Uptake of Pb2+ Using N-Vinyl Imidazole Based Uniform Porous Hydrogels

The uniform porous and continuous phase lead (II) adsorbent hydrogel, was prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA), acrylic acid (AAc), and N,N′-methylenebisacrylamide (MBAAm), with n-vinyl imidazole (VIM). A series of hydrogels, including different ratios of VIM, were prepared by photopolymerization and characterized. The influence of the uptake conditions such as pH, functional monomer percent, contact time, initial feed concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, were also tested. The selective chelation of heavy metal ions from synthetic wastewater was also studied. The affinity order on molar basis was observed as follows: Pb (II) > Zn (II) > Cd (II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms and it was seen that the Langmuir isotherm model was the best fit for the adsorption of Pb (II) ions in P(VIM/AAc/HEMA) hydrogel. Moreover, the limits of detection and the quantification values were determined. Regeneration of the hydrogels was easily performed with 1 M HCl and the same hydrogel can be reused five times almost without any loss of adsorption capacity. All these features make P(VIM/AAc/HEMA) hydrogels potential candidate adsorbent for heavy metal removal.     

Separation and preconcentration of some heavy‐metal ions using new chelating polymeric hydrogels

Two new chelating polymeric hydrogels, crosslinked polyacrylamide/triethylenetetraamine/CS₂Na (hydrogel I) and crosslinked polyacrylamide/diethylenetriamine/CS₂Na (hydrogel II), were prepared by the transamidation and dithiocarbamylation of crosslinked polyacrylamide. The products were characterized with elemental analysis and IR spectroscopy. In both polymeric hydrogels, the optimum pH for the removal of Cd(II), Pb(II), and Zn(II) ions ranged from 7 to 8, from 6 to 7, and from 7 to 8, respectively. The sorption isotherms of the investigated metal ions on the prepared hydrogels were developed, and the equilibrium data fitted the Langmuir and Freundlich isotherm models well. At the optimum pH for each metal ion, the maximum sorption capacities of hydrogel I toward Cd(II), Pb(II), and Zn(II) ions, estimated from the Langmuir model, were 5.3, 0.63, and 1.27 mmol/g, respectively, and those of hydrogel II were 4.1, 0.59, and 0.89 mmol/g, respectively. The experimental sorption capacities of hydrogel I toward Cd(II), Pb(II), and Zn(II) ions were 4.5, 0.6, and 1.2 mmol/g, respectively. In the case of hydrogel II, the capacities were 3.7, 0.52, and 0.88 mmol/g in the same prescribed order. The thermodynamic parameters (the free energy of sorption, enthalpy change, and entropy change) for cadmium, lead, and zinc sorption on the prepared polymers were also determined from the temperature dependence. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adsorption removal of Brilliant green and Safranin-O contaminants from water using a hydrogel based on carboxymethyl cellulose and sodium alginate crosslinked by epichlorohydrin

The current study investigates the adsorption properties of a chemically crosslinked hydrogel based on sodium alginate (NaALG) and carboxymethyl cellulose (CMC). The structural characteristics of the investigated hydrogel are described using information from Fourier Transform–infrared spectra, X-ray diffraction patterns and field emission scanning electron microscopy pictures. The NaALG/epichlorohydrin (ECH)/CMC hydrogel was synthesised under optimised conditions with respect to the swelling percentage. Various reaction parameters were varied to obtain the maximum swelling percentage. The synthesised hydrogel was taken as an adsorbent in the decolorisation of Brilliant green (BG) and Safranin-O (SO) dyes from water. According to the kinetic investigations, the decolorisation equilibrium of SO by NaALG/ECH/CMC was discovered in 4 hours (98.98%), while the removal of BG by NaALG/ECH/CMC took 6 hours (97.7%). Chemical processes were used to describe the decolorisation mechanisms, which significantly supported the pseudo-first-order model. NaALG/ECH/CMC hydrogel absorption was indicated to take place in monolayer adsorption form (Langmuir isotherm). The highest adsorption capacity for BG was discovered to be 864.8 mg g⁻¹ and for SO it was 193.1 mg g⁻¹, by synthesised hydrogel, where “mg” refers to the commercial colourant and not to the pure dye. Therefore, the synthesised hydrogel can be considered as a smart device for the adsorption of dye in water purification tasks.     

