Single Ion Solutions Research Articles

COMPETITIVE ADSORPTION OF Fe2+, Pb2+, AND Zn2+ IONS FROM MULTI-METAL ION SOLUTION ON AMMONIUM OXALATE MODIFIED KAOLINITE CLAY

The competitive adsorption of Fe2+, Pb2+, and Zn2+ ions from mixed multi-metal aqueous solution on ammonium oxalate-modified kaolinite clay (AOK) was studied to determine the competitive influence of the metal ions on the adsorption of other metal ions. The kaolinite clay was modified by treating it with 0.2 M of ammonium oxalate solution at 50 oC. The adsorption of the metal ions was carried out using initial concentrations of 20, 35, and 50 mg L-1 in both the single and multi-metal ion solutions. The results revealed that at a low concentration of 20 mg L-1, the adsorption capacity for the uptake of the metal ions on AOK is non-competitive. At higher adsorbate concentrations of 35 and 50 mg L-1, the single to multi-metal ions equilibrium adsorption capacity ratio value obtained was less than 1. This indicated an antagonistic effect on competing for the adsorption site in the following order: Pb2+ (9.9 mg g-1) > Fe2+ (3.85 mg g-1) > Zn2+ (2.85 mg g-1). The outcome revealed that ammonium oxalate-modified kaolinite is a potential adsorbent for remediation of multi-heavy metal-laden wastewater with preferentially higher affinity for Pb2+ ions than other metal ions.

Tris(2-benzimidazolyl)amine (NTB)-Modified Metal-Organic Framework: Preparation, Characterization, and Mercury Ion Removal Studies

Heavy metal ions (HMIs) are exceedingly hazardous to both humans and the environment, and the necessity to eliminate them from aqueous systems prompted the development of novel materials. In this study, tris(2-benzimidazolylmethyl)amine (NTB) was impregnated into MIL-101-(Cr) metal-organic framework using an incipient wetness impregnation approach, and the ability of the composite material to adsorb Hg2+ ions from the water was examined. The synthesized materials were analyzed with several physico-chemical techniques such as powder X-ray diffraction, elemental analysis, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption isotherms at 77 K, and X-ray photoelectron spectrometry. MIL-101-NTB quickly adsorbs 93.9% of Hg2+ ions within 10 min from a 10.0 ppm single ion solution. A better fit of the kinetic data to a pseudo-second-order model validated the chemisorption of Hg2+ ions on MIL-101-NTB. The experimental data fitted well with the Langmuir isotherm model, and the maximum adsorption capacity obtained at 125 ppm initial concentration was 111.03 mg/g. Despite the presence of other competing ions (Cu2+, Pb2+, and Cd2+), high Hg2+ ions removal efficiency (99.6%, 1.0 ppm initial concentration) was maintained in the diverse ion batch adsorption studies. A 0.2 M EDTA solution could desorb the Hg2+ ions, and cyclic Hg2+ ions sorption studies indicated that MIL-101-NTB might have a high Hg2+ ions removal efficiency for at least five consecutive cycles. Based on the FTIR and XPS analyses, Hg2+ ions chelation by NTB molecules and electrostatic interactions between Hg2+ ions and carboxylate groups in MIL-101-NTB are plausible mechanisms for Hg2+ ions adsorption.

Kinetic and isotherm of competitive adsorption cadmium and lead onto Saccharomyces cerevisiae autoclaved cells.

