Adsorption Capacity For Heavy Metal Ions Research Articles

Development of a composite MoS2/PEI nanofiltration membrane for radionuclides efficient removal from aquatic environments

The simultaneously efficient removal of radionuclides and heavy metals is an important and challenging topic for aquatic environmental protection. In this work, molybdenum disulfide (MoS2) with heavy metal ion adsorption capacity and positively charged polyethyleneimine (PEI) were used to fabricate a novel layer-by-layer (LbL) self-assembly composite membrane by a simple alternating immersion method. The unique structure with positive charge ensures high removal for toxic metals (RCs(I) = 99.83 %, RSr(II) = 100 %, RHg(II) = 99.2 %, RPb(II) = 98.13 %, RAs(III) = 98.5 %). The inherent low resistance channels in MoS2 provided the optimized composite membrane an elevated water flux. Long-term experiments and membrane regeneration also demonstrated that the membrane possesses exceptional stability and reusability in removing low levels of radionuclides Cs(I) and Sr(II) from water. This study confirms the feasibility of the MoS2-PEI composite membrane for the treatment of contaminated waters containing radionuclides and heavy metals.

Chitosan-based adsorptive membrane modified by carboxymethyl cellulose for heavy metal ion adsorption: Experimental and density functional theory investigations

Low adsorption capacity and weak mechanical stability are the main drawbacks of chitosan (CS)-based adsorptive membranes for heavy metal ion removal. Polyvinyl alcohol (PVA) has been used to improve the mechanical stability of CS membranes, but adsorption capacity is disregarded. In the current study, the surface of the chitosan/polyvinyl alcohol (CP) membrane was modified using carboxymethyl cellulose (CMC) to increase its heavy metal ion adsorption capacity. Experimental and density functional theory (DFT) calculations were used to evaluate the heavy metal ion (As3+ and Cr3+) adsorption capabilities of CP and carboxymethyl cellulose-functionalized CP (CMC-CP) membranes. The batch adsorption process presented a higher heavy metal adsorption capacity of the CMC-CP membrane (As3+/CMC-CP = 234.78 mg/g and Cr3+/CMC-CP = 230.12 mg/g) compared to the CP membrane (As3+/CP = 89.02 mg/g and Cr3+/CP = 75.61 mg/g). The heavy metal/CMC-CP complexes confirmed higher adsorption energies (As3+/CMC-CP = −23.62 kcal/mol and Cr3+/CMC-CP = −23.21 kcal/mol) than the heavy metal/CP complexes (As3+/CP = −3.47 kcal/mol and Cr3+/CP = −2.92 kcal/mol). The electronic band structure was higher for CMC-CP (5.42 eV) compared to CP (4.43 eV). Experimental and theoretical findings were close, implying that the CMC-CP membrane has superior heavy metal adsorption capability than the CP membrane.

Superior Heavy Metal Ion Adsorption Capacity in Aqueous Solution by High-Density Thiol-Functionalized Reduced Graphene Oxides.

The preparation of mercapto-reduced graphene oxides (m-RGOs) via a solvothermal reaction using P4S10 as a thionating agent has demonstrated their potential as an absorbent for scavenging heavy metal ions, particularly Pb2+, from aqueous solutions due to the presence of thiol (-SH) functional groups on their surface. The structural and elemental analysis of m-RGOs was conducted using a range of techniques, including X-ray diffraction (XRD), Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy equipped with energy-dispersive spectroscopy (STEM-EDS), and X-ray photoelectron spectroscopy (XPS). At pH 7 and 25 °C, the maximum adsorption capacity of Pb2+ ions on the surface of m-RGOs was determined to be approximately 858 mg/g. The heavy metal-S binding energies were used to determine the percent removal of the tested heavy metal ions, with Pb2+ exhibiting the highest percentage removal, followed by Hg2+ and Cd2+ ions having the lowest percent removal, and the binding energies observed were Pb-S at 346 kJ/mol, Hg-S at 217 kJ/mol, and Cd-S at 208 kJ/mol. The time-dependent removal study of Pb2+ ions also yielded promising results, with almost 98% of Pb2+ ions being removed within 30 min at pH 7 and 25 °C using a 1 ppm Pb2+ solution as the test solution. The findings of this study clearly demonstrate the potential and efficiency of thiol-functionalized carbonaceous material for the removal of environmentally harmful Pb2+ from groundwater.

