Ethylenediamine grafted poly(glycidylmethacrylate-co-methylmethacrylate) adsorbent for removal of chromate anions

Development of recoverable adsorbents for Cr(VI) ions by grafting of a dimethylamino group-containing monomer on polyethylene substrate and subsequent quaternization

A polymeric adsorbent for removal of hexavalent chromium (Cr(VI)) ions was developed by the photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to a polyethylene (PE) mesh and subsequent quaternization with iodoalkanes of different alkyl chain lengths. The grafting of DMAEMA and subsequent quaternization were verified by the FT-IR and XPS measurements. The Cr(VI) ion adsorption capacity of the DMAEMA-grafted PE meshes had the maximum value at the grafted amount of 2.6 mmol/g in a 0.20 mM K₂Cr₂O₇ solution at pH 3.0 and 30°C. The adsorption behaviour obeyed the pseudo-second order kinetic model and well expressed by Langmuir isotherm. These results suggest that the Cr(VI) ion adsorption occurs through the electrostatic interaction mainly between protonated dimethylamino groups and hydrochromate (HCrO₄^-) ions. The adsorption capacity of the quaternized PE-g-PDMAEMA meshes increased with an increase in the degree of quaternization and/or the alkyl chain length of the iodoalkanes used and the maximum adsorption ratio was obtained at the degree of quaternization of 54.2% for the iodoheptane-quaternized PE-g-PDMAEMA (PE-g-QC₇PDMAEMA) mesh. This value was about 1.86 times higher than that of the PE-g-PDAMEMA mesh. Cr(VI) ions were successfully desorbed from the PE-g-PDMAEMA and PE-g-QC₇PDMAEMA meshes in eluents such as NaOH, NaCl, and NH₄Cl. In 0.50 M NaCl, 0.10 M NH₄Cl, and 0.50 mM NaOH, the adsorption and desorption process was repeatedly performed without any considerable decrease and the desorption behaviour obeyed the pseudo-second order kinetic model. These results emphasise that the PE-g-PDMAEMA meshes and their quaternized products can be applied as an adsorbent for Cr(VI) ions.

Promoted adsorptive removal of chromium(vi) ions from water by a green-synthesized hybrid magnetic nanocomposite (NFe3O4Starch-Glu-NFe3O4ED)

A novel magnetic starch-crosslinked-magnetic ethylenediamine nanocomposite, NFe3O4Starch-Glu-NFe3O4ED, was synthesized via microwave irradiation. The characteristics of the assembled NFe3O4Starch-Glu-NFe3O4ED nanocomposite were evaluated via XRD, FT-IR, TGA, BET, SEM and HR-TEM analyses. Its particle size was confirmed to be in the range 11.25-17.16 nm. The effectiveness of the designed nanocomposite for the removal of Cr(vi) ions was explored using the batch adsorption technique. Equilibrium results proved that the adsorptive removal of the target metal ions from aqueous solution was highly dependent on the optimized experimental parameters. The maximum adsorptive removal percentage values (%R) of Cr(vi) ions on NFe3O4Starch-Glu-NFe3O4ED obtained at pH 2.0 were 85.27%, 91.90%, and 96.47% using 10.0, 25.0, and 50.0 mg L-1 Cr(vi), respectively, for an equilibrium time of 30 min. The adsorption process was found to be strongly influenced by the presence of interfering salts including NaCl, CaCl2, KCl, MgCl2, and NH4Cl. Kinetic studies were performed and it was found that the pseudo-second and Elovich models well fitted the experimental data with the possible suggested ion-pair interaction mechanism. Different isotherm models were employed to assess the adsorption equilibrium, which was revealed by fitting Langmuir, Temkin and Freundlich models. The maximum uptake capacity based on the Langmuir model was 210.741 mg g-1. The effect of temperature and thermodynamics confirmed that adsorption was spontaneous, feasible, and endothermic in nature. Finally, the validity and applicability of using the NFe3O4Starch-Glu-NFe3O4ED nanocomposite to remove Cr(vi) ions from real water matrices were confirmed in the range of 91.2-94.7 ± 2.2-3.7%.

