Synthesis and characterization of super dye adsorbent hydrogels based on acrylic acid and acryloyl tetrasodium thiacalix[4]arene tetrasulfonate

Acryloyl tetrasodium thiacalix[4]arene tetrasulfonate (ACSTCA) was synthesized via fictionalization of tetrasodium thiacalix[4]arene tetrasulfonate (STCA). Hydrogels based on acrylic acid (AA) (20–70 mol%) and ACSTCA (30–80 mol%) were prepared by solution copolymerization in water using methylene bisacrylamide and ammonium persulfate as crosslinker and initiator, respectively. The gels obtained exhibited a good ability for absorbing water. Swelling of the gels was improved with increase in ACSTCA content in the gel feed. Characterization of the synthesized monomer (ACSTCA) was performed using mass spectrometry and Fourier transform infrared (FTIR), ¹H and ¹³C NMR spectroscopies and the synthesized gels were characterized by FTIR. The thermal and mechanical properties of these copolymers were also studied using TGA and dynamic mechanical thermal analysis. The glass transition temperature and storage modulus of the copolymer were increased with increasing content of ACSTCA in the gel. Thermal stability was improved with increasing ACSTCA content in the structure of the copolymer. The results showed that the synthesized copolymer (ACSTCA‐AA) can effectively remove dye from wastewater. The dye removal capacity of the gels was investigated with a UV?visible spectrophotometer. In addition, the effect of key operation parameters such as the ACSTCA content in the structure of the copolymer, contact time, adsorbent dosage, pH of the solution and temperature on dye removal from aqueous solution was experimentally studied. The equilibrium data were analyzed using the Langmuir and Freundlich adsorption isotherms. The Freundlich isotherms provided a better fit to the data. Results from the kinetic studies revealed that the adsorption of malachite green onto the hydrogels followed a pseudo‐second‐order kinetic model. © 2015 Society of Chemical Industry     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

A Novel pH-Responsive p(AAm-co-METAC)/MMT Composite Hydrogel: Synthesis,Characterization and Its Absorption Performance on Heavy Metal İons

In this study, the preparation and characterization of the novel pH-sensitive poly(acrylamide-co-2-methacryloyloxy)ethyltrimethyl ammonium chloride)/montmorillonite (p(AAm-co-METAC)/MMT) composite superabsorbent hydrogels and their selective metal absorbtion properties were investigated. The adsorption of metal ions is highly dependent on the initial feed concentration, contact time, pH of the metal solution and adsorbent doses. The results were analyzed both by the Langmuir and Freundlich isotherms and the adsorption is found to follow pseudo-second-order kinetics. The adsorption capacity followed the order Zn²⁺ > Ni²⁺ > Cu²⁺ > Pb²⁺ and the maximum adsorption capacities of them were ～320, 285, 240 and 120 (mg g^?1), respectively.     

Competitive adsorption of Pb, Cu and Cd ions from aqueous solutions by multiwalled carbon nanotubes

The individual and competitive adsorption capacities of Pb²⁺, Cu²⁺ and Cd²⁺ by nitric acid treated multiwalled carbon nanotubes (CNTs) were studied. The maximum sorption capacities calculated by applying the Langmuir equation to single ion adsorption isotherms were 97.08 mg/g for Pb²⁺, 24.49 mg/g for Cu²⁺ and 10.86 mg/g for Cd²⁺ at an equilibrium concentration of 10 mg/l. The competitive adsorption studies showed that the affinity order of three metal ions adsorbed by CNTs is Pb²⁺>Cu²⁺>Cd²⁺. The Langmuir adsorption model can represent experimental data of Pb²⁺ and Cu²⁺ well, but does not provide a good fit for Cd²⁺ adsorption data. The effects of solution pH, ionic strength and CNT dosage on the competitive adsorption of Pb²⁺, Cu²⁺ and Cd²⁺ ions were investigated. The comparison of CNTs with other adsorbents suggests that CNTs have great potential applications in environmental protection regardless of their higher cost at present.     