Preparation of CTS/PAMAM/SA/Ca2+ hydrogel and its adsorption performance for heavy metal ions

As a new functional polymer material with three-dimensional polymer network structure, hydrogel is widely used in the removel of heavy metal ions pollutants in sewage. In this work, semi-dissolution acidification sol–gel transition method was used to prepare the hydrogel with chitosan/sodium alginate/calcium ion (CTS/SA/Ca2+) physical cross-linked double network structure without adding chemical cross-linking agent. Meanwhile, hyperbranched polyamide-amine with different generations which was rich in amino groups were introduced to improve the adsorption capacity of hydrogel, and the CTS/PAMAM/SA/Ca2+ hydrogel adsorbent with no secondary pollution, environmental protection and high adsorption capacity was obtained. Experimental results show that the hydrogel with third-generation hyperbranched polyamide-amine have the best comprehensive performance. Its maximum adsorption capacities for copper ions and cadmium ions could reach 174.82 mg/g and 157.72 mg/g respectively. Furthermore, it was found that the adsorption behaviors of copper ions and cadmium ions on the hydrogel conformed to the pseudo-second-order kinetic model and Langmuir adsorption isotherm model by studying the factors affecting the adsorption process. The CTS/PAMAM/SA/Ca2+ hydrogel has the advantages of high heavy metal ion adsorption capacity, uniform structure, and recyclability. As a functional material with simple preparation and excellent performance, it has good application potential and research value.

Multifunctional cellulose paper-based materials and their application in complex wastewater treatment

The rapid and efficient treatment of complex wastewater remains challenging. Herein, green paper-based materials with high wet strength, good oil-water separation property and high heavy metal ion adsorption capacity were prepared via a facile, cost-effective process. The introduction of amphoteric functional groups not only met the requirements for heavy metal ion adsorption, but also maintained the stable underwater superoleophobic properties of materials a wide pH range. The covalent crosslinking between cellulose fibers induced by polyethyleneimine and citric acid significantly improved the wet strength (up to 26.0 Nm/g) and the porosity. The membrane flux was increased up to 3515 L/(m2·h) and the separation efficiencies were higher than 98%. Moreover, the theoretical maximum adsorption capacities for Cd(II) and Pb(II) reached 73.29 and 93.75 mg/g, respectively. Combined with filtration technology, the materials can realize the continuous and efficient purification of complex wastewater.

Anionic Ln–MOF with tunable emission for heavy metal ion capture and l-cysteine sensing in serum

Efficient turn-on luminescent probes for l-cysteine sensing in serum are designed and synthesized based on an anionic Ln–K–MOF with tunable emission color and heavy metal ion adsorption capacity.

Research on the modification of PAN hollow fiber membrane with high heavy metal ions adsorption

PAN hollow fiber functional membrane with heavy metal ion adsorption capacity was prepared via layer-by-layer method using diazo-resin (DR). Ethylenediaminetetraacetic acid (EDTA) and graphene oxide (GO) with chelating function were used as modifier. Modification effect was studied by Fourier Transform Infrared Spectrometer (FTIR), contact angle test, scanning electron microscopy (SEM) and the copper ion adsorption capacity measurement. The result showed that EDTA and GO were successfully grafted on the surface of modified membrane and the hydrophilicity of the modified membrane increased. Roughness of membrane surface increased when the functional groups introduced on the surface. Adsorption for Cu2+ of modified membrane significantly improved.

Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for Cu(II) Through Microwave Pre-Pyrolysis.

An environment-friendly technique for synthesizing biomass-based mesoporous activated carbon with high nitrogen-/oxygen-chelating adsorption for Cu(II) is proposed. Bagasse impregnated with phosphoric acid is utilized as the precursor. To pyrolyze the precursor, two separate heating modes are used: microwave pyrolysis and conventional electric-heating pyrolysis. The resulting bagasse-derived carbon samples are modified with nitrification and reduction modification. Nitrogen (N)/oxygen (O) functional groups are simultaneously introduced to the surface of activated carbon, enhancing its adsorption of Cu(II) by complexing and ion-exchange. Characterization and copper adsorption experiments are performed to investigate the physicochemical properties of four prepared carbon samples and determine which heating method favors the subsequent modification for doping of N/O functional groups. In this technique, based on analyzing data of nitrogen adsorption, Fourier transform infrared spectroscopy, and batch adsorption experiments, it is proven that microwave-pyrolyzed carbon has more defect sites and, therefore, time-saving effective microwave pyrolysis contributes more N/O species to the carbon, although it leads to a lower specific surface area. This technique offers a promising route to synthesis adsorbents with higher nitrogen and oxygen content and a higher adsorption capacity of heavy-metal ions in wastewater remediation applications.