Heavy metal pollution has been regarded as a significant public health hazard during the industrialization, which also have exhibited various types of toxicological manifestations. Moreover, due to the high cost and toxic by-products, some conventional remediation methods were limited to heavy metals pollution control. In this work, autoclaved Saccharomyces cerevisiae was used as a biosorbent for the removal of Cd2+ and Pb2+ from single and binary ions aqueous solution system. The kinetics and isotherm of Cd2+ and Pb2+ were studied in different ion systems. The results showed that the competitive adsorption ability of S. cerevisiae to Pb2+ was stronger than that to Cd2+ in binary ions solution. To all the single ion solution of Cd2+ or Pb2+ and binary ions solution of Cd2+-Pb2+, there always existed that the adsorption of metal ions on S. cerevisiae fitted well with pseudo-second-order kinetic model and Langmuir isotherms model. The adsorption quantity qt in different solutions followed the sequence as qt (Cd2+-Pb2+) > qt (Pb2+-single) > qt (Pb2+-binary) > qt (Cd2+-single) > qt (Cd2+-binary). The autoclaved S. cerevisiae used in this research was one kind of rapid and favourable biosorbent for Pb2+ and Cd2+. In Pb2+ and Cd2+-containing solutions, sites competition and jointed toxicity of Pb2+ and Cd2+ on S. cerevisiae cells were the key to the total adsorption effect, and further researches were necessary in the next work. Thus, the current research presented that the autoclaved S. cerevisiae could be applied as an effective biosorbent for heavy metal adsorption from water environment and the design of eco-friendly technologies for the treatment of waste liquor.

Adsorption kinetics and isotherms of binary metal ion aqueous solution using untreated venus shell

Among available technologies to remove heavy metals from wastewater, biosorption has gained more attention due to its high removal efficiency, friendly operation, and inexpensive cost. Despite many studies on metal adsorption from single ion solutions, kinetics and isotherms of binary metal ions simultaneously adsorbed onto biosorbents have not been thoroughly investigated to provide insight on involving mechanisms. This study explored the adsorption potential of untreated venus shells (UVS) that can be utilized in economical and environmentally-friendly ways. In this work, UVS of different sizes were prepared without chemical treatment as a biosorbent. Characterization of UVS was accomplished using nitrogen adsorption isotherm, FTIR, and SEM-EDX. Batch adsorption was carried out to study the effect of initial metal ion concentration, adsorbent dosage, and size on removing Cu(II) and Zn(II) from a binary solution of both metal ions using UVS. The experimental values of maximum adsorption capacities of Cu(II) and Zn(II) were 0.446 and 0.465 mg/g, respectively. The adsorption data were analyzed using the pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion rate equations. The pseudo-second order and the intraparticle diffusion model yielded the best fit to the experimental data for Cu(II) and Zn(II) ions, respectively. The equilibrium isotherm was examined using the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (D–R), and Elovich models. The Freundlich model best fits the Cu(II) and Zn(II) equilibrium adsorption data. The results indicated that the adsorption of Cu(II) and Zn(II) onto UVS-600 adsorbent could undergo a chemisorption mechanism. Both metal ions in an aqueous solution were competitively adsorbed onto the heterogeneous active sites available on the shell surfaces. Cu(II) and Zn(II) ions in the binary system could result in ionic interference between the adsorbed ions and the active sites.

Transporter drives the biosorption of heavy metals by Stenotrophomonas rhizophila JC1.

To better understand the function of transporter in heavy metal detoxification of bacteria, the transporters associated with heavy metal detoxification in S. rhizophila JC1 were analyzed, among which four members were verified by RT-qPCR. In addition, the removal rates of four single metal ions (Cr6+, Cu2+, Zn2+, Pb2+) and polymetallic ions by strain JC1 were studied, respectively. We also researched the physiological response of strain JC1 to different metal stress via morphological observation, elemental composition, functional group and membrane permeability analysis. The results showed that in the single metal ion solution, removal capacities of Cu2+ (120 mg/L) and Cr6+ (80 mg/L) of S. rhizophila JC1 reached to 79.9% and 89.3%, respectively, while in polymetallic ions solution, the removal capacity of each metal ion all decreased, and in detail, the adsorption capacity was determined Cr6+>Cu2+>Zn2+>Pb2+ under the same condition. The physiological response analyses results showed that extracellular adsorption phenomena occurred, and the change of membrane permeability hindered the uptake of metal ions by bacteria. The analysis of transporters in strain JC1 genome illustrated that a total of 323 transporters were predicted. Among them, two, six and five proteins of the cation diffusion facilitator, resistance-nodulation-division efflux and P-type ATPase families were, respectively, predicted. The expression of corresponding genes showed that the synergistic action of correlative transporters played important roles in the process of adsorption. The comparative genomics analysis revealed that S. rhizophila JC1 has long-distance evolutionary relationships with other strains, but the efflux system of S. rhizophila JC1 contained the same types of metal transporters as other metal-resistant bacteria.

