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     

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solution was investigated. The copolymers used were (1) cellulose‐g‐polyacrylic acid (cellulose‐g‐pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose‐g‐p(AA–NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of N,N′‐methylene bisacrylamide (NMBA); (3) cellulose‐g‐p(AA–AASO₃H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2‐acrylamido‐2‐methyl propane sulphonic acid (AASO₃H) containing 10% (in mole) AASO₃H; and (4) cellulose‐g‐pAASO₃H obtained by grafting of AASO₃H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose‐g‐pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g_copolymer. Although the metal removal rate of cellulose‐g‐p(AA–NMBA) copolymer was lower than that of cellulose‐g‐pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g_copolymer. Cellulose did not remove any ion under the same conditions. In addition, cellulose‐g‐pAASO₃H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g_copolymer). The presence of AASO₃H in the graft chains of cellulose‐g‐p(AA–AASO₃H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose‐g‐pAA. All types of cellulose copolymers were found to be selective for the removal of Pb²⁺ over Cu²⁺ and Cd²⁺. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2034–2039, 2003     

Metal complexation studies of amylopectin‐graft‐poly[(N,N‐dimethylacrylamide)‐co‐(acrylic acid)]: a biodegradable synthetic graft copolymer

Synthesis of amylopectin‐graft‐poly[(N,N‐dimethylacrylamide)‐co‐(acrylic acid)] was carried out using solution polymerization technique with potassium persulfate as the initiator. The graft copolymer was characterized by measuring molecular weight using size exclusion chromatography, thermal analysis and Fourier transform infrared (FTIR) spectroscopy. The synthetic graft copolymer was used for the removal of some potentially toxic metal ions, Cu(II), Zn(II) and Ni(II), from their aqueous solutions. Various operating parameters like the amount of adsorbent, solution pH, contact time and temperature were studied. The adsorption data were well described by the pseudo‐second‐order and Langmuir isotherm models. Metal complexation studies were carried out experimentally using cyclic voltammetry and UV‐visible and FTIR spectroscopies. The metal complex structure was also studied theoretically using density functional theory with the Gaussian 09 program and the geometry of the complex structure was optimized. The metal complexation ability of the graft polymer was in the order Cu(II) > Ni(II) > Zn(II). Calculation of the various thermodynamic parameters was also done. The negative value of free energy change indicates the spontaneous nature of the adsorption. © 2015 Society of Chemical Industry     

Swelling of crosslinked poly(methylmethacrylate‐acrylic acid) copolymers in serum and saline solutions

In recent articles, our research group explored the use of crosslinked Poly(methylmethacrylate‐acrylic acid) and composites based on this copolymer for bone implant applications such as suture anchors. The swelling response of this system was studied first in vitro, using a 0.85 g/100‐mL saline solution (chosen because it simulates well the in vivo environment), and later in vivo by using samples implanted for various time periods in the lateral femoral condyles of New Zealand white rabbits. It was found that the swelling response of the crosslinked copolymer in vivo was much greater than that in the saline solution. The present investigation was conducted to determine the mechanism of excessive swelling in the in vivo tests. The approach used was to establish the changes occurring in the chemical structure of the copolymer due to immersion in serum. A number of hypotheses that can potentially explain the observed excessive swelling in serum were investigated and are discussed in this article. The results of this study indicate that the mechanism of excessive swelling in serum was the neutralization of  COOH groups in the copolymer to produce salts of acrylic acid, which are known to result in greater swell due to their higher degree of dissociation compared to free acid. It was also found that, for compositions containing the acrylic salts (produced by preswelling in high pH solutions and drying), the swelling behavior in serum was similar to that in saline solution, and more importantly, equilibrium swelling was reached in a relatively shorter time period, which has several practical advantages for bioimplant applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1653–1664, 2001     

Synthesis of superabsorbent starch‐graft‐poly(potassium acrylate‐co‐acrylamide) and its properties