Adsorption of Ag (I) Ions from Aqueous Solutions Using Photocured Thiol-Ene Hydrogel

In this present work, we reported the adsorption and recovery studies of a P(Penta3MP4/PEG-DA/HEMA) thiol-ene based hydrogel. Real-time infrared spectroscopy technique was used to identify the photopolymerization kinetics of thiol-ene based formulations. The chemical composition and surface morphology of hydrogels were also characterized. The influence of the adsorption conditions such as pH, hydrogel formulations, contact time, initial metal ion concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, were tested. Both the Langmuir and Freundlich isotherm models were applied to the method. The reusability of the hydrogels and the usability of the hydrogels for preconcentration studies were also investigated. The analytical parameters of the method were calculated and the recovery of silver ions from waste radiographic films was also applied to the hydrogels.     

Removal of copper(II) ions from aqueous solution onto chitosan and cross-linked chitosan beads

The adsorption of Cu(II) ions onto chitosan and cross-linked chitosan beads has been investigated. Chitosan beads were cross-linked with glutaraldehyde (GLA), epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE) in order to obtain sorbents that are insoluble in aqueous acidic and basic solution. Batch adsorption experiments were carried out as a function of pH, agitation period, agitation rate and concentration of Cu(II) ions. A pH of 6.0 was found to be a optimum for Cu(II) adsorption on chitosan and cross-linked chitosan beads. Isotherm studies indicate Cu(II) can be effectively removed by chitosan and cross-linked chitosan beads. Adsorption isothermal data could be well interpreted by the Langmuir equation. Langmuir constants have been determined for chitosan and cross-linked chitosan beads. The experimental data of the adsorption equilibrium from Cu(II) solution correlated well with the Langmuir isotherm equation. The uptakes of Cu(II) ions on chitosan beads were 80.71 mg Cu(II)/g chitosan, on chitosan-GLA beads were 59.67 mg Cu(II)/g chitosan-GLA, on chitosan-ECH beads were 62.47 mg Cu(II)/g chitosan-ECH and on chitosan-EGDE beads were 45.94 mg Cu(II)/g chitosan-EGDE. The Cu(II) ions can be removed from the chitosan and cross-linked chitosan beads rapidly by treatment with an aqueous EDTA solution and at the same time the chitosan and cross-linked chitosan beads can be regenerated and also can be used again to adsorb heavy metal ions.     

Removal of Lead and Cadmium Ions from Aqueous Solutions Using Sulphur and Oxygen Donor Ligand Bearing Hydrogels

A new thiourea and urea functional monomers were synthesized. A series of hydrogels were prepared by photopolymerization. The hydrogels were used for the removal of Pb(II) and Cd(II) ions from aqueous solutions. The influence of the uptake conditions such as the pH, the time, and the initial feed concentration on the metal ion binding capacity of hydrogel was tested. The selectivity of the hydrogels towards the different metal ions was also tested. The adsorption isotherm models were applied. The limits of detection and quantification were calculated. The usability of the hydrogels for preconcentration studies were also investigated.     

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.     

Preparation and characterization of porous chitosan–tripolyphosphate beads for copper(II) ion adsorption

Porous chitosan–tripolyphosphate beads, prepared by the ionotropic crosslinking and freeze‐drying, were used for the adsorption of Cu(II) ion from aqueous solution. Batch studies, investigating bead adsorption capacity and adsorption isotherm for the Cu(II) ion, indicated that the Cu(II) ion adsorption equilibrium correlated well with Langmuir isotherm model. The maximum capacity for the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, deduced from the use of the Langmuir isotherm equation, was 208.3 mg/g. The kinetics data were analyzed by pseudo‐first, pseudo‐second order kinetic, and intraparticle diffusion models. The experimental data fitted the pseudo‐second order kinetic model well, indicating that chemical sorption is the rate‐limiting step. The negative Gibbs free energy of adsorption indicated a spontaneous adsorption, while the positive enthalpy change indicated an endothermic adsorption process. This study explored the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, and used SEM/EDS, TGA, and XRD to examine the properties of adsorbent. The use of porous chitosan–tripolyphosphate beads to adsorb Cu(II) ion produced better and faster results than were obtained for nonporous chitosan–tripolyphosphate beads. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Pectin‐[(3‐acrylamidopropyl) trimethylammonium chloride‐co‐acrylic acid] hydrogel prepared by gamma radiation and selectively silver (Ag) metal adsorption

