Polymetallic Solutions Research Articles

Eco-friendly thiol-functionalized magnetic oxygenous carbon nitride nanocomposites for effective elimination of heavy metals

The increased pollution of water resources by toxic heavy metals poses a huge threat to the aqueous ecosystem. Since the low concentrations of heavy metals are often highly toxic but difficult to remove, novel efficient adsorbents still need to be explored. Herein, the superparamagnetic thiol-functionalized oxygenous carbon nitride nanocomposite (CNO/Fe3O4-SH) with multifunctional groups such as –NH2, –OH, –SH, and –COOH was fabricated by a simple and eco-friendly method. The maximum adsorption capacities of Pb2+, As3+, and Cd2+ ions on CNO/Fe3O4-SH at pH = 6 were 80.79, 71.78 and 66.19 mg/g, respectively, when their equilibrium concentrations were 20 mg/L. Under the equilibrium concentration below 0.01 mg/L, the adsorption capacities of these heavy metals over CNO/Fe3O4-SH were much higher than those of other adsorbents. The competitive adsorption investigations showed that the adsorption order in polymetallic solutions was Pb2+ > As3+ > Cd2+. Adsorption kinetics and isotherms studies indicated that the adsorption of Pb2+, As3+ and Cd2+ by CNO/Fe3O4-SH was attributed to monolayer adsorption and the adsorption process was controlled by chemical adsorption. The thermodynamic experiments showed that the adsorption processes were spontaneous and endothermic. After six adsorption/desorption cycles, CNO/Fe3O4-SH maintained its original morphology and adsorption ability, indicating its excellent regeneration performance, which had significant potential application in the decontamination of trace heavy metal ions in water.

Spent brewer's yeast as a selective biosorbent for metal recovery from polymetallic waste streams.

While the amount of electronic waste is increasing worldwide, the heterogeneity of electronic scrap makes the recycling very complicated. Hydrometallurgical methods are currently applied in e-waste recycling which tend to generate complex polymetallic solutions due to dissolution of all metal components. Although biosorption has previously been described as a viable option for metal recovery and removal from low-concentration or single-metal solutions, information about the application of selective metal biosorption from polymetallic solutions is missing. In this study, an environmentally friendly and selective biosorption approach, based on the pH-dependency of metal sorption processes is presented using spent brewer's yeast to efficiently recover metals like aluminum, copper, zinc and nickel out of polymetallic solutions. Therefore, a design of experiment (DoE) approach was used to identify the effects of pH, metal, and biomass concentration, and optimize the biosorption efficiency for each individual metal. After process optimization with single-metal solutions, biosorption experiments with lyophilized waste yeast biomass were performed with synthetic polymetallic solutions where over 50% of aluminum at pH 3.5, over 40% of copper at pH 5.0 and over 70% of zinc at pH 7.5 could be removed. Moreover, more than 50% of copper at pH 3.5 and over 90% of zinc at pH 7.5 were recovered from a real polymetallic waste stream after leaching of printed-circuit boards. The reusability of yeast biomass was confirmed in five consecutive biosorption steps with little loss in metal recovery abilities. This proves that spent brewer's yeast can be sustainably used to selectively recover metals from polymetallic waste streams different to previously reported studies.

Removal of selected contaminants of the soil and water environment on a model isolation barrier