Competitive adsorption of nickel(II) and cadmium(II) ions by chitosan cross-linked with sodium tripolyphosphate

This study investigates the adsorption of Ni(II) and Cd(II) ions from single and binary metal ion solutions onto chitosan and crosslinked chitosan beads, which was accomplished by an environmentally-friendly crosslinker, sodium tripolyphosphate. The synthesized adsorbents were characterized by swelling test, BET and SEM, and tested for Ni(II) and Cd(II) uptake after optimizing experimental factors, including adsorbent concentration (0.55 g/L) and initial pH (6.5). The single-ion equilibrium adsorption data fitted well by the Langmuir model. In the binary system, a decrease in adsorption capacity was observed, implying the existence of preference in the order of Ni(II) > Cd(II). Among the studied models for competitive adsorption, the extended Freundlich model fitted successfully for the adsorption equilibrium data. Characterization of loaded crosslinked chitosan beads showed amino and phosphate groups were responsible simultaneously for the metal ions uptake. Desorption experiments were also conducted by using a mixture of NaCl and H2SO4, showing acceptable results.

Study on Sewage Sludge-based Activated Carbons with Natural Mineral Modification for Enhanced Removal of Heavy Metal Ions from Aqueous Solution

Activated carbons were prepared from sewage sludge by chemical activation with pyrolusite (PAC) and lithium-silicon powder addition (LSAC) to develop effective adsorbents for the removal of Cu(II), Pb(II), Cd(II) and Cr(III) metal ions from aqueous solution. Both modifiers with an optimum dosage of 1% (wt.) were demonstrated to exhibit important effects on the formation of the adsorbent’s pore structure. PAC and LSAC showed 17.06% and 8.38% higher BET surface area than the common one without modification (AC). The XPS result showed that after modification, the hydroxyl and carboxyl groups on modified activated carbons surface were remarkably improved compared with the ordinary carbon. The adsorption results in single ion solution showed that the metal ions’ removal rates were 13~29% and 20~43%, respectively, by LSAC and PAC compared with AC’s. Adsorption isotherm and kinetics studies showed that the adsorption of heavy metal ions onto the modified adsorbents was well-fitted by the Langmuir isotherm and could be described by the pseudo-second-order kinetic model. In a multi-ions solution system, the produced carbons showed high affinity and good selective adsorptive capacity on Cu (II), Pb (II) removal, while an improvement in adsorption of Cd(II) and Cr(III) was observed. It will help a lot in wastewater industries due to its efficiency and low-price.

Selective separation of Cu(II) from a single metal ion solution by using O-amino thiophenol-modified flax fiber

A newly synthesized ortho-amino thio-phenol modified flax fibers (OATP-MFF) were prepared in two subsequent steps; at first flax fiber was pretreated with sodium periodate. Then the pretreated fibers were condensed with ortho-amino thio-phenol to form the modified flax fiber(OATP-MFF). The OATP-MFF was characterized by (FTIR) Fourier transform infrared spectra, SEM and energy-dispersive X-ray Spectroscopy (EDX). The newly synthesized OATP-MFF chelating fibers were utilized for selective separation of Cu(II) from aqueous solution by adsorption methodology. The effects of pH, the initial concentration of metal ions, the adsorbent dosage, the interfering ions and the contact time on the adsorption capacity of OATP-MFF chelating fibers were investigated. The maximum adsorption capacity of Cu(II) at the optimum conditions was 92 mg/g. The adsorption process fitted well the second-order model kinetic of. The chemical (adsorption) reaction is the rate-limiting step that was proved from the kinetic model.