Preparation of Poly(glycidyl methacrylate) (PGMA) and Amine Modified PGMA Adsorbents for Purification of Glucosinolates from Cruciferous Plants

Glucosinolates (GLs) are of great interest for their potential as antioxidant and anticancer compounds. In this study, macroporous crosslinked copolymer adsorbents of poly (glycidyl methacrylate) (PGMA) and its amine (ethylenediamine, diethylamine, triethylamine)-modified derivatives were prepared and used to purify the GLS glucoerucin in a crude extract obtained from a cruciferous plant. These four adsorbents were evaluated by comparing their adsorption/desorption and decolorization performance for the purification of glucoerucin from crude plant extracts. According to the results, the strongly basic triethylamine modified PGMA (PGMA-III) adsorbent showed the best adsorption and desorption capacity of glucoerucin, and its adsorption data was a good fit to the Freundlich isotherm model and pseudo-second-order kinetics; the PGMA adsorbent gave the optimum decolorization performance. Furthermore, dynamic adsorption/desorption experiments were carried out to optimize the purification process. Two glass columns were serially connected and respectively wet-packed with PGMA and PGMA-III adsorbents so that glucoerucin could be decolorized and isolated from crude extracts in one process. Compared with KCl solution, aqueous ammonia was a preferable desorption solvent for the purification of glucoerucin and overcame the challenges of desalination efficiency, residual methanol and high operation costs. The results showed that after desorption with 10% aqueous ammonia, the purity of isolated glucoerucin was 74.39% with a recovery of 80.63%; after decolorization with PGMA adsorbent, the appearance of glucoerucin was improved and the purity increased by 11.30%. The process of using serially connected glass columns, wet-packed with PGMA and PGMA-III, may provide a simple, low-cost, and efficient method for the purification of GLs from cruciferous plants.

Effective use of elderberry (Sambucus nigra) pomace in biosorption processes of Fe(III) ions

Elderberry (Sambucus nigra) pomace obtained as a result of processing in the food industry was examined for the bioremoval of Fe(III) ions from aqueous solutions in batch experiments. Several physicochemical properties of the biomass were analyzed using a variety of analytical methods, such as particle size distribution, elemental composition (SEM-EDS), X-ray diffraction analysis (XRD), thermogravimetry (TGA, DTG), specific surface area and average pore diameter (BET adsorption isotherms), volume of pores and pore volume distribution (BJH), morphology (SEM), mid-infrared analysis FT-IR. The impact of adsorbent dosage, initial concentration, pH and contact time on the process efficiency was studied. The calculated maximum adsorption efficiency and capacity was estimated at 99.5% and 33.25 mg/g, respectively. The biosorption kinetic analysis indicated that the removal process fits better to the pseudo-second order equation and the Langmuir model. Summing up, the biosorbent is a promising low-cost material for the highly effective iron recovery from effluents and improvement of water quality.

Selectivity of Copper by Amine-Based Ion Recognition Polymer Adsorbent with Different Aliphatic Amines

This paper investigates the selectivity of GMA-based-non-woven fabrics adsorbent towards copper ion (Cu) functionalized with several aliphatic amines. The aliphatic amines used in this study were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The non-woven polyethylene/polypropylene fabrics (NWF) were grafted with glycidyl methacrylate (GMA) via pre-radiation grafting technique, followed by chemical functionalization with the aliphatic amine. To prepare the ion recognition polymer (IRP), the functionalized amine GMA-grafted-NWF sample was subjected to radiation crosslinking process along with the crosslinking agent, divinylbenzene (DVB), in the presence of Cu ion as a template in the matrix of the adsorbent. Functionalization with different aliphatic amine was carried out at different amine concentrations, grafting yield, reaction temperature, and reaction time to study the effect of different aliphatic amine onto amine density yield. At a concentration of 50% of amine and 50% of isopropanol, EDA, DETA, TETA, and TEPA had attained amine density around 5.12, 4.06, 3.04, and 2.56 mmol/g-ad, respectively. The amine density yield decreases further as the aliphatic amine chain grows longer. The experimental condition for amine functionalization process was fixed at 70% amine, 30% isopropanol, 60 °C for grafting temperature, and 2 h of grafting time for attaining 100% of grafting yield (Dg). The prepared adsorbents were characterized comprehensively in terms of structural and morphology with multiple analytical tools. An adsorptive removal and selectivity of Cu ion by the prepared adsorbent was investigated in a binary metal ion system. The IRP samples with a functional precursor of EDA, the smallest aliphatic amine had given the higher adsorption capacity and selectivity towards Cu ion. The selectivity of IRP samples reduces as the aliphatic amine chain grows longer, EDA to TEPA. However, IRP samples still exhibited remarkably higher selectivity in comparison to the amine immobilized GMA-g-NWF at similar adsorption experimental conditions. This observation indicates that IRP samples possess higher selectivity after incorporation of the ion recognition imprint technique via the radiation crosslinking process.

