Duolite GT-73 Research Articles

Survey of Heavy Metal Contamination in Water Sources in the Municipality of Torola, El Salvador, through In Situ Sorbent Extraction

The presence of heavy metals in water resources directly affects consumer health. The quality of surface water resources in Central America is usually low due to the presence of metals and other pollutants. The lack of analytical instrumentation to perform routine monitoring of water has encouraged the development of easy tools to facilitate the determination of heavy metals in waters in remote sites. In this study, we evaluated the use of different sorbents, such as Adsorbsia As600 (titanium dioxide), Iontosorb Oxin, 8-hydroxyquinoline bearing functional groups, and Duolite GT-73, with thiol functionality, for Cd, Ni, Cu, Zn, and Al extraction. It was found that both Adsorbsia As600 and Iontosorb Oxin allowed the adsorption of all metals, and the recovery was achieved using either HCl or ethylenediaminetetraacetic sodium salt (EDTA) solutions. Hence, Adsorbsia As600 was employed for in situ sampling in the metal contamination evaluation of water samples (from 15 wells and nine storage tanks) from the municipality of Torola, Mozarán, El Salvador. The developed procedure allowed all the metals in the samples to be detected, and Ni and Al were found to be above Salvadoran guidelines for drinking water quality.

Mercury Distribution in the Deûle River (Northern France) Measured by the Diffusive Gradients in Thin Films Technique and Conventional Methods.

The distribution of mercury in surface water and in sediment from Deûle River in Northern France was studied by application of conventional sampling methods and by diffusive gradients in thin films technique (DGT). Concentration of total dissolved mercury in surface water was 20.8 ± 0.8 ng l(-1). The particulate mercury concentration was 6.2 ± 0.6 µg g(-1). The particulate mercury was accumulated in sediment (9.9 ± 2.3 mg kg(-1)), and it was transformed by methylating bacteria to methylmercury, mainly in the first 2-cm layer of the sediment. Total dissolved concentration of mercury in sediment pore water obtained by application of centrifugation extraction was 17.6 ± 4.1 ng l(-1), and it was comparable with total dissolved pore water mercury concentration measured by DGT probe containing Duolite GT-73 resin gel (18.2 ± 4.3 ng l(-1)), taking the sediment heterogeneity and different principles of the applied methods into account. By application of two DGT probes with different resin gels specific for mercury, it was found that approximately 30% of total dissolved mercury in sediment pore water was present in labile forms easy available for biota. The resolution of mercury DGT depth profiles was 0.5 cm, which allows, unlike conventional techniques, to study the connection of the geochemical cycle of mercury with geochemical cycles of iron and manganese.

Determination of mercury species by the diffusive gradient in thin film technique and liquid chromatography – atomic fluorescence spectrometry after microwave extraction

A diffusive gradient in thin films technique (DGT) was combined with liquid chromatography (LC) and cold vapor atomic fluorescence spectrometry (CV-AFS) for the simultaneous quantification of four mercury species (Hg2+, CH3Hg+, C2H5Hg+, and C6H5Hg+). After diffusion through an agarose diffusive layer, the mercury species were accumulated in resin gels containing thiol-functionalized ion-exchange resins (Duolite GT73, and Ambersep GT74). A microwave-assisted extraction (MAE) in the presence of 6M HCl and 5M HCl (55°C, 15min) was used for isolation of mercury species from Ambersep and Duolite resin gels, respectively. The extraction efficiency was higher than 95.0% (RSD 3.5%). The mercury species were separated with a mobile phase containing 6.2% methanol+0.05% 2-mercaptoethanol+0.02M ammonium acetate with a stepwise increase of methanol content up to 80% in the 16th min on a Zorbax C18 reverse phase column. The LODs of DGT–MAE–LC–CV-AFS method were 38ngL−1 for CH3Hg+, 13ngL−1 for Hg2+, 34ngL−1 for C2H5Hg+ and 30ngL−1 for C6H5Hg+ for 24h DGT accumulation at 25°C.