Comparative Study of Zn2+, Cd2+, and Pb2+ Removal From Water Solution Using Natural Clinoptilolitic Zeolite and Commercial Granulated Activated Carbon. Equilibrium of Adsorption

Abstract

The aim of this work is to study the effectiveness of regional, low-cost natural clinoptilolitic zeolite tuff in heavy metal ions removal from aqueous solution, through comparative study with commercial granulated activated carbon. The equilibrium of adsorption of Cd²⁺, Pb²⁺, and Zn²⁺ on both adsorbents have been determined at 25, 35, and 45°C in batch mode. The granulated activated carbon has shown around three times higher adsorption capacity for Cd²⁺ and Zn²⁺ than natural zeolite, and almost the same adsorption capacity for Pb²⁺ as the natural zeolite. The metal ion selectivity series Pb²⁺ > Cd²⁺ > Zn²⁺, on a mass basis, has been obtained on both adsorbents. The Langmuir and Freundlich model have been used to describe the adsorption equilibrium. The thermodynamic parameters were calculated from the adsorption isotherm data obtained at different temperatures. The study of the influence of the acidity of the metal ion aqueous solution has shown an increase of metal ion uptake with increase of the pH. The sorption mechanism of Cd²⁺, Pb²⁺, and Zn²⁺ on natural zeolite changes from ion-exchange to ion-exchange and adsorption of metal-hydroxide with increase of the pH from 2 to 6 (and 7 for Zn²⁺). The preliminary cost calculation, based on adsorbents maximum adsorption capacity and their price, have revealed the potential of natural zeolite as an economic alternative to the granulated activated carbon in the treatment of heavy metal polluted wastewater.     

Alanine containing porous beads for mercury removal from artificial solutions

N‐methacryloyl‐(L )‐alanine (MALA) was synthesized by using methacryloyl chloride and alanine as a metal‐complexing ligand or comonomer. Spherical beads with an average diameter of 150–200 μm were obtained by suspension polymerization of MALA and 2‐hydroxyethyl methacrylate (HEMA) conducted in an aqueous dispersion medium. Poly(HEMA–MALA) beads were characterized by SEM, swelling studies, surface area measurement, and elemental analysis. Poly(HEMA–MALA) beads have a specific surface area of 68.5 m²/g. Poly(HEMA–MALA) beads with a swelling ratio of 63%, and containing 247 μmol MALA/g were used in the removal of Hg²⁺ from aqueous solutions. Adsorption equilibrium was achieved in about 60 min. The adsorption of Hg²⁺ ions onto PHEMA beads was negligible (0.3 mg/g). The MALA incorporation into the polymer structure significantly increased the mercury adsorption capacity (168 mg/g). Adsorption capacity of MALA containing beads increased significantly with pH. The adsorption of Hg²⁺ ions increased with increasing pH and reached a plateau value at around pH 5.0. Competitive heavy metal adsorption from aqueous solutions containing Cd²⁺, Cu²⁺, Pb²⁺, and Hg²⁺ was also investigated. The adsorption capacities are 44.5 mg/g for Hg²⁺, 6.4 mg/g for Cd²⁺, 2.9 mg/g for Pb²⁺, and 2.0 mg/g for Cu²⁺ ions. These results may be considered as an indication of higher specificity of the poly(HEMA–MALA) beads for the Hg²⁺ comparing to other ions. Consecutive adsorption and elution operations showed the feasibility of repeated use for poly(HEMA–MALA) chelating beads. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1222–1228, 2006     

Adsorption for metal ions of chitosan coated cotton fiber

A kind of adsorbent for metal ions, cotton fiber coated by high loading of chitosan (SCCH) was prepared. Its structure was characterized by elemental analysis, scanning electronic microscopy (SEM), Fourier transform infrared spectrum (FTIR), and wide‐angle X‐ray diffraction (WAXD). The adsorption properties of SCCH for Cu²⁺, Ni²⁺, Pb²⁺, Cd²⁺, such as saturated adsorption capacities, static kinetics, and isotherm were investigated. The adsorption for Ni²⁺, Pb²⁺, and Cd²⁺ was controlled by liquid film diffusion, but by particle diffusion for Cu²⁺. The adsorption process for Cu²⁺, Ni²⁺, Cd²⁺ could be described with Langmuir or Freundlich equation, but only with Freundlich equation for Pb²⁺. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption and Separation of Mercury: Sorption-Desorption of Hg2+ with Cross-Linked Graft Copolymer of Acrylic Acid and its Application in the Metal Ion Separation Process

A selective and reliable method has been developed for the extraction and separation of mercuric ion with cross-linked graft copolymer of acrylic acid based on sorption-desorption studies. The graft copolymer acts as an ion exchanger. The physico-chemical properties of the exchanger, and optimum pH, time, and temperature for Hg²⁺ adsorption were determined. Metal ion adsorption kinetics, isotherms, and thermodynamics have been studied. A plausible mechanism for mercury ion extraction has been suggested. Mercuric ion has been separated quantitatively from various synthetic mixtures containing metal ions (Ni²⁺, Cd²⁺, Pb²⁺, and Zn²⁺).     