Preparation of a novel magnetic Pd(II) ion-imprinted polymer for the fast and selective adsorption of palladium ions from aqueous solutions

A novel magnetic ion-imprinted polymer with high accessibility to palladium ions was synthesized via co-precipitation polymerization. Accordingly, a ternary complex composed of PdCl₂ as an imprinting ion, 8-aminoquinoline (AQ) as a ligand, and 4-vinyl pyridine (4-VP) as a complexing monomer was applied to Fe₃O₄@SiO₂ as magnetic core, followed by precipitation polymerization using 2-hydroxyethyl methacrylate (2-HEMA) as a co-monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, and 2,2-azobisisobutyronitrile (AIBN) as an initiator in the presence of 2-methoxyethanol as a solvent. The palladium ions were leached out by a solution containing 50% (v/v) HCl. The synthesized polymer was characterized physically and morphologically using different techniques. In order to assess the conditions required for adsorption, as well as the selectivity and reusability, batch adsorption experiments were carried out. The experiments exhibited that the maximum adsorption capacity was about 65.75 mg g^-1 at 25 °C, while the pH solution and the adsorbent dose were 4 and 1 g L^-1, respectively. Kinetic studies of experimental data demonstrated that they correspond very much to the pseudo-second-order kinetic model. The development of the Langmuir and Freundlich isothermal models on the equilibrium data proved to correspond well to the Langmuir isotherm model. Interferences studies of the magnetic polymer demonstrated higher affinity and discernment for palladium ions than other co-existing ions in the solutions. Spontaneous (ΔG < 0) and exothermic (ΔH < 0) behavior of the adsorption process is confirmed by thermodynamic studies. In addition, the affinity of the spent polymer has not been dramatically reduced over at least five regeneration cycles.

An efficient and reusable quaternary ammonium fabric adsorbent prepared by radiation grafting for removal of Cr(VI) from wastewater

A novel quaternary ammonium polyethylene nonwoven fabric for removing chromium ions from water was prepared via radiation-induced grafting of glycidyl methacrylate and further modification with N,N'-dimethylethylenediamine. The structural and morphological characteristics of the adsorbent were analyzed using Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermogravimetry (TG/DTG), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The influences of several principal factors, including pH value, initial Cr(VI) concentration, contact time, and coexisting anions (including SO₄^2-, CO₃^2-, NO₃^-, PO₄^3-, and Cl^-), on adsorption performance were investigated via batch tests. The results showed that the optimum removal efficiency was 99.2% at pH 3 and the maximum adsorption quantity for Cr(VI) at 25 °C was 336 mg/g. The adsorption kinetic parameters were better fitted with the pseudo-second-order kinetic model, and the equilibrium data were described very well by the Freundlich isotherm model. Furthermore, the as-synthesized adsorbent exhibited excellent regeneration and recyclability while maintaining high adsorption performance after five adsorption/desorption cycles.

