Separation and determination of traces of heavy metals complexed with humic substances in river waters by sorption on indium-treated amberlite xad-2 resin

A nonionic macroreticular styrene/divnylbenzene copolymer, Amberlite XAD-2 resin is pulverized to 1–10 μm and treated with indium ions to saturate traced of cation exchange sites for the quantitative separation of humic complexes from cations. A 100-ml filtered sample is passed through an indium-treated XAD-2 column (16 diameter, 5 mm tall) at pH 5 at a flow rate of 2 ml min^? to sorb heavy metals complexed with humic and fulvic acids. Inorganic cations and anions, EDTA complexes and colloidal hydrated iron(III) oxide are not retained on the column at all. The heavy metals sorbed on the column are then ultrasonically desorbed with 0.5 M nitric acid and determined by graphite-furnace atomic absorption spectrometry. The results fo two river water samples obtained are in good agreement with those obtained when the macroreticular weak-base anion-exchanger DEAE-Sephadex A-25 is used.     

Determination of traces of heavy metals in positively charged inorganic colloids in fresh waters

Summary Determination of Traces of Heavy Metals in Positively Charged Inorganic Colloids in Fresh Waters After removal of suspended particulate matter by centrifugation followed by filtration through 0.4-m membrane filters, humic substances and other negatively charged species are sorbed on a small column of macroreticular weak-base anion exchanger DEAE-Sephadex A-25 at fast flow rates. Positively charged inorganic colloids pass through the column and are collected on a 0.015-m membrane filter, which is then ultrasonically treated with 1M nitric acid for the determination of copper, lead and cadmium by differential pulse anodic stripping voltammetry with a static mercury drop electrode. Up to O.2g 1^–1 of the heavy metals are found in positively charged inorganic colloids in river, pond and tap waters.     

Evaluation of humic complexes of trace metals in river water by adsorption on indium-treated XAD-2 resin and DEAE-Sephadex A-25 anion exchanger

A combined adsorption procedure for the analytical fractionation of humic/metal complexes in river water is described. It is based on an indium-loaded XAD-2 resin and a DEAE-Sephadex A-25 anion exchanger, respectively. After the separation of suspended particles, an aliquot of the water sample to be analysed is passed through an indium-loaded XAD-2 resin column to collect the metal-humic complexes. A second aliquot is directly passed through a DEAE-Sephadex A-25 anion exchanger column to collect humic complexes and other negatively charged metal species. Both column effluents are analysed by inductively coupled plasma-mass spectrometry or by graphite-furnace atomic absorption spectrometry for various trace metals (e.g., Al, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba). According to this fractionation procedure, significant amounts of iron, aluminium and copper in river water are found to be humic complexes, and less than 15% of nickel, cobalt and zinc are complexed with humic substances. Manganese, strontium and barium are hardly associated with humic substances.     

Multi-element preconcentration of heavy metal ions from aqueous solution by APDC impregnated activated carbon

Ammonium pyrrolidinedithiocarbamate impregnated activated carbon (APDC-AC) has been used for the preconcentration of Cd(II), Cu(II), Ni(II), and Zn(II) from aqueous solution by column solid phase extraction (SPE) technique. Trace metal ions in aqueous solution were quantitatively sorbed onto APDC-AC packed in a SPE column at pH 5.0 with a flow rate of 1.0 mL min⁻¹. The sorbed metals were eluted with 1 M nitric acid in acetone solution at a flow rate of 0.6 mL min⁻¹ and analyzed by flame atomic absorption spectrometry. The effects of sample volume, amount of APDC-AC, volume of eluent and ionic strength of working solution on metal ion recovery have been investigated. The present methodology gave recoveries from 90 to 106% and R.S.D. from 0.6 to 5.5%.     

Improved separation of cadmium-109 from silver cyclotron targets by anion-exchange chromatography in nitric acid—hydrobromic acid mixtures

A method is presented for improved separation of ¹⁰⁹Cd from silver cyclotron targets. After dissolution of the target material in nitric acid and removal of silver by precipitation with copper metal, at pH 5, the cadmium is separated from zinc, copper and other elements by anion exchange chromatography. The solution in 0.5 M nitric acid plus 0.1 M hydrobromic acid is percolated through a column containing 4 ml of AG1-X8 anion-exchange resin (100–200 mesh), equilibrated with the same acid mixture. Zinc, copper(II) and other elements are eluted with 50 ml of this mixture. Cadmium is retained and finally eluted with 50 ml of 3 M nitric acid. The cadmium is retained much more strongly from the hydrobromic acid mixture than from the 0.02 M hydrochloric acid used for such separations previously; the presence of the strongly absorbed nitrate anion in fairly high concentration completely eliminates the tailing of zinc observed in 0.02 M hydrochloric acid. A typical elution curve and results of quantitative separations are presented.     