Landfill leachate poses a threat to the soil and water environment. Protection against their migration is provided by sealing the bottom and sides of the landfill called containment barriers. Natural clay are used for their construction. Fine-grained industrial waste of a mineral nature has been proposed as an alternative to them. Two-component mixtures of ash from solid fuel combustion and waste coal sludge have been developed. The basic expected property of an isolation barrier is its impermeability. Also important is the sorption capacity of the material from which the barrier is made. Hence, the purpose of the study was to evaluate the potential of the obtained mixtures to remove selected heavy metals and PAHs from aqueous solutions. The examinations of static batch sorption and sorption under flow conditions were conducted in columns. Solutions containing Zn(II), Cd(II), and Pb(II) ions with initial concentrations of 100, 200, and 500 mg L−1 were used in the experiment. For all mixtures, regardless of the initial concentration, batch sorption of metals exceeded 99%. In polymetallic solutions, the competitive phenomena between zinc and cadmium ions were confirmed, resulting in a decrease in the efficiency of their removal from the solution. The column tests carried out using raw leachate from a municipal landfill showed the effectiveness of the mixture in removing PAHs, particularly noticeable for di- and hexacyclic hydrocarbons. The removal rate of the 5 analyzed PAH groups ranged from 47.49 to 70.0%. The obtained results confirmed the high sorption capacity of the tested material, which allows considering its use as a sorbent in environmental engineering.

Fabrication of nitrogen-doped graphene quantum dots hybrid membranes and its sorption for Cu(II), Co(II) and Pb(II) in mixed polymetallic solution

With the rapid development of new–energy batteries, heavy-metals pollution from spent batteries has drawn much attention. Various techniques are recently proposed to delete or eliminate such pollution. Among which, membrane sorption exhibits exceptional advantages for the separation of multi-metal solution. For such a purpose, nitrogen-doped graphene quantum dots (N-GQDs) hybrid membranes were fabricated via sol–gel technique and hydrothermal synthesis, in which the precursor powder of N-GQDs was obtained by the combination of urea (used as a nitrogen source) and citric acid (used as a carbon source). Subsequently, the N-GQDs precursor was mixed with silane and PVA to generate N-GQDs hybrid membranes (NHMs). Competitive sorption of Cu(II), Co(II) and Pb(II) in the mixed polymetallic solution, such as a mixed Cu(II), Co(II) and Pb(II) ternary solution, a mixed Cu(II), Pb(II), Ca(II), Co(II) and Cr(III) quintuple solution, was investigated. It indicated that Cu(II) sorption on NHMs had better selectivity in these mixed polymetallic solutions. Moreover, sorption mechanism of Cu(II), Co(II) and Pb(II) demonstrates that the sorption of NHMs for Cu(II) and Pb(II) abided by Elovich model, indicating the properties of heterogeneous chemisorption. Such a trend shows that the sorption via chemical process between the active sites on the top-layer of NHMs, and Cu(II) and Pb(II) is one of the dominant interfering factors. Desorption testing demonstrated that EDTA-2Na is a best de-sorbent for Cu(II) sorption on NHMs and the number of cycles of these membranes can reach up to 10 times. These findings suggest that NHMs can be used to adsorb Cu(II), Co(II) and Pb(II) from mixed polymetallic solution, indicating promising applications in the successive separation of wastewater containing multiple mixed toxic metals from spent new-energy batteries and other metal-containing wastewater.

Selective and sensitive adsorption of Au(III) by poly-N-phenylglycine

The sustainable utilization of metal resources and the imbalance between supply and demand for metals urgently require the recovery of metals from e-waste, which is considered an “urban mine.” In this study, poly-N-phenylglycine (PNPG) particles were firstly used to capture gold with adsorption capacity (1356.78 mg⋅g−1) and good sensitivity to Au(III) in low-concentration solutions at pH 1. The mechanism of Au(III) adsorption by PNPG mainly involved chemisorption and monolayer adsorption, as evidenced by the well-fitting pseudo-second-order model and Langmuir isotherm model. Electrostatic interactions and redox reactions occurred during adsorption, as characterized by zeta potential, XRD, TEM, FT-IR, and XPS. To solve the problem of removing the adsorbent after adsorption, the PNPG membrane was prepared in advance by vacuum filtration, and corresponding stability test experiments were conducted. SEM characterization revealed that the support layer did not participate in the adsorption process. The PNPG membrane remained active for a minimum of three cycles and could selectively capture Au(III) from uneven-concentration polymetallic solutions. Approximately 80% of the gold in the leaching solution of waste printed circuit boards of computers was selectively recovered using the prepared 2-mg PNPG membrane, proving the practical application of PNPG membranes for the recovery of gold from e-waste.