Aminated EVOH nanofiber membranes for Cr(vi) adsorption from aqueous solution

Ethylene vinyl alcohol (EVOH) nanofiber membranes were prepared by melt-blending extrusion with cellulose acetate butyrate ester (CAB) as the matrix and a high-speed flow deposition process. Then, aminated-EVOH (l-Lys/EVOH, Cy/l-Lys/EVOH and DETA/EVOH) nanofiber membranes were prepared for hexavalent chromium [Cr(vi)] removal by facile chemical modification on the surface of EVOH nanofiber membranes. Scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were carried out to test the morphology and structure of aminated-EVOH nanofiber membranes. Adsorption experiments suggested that amination was beneficial to adsorption, and the optimal pH for prepared membranes to Cr removal was 2.0. Adsorption kinetics analysis revealed that the adsorption process was successfully fitted with a Pseudo-second-order model. The Freundlich isothermal model well described the adsorption isotherm data. A thermodynamic study suggested that the adsorption process was endothermic and spontaneous. Aminated-EVOH nanofiber membranes exhibited excellent reusability for Cr removal. The Cr adsorption efficiency of DETA/EVOH nanofiber membranes retained up to 98.73% of the initial adsorption after 6 successive adsorption–desorption cycles.

Aminated-ethylene vinyl alcohol (l-Lys/EVOH, Cy/l-Lys/EVOH and DETA/EVOH) nanofiber membranes were prepared for hexavalent chromium [Cr(vi)] removal by facile chemical modification on the surface of EVOH nanofiber membranes.

Enhanced adsorption of hexavalent chromium by a biochar derived from ramie biomass (Boehmeria nivea (L.) Gaud.) modified with β-cyclodextrin/poly(L-glutamic acid)

This paper explored biochar modification to enhance biochar's ability to adsorb hexavalent chromium from aqueous solution. The ramie stem biomass was pyrolyzed and then treated by β-cyclodextrin/poly(L-glutamic acid) which contained plentiful functional groups. The pristine and modified biochar were characterized by FTIR, X-ray photoelectron spectroscopy, specific surface area, and zeta potential measurement. Results indicated that the β-cyclodextrin/poly(L-glutamic acid) was successfully bound to the biochar surface. Batch experiments were conducted to investigate the kinetics, isotherm, thermodynamics, and adsorption/desorption of Cr(VI). Adsorption capacities of CGA-biochar were significantly higher than that of the untreated biochar, and its maximum adsorption capacity could reach up to 197.21 mg/g at pH 2.0. Results also illustrated that sorption performance depended on initial solution pH; in addition, acidic condition was beneficial to the Cr(VI) uptake. Furthermore, the Cr(VI) uptake was significantly affected by the ion strength and cation species. This study demonstrated that CGA-biochar could be a potential adsorbent for Cr(VI) pollution control.

Synthesis of a Multifunctional Graphene Oxide-Based Magnetic Nanocomposite for Efficient Removal of Cr(VI)

A novel magnetic nanocomposite was synthesized using graphene oxide (GO), polyethylenimine (PEI), and Fe₃O₄ to removal hexavalent chromium (Cr(VI)) from water and soil. Therein, GO was functionalized with plenty of -NH₂ by the modification of PEI through an amidation reaction, and the resulting GO/PEI reacted with FeSO₄·7H₂O and NaBH₄ to obtain RGO/PEI/Fe₃O₄ (the optimal one is designated as ORPF) through an oxidation-reduction reaction. ORPF could effectively adsorb Cr(VI) through electrostatic attraction, and the adsorbed Cr(VI) ions were partially reduced to trivalent chromium (Cr(III)) with low toxicity by RGO (π electron). Afterward, the resulting ORPF-Cr could be conveniently removed from water with a magnet, achieving the maximum Cr(VI) removal capacity of 266.6 mg/g. Importantly, ORPF, once carried by sponge particles, could efficiently remove Cr(VI) from soil, and the resulting mixture could be facilely collected with a magnet on a filter net. Besides, the leaching experiment suggested that, when supported by filter paper, ORPF was able to decrease the number of leached Cr(VI) ions and meanwhile reduce them to Cr(III). This work provides a promising approach to remediate Cr(VI)-contaminated water and soil using a nanocomposite, which has a huge number of application prospects.

Graphene oxide/Fe3O4/SO3H nanohybrid: a new adsorbent for adsorption and reduction of Cr(vi) from aqueous solutions

A sulfonated magnetic graphene oxide (SMGO) hybrid was successfully synthesized via the nucleophilic substitution reaction and characterized.