Evaluation of magnetic chitosan beads for adsorption of heavy metal ions

Although many magnetic chitosan materials have been prepared for adsorption of metal ions, there is no standard method for comprehensive evaluation of material performance. The common practice simply compares either adsorption capacity (Q) or saturation magnetization (Ms) of interested materials; however, these two important parameters often work in opposite way. This study aims to establish two methods for evaluation of the overall performance of magnetic materials. The proposed methods consider both heavy metal ion adsorption capacity and magnetic recovery of the material after use. The first method introduces adsorption recovery index (ARI, ARI=Qt), which is calculated using Q and recovery time (t) needed for achieving 98% material recovery. Higher ARI value shows better performance of a magnetic material. The second method uses effort-vector data visualization, in which the position of a magnetic material is shown on a coordinate depicted using normalized Q and Ms value. The distance of the data point to the target (ideal Q and Ms value) indicates the performance of the material. The shorter the distance, the better the overall performance is. Two series of MCBs with different Fe3O4 chitosan mass ratios were prepared by using embedding method and chemical co-precipitation method respectively. They were used as model compounds for investigation of the feasibility of the proposed evaluation methods through adsorption of various metal ions (Ag+, Cu2+, Hg2+, Cr3+ and Cr6+) and MCBs recovery test. The best performers were able to be identified by using both methods and the results agreed with each other. Compared with ARI, the effort-vector data visualization was more straightforward and easier to use. This method was successfully applied to evaluate a wide selection of magnetic materials, including those prepared in this work and reported from literatures, for their overall performance.

Novel salep-based chelating hydrogel for heavy metal removal from aqueous solutions

A novel optimized chelating hydrogel was synthesized via graft copolymerization of acrylamide and 2-hydroxyethyl methacrylate (as two-dentate chelating co-monomer) onto salep (a multicomponent polysaccharide obtained from dried tubers of certain natural terrestrial orchids) using N,N′-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. Reaction parameters (N,N′-methylenebisacrylamide and ammonium persulfate amounts as well as acrylamide/2-hydroxyethyl methacrylate weight ratio) affecting the water absorption of the chelating hydrogel were optimized using a systematic method to achieve a hydrogel with high swelling capacity as possible. Heavy metal ion adsorption capacity of the optimized hydrogel for metal ions [Cu (II), Pb (II), Cd (II), and Cr (III)] were investigated in aqueous media containing different concentrations of these ions (5–50 ppm). The results showed that the hydrogel have great potential for heavy metal removal from aqueous solutions. The hydrogel formation was confirmed by Fourier transform infrared spectroscopy, and surface morphology study of the hydrogel was performed by scanning electron microscope. Copyright © 2016 John Wiley & Sons, Ltd.

Graphene oxides prepared by Hummers', Hofmann's, and Staudenmaier's methods: dramatic influences on heavy-metal-ion adsorption.

Graphene oxide (GO), an up-and-coming material rich in oxygenated groups, shows much promise in pollution management. GO is synthesised using several synthetic routes, and the adsorption behaviour of GO is investigated to establish its ability to remove the heavy-metal pollutants of lead and cadmium ions. The GO is synthesised by Hummers' (HU), Hofmann's (HO) and Staudenmaier's (ST) methodologies. Characterisation of GO is performed before and after adsorption experiments to investigate the structure-function relationship by using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy coupled with elemental detection spectroscopy is used to investigate morphological changes and heavy-metal content in the adsorbed GO. The filtrate, collected after adsorption, is analysed by inductively coupled plasma mass spectrometry, through which the efficiency and adsorption capacity of each GO for heavy-metal-ion removal is obtained. Spectroscopic analysis and characterisation reveal that the three types of GO have different compositions of oxygenated carbon functionalities. The trend in the affinity towards both Pb(II) and Cd(II) is HU GO>HO GO>ST GO. A direct correlation between the number of carboxyl groups present and the amount of heavy-metal ions adsorbed is established. The highest efficiency and highest adsorption capacity of heavy-metal ions is achieved with HU, in which the relative abundance of carboxyl groups is highest. The embedded systematic study reveals that carboxyl groups are the principal functionality responsible for heavy-metal-ion removal in GO. The choice of synthesis methodology for GO has a profound influence on heavy-metal-ion adsorption. A further enrichment of the carboxyl groups in GO will serve to enhance the role of GO as an adsorbent for environmental clean-up.

Biosorption of copper(II) and chromium(VI) by modified tea fungus

The tea fungus was found to have good adsorption capacities for heavy metal ions. In this work it was treated with HCl or NaOH at 20?C or 100?C, with the aim to improve its adsorption ability. The sorption of Cu(II) and Cr(VI) ions from aqueous solutions by raw and treated tea fungus was investigated in the batch mode. The largest quantity of adsorbed Cu(II), of about 55 mg/g, was achieved by tea fungus modified with NaOH at 100?C. For Cr(VI), the largest quantity of adsorbed anions, of about 58 mg/g, was achieved by the adsorbent modified with NaOH at 20?C. It was shown that acid modification of tea fungus biomass was not effective.

