High efficiency antimicrobial cellulose‐based nanocomposite hydrogels

Carboxymethyl cellulose hydrogels were developed through crosslinking process using maleic, succinic, or citric acids. The swelling capacities of the obtained hydrogels have been controlled through variation of the crosslinking reaction conditions. Further enhancement of the swelling properties was achieved by additional blending step of the carboxymethyl cellulose with polyethylene glycol. Biofunctionalization of the hydrogels was achieved through “in situ” incorporation of the silver nanoparticles during the crosslinked reaction. Chemical structure verifications and morphological characterizations of the hydrogels were performed using FTIR, XRD, EDX, and SEM analyses. Finally, the antimicrobial activity of the loaded silver hydrogels against G+ve, G?ve, and yeast Candida albicans was demonstrated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42327.     

Removal of methylene blue from aqueous solutions by using cold plasma‐ and formaldehyde‐treated onion skins

In this paper, the use of cold plasma‐treated and formaldehyde‐treated onion skins as a biosorbent has been investigated to remove methylene blue dye from aqueous solutions. The surface characteristics of the treated onion skins were investigated using Fourier Transform–infrared spectroscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. Equilibrium isotherms were analysed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results indicated that the data for adsorption of methylene blue onto onion skins fitted well with the Langmuir isotherm model. The sorption capacities for cold plasma‐treated and formaldehyde‐treated onion skins by Langmuir isotherm were found to be 250 and 166.67 mg/g, respectively. The equilibrium time was found to be 150 min for 50 mg/l dye concentrations. The maximum removals for cold plasma‐treated and formaldehyde‐treated onion skins obtained were 90.94 and 95.54% at natural pH 10.0 for adsorbent doses of 0.15 g/200 ml, respectively. The rates of sorption were found to conform to pseudo‐first‐order kinetics. Results indicated that onion skins could be used as a biosorbent to remove methylene blue dye from contaminated waters.     

Comparative study of PEO and PVA hydrogels for removal of methylene blue dye from wastewater

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.     

Removal of methylene blue from coloured effluents by adsorption onto SBA‐15

Adsorption has been proven to be the most efficient method for quickly lowering the concentration of dissolved dyes in an effluent. In this regard, activated carbon is the most widely used adsorbent for removal of dyes from aqueous solution. However, the high cost of production and regeneration make it uneconomical. Therefore, inorganic adsorbents (e.g. zeolites) with high surface areas have been used as alternatives to carbon adsorbents. Microporous zeolites ZSM‐5, NH₄‐Beta, MCM‐22 and mesoporous materials MCM‐41 have been investigated for the removal of dyes from aqueous solutions and they show effective adsorption performance. SBA‐15 possesses a larger pore size and pore wall thickness than MCM‐41. As a result, SBA‐15 has greater potential for the adsorption of methylene blue with larger molecule size and higher hydrothermal stability than the M41S family. SBA‐15 is an excellent adsorbent for methylene blue (MB), exhibiting 280 mg g^?1 adsorption capacity and about 100% fading rate for MB. The adsorptive process is so fast that adsorption equilibrium is achieved in 5 min. In addition, SBA‐15 can be effectively recovered by calcination and reused 10 times without significant loss in removal of MB from aqueous solution. The efficient adsorption of MB molecules onto SBA‐15 was ascribed to MB adsorbed into the pore channels of SBA‐15, which was confirmed by nitrogen physisorption analysis of the adsorbent before and after adsorption. The long reuse life of the adsorbent suggests a high potential for application in industry. Copyright © 2010 Society of Chemical Industry     

