure increased also swelling degree. The products were used as adsorbent for removal of brilliant cresyl blue (BCB) from aqueous solutions. It was observed that the adsorption of BCB onto the nanocomposite completed in 30 min. It was found that the adsorption kinetics followed a pseudo-second-order kinetic model. Equilibrium isotherm of nanocomposite was analyzed using Freundlich and Langmuir isotherms. It was seen that the Langmuir isotherm model fit the adsorption data. These hydrogel nanocomposites have been shown to have the potential to be used as novel, fast-responsive and high capacity adsorbent materials for the removal of cationic dyes which is a serious problem, especially in textile industry.  相似文献   

20.
Use of polyester‐type polyurethane foam (PUF) is an effective adsorbent for the removal of hazardous dye: crystal violet (CV) from an aqueous solution. In this adsorption study, the formation of hydrophobic ion pair (opposite charge attraction) between the charged species, i.e., cationic (basic) dye CV and anionic surfactant sodium dodecylsulfate (SDS) sorbed onto PUF. Chemical calculations were performed using quantum simulation to understand ion‐pair formation for CV–SDS at the semiempirical PM6 level. Adsorption studies were performed using 200 mg cylindrical PUF with an overhead stirrer in solutions containing varying compositions of the dye–surfactant mixture. The equilibrium thermodynamics and kinetics of the adsorption process were studies by measuring CV dye removal as a function of time and temperature. Results show that the formation of the dye–surfactant ion pair is necessary for effective adsorption onto PUF. Various adsorption isotherms, viz., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (DRK), Harkin‐Jura, and several kinetic models, viz., pseudo‐first order, pseudo‐second order, Elovich, and Intraparticle diffusion were used to fit the spectrophotometric result. The equilibrium adsorption data fit to the Langmuir isotherm gives the maximum adsorption of PUF as 33.39 mg g?1 from 200 mL 5.0 × 10?5 mol L?1 CV solution at 298.15 K. The kinetics study showed that the overall adsorption process follows pseudo‐second‐order kinetics. The Morris–Weber model suggests that an intraparticle diffusion process is active in controlling the adsorption rate. The Freundlich, Temkin, DRK adsorption isotherms showed that solute dye transfers from solution to the PUF adsorbent surface through physical adsorption. The Langmuir and Harkin‐Jura adsorption isotherms suggest that the adsorbent surface is homogeneous in nature. The thermodynamic data showed that the adsorption process is spontaneous and endothermic with a positive enthalpy change and a negative change in Gibb's energy.  相似文献   

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