Efficient Recovery of Noble Metal Ions (Pd2+, Ag+, Pt2+, and Au3+) from Aqueous Solutions Using N,N'-Bis(salicylidene)ethylenediamine (Salen) as an Extractant (Classic Solvent Extraction) and Carrier (Polymer Membranes).

This paper presents the results of the first application of N,N'-bis(salicylidene)ethylenediamine (salen) as an extractant in classical liquid–liquid extraction and as a carrier in membrane processes designed for the recovery of noble metal ions (Pd2+, Ag+, Pt2+, and Au3+) from aqueous solutions. In the case of the utilization of membranes, both sorption and desorption were investigated. Salen has not been used so far in the sorption processes of precious metal ions. Recovery experiments were performed on single-component solutions (containing only one type of metal ions) and polymetallic solutions (containing ions of all four metals). The stability constants of the obtained complexes were determined spectrophotometrically. In contrast, electrospray ionization high-resolution mass spectrometry (ESI-HRMS) was applied to examine the elemental composition and charge of the generated complexes of chosen noble metal ions and salen molecules. The results show the great potential of N,N'-bis(salicylidene)ethylenediamine as both an extractant and a carrier. In the case of single-component solutions, the extraction percentage was over 99% for all noble metal ions (molar ratio M:L of 1:1), and in the case of a polymetallic solution, it was the lowest, but over 94% for platinum ions and the highest value (over 99%) for gold ions. The percentages of sorption (%Rs) of metal ions from single-component solutions using polymer membranes containing N,N'-bis(salicylidene)ethylenediamine as a carrier were highest after 24 h of the process (93.23% for silver(I) ions, 74.99% for gold(III) ions, 69.11% and 66.13% for palladium(II) and platinum(II) ions, respectively), similar to the values obtained for the membrane process conducted in multi-metal solutions (92.96%, 84.26%, 80.94%, and 48.36% for Pd(II), Au(III), Ag(I), and Pt(II) ions, respectively). The percentage of desorption (%Rdes) was very high for single-component solutions (the highest, i.e., 99%, for palladium solution and the lowest, i.e., 88%, for silver solution), while for polymetallic solutions, these values were slightly lower (for Pt(II), it was the lowest at 63.25%).

Extraction behavior of germanium from synthetic leaching solution of secondary zinc oxide in tertiary amine (N235)-trioctyl phosphate (TOP) system

In continuation with our previous work, in the present study, the tertiary amine-trioctyl phosphate-sulfonated kerosene system was employed to recover Ge(IV) from the synthetic leachate of secondary zinc oxide. The effects of different complexing agents (tartaric acid, citric acid, oxalic acid, gallic acid, and salicylic acid) and impurities (Zn(II), Fe(III), Cd(II), Si(IV), and As(III)) on the extraction of Ge(IV) were investigated. Under comparable conditions, the extraction of Ge(IV) with the aforementioned complexants had the following order in terms of extraction efficiency: tartaric acid > citric acid > gallic acid > oxalic acid, or salicylic acid. The reason for the low extraction efficiency of Ge(IV) with the addition of oxalic acid was revealed by an extraction comparison using pure germanium and polymetallic solutions. Furthermore, a stoichiometry analysis of the extracted complex indicated that the extracted Ge(IV)-organic species was R3NH·Ge(OH)4(HT)·0.5TOP with the addition of tartaric acid. The concentration of Ge(IV) in the loaded organic phase was less than 1 mg/L when three-stage countercurrent stripping was adopted at an O/A ratio of 1/3 and 25 °C for 10.5 min.