Aqueous size-exclusion chromatography of humic acids on a sephadex gel column with diluted phosphate buffers as eluents

The elution behavior of humic acids on a Sephadex gel column is senstive to the composition, concentration, and pH of the eluent. the concentrations of the eluent in the literature are too high to obtain the correct molecular size distribution of humic acids. By reducing the concentration of phosphate buffer eluents to about a hundredth of conventional concentrations, the correct distribution is obtained. In the proposed method, 1 ml of 0.1% sample solution is introduced into a Sephadex G-50 column (2.2-cm diameter, 55 cm long) and humic acids are eluted with a 10^?3 M phosphate buffer solution (pH 7–9) at a flow rate of 1 ml min^?1.     

Preconcentration of cobalt with N-(dithiocarboxy)sarcosine and amberlite xad-4 resin

Cobalt reacts with N-(dithiocarboxy)sarcosine (DTCS) to form a 1:3 Co:DTCS complex which is so stable that after its formation no decomposition occurs even in 4M hydrochloric acid. The complex is sorbed on a column of Amberlite XAD-4 copolymer from an acidic solution and eluted with 10 ml of a 1:1:3 v v mixture of 1.0M ammonia solution (pH = 9), 0.1M EDTA and methanol. The absorbance of the eluted chelate is measured at 320 nm against water ( = 2.15 x 10(4) l.mole(-1).cm(-1)). The recovery of cobalt from 1 litre of tap-water or sea-water is quantitative. The effect of diverse ions can be eliminated by the addition of EDTA after chelation of the cobalt. The copper complex with DTCS is partly sorbed on the column because of its slow rate of decomposition by EDTA, but most of the copper chelate sorbed can be eluted with hydrochloric acid and any co-eluted with the cobalt chelate can be completely decomposed by heating the eluate. Cobalt enrichment factors of at least 100 are obtained, so the method is applicable to the determination of cobalt at the ng ml level.     

Kinetics of radioeuropium sorption on Gorleben sand from aqueous solutions and ground water

Kinetics of Eu sorption on sandy sediment from Gorleben, Germany, containing humic substances, was studied by radiotracer method in batch experiments at very low europium concentration (3.4^.10^-8 mol/l), with the aim to find kinetic parameters suitable for modeling Eu migration in bed of the sediment and to elucidate the mechanism of the sorption. Experiments were evaluated using a new simplified method taking into account simultaneous sorption/desorption of Eu on the walls of sorption vessel. Five kinetic functions were tested, of which that describing diffusion in inert surface layer of sorbent proved most suitable. The effects of pH (3.0-8.8) by addition of Aldrich humic acid (10 mg/l), addition of hydrogencarbonates (5^.10^-3 mol/l) and preequilibration of the sediment with solution or of Eu with solution were examined. From the results it has been concluded that the kinetics and mechanism of the sorption strongly depend on pH. At pH 4.8 Eu is sorbed mainly as humate complex from the solution of humic acid. The addition of humic acid accelerates the sorption. Carbonate complexes of Eu are the probable forms sorbed at pH 8.8. The presence of humic substances in the slightly alkaline solutions suppresses the rate of the sorption due to slow dissociation of Eu-humate complexes.     

Chromatographic separation and colorimetric determination of gold

Gold(III) is selectively sorbed from 1M hydrochloric acid by a short column containing a special acrylate resin. Then the gold is eluted from the column with acetone-hydrochloric acid, and the absorbance of the effluent is measured at 340 nm. Gold(III) may be successfully separated and determined in samples containing many other metal ions.     