Removal of Disperse Red 60 dye from aqueous solution using free and composite fungal biomass of Lentinus concinnus

Lentinus concinnus biomass was immobilized to carboxyl derivative of cellulose, carboxymethyl cellulose (CMC), in the presence of FeCl3 (0.1 mol L−1) via ionic cross-linking. The beads containing immobilized fungal biomass were incubated at 30 °C for three days to permit growth of the fungus. The free and immobilized fungal biomass were tested for adsorption of Disperse Red 60 (DR-60) from aqueous solution using bare CMC beads as a control system. The maximum adsorption of DR-60 on the free and immobilized fungal biomass was observed at pH 6.0. The adsorption of DR-60 by the free, and immobilized fungal biomass increased as the initial concentration of DR-60 in the medium increased up to 100 mg/L. The maximum adsorption capacity of the CMC beads, the free and immobilized fungal biomass (i.e. composite beads) were found to be 43.4, 65.7, and 92.6 mg g−1 dry sorbents, respectively. The equilibrium of the adsorption system was well described by Langmuir and Temkin isotherm models. Adsorption equilibrium was established in about 1.0 h. The adsorption of DR-60 on the fungal preparations followed pseudo-second-order kinetic model. It was observed that the immobilized fungal biomass has a high potential for the removal of DR-60 as a model dye from aqueous solution.

Removal of bisphenol A from aqueous medium using molecularly surface imprinted microbeads

The aim of this study is to prepare bisphenol A (BPA) imprinted polymers, which can be used for the selective removal of BPA from aqueous medium. The BPA-imprinted (MIP) and non-imprinted (NIP) microbeads were synthesized, and characterized by Zeta-sizer, FTIR, SEM and BET method. Bisphenol A was determined in solutions using liquid chromatography-mass spectroscopy (LC-MS). The effect of initial concentration of BPA, the adsorption rate and the pH of the medium on the capacity of BPA-imprinting polymer were studied. Adsorption capacity of BPA was affected by the amount of the incorporated functional monomer in the polymer network. BPA adsorption capacity of MIP-3 and NIP microbeads from aqueous medium was estimated as 76.7 and 59.9 mg g(-1), respectively. The binding efficiencies of BPA-MIP-3 microbeads for different phenolic compounds (i.e., BPA with p-toluidine, 4-aminophenol or 2-naphthol) were explored at binary solutions, and the binding capacities of BPA-imprinted microbeads were found to be 2.79 × 10(-1), 2.39 × 10(-1), 7.59 × 10(-2) and 5.48 × 10(-2) mmol g(-1) microbeads, respectively. The satisfactory results demonstrated that the obtained BPA-MIP microbeads showed an appreciable binding specificity toward BPA than similar structural compounds in the aqueous medium. Moreover, the reusability of BPA-MIP-3 microbeads was tested for several times and no significant loss in adsorption capacity was observed. Finally, the binary and multi-component systems results show that MIP-3 microbeads have special recognition selectivity and excellent binding affinity for template molecule "BPA".

Phragmites karkaas a Biosorbent for the Removal of Mercury Metal Ions from Aqueous Solution: Effect of Modification

Batch scale studies for the adsorption potential of novel biosorbentPhragmites karka(Trin), in its natural and treated forms, were performed for removal of mercury ions from aqueous solution. The study was carried out at different parameters to obtain optimum conditions of pH, biosorbent dose, agitation speed, time of contact, temperature, and initial metal ion concentration. To analyze the suitability of the process and maximum amount of metal uptake, Dubinin-Radushkevich (D-R) model, Freundlich isotherm, and Langmuir isotherm were applied. The values ofqmaxfor natural and treated biosorbents were found at 1.79 and 2.27 mg/g, respectively. The optimum values of contact time and agitation speed were found at 50 min and 150 rpm for natural biosorbent whereas 40 min and 100 rpm for treated biosorbent, respectively. The optimum biosorption capacities were observed at pH 4 and temperature 313 K for both naturalP. karkaand treatedP. karka.RLvalues indicate that comparatively treatedP. karkawas more feasible for mercury adsorption compared to naturalP. karka. Both pseudo-first-order and pseudo-second-order kinetic models were applied and it was found that data fit best to the pseudo-second-order kinetic model. Thermodynamic studies indicate that adsorption process was spontaneous, feasible, and endothermic.