Pectin‐[(3‐acrylamidopropyl) trimethylammonium chloride‐co‐acrylic acid] hydrogel has been prepared from the aqueous blend solution of pectin, (3‐acrylamidopropyl) trimethylammonium chloride (APTAC), and acrylic acid (AAc) by applying gamma radiation of different doses (1–25 kGy) from ⁶⁰Co gamma source. The hydrogels were characterized by equilibrium swelling, Fourier transform infrared, differential scanning calorimetry, and scanning electron microscopy. The hydrogels were used in multielement adsorption and it was found that pectin‐(APTAC‐co‐AAc) gel is highly selective toward silver (I) ion among 27 metal ions. The data obtained from equilibrium adsorption studies were fitted in Langmuir and Freundlich adsorption isotherm models and model parameters evaluated. The maximum adsorption capacity of pectin‐(APTAC‐co‐AAc) gel was found to be 67.6413 mg/g of dry gel at sample volume of 25 mL. The kinetic data were tested using pseudo‐first order and pseudo‐second order kinetic models and different adsorption diffusion models such as film diffusion and intra‐particle diffusivity model. Thiourea solution was used for desorption of adsorbed metal ions from the hydrogel. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45906.     

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.     

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     

Acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐ methylpropane sulfonic acid‐based hydrogels: Synthesis,characterization and their application in the removal of heavy metals

Crosslinked acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐methylpropane sulfonic acid (AN/AAx/AMPS)‐based hydrogels were prepared by free radical crosslinking solution polymerization technique. The chemical structures of the hydrogels were characterized by FT‐IR analysis. The morphology of the dry hydrogel sample was examined by scanning electron microscope (SEM). These hydrogels were used for the removal of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was arranged in the order of Cd(II) > Fe(III) > Cu(II). It was observed that the specific interaction between metal ions and ionic comonomer in the hydrogel affected the metal binding capacity of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption characterization of lead(II) and cadmium(II) on crosslinked carboxymethyl starch

The adsorption of Pb(II) and Cd(II) ions with crosslinked carboxymethyl starch (CCS) was investigated as function of the solution pH, contact time, initial metal‐ion concentration, and temperature. Isotherm studies revealed that the adsorption of metal ions onto CCS better followed the Langmuir isotherm and the Dubinin–Radushkevich isotherm with adsorption maximum capacities of about 80.0 and 47.0 mg/g for Pb(II) and Cd(II) ions, respectively. The mean free energies of adsorption were found to be between 8 and 16 kJ/mol for Pb(II) and Cd(II) ions; this suggested that the adsorption of Pb(II) and Cd(II) ions onto CCS occurred with an ion‐exchange process. For two‐target heavy‐metal ion adsorption, a pseudo‐second‐order model and intraparticle diffusion seem significant in the rate‐controlling step, but the pseudo‐second‐order chemical reaction kinetics provide the best correlation for the experimental data. The enthalpy change for the process was found to be exothermic, and the ΔS^θ values were calculated to be negative for the adsorption of Pb(II) and Cd(II) ions onto CCS. Negative free enthalpy change values indicated that the adsorption process was feasible. The studies of the kinetics, isotherm, and thermodynamics indicated that the adsorption of CCS was more effective for Pb(II) ions than for Cd(II) ions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Application of anionic acrylamide‐based hydrogels in the removal of heavy metals from waste water

Crosslinked acrylamide (AM) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) homopolymers and copolymers were prepared by free radical solution polymerization using N,N′‐methylenebisacrylamide as the crosslinker. The chemical structures of hydrogels were characterized by FTIR analysis and the results were consistent with the expected structures. These hydrogels were used for the separation of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was Cd(II) > Cu(II) > Fe(III). It was observed that the specific interaction between metal ions and ionic comonomers in the hydrogel affected the metal binding capacity of the hydrogel. The recovery of metal ions was also investigated in acid media. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of Rice Straw-Based Hydrogels for Purification of Wastewater

The use of rice straw waste (RS) as a substrate for the preparation of metal adsorbents hydrogels has been demonstrated. Four types of RS-based hydrogels were prepared, and evaluated for their effectiveness on purification of wastewater loaded with Cu(II), Fe(II), Zn(II) and Mn(II). Freundlich and Langmuir adsorption equations were used for estimating the adsorption capacities. The results indicated that the hydrogels have significant effect on removing the metal ions from wastewater. The removal efficiency exceeded 95% for Cu(II) and Mn (II) ions and 85 for Fe (II) and Zn (II) ions.     