Use of alcoholic solutions for the isolation and purification of americium and curium with anion-exchangers

The sorption of transplutonium (TPE), rare-earth (RE) and other elements by anion-exchangers (Dowex 1 type) from aqueous alcoholic solutions of nitric acid and ammonium thiocyanate was investigated. This investigation allowed the development of simple and effective methods of americium—curium separation from frradiated plutonium. Plutonium, TPE (in a +3 oxidation state) and RE are firmly sorbed by the anion-exchanger from 1 M HNO₃ in 90% alcohol, Fe, Al and fission products Cs, Sr, Nb, Zr, and Ru pass through the column under these conditions. The RE separation from TPE is achieved by washing the column with 0.5M NH₄SCN in 80% alcohol. The column is then washed with 0.5 M HNO₃ in 85% alcohol, and americium—curium separation proceeds. Use of this method for recovery of an irradiated plutonium target containing 100 mg Pu, Am and Cm is described.     

Recovery of plutonium from phosphate containing aqueous analytical waste solutions using macroporous anion exchange resin

Distribution ratios of Pu(IV) between 7.5M HNO₃+0.75M H₃PO₄+0.3M H₂SO₄ media and a macroporous anion-exchange resin Amberlyst A-26 (MP) increased from 40 to 250 when 1M aluminium nitrate was added to the aqueous medium. When 1M ferric nitrate was used in place of aluminium nitrate the distribution ratio further increased to 850. The 10% Pu(IV) breakthrough capacities with a 5 ml bed resin column, using synthetic feed solutions containing 1M aluminium nitrate, were 1.4 g l^–1, 3.2 g l^–1 at flow rates of 30 ml per hour and 10 ml per hour, respectively. The corresponding 10% Pu(IV) breakthrough capacities in the presence of 1M ferric nitrate were 8.5 g l^–1 and 12.8 g l^–1. More than 97% of plutonium could be recovered from actual analytical phosphate waste solutions.     

Sorption and desorption of Eu(III) on alumina

Summary Effects of ionic strength and of fulvic acid on the sorption of Eu(III) on alumina were investigated by using a batch technique. The experiments were carried out at T=25±1 °C, pH 4-6 and in the presence of 1M NaCl. The results indicate that sorption isotherms of Eu(III) are linear at low pH values. The sorption-desorption of Eu(III) on alumina at pH 4.4 is reversible, but a sorption-desorption hysteresis is found at pH 5.0. Fulvic acid has an obvious positive effect on the sorption of Eu(III) on alumina at low pH values. The migration of Eu(III) in alumina was studied by using column experiments and ^152+154Eu(III) radiotracer at pH 3.8. For column experiments, Eu(III) sorbed on alumina can be desorbed completely from the solid surface at low pH values. The findings are relevant to the evaluation of lanthanide and actinide ions in the environment.     

Determination of trace metals accumulated and internalized by marine phytoplankton; interferences with colloidal organic matter

In the present work, we study the effects that aggregation of humic acids in seawater, and its adsorption to surfaces, can have on the determination of Cu and Pb accumulation by phytoplankton within the context of metal bioavailability studies, using the diatom Thalassiosira weissflogii. Two methods commonly used for collection of algae to analyse metal content, filtration and centrifugation, were compared, and a procedure to differentiate the metal internalized by the alga from that adsorbed to cell walls-washing with 0.01?M ethylenediaminetetraacetic acid (EDTA)- was optimized for its use in seawater and in the presence of humic acids. The present results highlight the possibility of obtaining biased results if filtration is used to isolate the algae, and show that centrifugation is a more suitable procedure minimizing contribution of particulate and colloidal forms of metals to the measured cellular and intracellular metal contents. Thus a combination of centrifugation to isolate the algae from the medium with a 10 minutes washing with a washing agent composed of EDTA 0.01?M at pH 8 and NaCl and KCl to 0.5?M ionic strength is recommended to extract metals adsorbed to the surfaces of marine phytoplankton for a seawater containing humic substances. The importance of discriminating between internalized metal and total cellular metal in bioavailability studies is noted, given the different effects of humic substances on metal accumulation in the different cellular pools.     

Removal of humic acid and surfactant interferences in trace metal determinations by differential-pulse anodic stripping voltammetry with use of adsorption and chelate ion-exchanger columns in a flow-injection system

A flow-injection differential-pulse anodic stripping voltammetry (d.p.a.s.v.) method is modified so that interferences from humic acids or surfactants are eliminated. The injected, slightly acidic sample is passed through a silica anion-exchanger column to remove compoundswith a strong tendency to adsorb to the electrode. The sample then passes to a chelate ion-exchange column containing immobilized 8-quinolinol. The metal ions are retained and later eluted with acid into the voltammetric cell. The results show that the interferences from up to 500 mg 1^–1 humic acid or at least 50 mg 1^-1 Triton X-100 can be removed and that the metal ion can be determined in a range similar to that for normal d.p.a.s.v. methods. The complete cycle time for a determination was 12 min.     