Evaluation of fluoride and cadmium adsorption modification of corn stalk by aluminum trichloride

The aluminum-modified corn stalk biochar (AlCl3-BC) were prepared to adsorb fluoride from single ion solution and from binary mixtures with cadmium. FTIR spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and zeta potentiometry revealed that surface functional groups, crystal and physical structure of biochar were significantly improved by AlCl3 modification. The fluoride adsorption process consisted with pseudo-first order kinetics model and both Langmuir and Freundlich models well. The AlCl3-BC exhibited greater adsorption capacities than the original biochar (BC) with adsorption capacity of 81.65 mg g−1 at 35 °C. Both BC and AlCl3-BC showed higher capacities than those reported for other biochar. The fluoride adsorption capacity Qe from a binary solution of fluoride and cadmium gradually decreased as the initial cadmium concentration increased at fixed initial fluoride concentrations, while adsorption of cadmium increased. As the initial fluoride concentrations increased from 5 to 20 mg L−1, the Qe of fluoride increased as the Qe of cadmium decreased, indicating that fluoride adsorption by BC and AlCl3-BC was clearly reduced in the presence of cadmium. This research suggested that AlCl3-BC is a promising candidate material for single ion fluoride removal and could also achieve synergetic removal of fluoride and cadmium from contaminated water bodies.

Microbial potentiometric sensor technology for real-time detecting and monitoring of toxic metals in aquatic matrices

Considering that toxic metals can affect metabolic processes in microorganisms adversely, it can be hypothesized that these metals in water matrices would induce a decrease in metabolic activity of the biofilm microorganisms populating the surface of a sensing electrode, which could be registered as a change in the open-circuit potential (OCP) generated by the biofilm microorganisms. The goal of this study was to test this hypothesis and demonstrate the underlying principle that microbial potentiometric sensor (MPS) technology could be used for long-term and real-time monitoring and detection of rapid changes in metal concentrations in realistic aquatic environments. To address the goal, four objective were addressed: (1) a batch reactor with three graphite-based MPS electrodes was fabricated; (2) a set of single-ion solutions and one multiple ion solution were prepared reflecting realistic concentrations of metals found in electroplating wastewaters; (3) the responses of the MPS to the simultaneous presence of multiple toxic metal ions in a single solution were measured; and (4) the changes of the MPS signals to the presence of individual metal ion solutions were examined. While the hypothesis was validated, the study also revealed that the MPS was sufficiently sensitive to not only detect, but also quantify, toxic metal ion concentrations in aqueous solutions. The coefficients of determination, which were R2>0.995, and responsiveness of <1 μmol/L for some toxic metal cations, strongly support the performance of MPS technology in the echelons of expensive analytical tools capable detecting and measuring trace elements.The magnitude of the MPS response was toxic metal specific. When the molar concertation normalizes the inhibition portion of the signal area, the assessed sensitivity order was: Se>Cd>Pb>Ag>Ni> Zn. The study provides valuable information for enforcement agents, environmental professionals, and wastewater treatment operators, so toxic metal pollution and its detrimental impacts can be prevented and mitigated.

First principles molecular dynamics investigation on the water-ion interaction: A case of diluted CsI solution

Diluted CsI solution as well as artificial single Cs+ and I− solutions are investigated by first principles molecular dynamics. It is revealed that the ions mainly affect water molecules within the first solvation shell, meanwhile shifting the water dipole moment distributions to smaller value regions. However, the water dynamics in terms of residence time, hydrogen bond dynamics and water reorientational dynamics is quite different in different simulated systems. Comparing the results from diluted CsI solution to single ion solutions, no cooperative or additive effect of ion pair is evident at the time scale of hundred picosecond.