Kinetic, Isotherm and Thermodynamic Analysis on Adsorption of Cr(VI) Ions from Aqueous Solutions by Synthesis and Characterization of Magnetic-Poly(divinylbenzene-vinylimidazole) Microbeads

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53-212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N(2) adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin-Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol(-1), which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field.

Adsorption of chromium (VI) from aqueous solutions by cellulose modified with β-CD and quaternary ammonium groups

Cellulose powder was grafted with the vinyl monomer glycidyl methacrylate using ceric ammonium nitrate as initiator and was further derived with β-CD and quaternary ammonium groups to build Cell-g-GMA-β-CDN(+) adsorbent. Epoxy cellulose was made up of Cell-g-GMA and Cell-hydro-g-GMA, and was found to contain 3.71 mmol g(-1) epoxy groups. The adsorption process of the modified cellulose was described by the Langmuir model of adsorption well, and the maximum adsorption capacity of chromium (VI) reached 61.05 mg g(-1). The adsorption-desorption tests of β-CDN(+)-type cellulose derivatives exhibited that the reproducibility of the adsorbent was well and the adsorbent could be reused five times at least.

Synthesis of Cr(VI)-imprinted poly(4-vinyl pyridine-co-hydroxyethyl methacrylate) particles: its adsorption propensity to Cr(VI)

The aim of this study is to prepare ion-imprinted polymers, which can be used for the selective removal of Cr(VI) anions from aqueous media. 4-Vinyl pyridine (4-VP) was used as functional monomer. The Cr(VI)-imprinted poly(4-vinyl pyridine-co-2-hydroxyethyl methacrylate), poly(VP-HEMA), particles were prepared by bulk polymerization. The Cr(VI)-imprinted polymer particles were grained from the bulk polymer, and the template ions (i.e., Cr(VI)) were removed using thiourea (0.5%, v/v) in 0.5M HCl. The Cr(VI)-imprinted polymer contained 21.4 μmol 4-VP/g polymers. The specific surface area of the IIP2 particles was found to be 34.5m(2)/g (size range of 75-150 μm), and the swelling ratio was about to 108%. The effect of initial concentration of Cr(VI) anions, the adsorption rate and the pH of the medium on adsorption capacity of Cr(VI)-imprinting polymer were studied. The maximum experimental adsorption capacity was 3.31 mmol Cr(VI)/g polymer. Under competitive condition, the adsorption capacity of Cr(VI)-imprinted particles for Cr(VI) is 13.8 and 11.7 folds greater than that of the Cr(III) and Ni(II) ions, respectively. The first- and second order kinetics models were estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. The Langmuir adsorption isotherm model was well described the Cr(VI)-imprinted system and the maximum adsorption capacity (Q(max)) was found to be 3.42 mmol/g. Moreover, the reusability of the poly(VP-HEMA) particles was tested for several times and no significant loss in adsorption capacity was observed.

Application of bifunctional magnetic adsorbent to adsorb metal cations and anionic dyes in aqueous solution

A magnetic adsorbent, amine-functionalized silica magnetite (NH(2)/SiO(2)/Fe(3)O(4)), has been synthesized to behave as an anionic or cationic adsorbent by adjusting the pH value of the aqueous solution to make amino groups protonic or neutral. NH(2)/SiO(2)/Fe(3)O(4) were used to adsorb copper ions (metal cation) and Reactive Black 5 (RB5, anionic dye) in an aqueous solution in a batch system, and the maximum adsorption were found to occur at pH 5.5 and 3.0, respectively. The adsorption equilibrium data were all fitted the Langmuir isotherm equation reasonably well, with a maximum adsorption capacity of 10.41 mg g(-1) for copper ions and of 217 m g g(-1) for RB5. A pseudo-second-order model also could best describe the adsorption kinetics, and the derived activation energy for copper ions and RB5 were 26.92 kJ mol(-1) and 12.06 kJ mol(-1), respectively. The optimum conditions to desorb cationic and anionic adsorbates from NH(2)/SiO(2)/Fe(3)O(4) were provided by a solution with 0.1M HNO(3) for copper ions and with 0.05 M NaOH for RB5.