Waste Jute Fabric as a Biosorbent for Heavy Metal Ions from Aqueous Solution

The influence of the chemical composition on the biosorption potential of waste jute fabric for Ni2+, Cu2+, and Zn2+ was investigated. The raw jute fabric was treated with sodium hydroxide or sodium chlorite to selectively remove hemicelluloses and lignin, respectively. All jute fabrics were characterized by determination of their chemical composition as well as functional group content. The effects of solution pH, contact time, and initial metal ion concentration on the biosorption from monometallic and polymetallic solution by jute fabrics were investigated. The maximum biosorption capacity for all heavy metal ions was observed at pH 5.5. Concerning the contact time, the raw jute fabric shows more than 72 % of the total uptake capacity of Ni2+, Cu2+, and Zn2+ within 1 h, while the jute fabrics with lower hemicelluloses and lignin content show between 72–85 % of the total uptake capacity within 3 h. Increased initial metal ion concentration from 10 to 20 mg/l in monometallic solution caused an increase in the total uptake capacity of jute fabrics with lower hemicelluloses and lignin content for 47–69 % (Ni2+), 42–63 % (Cu2+), and 22–37 % (Zn2+). The biosorption capacity of alkali treated jute fabrics was affected by the changes in the total amount of carboxyl and aldehyde groups that accompany the hemicelluloses removal. In the case of the oxidative treatment, the biosorption capacity was affected by the lignin content as well as the amount of introduced carboxyl groups. The best biosorption performance possesses jute fabric with 63.2 % lower lignin content as well as 81.1 % higher amount of carboxyl groups; biosorption capacity toward Ni2+, Cu2+, and Zn2+ in monometallic solution is about 2.4; 2.2 and 3.5 times higher compared to the raw jute fabric, respectively. All jute fabrics exhibited the same affinity order (which is independent on the initial metal ion concentrations) toward heavy metal ions: Ni2+ > Cu2+ > Zn2+ in the case of competitive biosorption. An increase in the initial metal ion concentration for two times in the polymetallic solution caused about a 35–59 % increase in the total uptake capacity of Ni2+, while the total uptake capacities of Cu2+ and Zn2+ increased for 19–38 % and 18–65 %, respectively.

The separation of Ni(II) over base metal ions in acidic polymetallic medium: Synergistic extraction and structural evidence

The selective extraction of Ni(II) from a polymetallic solution was achieved with an extractant mixture containing dinonylnaphthalene disulfonic acid (H2DNNDS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC, LII). The equilibrium results indicated that Ni(II) extraction was sensitive to the molar fraction of 4PC in the mixture containing H2DNNDS and 4PC. It was found that individual H2DNNDS or 4PC resulted in low extraction efficiency of Ni(II). Interestingly, when the mole fraction of 4PC in the mixture surpassed 50%, significant synergistic effect was observed for Ni(II) separation over Fe(III), Al(III), Ca(II), Mg(II) and Mn(II), thus highlighting the synergistic role of 4PC. In order to provide structural evidence for synergistic mechanism, two nickel model complexes were synthesized with 1,5-naphthalene disulfonic acid (H2NDS) in the absence/presence of methyl isonicotinate (LI), which were the corresponding short-chain analogues of H2DNNDS and 4PC, respectively. Combined with single crystal X-ray diffraction of nickel model complexes, the coordination chemistry of nickel complex in the loaded organic phases was disclosed with the Fourier Transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results showed that Ni(II) was directly coordinated with two monodentate ligands LI and four water molecules, while no direct interaction existed between Ni(II) and the O atoms of the deprotonated H2NDS in both two nickel model complexes. Hydrogen-bonding interaction between the H atom of coordinated water and the O atom of the deprotonated H2NDS played important role in stabilization of coordination configuration. The selective extraction of Ni(II) might be attributed to the incorporation of the pyridine based nitrogen donor into the inner coordination sphere of Ni(II) to supplant coordinated water.