The superabsorbent's ability to resist deformation and to resist deswelling under externally applied pressures is important in practical application. For instance, it is used in infant diapers, in soil for agriculture, and in forestry. In this article, we report on the synthesis of a superabsorbent/starch‐graft‐poly(potassium acrylate‐co‐acrylamide) by inverse suspension polymerization. The effects of reaction conditions, such as monomeric concentration, ratio of water to oil, reaction temperature, and obtaining spherical resin, were investigated. Experiments showed that the superabsorbent has a good compressive strength and keeps the shape of particles after absorbing water. After mixing with soil it does not become sticky, and the loose structure can better retain air. It is fit to retain water in soil. In addition, thermogravimetric analysis revealed the superior thermal stability of the grafted product and its large particle size also reduces risk of air pollution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1536–1542, 2003     

Synthesis of starch‐graft‐polyacrylonitrile hydrolyzate and its characterization

The graft copolymerization of three vinyl monomer species, acrylonitrile (AN), acrylamide (AAm), and acrylic acid (AA), onto starch was carried out with ceric salt (Ce salt) as an initiator. With 3 mmol/L Ce salt, the monomer activity onto starch decreased in the following order: AN > AAm > AA. Grafting efficiency with AN as the grafting monomer was greater than 90%, but with AA and AAm, it was less than 50%. Starch‐graft‐polyacrylonitrile was hydrolyzed to introduce amide and carboxyl groups into starch. The hydrolyzates were analyzed with infrared spectroscopy. The hydrolysis reaction was accelerated with increasing alkali concentration, reaction temperature, and time. The water absorbancy of the hydrolyzate increased with an increasing carboxyl molar fraction in the polymer, and it dissolved in water above a 0.6 molar fraction. The absorbancy of water was 2 times higher than that of a NaCl aqueous solution. The copper‐ion‐exchange capacity of the sample was greater in graft copolymers with higher carboxyl group contents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1437–1443, 2001     

On promoting intercalation and exfoliation of bentonite in high‐density polyethylene by grafting acrylic acid

Acrylic acid (AA) grafted high‐density polyethylene (HDPE)/bentonite (BT) composites and HDPE/BT composites were prepared via melt compounding. XRD and TEM results indicated that the modification of AA grafting promoted the dispersion and intercalation of BT in HDPE matrix; IR proved that there were interactions between AA and BT sheets. Consequently, with increasing BT content, the tensile strength and Young's modulus of HDPE‐g‐AA/BT nanocomposites increased, while that of HDPE/BT composites decreased. Moreover, the addition of BT to HDPE‐g‐AA decreased the ability of crystallization of the matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2429–2434, 2005     

New polymeric structures designed for the removal of Cu(II) ions from aqueous solutions

New polymeric structures obtained by chemical transformations of maleic anhydride/dicyclopentadiene copolymer with triethylenetetraamine, p‐aminobenzoic acid, and p‐aminophenylacetic acid were used for the removal Cu(II) ions from aqueous solutions. The experimental values prove the importance of the chelator nature and of the macromolecular chain geometry for the retention efficiency. The retention efficiency (η_r), the retention capacity (Q _e ), and the distribution coefficient of the metal ion into the polymer matrix (K _d ) are realized by evaluation of residual Cu(II) ions in the effluent waters, by atomic adsorption. Also are discussed the influence of pH, the thermal stability of the polymer, and their polymer–metal complex, as well as the particular aspects regarding the contact procedure and the batch time. Based on the polymers and polymer–metal complexes characterization a potential retention mechanism is proposed. All polymer supports as well theirs metal–complexes are characterized by ATD and FTIR measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1397–1405, 2007     

Preparation and application of acrylonitrile‐grafted cyanoethyl cellulose for the removal of copper (II) ions

Cyanoethyl cellulose (CE‐Cell) with two different degrees of substitution of 0.37 and 0.60 were prepared from cotton linter. The ionic‐xanthate method was used to graft the acrylonitrile onto CE‐Cell to form acrylonitrile‐grafted cyanoethyl cellulose (GCE‐Cell). The conditions of grafting such as sodium hydroxide concentration, grafting time, monomer concentration, and temperature were optimized. The hydrolyzed CE‐Cell and GCE‐Cell were applied for the adsorption of copper (II) ions from aqueous solution. IR spectroscopy was also used for further evaluation of CE‐Cell and GCE‐Cell. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 329–334, 2006     