Preparation of Chelating Resins Containing a Pair of Neighboring Carboxylic Acid Groups and the Adsorption Characteristics for Heavy Metal Ions

Abstract

For the functional enhancement of chelating resins containing carboxylic acids, copolymer beads were prepared by suspension polymerization of styrene (St), methyl methacrylate (MMA), and divinylbenzene (DVB) in the presence of toluene as diluent. The phenyl rings of the beads were directly chloromethylated, and the carboxylic ester groups of the beads were converted into hydroxymethyl groups by reduction followed by chlorination to give chloromethyl groups, respectively. The chelating resins containing a pair of neighboring carboxylic acid groups (NCAGs) were obtained by the alkylation of chloromethyl groups in copolymer beads with diethyl malonate in the presence of sodium hydride followed by hydrolysis using aqueous alkali solution. Accordingly, the structural effects of the resins on the adsorption of heavy metal ions were investigated. Poly(St‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, and Cu²⁺, whereas poly(MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Cu²⁺, Cd²⁺, and Co²⁺. On the other hand, poly(St‐co‐MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, Co²⁺, and Cu²⁺: a synergistic effect on the adsorption of heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, and Co²⁺ was observed. The adsorption ability of poly(St‐co‐MMA‐co‐DVB)‐based chelating resin among three kinds of chelating resins was relatively good.     

Synthesis and adsorption properties of macroporous cross‐linked polystyrene that contains an immobilizing 2,5‐dimercapto‐1,3,4‐thiodiazole with tetraethylene glycol spacers

A novel chelating resin macroporous cross‐linked polystyrene immobilizing 2,5‐dimercapto‐1,3,4‐thiodiazole via a hydrophilic tetraethylene glycol spacer (PS‐TEG‐BMT) is synthesized and the structure is characterized by means of Fourier transform infrared spectroscopy (FTIR), energy dispersive X‐ray microanalysis (EDX), and elementary analysis. Its adsorption capacity for several metal ions such as Hg²⁺, Ag⁺, Ni²⁺, Pb²⁺, Cd²⁺, Fe³⁺, Bi³⁺, Zn²⁺, and Cu²⁺ are investigated. The initial experimental result shows that this resin has higher adsorption selectivity for Hg²⁺ and Ni²⁺ than for the other metal ions and the introduction of hydrophilic TEG spacer is beneficial to increase adsorption capacities. The result also shows that the Langmuir model is better than the Freundlich model to describe the isothermal process of PS‐TEG‐BME resin for Hg²⁺. Five adsorption‐desorption cycles demonstrate that this resin are suitable for reuse without considerable change in adsorption capacity. POLYM. ENG. SCI., 45:1515–1521, 2005. © 2005 Society of Plastics Engineers     

ION EXCHANGE PROPERTIES OF THE SULFUR-MODIFIED BIOTITE

ABSTRACT

The ion exchange behavior of a sulfur-modified biotite towards Pb²⁺, Hg²⁺, Co²⁺, Cu²⁺, Cd²⁺ and Zn²⁺ ions has been studied. The ion exchange isotherms of divalent cations were determined and concentration equilibrium constants as a function of metal loading were analyzed. Sulfur modified biotite exhibits high affinity for Hg²⁺, Pb²⁺, Cu²⁺ and Cd²⁺ ions in individual solutions and in the presence of electrolytes. About 200 mg Hg/g uptake in 1·10^?3 M Hg²⁺ solution and ～ 35 mg Hg/g in groundwater simulant or an alkaline simulant 2 M in NaN0₃ + 1 M in NaOH was found. The possibility of a complex ion exchange and precipitation mechanism of the sulfur modified biotite towards the soft cations is proposed.     