Improving the Adsorption of Heavy Metals from Water Using Commercial Carbons Modified with Egg Shell Wastes

We introduce the application of hen egg shell waste to improve the adsorption capacities of heavy-metal ions using commercial carbons via the modification of their surface chemistry. Specifically, a calcium solution extracted from egg shell waste has been used as a low-cost activation agent to improve the adsorption properties of three commercial carbons. An orthogonal array of the Taguchi method has been applied to identify the optimal conditions for the adsorbent modification process using the Zn2+ batch adsorption, at 30 °C and pH 5, as the response variable. Our results show that maximum adsorption capacities of Cd2+, Ni2+, and Zn2+ ions, at 30 °C and pH 5, may increase up to 15 times, with respect to the results obtained using the commercial adsorbent without modification. The improvement of adsorbent performance may be related to the formation of calcium phosphate on the carbon surface. Finally, adsorption studies in binary metal solutions were performed to identify the competitive effects in multic...

A novel method for obtaining a high-concentration chitosan solution and preparing a high-strength chitosan hollow-fiber membrane with an excellent adsorption capacity

The biopolymer chitosan (CS) has been widely studied for various environmental and biomedical applications. However, the production of homogeneous CS solutions with high concentrations and the preparation of CS hollow-fiber membranes with high mechanical strengths for practical applications have been a great challenge so far. In this study, a novel dilute-dissolution and evaporating-concentration method was developed to allow highly concentrated homogeneous CS solutions to be easily prepared (up to 18 wt % as compared to ≤5 wt % prepared by the conventional method). CS hollow-fiber membranes prepared from high-concentration CS solutions showed greatly improved mechanical strengths (with tensile strengths up to 3.4 MPa), comparable to or even better than other hollow fibers made from many conventional industrial synthetic polymers. The prepared hollow-fiber membranes were found to possess very high adsorption capacities for heavy-metal ions (up to 206.6 mg of Cu2+/g of CS fiber at pH 5), which were attributed to the low crystallinity of CS and the porous structure achieved in the hollow-fiber membranes. As a potential application example, the performance of the prepared hollow fibers for the adsorption of copper ions in real wastewater from a wafer fabrication factory in Singapore was also examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Enhanced swelling and adsorption properties of AAm‐AMPSNa/clay hydrogel nanocomposites for heavy metal ion removal

AbstractNovel type hydrogel‐clay nanocomposites based on the acrylamide (AAm)‐ 2‐acrylamido‐ 2‐methylpropane sulfonic acid (AMPS) sodium salt and clay were synthesized via in situ copolymerization in aqueous solution. Samples were characterized by determining total basic group (TGB) content and swelling degree, XRD analysis, and FTIR spectroscopy. Effects of monomer ratio and clay amount on the swelling properties of the samples were investigated. It was found that the hydrogel/clay nanocomposites exhibited improved swelling capacity compared with the hydrogels. Samples were used to remove heavy metal ions (Cu (II), Cd (II), and Pb (II)) from aqueous solution in competitive and non‐competitive conditions for the first time. The effects of time and pH of the initial metal ion solution on the adsorption capacity were investigated and selectivity properties of the samples were evaluated. It was found that incorporation of a low amount of clay (10% (wt)) into the polymer structure increased the heavy metal ion adsorption capacity of the sample. It was concluded that the AAm‐AMPS/clay nanocomposites could be used as novel type, fast‐responsive, and high capacity sorbent materials in heavy metal removing processes. Copyright © 2007 John Wiley & Sons, Ltd.

Packed-bed columns with dye-affinity microbeads for removal of heavy metal ions from aquatic systems

A dye ligand Cibacron Blue F3GA, was covalently coupled with polyhydroxyethylmethacrylate (PHEMA) microbeads in the 150–200 μm particle size range. The sorbent carrying 22.3 μmol Cibacron Blue F3GA per gram of polymer was then used to remove Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions in a packed-bed column system. Heavy metal ion adsorption capacity of the column was investigated as a function of heavy metal ion-bearing solution flow rate and the inlet heavy metal ion concentration. The maximum metal ion uptake values found were: 80.60, 96.98, 78.36, 103.98 μmol/g polymer for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. The heavy metal adsorption capacity of the microbeads decreased with an increase in the circulation rate of aqueous solution. The order of affinity based on molar uptake was Zn(II)>Cd(II)>Pb(II)>Cu(II). Removal percentages of heavy metals related to flow time were determined for different flow rates and initial metal ion concentrations. It was observed that PHEMA microbeads carrying Cibacron Blue F3GA can be regenerated by washing with a solution of nitric acid (0.05 M). The desorption ratio was as high as 98.5%.