Theoretical analysis and experimental study on metal separation of tungsten-containing systems

Based on the leaching solution of tungsten secondary resource, the metal separation properties of tungsten-containing systems such as the W-Mg-Si-H2O, the W-Al-H2O, the W-Fe-Mo-H2O and the W-Ca-V-H2O, were investigated by theoretical E-pH diagrams and experiments. The results demonstrated that the precipitation rates of Si and W were 99% and 2.4% respectively at pH = 9 in W-Mg-Si-H2O system; the precipitation rates of Al and W were 99.8% and 3.0% respectively at pH = 7 in W-Al-H2O system; the precipitation rates of W and Mo were 95% and 24% respectively at pH = 7 in W-Fe-Mo-H2O system; the precipitation rates of V and W were 91.2% and 4.3% respectively at pH = 13 with Ca:V = 3:1 in V-Ca-W-H2O system. The theoretical predictions were in good agreement with the experimental results. The metal separation for a tungsten-containing polymetallic solution of W, Mo, V, Si and Al, was designed and the parameters were optimized through the orthogonal experiments. The metals of (Si/Al), V, W and Mo were separated step by step with the precipitation rates exceeding 92%. This study provided a reference to metal comprehensive separation and recovery for the tungsten secondary resources.

Improvement of metals leaching optimal parameters from technogenic waste dumps with using mesophilic association of acidophilic chemolithotrophic bacteria

The results of improving the standard parameters of the process of bacterial leaching of metals, which allow to shorten the term of carrying out technological process and increase the efficiency of the extraction of germanium and other useful components are provided in article. To achieve the goal the mineralogical and chemical analysis of waste dumps have been made and the composition and leaching potential of the main groups of microorganisms of waste dumps were established also. Bacterial leaching was carried out using the mesophilic association of acidophilic chemolithotrophic bacteria, which are characterized by a high level of leaching activity. To determine the optimal parameters of the biotechnological process were compared results obtained with used: standard 9K medium with ferrous iron as an energy source; at constant elevated values of the oxidation-reduction potential at the level of 0.650 V; with ferric iron as an oxidizing agent, and using an optimized nutrient medium (OPM), the composition of which has been determined on the basis of mathematical optimization. The obtained results showed, that the using of ferric iron, OPM and elevated values the oxidation-reduction potential allow to shorten the term of leaching process and increase the recovery of germanium and other metals by 2 to 5 times. Moreover, the advantage of leaching with OPM is the absence of iron ions, which are an impurity and interfere with further sorption recovery of germanium from polymetallic solutions to produce germanium concentrate. Thus, optimum process parameters of bacterial leaching of metals, allows using them depending on the conditions and needs receiving of the targets metals from waste dumps.

Early gene expression in Pseudomonas fluorescens exposed to a polymetallic solution.

The molecular response of Pseudomonas fluorescens cells exposed to a mixture of heavy metals remains largely unknown. Here, we studied the temporal changes in the early gene expression of P. fluorescens cells exposed to three doses of a polymetallic solution over two exposure times, through the application of a customized cDNA microarray. At the lowest metal dose (MD/4), we observed a repression of the Hsp70 chaperone system, MATE and MFS transporters, TonB membrane transporter and histidine kinases, together with an overexpression of metal transport (ChaC, CopC), chemotaxis and glutamine synthetase genes. At the intermediate metal dose (MD), several amino acid transporters, a response regulator (CheY), a TonB-dependent receptor and the mutT DNA repair gene were repressed; by contrast, an overexpression of genes associated with the antioxidative stress system and the transport of chelates and sulfur was observed. Finally, at the highest metal dose (4MD), a repression of genes encoding metal ion transporters, drug resistance and alginate biosynthesis was found, together with an overexpression of genes encoding antioxidative proteins, membrane transporters, ribosomal proteins, chaperones and proteases. It was concluded that P. fluorescens cells showed, over exposure time, a highly complex molecular response when exposed to a polymetallic solution, involving mechanisms related with chemotaxis, signal transmission, membrane transport, cellular redox state, and the regulation of transcription and ribosomal activity.

