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
Batch lignocellulose-g-poly(acrylic acid)/montmorillonite (LNC-g-PAA/MMT) hydrogel nanocomposites were applied as adsorbents. The nanocomposites were characterized by FTIR, XRD, SEM, and TEM. The results showed that montmorillonite (MMT) could react with the monomers and change the structure of polymeric network of the traditional superabsorbent materials, an exfoliated structure was formed in the nanocomposites. The effect of process parameters such as MMT content (wt%), contact time (t), initial concentration of dye solution (C0), adsorption temperature (T), and pH value (pH) of the dye solution for the removal of methylene blue (MB) from aqueous solution were also studied. The results showed that the adsorption capacity for MB increased with increasing contact time, initial dye concentration, and pH value, but decreased with increasing MMT content and temperature. The adsorption kinetics were better described by the pseudo-second-order equation, and their adsorption isotherms were better fitted for the langmuir equation. By introducing 20 wt% MMT into LNC-g-PAA polymeric network, the obtaining hydrogel composite showed the high adsorption capacity 1994.38 mg/g and economic advantage for MB. The desorption studies revealed that the composite provided the potential for regeneration and reuse after MB dye adsorption, which implied that the composite could be regarded as a potential adsorbent for cationic dye MB removal in a wastewater treatment process. 相似文献
In this study, removal of methylene blue (MB) from aqueous solution by poly(AMPS-co-IA) hydrogels was examined by batch equilibration technique. The effects of monomer ratio, concentration of initiator and
crosslinker, pH, adsorption time, initial dye concentration and adsorption temperature on the removal of MB were studied.
The results show that the removal of MB was highly effected by preparation conditions of hydrogel. The maximum removal was
observed at 10/90 IA/AMPS monomer ratio, 1.0% KPS, and 10.0% MBAAm concentrations. Removal of MB was strongly affected by
pH. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption
of MB on hydrogel followed pseudo-second-order kinetics. It was found that the adsorption isotherm of the MB fit Langmuir-type
isotherms. From the Langmuir equation, the adsorption capacity was found as 1,000 mg/g for MB dye. Thermodynamic parameters
suggest that the adsorption is a typical physical process, spontaneous, and exothermic in nature. Ten adsorption—desorption
cycles demonstrated that the hydrogels were suitable for repeated use without considerable change in adsorption capacity.
The results revealed that this hydrogels have potential to be used as an adsorbent for the removal of MB from aqueous solution. 相似文献
Hydrogels for absorbing metal ions in wastewater have attracted more attentions in the environmental field especially for recent years. The removal efficiency of hydrogel adsorbents for eliminating metal ions is highly related with the effective contact between adsorbents and adsorbates. However, poor water absorption capacity of the hydrogel adsorbents would restrict on the expose of adsorption sites to the targeted subjects, causing undesirable removal ratio (RR) especially for metal ions at trace level. Thereby, the reported hydrogel adsorbents mainly focus on the removal of high content but not the trace level of metal ions so far. In this work, poly(acrylamide) (PAM)/poly(acrylic acid) (PAA)/Ca(OH)2 composite hydrogel is applied to adsorb trace metal ions. Swelling ratio of such PAM/PAA/Ca(OH)2 gel reaches 2,530 g/g, resulting in effective exposure of active sites and further expected RR for trace metal ions. The RRs of such adsorbent for Cu2+ (initial concentration C0 = 0.064 mg/L), Al3+ (C0 = 0.27 mg/L), Co2+ (C0 = 0.59 mg/L), Cr6+ (C0 = 0.52 mg/L), Mn2+ (C0 = 0.55 mg/L), Ni2+ (C0 = 0.59 mg/L), Zn2+ (C0 = 0.65 mg/L), Ag+ (C0 = 1.08 mg/L), and La3+ (C0 = 1.39 mg/L) are 56.6, 80.8, 41.3, 29.3, 34.6, 44.6, 55.9, 45.8, and 35.5%, respectively. This work broadens the application of hydrogel adsorbent for eliminating trace metal ions from polluted water. 相似文献