Studies on the recovery of Pu(IV) from hydrochloric acid-oxalic acid solutions using an anion exchange method

Sorption of Pu(IV) from hydrochloric acid-oxalic acid solutions has been investigated using different anion exchangers, viz., Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) for the recovery of plutonium from plutonium oxalate solutions. Distribution ratios of Pu(IV) for its sorption on these anion exchangers have been determined. The sorption of Pu(IV) from hydrochloric acid solutions decreases drastically in the presence of oxalic acid. However, addition of aluminium chloride enhances the sorption of plutonium in the presence of oxalic acid, indicating the feasibility of recovery of plutonium. Pu(IV) breakthrough capacities have been determined with a 10 ml resin bed of each of these anion exchangers at a flow rate of 60 ml per hour using a solution of Pu(IV) with the composition: 6M HCl+0.05M HNO₃+0.1M H₂C₂O₄+0.5M AlCl₃+100 mg.l^–1 Pu(IV). The 10% Pu(IV) breakthrough capacities for Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) are 15.0, 8.9 and 6.2 g of Pu(IV) l^–1 of resin respectively.     

Separation of95Zr and95Nb from each other and from other fission products by adsorption and desorption on silica gel using hydrochloric acid solutions

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of⁹⁵Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the⁹⁵Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—⁹⁵Zr free from other products—⁹⁵Nb free from other products, respectively.     

Pre-concentration efficiency of chelex-100 resin for heavy metals in seawater : Part 2. Distribution of Heavy Metals on a Chelex-100 Column and Optimization of the Column Efficiency by a Plate Simulation Method

Seawater was spiked with heavy metals and passed through a Chelex-100 column string consisting of ten minicolumns. The recoveries of metals from each minicolumn are used to study their distribution on a column. A simplified model was constructed to simulate the chelating efficiency of columns of various sizes, at various pH and flow rates. It is shown that a column containing 2 g of resin in the magnesium form with a flow rate of 4 ml min^?1 is suitable for pre-concentration of Cd, Cu, Co, Mn, Ni, Pb, and Zn in seawater after adjustment to pH 6.5.     

A Multicolumn Ion Chromatographic Determination of Nitrate and Sulfate in Waters Containing Humic Substances

Abstract

A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L^?1 of nitrate or sulfate in water containing 45mgL^?1 of humic acid.     

Anion-exchange separation and spectrophotometric determination of vanadium in silicate rocks

A combined anion-exchange-spectrophotometric method has been developed for the determination of vanadium in silicate rocks. A rock sample weighing about 0.1 g is decomposed with a mixture of sulphuric and hydrofluoric acids and after removal of HF the residue is taken up with dilute sulphuric acid. This solution is adjusted to be 0.05M in sulphuric acid and contain 0.3% hydrogen peroxide, and is passed through a column of Amberlite CG 400 (sulphate form). The sorbed vanadium is eluted with 30 ml of 1M hydrochloric acid. The effluent is evaporated to dryness, made 0.1M in hydrochloric acid and 3% in hydrogen peroxide content, and passed through a column of Amberlite CG 400 (chloride form) to get rid of accompanying thorium and zirconium. Vanadium is stripped by elution with 20 ml of 1M hydrochloric acid and subsequently determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. The detection limit is 0.4 ppm.     

The determination of copper in sea water by atomic absorption spectrometry with a graphite atomizer after elution from chitosan

Copper in sea water was determined by passing 1 1 of persulphate-pretreated sea water through a 30×3 mm chitosan column, and eluting with 20 ml of a 1% solution of 1,10-phenanthroline, or with 20 ml of 1 M sulphuric acid. Copper was determined in the eluates by hot graphite atomic absorption spectrometry. The result for Adriatic sea water (Ancona, Italy) was 6.06±0.56 μg Cu 1^?1. Diethylaminoethylcellulose, p-aminobenzylcellulose and Dowex A-1OO were also tested; Dowex A-100 collects only a minor part of the copper present in sea water.