Removal of Pb(II) from solution using cellulose‐containing materials

The potential of cheap cellulose‐containing natural materials such as coir, jute, sawdust and groundnut shells for removal for Pb(II) from aqueous solution of lead nitrate was assessed before and after modifying them with a monochlorotriazine type of dye. The materials showed enhanced adsorption capacity of Pb(II) due to the specific dye loading. This was attributed to chelation and an ion exchange mechanism. The maximum cation uptake values obtained were 0.127, 0.087, 0.090, and 0.106 mmol g^?1 for coir, sawdust, jute and groundnut shell in their dyed forms, respectively. The kinetics of both undyed and dyed coir was analysed and the second order rate equation was observed to provide the best correlation of the experimental data. Adsorption isotherm models were developed. The best fit was obtained in the Langmuir model. When subjected to repeated adsorption–desorption cycles, with an intermediate step of mild sodium hydroxide treatment, both dyed and undyed coir retained its adsorptive capacity even after five cycles of reuse. Copyright © 2004 Society of Chemical Industry     

Removal of methylene blue from aqueous solution by electrophoretically deposited titania‐halloysite nanotubes coatings

Two‐component suspensions of titania and halloysite nanotubes (HNTs) were prepared in ethanol with 0.5 g/L (optimum concentration) of polyethyleneimine (PEI) and different wt% of HNTs. Kinetics of Electrophoretic deposition (EPD) decreased with increasing the HNTs content in suspensions due to their less mobility compared with titania particles. HNTs reinforced the microstructure of coatings and reduced or completely prevented from cracking during drying and heat‐treatment steps. Removal of methylene blue (MB) via adsorption by HNTs coatings was faster than its photocatalytic degradation by titania coating. Dispersion of HNTs (up to ≈30 wt%) in the matrix of titania resulted in the synergistic catalytic effect in MB removal. The synergistic effect was because of the shorter traveling distance of MB molecules adsorbed on HNTs toward the photocatalytic active site of titania particles in composite coatings. However, the synergistic effect was destroyed with increasing the HNTs content in coating. Difference between the amount of MB removed by titania and composite coatings increased at longer times (≥60 minutes). Mass transfer of MB adsorbed on HNTs toward the photocatalytic active sites of adjacent titania particles can compensate the decline in the mass transfer from solution at longer times.     

Removal of reactive dyes from wastewater using Fe(III) coagulant

The coagulation-flocculation process was employed for the treatment of reactive dye wastewaters, with ferric chloride hexahydrate employed as the coagulant. The process was found to be very effective with a more than 99.5% colour removal. Typical representatives of monochlorotriazine reactive dyes, with azo and anthraquinone chromophores, were CI Reactive Red 45 and CI Reactive Green 8, which were chosen as the model dyes. In order to determine the optimum pH range and coagulant concentration, a series of jar tests was done. Further experiments were conducted using a square flocculation tank with turbine impeller applying rapid and slow mix operations. The optimisation of initial rapid mixing, which has an important role in the overall coagulation process efficiency, was carried out. The optimum combination of velocity gradient and time of rapid mix was suggested for reactive dye wastewater treatment. Sedimentation curves for both model dyes were also obtained.     

Development and characterization of cellulose‐based hydrogels for use as dietary bulking agents

In the last decade, cellulose‐based hydrogels have been receiving increasing attention for a number of applications because of their smart swelling behavior, biodegradability, and biocompatibility. Given the dramatic spreading of obesity and overweight in the industrialized countries and the lack of scientific consensus over currently available dietary supplements, it was recently proposed that such hydrogels might be used as orally administered bulking agents in hypocaloric diets, because the hydrogel swelling in the stomach may greatly reduce the space available for food intake, thus giving a sense of fullness. This study is focused on the synthesis of cellulose‐based hydrogels, starting from pharmaceutical and food grade cellulose derivatives, and shows that such hydrogels possess good swelling properties in water solutions mimicking the environmental conditions of the stomach and the intestine, as well as a good biocompatibility. The crosslinking agent used was a “zero‐length” crosslinker, that is, a water soluble carbodiimide, which is washed out from the gel after the synthesis and does not affect the gel compatibility, as shown by preliminary biocompatibility assays. The experimental results confirmed that cellulose‐based hydrogels might be a scientifically valid dietary adjuvant in the treatment of obesity and overweight, and provide further scientific evidence for future experiments on humans. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Removal of methylene blue (aq) using untreated and acid‐treated eucalyptus leaves and GA‐ANN modelling