Development of the diffusive gradient in thin films technique for the measurement of labile mercury species in waters

The diffusive gradients in thin films (DGT) technique, utilizing resin gel with ion-exchange resin Duolite GT73 and new ion-exchange resin Ambersep GT74, was investigated for the accumulation of four mercury species (Hg2+, CH3Hg+, C2H5Hg+, C6H5Hg+). The diffusion coefficients of mercury species in agarose gel calculated on the basis of Fick’s Law were mercury species-specific. The diffusion coefficients of Hg2+ and CH3Hg+ at 25°C (9.07±0.23×10−6cm2s−1 and 9.06±0.30×10−6cm2s−1, respectively) were very similar, but the diffusion coefficients of C2H5Hg+ (6.87±0.23×10−6cm2s−1) and C6H5Hg+ (3.86±0.19×10−6cm2s−1) were significantly lower. Influence of experimental conditions (pH, selected cations, chlorides and humic substance) on mercury species accumulation by DGT was studied. The DGT technique was applied to river water spiked with mercury species.

Determination of trace indium in urine after preconcentration with a chelating‐resin‐packed minicolumn

A simple and rapid chelating-resin-packed column has been developed for preconcentration of trace indium in biological samples. A large-sized urine sample was pumped through a minicolumn at a flow rate of 1.0 mL/min by using a peristaltic pump, and the eluents were analyzed using graphite furnace atomic absorption spectrometry (GFAAS). Four commercially available chelating resins including Chelex-100, Amberlite IRC-50, Duolite GT-73, and Celite 545-AW were studied for evaluating the indium sorption performance. Several parameters, such as pH, resin amount, eluent volume, eluent flow rate, and the volume of sample, were investigated and optimized. A 100-200 mL of the sample was loaded into a column containing 1.2 g of wet Chelex-100 and subjected to the ion-exchange procedure. The retained analytes were eluted with 5.0 mL of 0.1 M HNO(3) and quantified by GFAAS. The correlation coefficient in the range 10-250 ng/mL was of 0.9994. The limit of detection of the proposed method was 2.75 ng/mL. The method developed was successfully applied to analysis of spiked urine samples with good recoveries of 93-103% (n = 6) and reproducibility (relative standard deviation < 4.9%). The accuracy of procedure was confirmed by indium determination in spiked certified reference materials.

Characterization of sorption gels used for determination of mercury in aquatic environment by diffusive gradients in thin films technique

Abstract The influence of pH, ionic strength and selected natural ligands on the measurement of mercury by the diffusive gradients in thin films technique (DGT) using recently introduced sorption gels was determined. Sorption gels containing Chelex 100, Spheron-Thiol, Duolite GT73 and modified Iontosorb AV resins were investigated, with the sorption capacity determined for all used sorption gels. The minimum DGT measurable concentrations were calculated from 3 times the standard deviation of mercury amount in unexposed sorption gels.

Application of New Resin Gels for Measuring Mercury by Diffusive Gradients in a Thin-films Technique

A possible replacement of previously recommended Spheron-Thiol resin gel for measuring mercury by diffusive gradients in a thin film (DGT) was studied. Duolite GT73 resin and newly prepared 6-mercaptopurine modified Iontosorb AV as binding phases were tested. The preparation procedure of resin-embedded gels was optimized and DGT with new resin gels verified. The verified DGT containing new resin gels was used for in situ mercury measurement in Svitava River.

Recovery of palladium(II) from chloride and chloride–nitrate solutions using ion-exchange resins with S-donor atoms

Pd(II) ions sorption from the model solutions of the composition: 0.1–8.0 M HCl – 0.0011 M Pd(II) and 0.1–0.9 M HCl – 0.9–0.1 M HNO3 – 0.0011 M Pd(II) on the ion exchangers with the thiol (Duolite GT-73) and thiourea (Lewatit TP-214) functional groups was discussed. These ion exchangers possess a considerable ion exchange capacity in the model chloride–nitrate and chloride systems e.g. 1.16 mmol Pd(II)/g of Lewatit TP-214 in 0.1 M HCl solution. In the purification of Pd(II) of Cu(II), Ni(II) and Al(III) salts macroquantities, the best results were obtained by means of Lewatit TP-214

Speciation and preconcentration of inorganic antimony in waters by Duolite GT-73 microcolumn and determination by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS)

A selective matrix removal/separation/enrichment method, utilizing a microcolumn of a chelating resin with SH functional groups (Duolite GT-73), was proposed for the determination of Sb(III) in waters by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS). The resin was selective to Sb(III) at almost all pH and acidity values employed, whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with l-cysteine. Spike recoveries were tested at various concentration levels in different water types and were found to vary between 85 and 118%. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined (13.3 ± 1.1 μg l −1) and the certified value (13.79 ± 0.42 μg l −1). The method was applied to several bottled drinking water samples for antimony determination with and without preconcentration and none of the samples were found to contain antimony above the permissible level (5 μg l −1). The characteristic concentration (the concentration of the analyte corresponding to an absorbance of 0.0044) was 0.55 μg l −1 and the 3 s limit of detection (LOD) based on five times preconcentration was 0.06 μg l −1. The applicability of the microcolumn separation/preconcentration/matrix removal method for flow injection systems was also demonstrated.