Simultaneous removal of humic acid and heavy metal from aqueous solutions using charged ultrafiltration membranes

Lab-made negatively charged ultrafiltration (UF) membranes were used for simultaneous removal of humic acid (HA) and heavy metals from water. Effects of the HA/metal ratio, solution pH and ionic strength on rejection coefficients of HA and metals were investigated. The results showed that the rejection coefficients of both HA and metals increase with the increase of pH and the HA/metal ratio, and the decrease of ionic strength. This study indicated that charged UF could be an effective method for the simultaneous removal of HA and heavy metal harnessing the principle of complexation UF and electrostatic repulsion between the membrane and the HA–M complex of the same charges.     

Factors influencing absorbent properties of saponified starch‐g‐(acrylic acid‐co‐acrylamide)

Mixtures of acrylamide (AM) and acrylic acid (AA) were grafted onto gelatinized maize starch by using ceric ammonium nitrate (CAN) as an initiator. These graft copolymers were hydrolyzed with alkali to yield hydrogels. The effects of different reaction variables, such as the concentration of the initiator and crosslinker, initial dilution of monomers, gelatinization conditions of starch, and the ratio of AM and AA in the monomer feed, on the water absorption capacities of these hydrogels have been examined. Absorption increases on gelatinizing starch at a higher temperature for a longer time as smaller granules gelatinize only under these conditions. The higher proportion of AA in the monomer feed enhances absorption due to formation of polyelectrolyte. The optimum conditions for obtaining maximum water absorbency established in the present study are granular maize starch = 2.0 g; gelatinization temperature = 95°C; gelatinization time = 60 min; AM = 1.0 g; AA = 4.0 g; CAN = 0.008 mol/L; N,N′‐methylene bisacrylamide = 1%. The product so formed was saponified with NaOH and then precipitated in excess of methanol. The dried and finely powdered product showed the maximum water absorbency of 510 g/g. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2480–2485, 2000     

Removal of Cd(II), Hg(II), and Pb(II) ions from aqueous solution using p(HEMA/chitosan) membranes

An interpenetration network (IPN) was synthesized from 2‐hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV‐initiated photo‐polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane–metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second‐order kinetic equations and the Langmuir isotherm model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of polyethylene‐graft‐poly(styrene‐co‐maleic anhydride) and its compatibilizing effects on polyethylene/starch blends

Low density polyethylene (LDPE) was reacted with benzoyl peroxide (BPO) and 2,2,6,6‐tetramethyl‐l‐piperidinyloxy (TEMPO) to prepare a latent macroinitiator, PE–TEMPO. Little polymer was synthesized when maleic anhydride (MAH) was bulk polymerized in the presence of the PE–TEMPO. However, addition of styrene accelerated the polymerization rate and PE‐grafted‐poly(styrene‐co‐maleic anhyride) [PE‐g‐P(ST‐co‐MAH)] was produced to a high yield. Chemical reaction between MAH units and hydroxyl groups of starch was nearly undetectable in the PE/PE‐g‐P(ST‐co‐MAH)/starch blend system, and the tensile properties of the blend were not enhanced significantly. However, addition of tetrabutyl titanate (TNBT) during the blending procedure improved the tensile properties significantly through an increased interfacial adhesion between the components in the blend system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2434–2438, 2003     

Adsorption of Cu2+ and Ni2+ from Aqueous Solution by Arabinoxylan Hydrogel: Equilibrium,Kinetic, Competitive Adsorption

In this work, arabinoxylan-graft-acrylic acid (AX-g-AA) hydrogel was prepared and used as an adsorbent to remove and recover Cu²⁺ and Ni²⁺ from aqueous solutions. The influences of pH, ligand content on the adsorption capacity of the hydrogel, adsorption equilibrium, and kinetic were studied in detail. The competitive adsorption and recovery of heavy metal ions, regeneration and reusability of the hydrogel were present. Furthermore, the relationship between the physiochemical properties of the adsorbent and its adsorption performance was also studied. The results showed that a more expanded network favored the diffusion and adsorption of metal ions. Cu²⁺ and Ni²⁺ uptake by this hydrogel was pH and concentration dependent with the maximum loading of 330.1 mg/g for Cu²⁺ and 248.7 mg/g for Ni²⁺. The pseudo-second-order kinetics suggested that the ion exchange process was chemisorption-controlled. The Langmuir equation could well describe the isotherm data. Cu²⁺ and Ni²⁺ adsorbed on the hydrogel could be effectively recovered in a diluted HNO₃ solution (0.01 M) in 30 min. AX-g-AA hydrogel also exhibited highly efficient reusability, and thus could be used repeatedly.     