Application of magnetic particles modified with amino groups to adsorb copper ions in aqueous solution

A magnetic adsorbent can be easily recovered from treated water by magnetic force, without requiring further downstream treatment. In this research, amine-functionalized silica magnetite has been synthesized using N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TPED) as a surface modification agent. The synthesized magnetic amine adsorbents were used to adsorb copper ions in an aqueous solution in a batch system, and the maximum adsorption was found to occur at pH 5.5 +/- 0.1. The adsorption equilibrium data fitted the Langmuir isotherm equation reasonably well, with a maximum adsorption capacity of 10.41 mg/g. A pseudo second-order model could best describe the adsorption kinetics, and the derived activation energy was 26.92 kJ/mol. The optimum condition to desorb Cu2+ from NH2/SiO2/Fe3O4 was provided by a solution with 0.1 mol/L HNO3.

Synthesis, characterization and properties of ethylenediamine-functionalized Fe3O4 magnetic polymers for removal of Cr(VI) in wastewater

A series of ethylenediamine (EDA)-functionalized magnetic polymers (EDA-MPs) have been prepared via suspension polymerization with the usage amount of the functional monomer glycidylmethacrylate (GMA) varied during the suspension polymerization procedure. The EDA-MPs were characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), X-ray diffractometer (XRD), thermogravimetry and differential thermogravimetry analysis (TG-DTA), Fourier-transformed infrared spectroscopy (FTIR) and elementary analyzer (EA). The adsorption properties of the EDA-MPs for the removal of Cr(VI) in wastewater were deeply studied. The results showed the adsorption efficiency was highly pH dependent and decreased with the increasing of initial concentration of Cr(VI). The adsorption data taken at the optimized condition, i.e., 35 degrees C and pH of 2.5 were well fitted with the Langmuir isotherm. The maximum adsorption capacities (q(m)) of EDA-MPs to Cr(VI) were highly related to the contents of EDA-MPs, i.e., the q(m) of EDA-MPs to Cr(VI) calculated from the Langmuir isotherm increased from 32.15 to 61.35 mg g(-1) with the increasing of the usage amount of GMA. The adsorption kinetic data were modeled by the pseudo-second-order rate equation, and the adsorption of Cr(VI) by all the present EDA-MPs reached equilibrium in 60 min.

Kinetics of hexavalent chromium sorption on amino-functionalized macroporous glycidyl methacrylate copolymer

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and functionalized with ethylene diamine and diethylene triamine. The kinetics of Cr(VI) sorption by amino-functionalized poly(GMA-co-EGDMA) was investigated under non-competitive conditions. Competitive kinetics was studied from following multicomponent solutions: Cu(II) and Cr(VI); Cu(II), Co(II), Cd(II) and Ni(II); Cr(VI), Cu(II), Co(II) and Cd(II) solutions. Two kinetic models (the pseudo-first and pseudo-second-order) were used to determine the best-fit equation for the metals sorption by poly(GMA-co-EGDMA)-en and poly(GMA-co-EGDMA)-deta.

Rapid removal of heavy metal cations and anions from aqueous solutions by an amino-functionalized magnetic nano-adsorbent

A novel magnetic nano-adsorbent has been developed by the covalent binding of polyacrylic acid (PAA) on the surface of Fe(3)O(4) nanoparticles and the followed amino-functionalization using diethylenetriamine (DETA) via carbodiimide activation. Transmission electron microscopy image showed that the amino-functionalized Fe(3)O(4) nanoparticles were quite fine with a mean diameter of 11.2+/-2.8 nm. X-ray diffraction analysis indicated that the binding process did not result in the phase change of Fe(3)O(4). Magnetic measurement revealed they were nearly superparamagnetic with a saturation magnetization of 63.2 emu/g Fe(3)O(4). The binding of DETA on the PAA-coated Fe(3)O(4) nanoparticles was demonstrated by the analyses of Fourier transform infrared (FTIR) spectroscopy and zeta potential. After amino-functionalization, the isoelectric point of PAA-coated Fe(3)O(4) nanoparticles shifted from 2.64 to 4.59. The amino-functionalized magnetic nano-adsorbent shows a quite good capability for the rapid and efficient adsorption of metal cations and anions from aqueous solutions via the chelation or ion exchange mechanisms. The studies on the adsorption of Cu(II) and Cr(VI) ions revealed that both obeyed the Langmuir isotherm equation. The maximum adsorption capacities and Langmuir adsorption constants were 12.43 mg/g and 0.06 L/mg for Cu(II) ions and 11.24 mg/g and 0.0165 L/mg for Cr(VI) ions, respectively.