Novel magnetic nanocomposite of calcium alginate carrying poly(pyrimidine-thiophene-amide) as a novel green synthesized polyamide for adsorption study of neodymium, terbium, and dysprosium rare-earth ions

In this paper, a novel polyamide containing pyrimidine and methine thiophene linkages (poly(pyrimidine-thiophene-amide) (P(P-T-A))) was synthesized. Then, the magnetic calcium alginate nanocomposite containing P(P-T-A) (CA-P(P-T-A)-Ni0.2Zn0.2Fe2.6O4 (NZFO)) was synthesized for studying neodymium (Nd+3), terbium (Tb+3), and dysprosium (Dy+3) ions adsorption in the single ion solutions. The obtained results of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDX), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and Fourier transform infrared (FT-IR) indicated the successful synthesis of the materials. The value of saturation magnetization of the nanocomposite was reported to be 15.28 emu/g, indicating an appropriate magnetic response. Under the optimum conditions, adsorption efficiency for Nd+3, Tb+3, and Dy+3 was 96.73, 94.82, and 97.58 %, respectively. According to the experimental results, it can be stated that the data of REEs adsorption were efficiently fitted by nonlinear pseudo-second-order kinetic model. Adsorption isotherms were also evaluated by fitting with Freundlich and Langmuir isotherm models. A better fit was achieved by Freundlich model in the case of Tb+3 and Dy+3 ions, while Langmuir isotherm fitting reported a better result for Nd+3 adsorption data. Moreover, the changes in Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) values presented a feasible and endothermic ions adsorption process onto the nanocomposite that occurred spontaneously under the investigated conditions. The obtained results indicated that the nanocomposite can be considered as a potential adsorbent for the efficient adsorption of the investigated ions.

Competitive and non-competitive zinc, copper and lead biosorption from aqueous solutions onto flax fibers

Competitive and non-competitive batch experiments were conducted on flax fibers to study Zn2+, Cu2+, and Pb2+ ions biosorption performance. Biosorption efficiency was dependent on contact time, pH, and biosorbent concentration. The results under competitive conditions were different from those obtained in non-competitive form. A high affinity of lead, with a selectivity sequence in general of Pb > Cu > Zn was observed. The biosorption data fitted very well the Langmuir model for lead in both types of solutions and for zinc and copper in the monometal form. The fit with the Freundlich model was not as successful, except for copper in the ternary system. Regarding zinc under competitive conditions, the sorption process was quite difficult and thus the equilibrium data could not fit well the adsorption models. The maximum adsorption capacities (mmol.kg−1) were respectively 112, 122 and 71, for Pb, Cu and Zn in the single metal ion solution and 82, 57 and 8 only in the ternary, showing thus a high competition between metal ions when added simultaneously. Overall, lead could still be efficiently removed in spite of the presence of other ions while zinc would be overcome in the presence of lead and copper.

Application of waste cotton yarn as adsorbent of heavy metal ions from single and mixed solutions.

In this study, waste cotton yarn was used for the removal of Pb (II), Cd (II), Cr (III), and As (V) from aqueous solution. Adsorption of heavy metal ions was tested from single ion solutions, while competitive studies were performed using two- and four-ion mixtures. In order to change the structure of the material, cotton yarn was modified by sodium hydroxide solution. The surface of raw and modified cotton yarn were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and streaming potential method for determination of an isoelectric point. Sorption studies were performed on the basis of pH, kinetics, isotherms, and desorption results. It has been shown that waste cotton yarn modification, typically, does not improve the sorption capacity of the material and that the unmodified material could be used for the removal of examined heavy metal ions. Selectivity was in order Pb > Cd > Cr > As. Desorption studies have indicated to the possible reusability of the sorbent only in the case of Pb removal. A potential application of spent waste sorbent for the soil quality improvement has been considered.