Mechanism of Hg(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by Aspergillus niger spores

ABSTRACT

Recent work has focused on the removal of Pb²⁺, Hg²⁺, and Cd²⁺ by using an organ of Aspergillus niger – spores, which were spherical particles with small diameter (2 µm) characterized by negative charge. Results shown that the biosorption of Pb²⁺, Hg²⁺, and Cd²⁺ from aqueous solutions using spores was analyzed at varying biosorbent dosages, pH levels, contact times and initial heavy metal concentrations. The maximum biosorption capacities of Pb²⁺, Hg²⁺, and Cd²⁺ were 23.9, 27.2, and 21.5 mg/g at a natural pH with the initial concentration were 30 mg/L, respectively. The sequence of biosorption capacity for cationic heavy metals was Pb²⁺>Cd²⁺>Hg²⁺. Spores exhibited a short biosorption equilibrium time of 60 min at a pH range of 4.0–6.0, and the main biosorption mechanism was electronic attraction, ion exchanges and complexation(involved in C = C, C-H, C-O, N-H), the data fit well in the pseudo-second-order kinetic equation and the Freundlich isotherm. In addition, Spores can grow on many kinds of moist agriculture waste without any added nutrition. The results showed that spores could be considered as a potential biosorbent for the removal of cationic heavy metals from aqueous solutions.     

Synthesis and evaluation of chitosan aryl azacrown ethers as adsorbents for metal ions

New azacrown ether chitosan derivatives (CTS–OC, CTS–NC) were synthesized by reaction of aryl mesocyclic diamine with the C6 hydroxyl group or C2 amino group in chitosan. Their structures were confirmed by elemental analysis, infrared spectra analysis, and X‐ray diffraction analysis. The adsorption and selectivity properties of the aryl azacrown ethers chitosan derivatives for Hg²⁺, Cd²⁺, Pb²⁺, Ag⁺, and Cr³⁺ were also investigated. The experimental results showed that the two chitosan–azacrown ethers have good adsorption capacity for Pb²⁺, Cd²⁺, and Hg²⁺. The adsorption capacity of CTS–OC are higher than that of CTS–NC for Pb²⁺ and Cd²⁺. The chitosan–azacrown ethers have high selectivity for the adsorption of Pb²⁺ and Hg²⁺ with the coexistence of Cd²⁺. The selectivity properties of CTS–OC are better than those of CTS–NC. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3093–3098, 2000     

Adsorption of Pb2+ and Cd2+ onto a Novel Activated Carbon‐Chitosan Complex

A novel activated carbon‐chitosan complex adsorbent (ACCA) was prepared via the crosslinking of glutaraldehyde and activated carbon‐(NH₂‐protected) chitosan complex under microwave irradiation. The surface morphology of this adsorbent was characterized. The adsorption of ACCA for Pb²⁺ and Cd²⁺ was investigated. The results demonstrate that ACCA has higher adsorption capacity than chitosan. The adsorption follows pseudo first‐order kinetics. The isotherm adsorption equilibria are better described by Freundlich and Dubinin‐Radushkevich isotherms than by the Langmuir isotherm. The adsorbent can be recycled. These results have important implications for the design of low‐cost and effective adsorbents in the removal of heavy metal ions from wastewaters.     

Competitive Adsorption of Ag+, Pb2+, Ni2+, and Cd2+ Ions on Vermiculite

Competitive adsorption of Ag⁺, Pb²⁺, Ni²⁺, and Cd² ions on vermiuculite in a binary, ternary, and quaternary mixture was investigated in batch experiments. The effects of the presence of Ag⁺, Ni²⁺, and Cd²⁺ ions on the adsorption of Pb²⁺ ions were investigated in terms of the equilibrium isotherm. Experimental results indicated that Pb²⁺ ions always favorably adsorbed on vermiculite over Ag⁺, Ni²⁺, and Cd²⁺ ions. The adsorption equilibrium data of Pb²⁺ ions better fitted the Langmuir model than the Freundlich model. The results showed that the pseudo-second-order kinetics model was in good agreement with the experimental results for all metal ions, and the adsorption rate among the metal ions followed Ag⁺ > Pb²⁺ > Ni²⁺ > Cd²⁺. The desorption and regenration study indicated that vermiculite can be used repeatedly and be suitable for the design of a continuous process.     