On the Applicability of Duolite GT-73 to Column Preconcentration of Gold and Palladium Prior to Determination by Inductively Coupled Plasma Atomic Emission Spectrometry

The preconcentration of Au and Pd on Duolite GT-73 chelating resin with the thiol functional group was investigated prior to determination of these noble metals by means of inductively coupled plasma atomic emission spectrometry. It was found that AuIII and PdII were retained on the resin along with other concomitant metals (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) from different HCl-containing media. A two-step elution procedure was developed for the release of the noble metals. First 4.0 mol L−1 HNO3 solution was used to elute the base metals. The recovery of Au and Pd was performed afterwards using 0.50 mol L−1 solution of (NH2)2CS. Retrieval of Au and Pd retained on Duolite GT-73 was also carried out by decomposition of the resin in the open vessel system using H2SO4 with H2O2. The detection limits of Au and Pd evaluated for the devised protocol, with a preconcentration factor of 50, were 0.085 µg L−1 and 0.28 µg L−1, respectively. The proposed method was applied to the determination of Au and Pd in spiked electrolytic bath samples.

Preconcentration of mercury using duolite GT-73 in the analysis of water samples by inductively coupled plasma atomic emission spectrometry.

Duolite GT-73 resin was used for the preconcentration of Hg(II) from hydrochloric acid media as well as separation of the analyte from diversity of the co-existing metal ions (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) in off-line column operation. Due to the high affinity of the resin to the transition metals, Hg was adsorbed alongside with the foreign metals investigated. A complete release of the concomitant metals from the resin without the desorption of Hg was carried out using solutions of HCl and HNO3. A quantitative recovery of Hg was obtained by digestion of the resin using a H2SO4 and H2O2 mixture in an open-vessel system. An enrichment factor of 40 was achieved. The devised procedure was applied for the determination of Hg(II) in tap-water samples.

Preparation of chelating agents from sugarcane bagasse by microwave radiation as an alternative ecologically benign procedure

Microwave radiation was utilized to produce neutral chelating agents (BCA) from sugarcane bagasse. BCA were prepared by reaction of urea with reactive sites present in bagasse such as hydroxyl and carboxylic groups. BCA prepared through microwave radiation had slightly lower yield (83%) compared to the conventional oven-drier process (87%). BCA demonstrated maximum chelating adsorption capacity (Qmax) of 1.2 mmol g−1 for Cu(II) at pH of 5.5 and 1.4 mmol g−1 for Hg(II) at pH 6.0. These results could be comparable with the Qmax of 1.46 mmol g−1 for Cu(II) and 2.4 mmol g−1 for Hg(II) obtained from Duolite GT-73, a commercial chelating resin, macroreticular with tiol (S–H) functional groups.

In situ remediation of groundwater contaminated by heavy- and transition-metal ions by selective ion-exchange methods.

Laboratory studies were conducted to investigate the feasibility of using ion-exchange resins in permeable reactive barriers (PRBs) for the remediation of groundwater contaminated by heavy and transition metals. Ion-exchange resins represent an essentially neglected class of materials which may, in addition to iron, activated carbon, and zeolites, prove effective for use in PRBs. Four resins were considered: two commercially available resins, Duolite GT-73 (Rohm and Haas) and Amberlite IRC-748 (Rohm and Haas), and two solvent-impregnated resins (SIRs). The SIRs were prepared from Amberlite IRA-96 (Rohm and Haas) and two different thiophosphoric extractants. All four resins are able to reduce cadmium, lead, and copper concentrations from 1000 microg/L (typical for contaminated groundwaters) to below 5 microg/L. Significantly, all of the resins are effective for the capture of cadmium, copper, and lead, even in the presence of CaCl2 and clay. Because of their high hydraulic conductivity, the use of these resins in clusters of wells, as an alternative to continuous walls, is considered in the design of effective PRBs. Numerical solution of the groundwater flow equations shows that, depending on the well configuration, most (or all) of the contaminated groundwater can pass through the resins. These results demonstrate the possibility of using selective ion-exchange resins as an effective, active material in PRBs for in situ groundwater remediation.