Adsorption of positively and negatively charged heavy metal ions from wastewater by heteroaggregates of biopolymer particles

Environmentally benign biopolymer particles formed from natural carbohydrate polymers alginate and chitosan have shown great capacity for adsorption of heavy metal ions from wastewater. In this study, heteroaggregates of large alginate beads (∼1.8 mm) and chitosan nanoparticles (∼250 nm) have been used to adsorb molybdate and copper ions from single ion and mixed ion solutions in order to study the equilibrium adsorption properties. Three distinct heteroaggregation regimes have been studied in order to determine how the structure and composition affect adsorption capacity. Significantly enhanced adsorption was observed for heteroaggregates compared to the sum of their individual components, in both single ion and mixed ion solutions, indicating the presence of synergistic effects. The resulting adsorption capacity values for heteroaggregates are highly competitive with previous literature results and reach a maximum capacity of approximately 200–600 mg/g adsorption of either ion in a mixed ion solution, based on the adsorbent dry mass. In addition, synergistic and competitive effects were investigated in mixed ion solutions containing oppositely charged copper and molybdate ions, in an effort to mimic more realistic wastewater, and in contrast to typical competitive adsorption studies involving only like charged ions. Moreover, the observed interaction of both ions with heteroaggregates and their components suggested that opposite charge attraction is a more effective adsorption mechanism than complexation. Finally, the heteroaggregates represent a potential path forward for using nanoparticles in practical adsorption, where the large alginate beads act as supports for the nanoparticles and as effective adsorbents.

Adsorption of various metals by carboxymethyl-β-cyclodextrin-modified Zn[sbnd]Al layered double hydroxides

Herein we studied metal ion adsorption in aqueous solution by ZnAl layered double hydroxides (ZnAl LDH) modified with carboxymethyl-β-cyclodextrin (CM-β-CD) ions (CM-β-CD•Zn-Al LDH). In single-ion solutions containing Li+, Nd3+, or Pb2+, CM-β-CD•Zn-Al LDH adsorbed Nd3+ and Pb2+ but adsorbed very little Li+. Maximum adsorption followed the order Pb2+ > Nd3+ > Li+. In a mixed solution containing Li+, Nd3+, Ni2+, Cu2+, and Pb2+, the adsorption rate followed the order Cu2+ ≫ Pb2+ > Nd3+ > Ni2+ > Li+.

Characterization of heavy metal toxicity in some plants and microorganisms—A preliminary approach for environmental bioremediation

In situ bioremediation processes are important for control of pollution and clean-up of contaminated sites. The study and implementation of such processes can be designed through investigations on natural mechanisms of absorption, biotransformation, bioaccumulation and toxicity of pollutants in plants and microorganisms. Here, the phytotoxic effects of Cr(VI) and Cd(II) on seed germination and plant growth of Lepidium sativum have been examined at various concentrations (30−300 mg/L) in single ion solutions. The studies also addressed the ecotoxicity of metal ions on Azotobacter chroococcum and Pichia sp. isolated from soil. Microbial growth was estimated by weighing the dry biomass and determining the enzymatic activities of dehydrogenase and catalase. The results showed that Cr(VI) and Cd(II) can inhibit L. sativum seed germination and root development, depending on the metal ion and its concentration. The phytotoxic effect of heavy metals was also confirmed by the reduced amounts of dried biomass. Toxicity assays demonstrated the adverse effect of Cr(VI) and Cd(II) on growth of Azotobacter sp. and Pichia sp., manifested by a biomass decrease of more than 50 % at heavy metal concentrations of 150−300 mg/L. The results confirmed close links between phytotoxicity of metals and their bioavailability for phytoextraction. Studies on the bioremediation potential of soils contaminated with Cr(VI) and Cd(II) using microbial strains focusing on Azotobacter sp. and Pichia sp. showed that the microbes can only tolerate heavy metal stress at low concentrations. These investigations on plants and microorganisms revealed their ability to withstand metal toxicity and develop tolerance to heavy metals.