CDNA microarray assessment of early gene expression profiles in Escherichia coli cells exposed to a mixture of heavy metals.

Many contaminated sites are characterized by the presence of different metals, thus increasing the complexity of toxic responses in exposed organisms. Within toxicogenomics, transcriptomics can be approached through the use of microarrays aimed at producing a genetic fingerprint for the response of model organisms to the presence of chemicals. We studied temporal changes in the early gene expression profiles of Escherichia coli cells exposed to three metal doses of a polymetallic solution over three exposure times, through the application of cDNA microarray technology. In the absence of metals, many genes belonging to a variety of cellular functions were up- and down-regulated over time. At the lowest metal dose, an activation of metal-specific transporters (Cus and ZraP proteins) and a mobilization of glutathione transporters involved in metal sequestration and trafficking was observed over time; this metal dose resulted in the generation of ROS capable of stimulating the transcription of Mn-superoxide dismutase, the assembly of Fe-S clusters and the synthesis of cysteine. At the intermediate dose, an overexpression of ROS scavengers (AhpF, KatG, and YaaA) and heat shock proteins (ClpP, HslV, DnaK, and IbpAB) was observed. Finally, at the highest dose, E. coli cells showed a repression of genes related with DNA mutation correctors (MutY glycopeptidases).

Ecotoxicity Evaluation of Industrial Discharge Waters and Metallic Solutions using Two Organisms (Lactuca sativa and Daphnia magna)

Surface treatment industrial discharge water is a complex anthropogenic source of pollutants, including organic pollutants (PAHs, VOCs…) and numerous metal ions. We attempted to identify the main toxicants comparing impact assessment of real polycontaminated effluents and reconstituted polymetallic solutions via ecotoxicological bioassays performed with Daphnia magna immobilization test (24 h) and Lactuca sativa germination test (168 h). We focused first on 2 (Ni and Zn) then on 5 metals (Ni, Zn, Co, Cr, Al). Our results showed differences between metal toxicity order: Zn>Al>Ni>Cr~Co, for daphnids and Ni>Zn>Al~Co>Cr for lettuce. However, discharge waters remained more toxic than synthetic solutions: those 5 metals were not entirely responsible for the discharge water ecotoxicity. We also found D. magna to be more sensitive than L. sativa. This last assessment should be interpreted with care, knowing that immobilization and germination tests are respectively acute and chronic toxicity bioassays. Thus, battery tests are appropriate to evaluate industrial discharge water samples, and should be increasingly used as eco toxicological standards.

Resin-asphaltene concentrates as base for carbon sorbent production

Products with a substantial content of resinous-asphaltenic compounds were obtained by redox reaction of acid tar and asphalt of petroleum residue deasphaltization with propane and gasoline. Addition of their polycondensates with furfural to the charge makes it possible to produce finely porous carbon adsorbents characterized by higher selectivity in gold and silver extraction from multicomponent polymetallic solutions in comparison with industrial adsorbents.

Carbon adsorbents from of shale oils and phenols

The liquid products of shale conversion—shale oil and shale phenols (a mixture of alkylresorcinols) and their solutions in commercial furfural, which are used as a new binding agent—make it possible to form carbon adsorbents with high mechanical strength (to 97%), microporosity (to 0.70 cm3/g), and higher sorption capacity than that of industrial adsorbents. The medium-combustion-loss samples exhibited higher selectivity in the extraction of noble metals from the multicomponent polymetallic solutions than those formed of traditional wood tar. They also outperform industrial adsorbents in these characteristics. It is possible to apply them to the absorption and concentration of aromatic hydrocarbons and to use them at atomic power plants, transport, and air conditioning plants for food and vegetable storage.