THE CHARACTERISATION OF SILVER SORPTION BY CHELATING RESINS CONTAINING THIOL AND AMINE GROUPS

We investigated the sorption capacity towards Ag(I) of three different resins bearing a thiol chelating group, Duolite GT-73, Purolite Thiomethyl and Spheron Thiol, as well as Chelamine, a resin with a tetraethylenepentaamine moiety. The metal sorbed by the resins at 0.01 M HNO3 follows the order: Purolite Thiomethyl > Duolite GT-73 > Spheron Thiol. As this result does not correlate with the sulphur content of each resin we studied the physical characteristics of the resins in an attempt to find an explanation for this behaviour. In the case of Chelamine, a nitrogen containing resin, silver sorption increases when pH increases, reaching a value of 1.2 mmol/g at pH around 6. A kinetic study of the three polymers with the same functional group (–SH) was also performed in order to discover more about the sorption mechanism. The differences observed between the three polymers are explained taking into consideration the nature of the polymeric matrix and the resin morphology. Finally, we study the elution process of silver and find that, with each resin, thiourea 0.1 M in HNO3 0.1 M is the most effective elution agent.

Removal of selected metal ions from aqueous solution using modified corncobs

The objective of this study was to convert corncobs to metal ion adsorbents for wastewater treatment. Ground corncobs were modified with either 0.6 M citric acid (CA) or 1.0 M phosphoric acid (PA) to help improve their natural adsorption capacity. The effect of a combination of wash and modification treatment was tested for corncob adsorption efficiency with five different metal ions (cadmium, copper, lead, nickel, zinc) individually or in a mixed solution containing each metal at a 20 mM concentration. Results were compared to those of commercial resins Amberlite IRC-718, Amberlite 200, Duolite GT-73 and carboxymethylcellulose (CMC). Modified corncobs showed the same adsorption efficiency as Duolite GT-73 for cadmium, copper, nickel and zinc ions and had greater adsorption than CMC for nickel and zinc ions. For mixed metals, the modified corncobs exhibited the same adsorption efficiency as Duolite GT-73 for cadmium and copper ions and the same or higher adsorption than Amberlite IRC-718 for lead ions. Adsorption capacities of modified samples were compared to those of Amberlite IRC-718, Amberlite 200 and Duolite GT-73. Commercial resins generally had higher adsorption capacities than modified corncobs. However, the adsorption capacity of modified corncobs for copper and lead ions was equivalent to Duolite GT-73, but was lower than for Amberlite IRC-718 or Amberlite 200. Depending on the specific metal ion and the presence or absence of other metal ions, chemically modified corncobs were at least equivalent in adsorption properties to all of the commercial cation exchange resins examined in this study.

Mercury removal from water by ion exchange resins adsorption

In this paper a detailed experimental and theoretical analysis of the adsorption process of mercury by ion exchange resins is presented. Experiments have been performed to study adsorption efficiency, the effect of pH on the uptake of mercury and the adsorption kinetics. The experimental apparatus was a batch mechanically stirred reactor (volume 1.5 dm 3), under almost isothermal conditions (±0.1°C). The resin used in this study is Duolite GT-73, a chelating resin, macroreticular with thiol (S-H) functional groups. The studied resin has a very high adsorption efficiency, reaching 30–40% in weight and the efficiency decreases, decreasing pH, due to competition between ions H + and Hg 2+. Such a high efficiency confirms previous results and justifies the great interest for the application of ion exchange resins in water treatment plants. As in previous works, measurements of process kinetics show that the adsorption rate decreases as the initial mercury concentration is increased. This fact suggests that intraparticle diffusion rate can be the controlling step for the adsorption process. To verify this, a simplified mathematical model has been identified, accounting for a diffusional resistance inside solid particles and where the equilibrium relationship between Hg concentration in the liquid and in the solid is described by the Freundlich isotherm, neglecting H + competition: this model is very effective in the prediction of the change in the adsorption kinetics with the initial Hg concentration. Hence this preliminary approach can be held as the reference starting point for the adsorption model: further developments will concern the equilibrium thermodynamics (H + competition).