Amine-functionalized metal organic frameworks MIL-101(Cr) adsorbent for copper and cadmium ions in single and binary solution

ABSTRACT In this study, functionalized MIL-101(Cr) with amine group (ED-MIL-101(Cr)) was Synthesized. Using grafted MOF, adsorption experiments of Cu(II) and Cd(II) ions in single and binary solutions were performed. The adsorption results were fitted well by the Langmuir and extended Freundlich models for single ion and binary ion solutions, respectively. Data revealed that ED-MIL-101(Cr) possess maximum adsorption capacities (mg/g) of 69.9 and 63.15 for Cu(II) and Cd(II), respectively,with affinity order Cu(II) ˃ Cd(II) in binary ion solution. The kinetic data was well described by the pseudo-second-order model. The amino-functionalized MIL-101(Cr) can be a promising candidate for metal ion removal from the aqueous environment.

Adsorption of Ce3+ and Nd3+ by diglycolic acid functionalised electrospun polystyrene nanofiber from aqueous solution

Highly selective and stable ligands with fast kinetics for rare earth element extraction are not well developed. Durable attachment of ligands to the support would make regeneration possible. Polystyrene nanofiber supports (PS-nF) were prepared using the electrospinning method. Thereafter, PS-nf were chemically modified with diglycolic anhydride (DGA) to produce novel electrospun polystyrene diglycolic acid nanofiber (PS-DGAnf) adsorbents. The immobilisation reaction proceeded via an electrophilic aromatic substitution of the ligand onto the PS nanofiber. The maximum gravimetric loading of DGA on PS nanofiber was 0.827 g g−1. The unmodified and modified nanofibers were characterised by ATR-FTIR, HR-SEM, BET and TGA. After optimising pH, time and concentration, the equilibrium adsorption and binding kinetics of cerium (Ce3+) and neodymium (Nd3+) ions on the nanofibers surface were examined at pH 6. The adsorption capacity of PS-DGAnf for Ce3+ and Nd3+ at pH 6.0 was 152.5 mg g−1 (1.09 mmol/g) and 146.2 mg g−1 (1.01 mmol/g) respectively. Selectivity of Ce3+ over Ni2+, Co2+ and Sr3+ was also studied at pH 6. The amount of Ce3+ adsorbed even in the presence of interfering ions was 100.3 mg g−1, which was only a little lower than 119.4 mg g−1 obtained in a single ion solution. The rapid adsorption kinetics of Ce3+ and Nd3+ ions were achieved within 15 mins. The desorption and regeneration was carried out with 1 M nitric acid and the developed PS-DGAnf adsorbent could be reused for 4 cycles without any substantial loss to its adsorption abilities.

Spherical Chitosan/Gelatin Hydrogel Particles for Removal of Multiple Heavy Metal Ions from Wastewater

This article describes a simple preparation of chitosan/gelatin (CG) spherical hydrogel particles for the effective removal of multiple heavy metal ions. The CG hydrogel particles were prepared by inverse emulsion from the aqueous solutions of chitosan, gelatin, and glutaraldehyde. The oven-dried C2G1 hydrogel particles showed a maximum removal efficiency of 98% for Hg(II) ions in a single metal ion solution and which was higher than C1G1 (85%) and C1G2 (58%) particles. This result was affected by the composition of the hydrogels rather than the pore size or degree of swelling. Remarkably, the removal efficiencies for the Pb(II), Cd(II), Hg(II), and Cr(III) ions reached about 73%–94% in a multiple metal ion solution. The results indicate that the CG hydrogel particles can be used to remove coexisting heavy metal ions from wastewater, providing a versatile method to remove multiple metal ions from natural or industrial wastes.