Heavy Metal Ion Sorption Properties of Porous Glass Beads with a Core‐Shell Structure

Porous glass beads with a core‐shell structure have been successfully prepared through subcritical water treatment. The product has high capacity and fast mass transfer property due to its structure, and may serve as an inorganic adsorbent. Accordingly, the kinetics, the equilibrium isotherm, and the column breakthrough curve of this material were measured using Cu(II) as a model target ion. The results indicate that the material has an advantage over some other adsorbents, such as kaolinite and clinoptilolite, in both adsorption capacity and kinetics. The adsorption capacity for Cu(II) is almost twice as much as that of the Na‐mordenite. The pseudo‐second order kinetic and the Langmuir isotherm fit the experimental data. An adsorption mechanism was hypothesized in which the non‐bridging oxygen ions in the glass network were hypothesized to be the functional site.     

Investigation of Heavy Metal Ion Adsorption Characteristics of Poly(N,N Dimethylamino Ethylmethacrylate) Hydrogels

Abstract

In this study, Poly(N,N dimethyl‐amino ethylmethacrylate) (Poly(DMAEMA)) hydrogels with varying compositions were prepared in the form of rods by irradiating ternary mixtures of N,N‐dimethylamino ethylmethacrylate/ethyleneglycoldimethacrylate/water with gamma rays at ambient temperature. Swelling studies of poly (DMAEMA) hydrogels were performed at different pH values and maximum swelling values reached at pH 2. The adsorption characteristics of Pb(II), Cd(II), Ni(II), Zn(II), Cu(II), and Co(II) ions to poly(N,N dimethylamino ethylmethacrylate) hydrogels were investigated by a batch process. The order of affinity based on amount of metal ion uptake was found as follows: Cu(II)>Zn(II)?Co(II)>Pb(II) >> Ni(II)>Cd(II). In the adsorption studies of Cu(II), Zn(II), Co(II), Pb(II), Ni(II), and Cd(II) ions the Langmuir type adsorption isotherms were observed for all gel systems.     

Hexafunctional poly(propylene glycol) based hydrogels for the removal of heavy metal ions

Two types of degradable poly(propylene glycol) (PPG) hydrogels that are suitable for the absorption of heavy metals have been presented. The PPG‐O‐P(O)Cl₂ fragments obtained by treating hexafunctional PPG with phosphorous oxychloride (POCl₃) react with 1,3‐propanediamine (PDA; Gel‐1 ) or PDA together with 1,2‐ethanedithiol ( Gel‐2 ), to yield cross‐linked and water‐swellable hydrogels in a one‐pot method. This protocol for the fabrication of PPG hydrogels exhibits promising advantages over prior methods including a short reaction time, mass‐production, easy separation, and high yield. A series of heavy metal ions were employed to test the adsorptive properties of the hydrogels. Gel‐2 shows better adsorption capacity than Gel‐1 for all the metal ions and the metal ions adsorption efficiency of the two types of hydrogels is in the order of Fe(III) > Pb(II) > Cd(II) > Zn(II) > Cu(II) > Ni(II) > Co(II) > Hg(II). The amounts of metal ions adsorbed increases with metal ion concentration and hydrogel dosage, but decreases with temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40610.     

Adsorption of Divalent Cobalt from Aqueous Solution onto Chitosan–Coated Perlite Beads as Biosorbent

Abstract

Chitosan coated perlite beads are prepared by drop‐wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The resulting beads are characterized using FTIR, SEM, EDXRF, and Surface area analysis and the chitosan content of the beads is 23% as determined by a pyrolysis method. Adsorption of Co (II) metal ions from aqueous solution on chitosan coated perlite beads is studied under both equilibrium and dynamic conditions. In the present investigation, a first order reversible rate equation is used to understand the kinetics of metal removal and to calculate the rate constants at different initial concentrations. The equilibrium characteristics of metal ion on newly developed biosorbent are studied and the experimental adsorption data are well fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters are evaluated. The effect of pH, agitation time, concentration of adsorbate, and amount of adsorbent on the extent of the adsorption are investigated. The sorbent loaded with metal is regenerated with 0.10 mol dm^?3 sodium hydroxide solution. The adsorption desorption cycles indicated that the chitosan coated perlite could be regenerated and reused to remove Co (II) from waste water.     

Swelling and auramine-<Emphasis Type="Italic">O</Emphasis> adsorption of carboxymethyl cellulose grafted poly(methyl methacrylate)/Cloisite 30B nanocomposite hydrogels

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