High-strength polyethylene (HSPE), polypropylene (PP), poly(ethylene terephthalate) (PET), and poly(vinyl alcohol) (PVA) textile yarns have been surface-photografted with various functional monomers, such as acrylic acid (AA), acrylamide (AM), glycidyl acrylate (GA) and 4-vinyl pyridine (VP), by means of the continuous presoaking process developed. The dyeing of these surface-modified yarns with various textile dyes has been investigated. In general, considerable improvements of dyeability have been observed. The dye adsorption of the surface-photografted fibers is influenced by many factors, such as type of fiber, amount and properties of the functional monomer grafted on the surface of the fibers, type of textile dye, etc. The fibers surface-grafted with a monomer containing basic groups, such as acrylamide and 4-vinyl pyridine, are efficiently dyed with an acid dye. Conversely, a fiber surface-grafted with acidic functional monomer is easily dyed to deep shades with basic dyes. The dye adsorption increases monotonically with increasing grafting measured in ESCA spectra as relative intensities of relevant lines. The ungrafted HSPE, PP and PET fibers can be dyed to some extent with certain dyes. In the present work, the dye adsorption increased by 3.4 times for HSPE fiber grafted with GA and dyed with the metal complex dye IO, by 7.9 times for PP fiber grafted with AA and dyed with the basic dye MB, by 6.1 times for PET with AM and with the direct dye SL, and by about 15.3 times for PVA with VP and with the acid dye TE. 相似文献
A novel chitosan (CTS)-based double network Poly(2-acrylaMido-2-Methyl-1-propanesulfonic acid)/Polyacrylamide/CTS hydrogel was synthesized by irradiation initiated. Laponite RD (RD) was used as both dopant and the cross-linking agent. Then the fabricated hydrogel was applied as an efficient adsorbent to remove the methylene blue (MB) in an aqueous solution. This hydrogel has both high strength and good adsorption properties for MB. The results from Brunauer–Emmett–Teller method confirmed that the hydrogel has a large specific surface area (96 m2/g) and developed pore structure, which is available for the contact between the adsorbent and dye molecules. In the adsorption process, the RD provides plenty of negative charges as adsorption sites for MB molecules. The influence of pH, temperature, and adsorbent dose on the adsorption performance was investigated in detail. The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm. Besides, the mechanical strength of the hydrogel was also investigated in this work. 相似文献
Present work focused on synthesis of green hydrogel polymer of gum rosin alcohol/psyllium crosslinked poly (acrylic acid) [(GrA-Psy)-cl-PAA] under vacuum condition. Use of both psyllium and gum rosin alcohols as backbones could lessen the burden on the environment, as more natural aspect is drawn in the hydrogel polymer. The various reaction parameters for the synthesis of hydrogel polymer were systematically optimized as a function of percentage swelling. The optimized ecofriendly hydrogel polymer was characterized using XRD, FTIR, FE-SEM and TGA techniques, which supported the successful formation of crosslinked three-dimensional network structures. (GrA-Psy)-cl-PAA was further studied as an adsorbent for the removal of methylene blue dye from an aqueous solution. Adsorption parameters such as the amount of adsorbent and pH were optimized to obtain the maximum percentage of dye removal. Kinetics of the adsorption process was analyzed using pseudo-first-order, pseudo-second-order and Elovich kinetic models. Adsorption kinetics followed pseudo-second-order model (non-linear) for all the concentrations studied. Non-linear forms of Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherm models were studied for the adsorption process and it was observed that it goes well with both Langmuir and Freundlich isotherms. Thermodynamic parameters were also evaluated which indicated that the adsorption process was exothermic and spontaneous. Furthermore, the candidate polymer retained a reusability tendency for two consecutive cycles of adsorption/desorption. Thus, the synthesized novel material was taken as a potential to act as green adsorbent in treatment of industrial wastewater. 相似文献
This work developed an effective way to improve the methylene blue (MB) adsorption performance of cellulose-based hydrogel by modified with tannic acid (TA). HEC-co-p(AA-AM)/TA hydrogel was synthesized by grafting of acrylic acid (AA) and acrylamide (AM) onto hydroxyethyl cellulose (HEC), followed by modified with TA. Fourier transform infrared spectroscopy manifested that AA and AM were successfully grafted onto the hydrogel, and TA was immobilized in the hydrogel. Field emission scanning electron microscope demonstrated that the hydrogel after TA modification had a homogeneous pore structure. Brunauer-Emmett-Teller (BET) surface areas, total pore volume, and average pore diameters of the hydrogel are 11.821 m2 g−1, 0.0641 cm3 g−1, and 2.538 nm, respectively. The high swelling ratio (1179.2 g g−1 in deionized water) was in favor of the MB adsorption. The results of the adsorption experiments illustrated that HEC-co-p(AA/AM) hydrogel had excellent MB adsorption performance. As the pH increases, the electrostatic attraction is enhanced, and the adsorption capacity is improved. The adsorption process was more fit with pseudo-second-order kinetics, and the maximum adsorption capacity (3438.27 mg g−1) was determined by Langmuir model. Thermodynamic studies suggested that the adsorption process is spontaneous, exothermic, and entropy reduction. X-ray photoelectron spectroscopy analysis confirmed that MB molecules were reacted with the oxygen atoms in hydroxyl and carboxyl groups by ion-exchange. High reusability demonstrated that the hydrogel could be a potential candidate for removal cationic dye from industrial effluents. 相似文献