Functionalized macroporous copolymer of glycidyl methacrylate: The type of ligand and porosity parameters influence on Cu(II) ion sorption from aqueous solutions

The removal of heavy metals from hydro-metallurgical and other industries' wastewaters, their safe storage and possible recovery from waste- water streams is one of the greater ecological problems of modern society. Conventional methods, like precipitation, adsorption and biosorption, electrowinning, membrane separation, solvent extraction and ion exchange are often ineffective, expensive and can generate secondary pollution. On the other hand, chelating polymers, consisting of crosslinked copolymers as a solid support and functional group (ligand), are capable of selectively loading different metal ions from aqueous solutions. In the relatively simple process, the chelating copolymer is contacted with the contaminated solution, loaded with metal ions, and stripped with the appropriate eluent. Important properties of chelating polymers are high capacity, high selectivity and fast kinetics combined with mechanical stability and chemical inertness. Macroporous hydrophilic copolymers of glycidyl methacrylate and ethylene glycol dimethacrylate modified by different amines show outstanding efficiency and selectivity for the sorption of precious and heavy metals from aqueous solutions. In this study poly(GMA-co-EGDMA) copolymers were synthesized with different porosity parameters and functionalized in reactions with ethylene diamine (EDA), diethylene triamine (DETA) and triethylene tetramine (TETA). Under non-competitive conditions, in batch experiments at room temperature, the rate of sorption of Cu(II) ions from aqueous solutions and the influence of pH on it was determined for four samples of amino-functionalized poly(GMA-co-EGDMA). The sorption of Cu(II) for both amino-functionalized samples was found to be very rapid. The sorption half time, t1/2, defined as the time required to reach 50% of the total sorption capacity, was between 1 and 2 min. The maximum sorption capacity for copper (2.80 mmol/g) was obtained on SGE-10/12-deta sample. The sorption capacity of Cu(II) ions increases with increasing pH and has maximum at pH ~5. In the experimental pH range, the maximum sorption capacity of Cu(II) ions again is reached on SGE-10/12-deta. By comparing literature data and obtained results it is possible to conclude that amino-functionalized macroporous copolymers based on glycidyl methacrylate are efficient for sorption of Cu(II) ions from aqueous solutions and sorption capacity for copper mostly depends on type of amine with which the basic copolymer is functionalized.

Kinetics of mercury ions removal from synthetic aqueous solutions using by novel magnetic p(GMA-MMA-EGDMA) beads

Poly(glycidylmethacrylate-methylmethacrylate), p(GMA-MMA-EGDMA), magnetic beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the beads were converted into amino groups via ring opening reaction of the ammonia and, the aminated magnetic beads were used for the removal of Hg(II) ions from aqueous solution in a batch experiment and in a magnetically stabilized fluidized bed reactor (MFB). The magnetic p(GMA-MMA-EGDMA) beads were characterized with scanning electron microscope (SEM), FT-IR and ESR spectrophotometers. The optimum removal of Hg(II) ions was observed at pH 5.5. The maximum adsorption capacity of Hg(II) ions by using the magnetic beads was 124.8+/-2.1 mgg(-1) beads. In the continuous MFB reactor, Hg(II) ions adsorption capacity of the magnetic beads decreased with an increase in the flow-rate. The maximum adsorption capacity of the magnetic beads in the MFB reactor was 139.4+/-1.4 mgg(-1). The results indicate that the magnetic beads are promising for use in MFB for removal of Hg(II) ions from aqueous solution and/or waste water treatment.