In the present batch study, eucalyptus leaves (EUL), H₂SO₄‐treated eucalyptus leaves (SEUL), and H₃PO₄‐treated eucalyptus leaves (PEUL) are used as bio‐adsorbents for the removal of methylene blue (MB). The bio‐adsorption is executed to inspect the results of the variation between different experimental variables such as pH (2–10), adsorbent dose (1–10 g/L), contact time (5–360 min), and temperature (298–318 K) on the bio‐adsorption of MB. The Langmuir isotherm (R² = 0.99) fitted adequately to the bio‐adsorption data for the initial MB concentrations of 10–300 mg/L. It is also necessary to mention that the MB bio‐adsorption occurred in the order of a monolayer on the EUL, SEUL, and PEUL. The bio‐adsorption kinetics have been fitted by the pseudo‐second‐order model (R² ≥ 0.99) for various MB concentrations. The maximum bio‐adsorption capacity was 194.34 mg/g and was achieved for the H₃PO₄‐treated eucalyptus leaves (PEUL). These results showed that EUL, SEUL, and PEUL may be utilized as a favourable low‐cost bio‐adsorbent to eliminate MB from aqueous solutions. With safe disposal methods in mind, this investigation has revealed the eco‐friendliness of the bio‐adsorbents. A prediction of the removal percentage of methylene blue using a genetic algorithm (GA) from the data collected from the experiment has also been tested. The results related to the prediction using the GA‐ANN are accurate.     

Composite effect of silica nanoparticle on the mechanical properties of cellulose‐based hydrogels derived from cottonseed hulls

Recently, cellulose‐based hydrogel nanocomposite materials have been attracted increasing attention owing to their potential applications in different areas including medical, electrical, optical, and magnetic fields. This is due to the fact that cellulose is one of the most abundant resources and possesses several unique properties required in medical fields, whereas silica nanoparticles (nSiO₂) play an important role in developing materials with high functionality. In this study, cottonseed hull (CSH) was used as a source of cellulose and nSiO₂ was used to prepare hydrogel nanocomposite films via phase inversion method without chemical crosslinking agent of cellulose. CSH was first pre‐treated with sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) for delignification and bleaching, respectively. The pre‐treated CSH exhibited whiter fiber and lower amount of lignin as compared with the untreated CSH. The properties of cellulose‐base hydrogel were found to be improved as a result of the addition of nSiO₂ at 2–6 wt % for tensile strength and up to 10 wt % for modulus and elastic modulus (G′). However, the elongation at break was decreased with the incorporation of nSiO₂. Moreover, the TEM images displayed the nano‐grape structure of nSiO₂ surrounded by cellulose molecules. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44557.     

Removal of heavy metals from model wastewater by using carboxymehyl cellulose/2‐acrylamido‐2‐methyl propane sulfonic acid hydrogels

A series of functional copolymer hydrogels composed of carboxymethyl cellulose (CMC) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) were synthesized using γ‐radiations‐induced copolymerization and crosslinking. Preparation conditions were optimized, and the swelling characteristics were investigated. The ability of the prepared hydrogels to recover some toxic metal ions from their aqueous solutions was studied. The prepared hydrogel showed a great capability to recover metal ions such as: Mn⁺², Co⁺², Cu⁺², and Fe⁺³ from their solutions. The data revealed that the chelating ability of the prepared hydrogels is mainly dependent on their internal composition, in addition to the physical properties of the metal ion solution such as pH and metal ion concentration. The data show that the chelating ability of the prepared hydrogels increases by increasing the AMPS content in the hydrogel as well as the increment in the pH of the solution and the metal ion concentration. The prepared CMC/AMPS copolymer hydrogels are chemically stable enough to be reused for at least five times with the same efficiency. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Removal of methylene blue from aqueous solutions by poly(2-acrylamido-2-methylpropane sulfonic acid-co-itaconic acid) hydrogels

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.     