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

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

Effect of an allyl pretreatment of starch on the grafting efficiency and properties of allyl starch‐g‐poly(acrylic acid)

Starch was pretreated with allyl etherification to enhance the grafting efficiency of the copolymerization of granular starch with acrylic acid and to improve the properties of starch‐g‐poly(acrylic acid) used as a warp sizing agent. The graft copolymerization was carried out in an aqueous dispersion with ferrous ammonium sulfate and hydrogen peroxide as initiators. Through the introduction of allyl groups into starch before the copolymerization, the grafting efficiency could evidently be enhanced, and properties such as fiber adhesion and film behaviors of the copolymer were improved. The pretreatment was capable of enhancing the grafting efficiency by about 10–20% when the degree of substitution of allyl starch ranged from 0.011 to 0.037. The adhesion and film behaviors also depended on the modification extent of the starch pretreatment and on the grafting ratio of the copolymer. The adhesion reached a maximum at a degree of substitution of 0.025, and the film behaviors were best when the degree of substitution ranged from 0.011 to 0.025. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of cassava starch‐g‐poly(methyl methacrylate) copolymers with benzoyl peroxide as an initiator

Graft copolymers of cassava starch and methyl methacrylate (MMA) were synthesized by free‐radical polymerization with benzoyl peroxide (BPO) as an initiator in an aqueous medium at 80°C. The formation of graft copolymers was confirmed by analysis of the obtained products with Fourier transform infrared spectroscopy and scanning electron microscopy. The effects of the amount of cassava starch, the amount of MMA monomer, the amount of BPO, and the reaction time on the grafting characteristics were studied. The optimum condition for grafting were obtained when 5 g of cassava starch, 5 g of MMA, 0.1 g of BPO, and a reaction time of 3 h were used. These condition provided a graft copolymer with 25.00% add‐on, 81.40% monomer conversion, 54.30% homopoly(methyl methacrylate) formed, 45.70% grafting efficiency, 37.20% grafting ratio, and 95.54% yield. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4083–4089, 2006     

Synthesis and characterization of poly(ether sulfone)‐graft‐polydimethylsiloxane copolymers

Novel poly(arylene ether sulfone) (PAES) polymers containing polydimethylsiloxane (PDMS) side chains were synthesized and characterized with NMR and Fourier transform infrared spectroscopy. The thermal properties of the copolymers were evaluated with differential scanning calorimetry and thermogravimetric analysis. The polymers showed perfect thermal stability, as the decomposition temperatures were all above 380°C, and exhibited glass‐transition temperatures in the range 130–188°C. Furthermore, the surface properties of the copolymers were evaluated by X‐ray photoelectron spectroscopy and contact angle analysis. The results show that the hydrophobic abilities of the graft copolymer surfaces were improved significantly compared to PAES through the introduction of the PDMS chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Enhanced removal of nickel(II) ions from aqueous solutions by SDS-functionalized graphene oxide

In this paper, a one-pot and easy-to-handle method at room temperature without additional chemicals for the modification of graphene oxide (GO) with surfactant is found. Removal of nickel (II) ions from aqueous solutions by GO and surfactant (sodium dodecyl sulphate) modified graphene oxide (SDS-GO) was studied spectrophotometrically at room temperature as a function of time, initial concentration and pH. Adsorption capacity of the adsorbent was increased dramatically (from 20.19 to 55.16 mg/g found by Langmuir model) due to the functionalization of the surface by SDS. The driving force of the adsorption of Ni(II) ions is electrostatic attraction and Ni(II) ions adsorbed on the GO surface chemically besides ion exchange.