Binding of heavy metal ions by formaldehyde-polymerized peanut skins

Peanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag¹⁺, Cd²⁺, Cr⁶⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, as well as Ca²⁺ and Mg²⁺, were contacted with formaldehyde-treated peanut skin. Quantitative removal could be achieved with Ag¹⁺, Cd²⁺, Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺. Capacity of the substrate for ions was promising for Pb²⁺ (2.1 meq/g substrate), Cu²⁺ (3.0 meq/g), and Cd²⁺ (1.3 meq/g). Sorption from a solution containing Cd²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, on a packed column of formaldehyde-treated peanut skin indicated that Hg²⁺, Pb²⁺, and Cu²⁺ were rapidly and completely bound to the packing, while Cd²⁺, Ni²⁺, and Zn²⁺ were poorly bound until the preferred ions had been removed from solution.     

The use of dyestuff-treated rice hulls for removal of heavy metals from waste water

Rice hulls, when coated with the reactive dye of Procion Red or Procion Yellow, was found to be highly effective for removal of many metal ions from aqueous solutions both in batch and column method. When 120–130 ppm solutions were used, quantitative removal could be achieved with Pb²⁺, Cd²⁺, and Hg²⁺. After the adsorption of metal ions, the substrate could be recovered almost completely by treating with dilute hydrochloric or nitric acid solution, and used repeatedly.     

HEAVY METALS REMOVAL FROM AQUEOUS SOLUTIONS USING TiO2, MgO,AND Al2O3 NANOPARTICLES

This study investigated the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ from aqueous solutions using nanoparticle sorbents (TiO₂, MgO, and Al₂O₃) with a range of experimental approaches. The maximum uptake values (sum of four metals) with multiple component solutions were 594.9, 114.6, and 49.4 mg g^?1, for MgO, Al₂O₃, and TiO₂, respectively. The sorption equilibrium isotherms were described using the Freundlich and Langmuir models. The best interpretation for experiment data was given by the Freundlich model for Cd²⁺, Cu²⁺, and Ni²⁺ in single- and multiple-component solutions. A first-order kinetic model adequately described the experimental data using MgO, Al₂O₃, and TiO₂. SEM-EDX both before and after metal sorption and soil solution saturation indices (SI) in MgO nanoparticles indicated that the main sorption mechanism for heavy metals was attributable to adsorption and precipitation, whereas heavy metal sorption by TiO₂ and Al₂O₃ adsorbents was due to adsorption. These nanoparticles may potentially be used as efficient sorbents for heavy metal removal from aqueous solutions. MgO nanoparticles were the most promising sorbents because of their high metal uptake.     

SORPTION PROCESSES OF NATURAL IRANIAN BENTONITE EXCHANGED WITH CD2+, CU2+, NI2+, AND PB2+ CATIONS

Experimental studies on the retention of cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), and lead (Pb²⁺) by bentonite samples from Iran were conducted using single- and multiple-component solutions. Based on the sorption capacity of bentonite the following order was obtained for single- and multiple-component solutions: Pb²⁺ > Cd²⁺ > Ni²⁺ > Cu²⁺. The maximum adsorption capacities of bentonite with metals in single- and multiple-component solutions were 29.5%, 22.5%, 19.2%, and 17.1% and 13.5%, 13.4%, 12.1%, and 9.1% for Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺, respectively. Desorption isotherms of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ deviated significantly from the sorption isotherms, thereby indicating irreversible or very slowly reversible sorption. Finally, soil solution saturation indices and metal speciation were assessed using the Visual MINTEQ 2.6 program and the probability of mineral precipitation was supported by scanning electron microscopy.     

Synthesis of polystyrene‐supported glucosamine resin and its adsorption properties for metal ions

A novel chelating resin polystyrene‐supported glucosamine was prepared by the reaction of chloromethylated polystyrene with glucosamine hydrochlorate, using anhydrous potassium carbonate as catalyst and dimethylformamide as solvent. Infrared spectra and elementary analysis were used to confirm its structure. The adsorption of the resin for Cu²⁺, Ni²⁺, Hg²⁺, Co²⁺, Cd²⁺, and Pb²⁺ was investigated, as well as various factors affecting the adsorption such as time, temperature, ion concentration, and pH. The results showed that the resin had good adsorption capacities for Cu²⁺, Ni²⁺, and Hg²⁺. The adsorption was controlled by liquid film diffusion and adsorption isothermal data could be well interpreted by the Freundlich equation. Values of adsorption activation energy and adsorption Gibbs free energy were calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 890–896, 2005