活性炭对水中亚甲基蓝的吸附性能研究

以活性炭为吸附剂,亚甲基蓝(MB)为吸附质,考察了吸附剂用量、吸附时间、温度对活性炭去除亚甲基蓝的影响。分别采用伪一级、伪二级动力学模型和Langmuir,Freundlich吸附等温线模型对吸附动力学和等温线进行分析。实验表明,在活性炭用量为0.667 g/L,吸附时间为360 min,反应温度为298 K时,活性炭对亚甲基蓝的最大吸附量为249.081 mg/g。吸附反应在前30 min内速率很快,并约在360 min内达到吸附平衡,吸附动力学符合伪二级动力学模型。吸附反应为放热反应,等温吸附过程符合Langmuir和Freundlich吸附等温模型,相关系数高于0.99。活性炭对去除水中亚甲基蓝效果好,是一种优良的吸附剂。     

Removal of basic dyes from aqueous solutions by crosslinked‐acrylic acid/acrylamidopropane sulfonic acid hydrogels

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     

Electrospinning of cellulose‐based nanofibers

Cellulose derivatives of carboxymethyl cellulose sodium salt (CMC), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and enzymatically treated cellulose have been electrospun, and the microstructure of the resulting nanofibers has been analyzed by scanning electron microscopy (SEM). Before electrospinning, the solutions were characterized by viscometry and surface tension measurements, and the results were correlated with spinnability. Four different CMC derivatives, varying in molecular weight (M_w), degree of substitution (DS), and substitution pattern, have been electrospun in mixtures with poly(ethylene oxide) (PEO), and nanofibers of various characteristics have formed. The CMC‐based nanostructures, i.e., the nonwoven sheet and individual nanofibers, proved to be independent of M_w and DS but largely dependent on the substitution pattern. The nonwoven sheets varied in homogeneity, and beads appeared on the individual fibers. Depending on the chemical nature of the CMC, the extraction of PEO resulted in pure CMC nanostructures of varying appearance, indicating that the distribution of PEO and CMC in the nanofibers also varied. Two different HPMC derivatives, varying in DS, were electrospun into nanofibers. Homogeneous nonwoven sheets based on nanofibers of similar appearance are formed, independent of the substitution content of the HPMC sample. Preliminary fibers were obtained from enzymatically treated cellulose in a solvent system based on lithium chloride dissolved in dimethyl acetamide (LiCl: DMAc). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1473–1482, 2007     

Removal of basic dyes from aqueous solutions using starch‐graft‐acrylic acid copolymers

Graft copolymerization of acrylic acid (AA) onto starch was carried out with ceric ammonium nitrate as initiator under nitrogen atmosphere. The grafting percentages (GP%) of starch‐graft‐AA (St‐gr‐AA) copolymers were determined. When the AA molar concentrations were 0.3 and 0.5 mol/L, GP% of St‐gr‐AA copolymers were 10.5% (St‐gr‐AA‐1) and 14% (St‐gr‐AA‐2), respectively. St‐gr‐AA copolymers have been used for the adsorption of basic dye (Safranine T) from aqueous solutions. Effects of various parameters such as treatment time, initial pH of the solution (pH = 2–6), initial dye concentration (50– 500 mg/L), and GP% of starch graft copolymers were investigated.Basic dye removal capacities of the copolymers increase along with the augment of initial concentration of the adsorbate, GP% of the copolymers, and pH. The adsorption capacities for St‐gr‐AA‐1 and St‐gr‐AA‐2 reach 116.5 and 204 mg/g, respectively. Equilibrium adsorption data were obtained and fitted very well to Freundlich model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Enhanced swelling and methylene blue adsorption of polyacrylamide‐based superabsorbents using alginate modified montmorillonite