Selective Sulphide Precipitation of Heavy Metals from Acidic Polymetallic Aqueous Solution by Thioacetamide

The selective separation and recovery of copper, cadmium, zinc, and nickel from a polymetallic solution with sulphide precipitation using thioacetamide have been investigated. Selective metal sulphide precipitation was studied as a function of pH, contact time, and temperature. The results showed that it was possible to separate metals by accurately controlling the pH and temperature. Below pH 2.5, copper precipitation was complete. The cadmium, zinc, and nickel selective precipitations were performed at pH of 4, 5.5, and 7.5, respectively. Temperature also had important effects on the selective separation, and metals precipitation yields increased with increasing temperature. Thioacetamide hydrolysis kinetics and its activation energies in various conditions were calculated. The metal sulphide precipitates were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results showed that the produced precipitates had high purity.

Carbon adsorbents and ionites from a copolymer of petroleum asphaltites

Radiation-resistant cation exchangers with a static exchange capacity to 5.91 mg-equiv/g and a mechanical strength to 95% were prepared based on a grafted copolymer of asphaltite and acrylonitrile. The adsorbents prepared in accordance with an industrial process using a charge mixture containing the copolymer exhibited higher sorption properties, as compared with those of the commercial adsorbent SKT, in the sorption of silver from multicomponent polymetallic solutions. The selectivity factor for silver was 3.55, as compared with 1.85 for SKT.

Comparative study of dewatering characteristics of metal precipitates generated during treatment synthetic polymetallic and AMD solutions

The sludge dewatering characteristics expressed in terms of settling, filtration and centrifugation of metal precipitates generated during treatment of polymetallic solutions and synthetic acid mine drainage have been evaluated in this research. Results show that dewatering properties of metallic sludge vary depending on the type of matrix (Cl −; SO 4 2−), precipitating agent, and metals present in effluent. Metal hydroxides (at pH 10.0) and metal phosphates precipitates (at pH 7.0) are amorphous in nature, thus difficult to dewater. In these treatment methods, the substitution of chloride matrix by sulphate one improves considerably dewatering properties (specific resistance to filtration = 6.60 × 10 13 and 2.35 × 10 13 m/kg for the chloride and sulphate matrix, respectively). In the case of sulphide and carbonate treatments (pH 8.0), precipitates obtained are semi crystalline, and crystalline form, respectively, and no influence of the matrix was detected on dewatering characteristics.

Polymer Structure and Metal Ion Selectivity in Silica Polyamine Composites Modified with Sodium Chloroacetate and Nitriloacetic Acid (NTA) Anhydride

Previously, silica polyamine composite (SPC) materials (BP-1 and WP-1) containing amine chelating groups were prepared using two polyamines, polyallylamine (PAA), and polyethyleneimine (PEI). In this paper the amine ligands of BP-1 and WP-1 were modified with chloroacetate, yielding the new SPC materials BP-2 and WP-2. We have found that the acetate groups were bound to the amine groups to a greater extent on the SPC prepared using PAA (BP-1) relative to the SPC prepared with PEI (WP-1). BP-2 was selective for Cu2+ over other divalent metal ions from polymetallic solutions in the pH range of 1 to 3. In contrast, WP-2 was selective for Cu2+ over other divalent metal ions at pH 1 only and coloaded significant amounts of Ni2+ at pH 2 and pH 3. Thus, polyamine structure impacts the metal selectivity of the resultant SPC materials, BP-2 and WP-2. Two novel SPCs were prepared from nitriloacetic acid (NTA) anhydride using BP-1 and WP-1, yielding BP-NT and WP-NT, respectively. The resultant materials possess a unique chelating ligand, in which an iminodiacetic acid (IDA) group is covalently bonded to the SPC amine groups via an amide bond. The two materials (BP-NT, WP-NT) have similar metal selectivity profiles indicating that polyamine structure is not influential. Increased ligand denticity and the amide linker prevent the polymer from playing a large role in selectivity. The resulting materials have the ability to remove divalent and trivalent metal ions from low pH aqueous solutions. These materials can be regenerated by treatment with acid solution and showed no evidence of amide bond hydrolysis under acidic conditions.