Concentrating Low-Level Tritiated Water through Isotope Exchange

Trapping of tritium on polymers with specific functional groups was investigated as a means of treating waste streams containing low levels of tritium. Chemical exchange of tritium with hydrogen on the functional group was used as the mechanism for trapping. The polymers tested include Aurorez polybenzimidazole resin beads, Chelex 100 resin beads, Duolite GT-73, microcrystalline cellulose, and polyethylenimine. The tests were performed under simulated operating conditions on water obtained from the Radioactive Liquid Waste Treatment Facility at Los Alamos National Laboratory. Tritiated water from the Tritium Systems Test Assembly is discharged to this plant. Polyethylenimine is a water-soluble polymer that was tested using a stirred membrane cell with an ultrafiltration membrane. All of the polymers except polyethylenimine took up tritium from the water. Polybenzimidazole demonstrated the highest tritium uptake. The results are explained on the basis of the type of functional group, hydrogen bonding, and rigidity of the molecular structure of the polymer. The theoretical calculations indicate that significant isotope discrimination requires high-frequency modes with hydrogen bonding contribution and support the experimental findings. Modeling suggested trends that may lead to structures that are more efficient in trapping tritium.

SORPTION OF TRACE HEAVY METALS BY THIOL CONTAINING CHELATING RESINS

ABSTRACT The sorption of copper, cadmium, nickel and zinc ions on thiol (-SH) based chelating polymeric resins (thiomethyl resin and Duolite GT-73) has been investigated. The physical and chemical characterisation of these polymers in the form of scanning electron micrographs (SEM), BET and Langmuir surface area measurements, Fourier transform infra red spectroscopy (FTIR) analysis, X-ray photoelectron spectroscopy (XPS) analysis, atomic composition measurement, sodium capacity determination and zeta potential measurements have been conducted to assess their performance as sorbents for trace toxic metal removal. Density functional theory (DFT) has been used to analyse the pore size distribution data. The adsorption of metal ions from aqueous solution on these sorbents has been studied in batch equilibrium experiments. The influence of pH on metal adsorption capacity has also been examined. The kinetic performance of these polymers has been assessed and the results have been analysed by a pore diffusion model. The resins have been used in mini-columns to study the selectivity towards the desired metal ion. The desorption of metal ions has been studied using hydrochloric acid (1 M and 4 M), sulphuric acid (1 M and 4 M) and acidified thiourea. The present study confirms that these thiol based chelating resins are very effective for selective removal of trace heavy metals from water.

Recovery of palladium(II) and gold(III) from diluted liquors using the resin duolite GT-73

The adsorption of Pd(II) and Au(III) on the Duolite GT-73 has been investigated. The results obtained in chloride media showed a higher adsorption for Au(III) (0.58±0.03 mmol/g resin) than for Pd(II) (0.262±0.015 mmol/g resin); however, the adsorption for Pd(II) is faster. The influence of several variables such as the hydrochloric acid concentration in both metals adsorption and the addition of thiocyanate and dioxan in the study of Pd(II) has also been considered. None of the variables tested result in an improvement of the resin capacity of the metal considered, only a slightly higher adsorption for Pd(II) is observed for a HCl concentration of 0.01 M. The adsorption of Pd(II) has also been carried out in the nitrate medium, in this case the experiments were limited by the low solubility of Pd(II) in this medium (HNO 3=1.0 M). The metal adsorption found was 0.35 mmol/g resin. Acidified thiourea or sodium thiocyanate solutions as well as a hydrochloric acid solution were used for the elution of the metals, the concentrated thiourea at high acidity being the most effective one for Pd(II) as well as for Au(III). In general, the greater both the concentration of thiourea and the acidity of the solution, the easier the elution of the two metals. On the other hand, Cu(II) was readily eluted by hydrochloric acid, in contrast elutions of Au(III) and Pd(II) are less easy. Separation of Pd(II) and Au(III) from Ni(II) and Cu(II) aqueous solutions by using Duolite GT-73 is discussed. Separation of metal mixtures was carried out at different pH to improve the selective adsorption.

Photometric method for the determination of Pb2+ followingseparation and preconcentration using a templated ion-exchange resin

A novel Pb2+ ion-exchange resin based on a Pb2+ ion templated polymer was used for removal and preconcentration of Pb2+ from tap and sea-water. The results from the templated resin were compared with results obtained using three other ion-exchange resins: Chelex-100, thiol-based Duolite GT-73 and a proprietary NASA polyacrylic acid resin. The ion templated resin, being most selective toward Pb2+ ions, provides a fast and virtually interference-free preconcentration procedure. The templated resin also offers an opportunity for a field-ready test kit for the determination of Pb2+ in environmental samples based on colorimetric analysis.