The formation of interpolymer complexes (IPC) between poly(acrylic acid) (PAA) and poly(acrylamide) (PAM), poly(N,N-dimethylacrylamide) (PDMA), and statistical copolymers of acrylamide (AM) and N,N-dimethylacrylamide (DMA) has been studied as a function of pH, salt concentration and temperature (0–70 °C). The cloud points of dilute solutions were measured by turbidimetry and phase diagrams were determined as a function of temperature and pH in pure water and as a function of pH and salt concentration at room temperature. For each temperature and salt concentration a critical pH (pHcrit) below which IPC are observed was defined. In the case of PAA/PAM, pHcrit continuously decreased with increasing temperature, from pH 3.5 at 0 °C to pH 1.9 at 60 °C (UCST-type). In the case of PAA/PDMA, pHcrit, increased with temperature. The LCST-type behavior of the hydrogen-bonding complex formed between PAA and PDMA was attributed to the dimethyl substitution of amide groups that puts in hydrophobic interactions at high temperature. PAA and statistical copolymers P(AM-co-DMA) showed an intermediate behavior between PAA/PAM and PAA/PDMA with a continuous shift from UCST-type to LCST-type with increasing amount of DMA. This behavior can be attributed to changes in configurational entropy due to the IPC formation and (for PDMA) to the release of water molecules initially confined in hydrophobic hydration cages around DMA units. While at low salt concentration, the stability of PAA/PAM and PAA/PDMA complexes only slightly increases with the screening of ionized acrylic units, there is a sharp increase of pHcrit at high salt concentration in relation with the weakening of the solvent quality. In this regime, the complex formation of PAA/PDMA is greatly enhanced compared to PAA/PAM due to the interference of hydrophobic interactions. 相似文献
In the present study, synthesis of poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite with different amount of bis[2-(methacryloyloxy)ethyl] phosphate as a crosslinker was successfully carried out for the removal of crystal violet (CV), methylene blue (MB) and methyl red (MR) from aqueous solution. Hydrogel nanocomposite was characterized by FT-IR, SEM, EDS, XRD and TGA analysis. Several important parameters were investigated to obtain maximum adsorption capacity. Adsorption behavior of hydrogel nanocomposite was investigated for the adsorption of dyes and it was found to remove about 80% for CV, 89% for MB and 51% for MR in 50 mg/L of dyes solutions at pH 7 and about 86% for CV, 93% for MB and 23% for MR at pH 12. Kinetic studies revealed that the applicability of pseudo-first-order and pseudo-second-order model for the adsorption of CV, MB and MR. The adsorption isotherm was studied in 25, 35, 45 and 55 °C using Langmuir, Freundlich, Temkin and Jovanovic models and the adsorption data were well described by Freundlich isotherm model. Hydrogel nanocomposite showed 155, 176 and 113 mg/g maximum adsorption capacity for CV, MB and MR respectively. Negative values of ΔG0 for all three dyes suggested the feasibility of dyes removal and support for spontaneous adsorption of CV, MB and MR on hydrogel nanocomposite. Desorption of dyes from the dye loaded hydrogel nanocomposite was simply done in ethanol. The results indicate that the prepared poly(AAm-co-AMPS)/Na-MMT hydrogel nanocomposite is an efficient adsorbent with high adsorption capacity for the aforementioned dyes.
The adsorption isotherms of poly(acrylic acid) (PAA) onto alumina powder have been determined as a function of pH, ionic strength, and magnesium-ion concentration. The adsorption of PAA is strongly enhanced by magnesium ions in alkaline media but less affected under acidic conditions. The adsorption isotherms display a maximum when PAA is fully complexed with magnesium ions in the solution, corresponding to a ratio of 0.25 ± 0.05 [Mg2+]/[acrylic acid monomer]. The decrease in adsorbed amount with an increase in PAA concentration at constant magnesium-ion concentration is related to a decrease in the complexation ratio. 相似文献
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