Polyacrylamide/sodium alginate modified montmorillonite (PAM/SA‐MMT) superabsorbent composites were synthesized by free‐radical polymerization under normal atmospheric conditions. They were characterized by X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). Their water absorbency and methylene blue (MB) adsorption behaviors were studied. Compared with PAM/MMT composites, PAM/SA‐MMT composites demonstrated greater water absorbency (863 g g^?1 in distilled water and 101 g g^?1 in 0.9 wt % NaCl solution) and higher adsorption capacity of 2639 mg g^?1 for MB. The adsorption behaviors of the composites showed that the isotherms and adsorption kinetics were in good agreement with the Langmuir equation and pseudo‐second‐order equation, respectively. FTIR analysis suggested that the MB adsorption of PAM/SA‐MMT composites via a mechanism combined electrostatic, H‐bonding and hydrophobic interaction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40013.     

Removal of copper ions from aqueous solutions by adsorption onto wheat straw cellulose‐based polymeric composites

The wheat straw cellulose‐based hydrogels were synthesized by graft copolymerization followed by semi‐interpenetrating network technology. The prepared hydrogels were characterized through various methods including Fourier transform infrared spectra, scanning electron microscope, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. Batch adsorption experiments were carried out to investigate the adsorption performances of hydrogels toward Cu(II) ions. The results suggested that the introduction of semi‐interpenetrating network polymers, sodium alginate and poly(vinyl alcohol), could greatly enhance the adsorption property of hydrogels. And the wheat straw cellulose‐g‐poly(potassium acrylate)/sodium alginate hydrogel showed a highest Cu(II) ions adsorption capacity of 130 mg/g. The equilibrium isotherm and adsorption kinetics were also studied. Besides, the mass transfer coefficients and the thermodynamics of Cu(II) ions adsorption were also probed. Finally, the X‐ray photoelectron spectroscopy analysis further demonstrated that the Cu(II) ions adsorption was mainly via complexation reaction of ? NH₂ and O‐containing groups in hydrogels. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46680.     

Adsorption of methylene blue on hemicellulose‐based stimuli‐responsive porous hydrogel

A stimuli‐responsive porous hydrogel was synthesized from wheat straw hemicellulose using CaCO₃ as the porogen, and its application for the removal of methylene blue was studied. The porous structure of the prepared hydrogel was confirmed by SEM analysis. The effects of pH and polyelectrolyte on the swelling of the hydrogels were discussed, and the porous hydrogels showed excellent sensitivity to pH and salt. The deswelling kinetic study indicated that the hydrogels exhibited rapid shrinking in NaCl aqueous solutions. The methylene blue adsorption on the hydrogels was investigated, and the obtained adsorption data was fitted to the pseudo‐first‐order, pseudo‐second‐order and intra‐particle diffusion kinetics models, and the pseudo‐first‐order kinetic model could describe the adsorption process, and the adsorption process of methylene blue on the hydrogels was controlled by external film diffusion. This study reported that the hemicellulose‐based porous hydrogel is promising for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41606.     

Water and synthetic urine sorption capacity of cellulose‐based hydrogels under a compressive stress field

A new apparatus was developed and used to investigate the swelling behavior of crosslinked hydrophilic polymers under an applied load as a function of the absorbed weight in both water and water solutions. A model able to predict the material water uptake as a function of the isotropic compressive stress was also studied. Centrifugation tests were performed to measure the material retention capacity under load, in both water and synthetic urine. The polymers studied in the tests were from a particular class of superabsorbent hydrogels based on cellulose derivatives chemically crosslinked with divinyl sulfone. The hydrogels showed high sorption and retention capacity in both water and water solutions, both in the free state and under load, and significant variations were observed during the modulation of the dry sample porosity.© 2004 Wiley Periodicals, Inc.J Appl Polym Sci 91: 3791–3796, 2004