Diethyldithiocarbamate (DDTC) extraction of copper(II) and iron(III) associated with humic substances in water

Summary The extraction behaviour of copper(II) and iron(III) was studied in the presence of humic substances (humic and fulvic acids) by using DDTC and chloroform. Copper-humic complexes were nearly completely extracted over the pH range 3–9, indicating that DDTC reacted with copper more strongly than humic substances. Iron-humic substances, mainly existing as hydrated iron(III) oxide covered with humic substances, were not extracted quantitatively (recovery <70%), though hydrated iron(III) oxide itself was extracted with greater than 93% yields at pH 5–9. For complete extraction of the humic species, ammonium pyrrolidinedithiocarbamate (APDC) was useful, because it allowed extraction from slightly acidic solutions where the binding of iron-humic substances became weak.     

Adsorption of Cu(II), Zn(II), Ni(II), Pb(II), and Cd(II) from aqueous solution on Amberlite IR-120 synthetic resin

The adsorption of copper(II), zinc(II), nickel(II), lead(II), and cadmium(II) on Amberlite IR-120 synthetic sulfonated resin has been studied at different pH and temperatures by batch process. The effects of parameters such as amount of resin, resin contact time, pH, and temperature on the ion exchange separation have been investigated. For the determination of the adsorption behavior of the resin, the adsorption isotherms of metal ions have also been studied. The concentrations of metal ions have been measured by batch techniques and with AAS analysis. Adsorption analysis results obtained at various concentrations showed that the adsorption pattern on the resin followed Freundlich isotherms. Here we report the method that is applied for the sorption/separation of some toxic metals from their solutions.     

Investigation of Copper(II) Interference on the Anodic Stripping Voltammetry of Lead(II) and Cadmium(II) at Bismuth Film Electrode

The bismuth‐coated electrode is known to be prone to errors caused by copper(II). This study investigates copper(II) interference at bismuth film electrode for the detection of lead(II) and cadmium(II). It was conducted using glassy carbon electrode, while the bismuth film was plated in situ simultaneously with the target metal ions at ? 1200 mV. Copper(II) presented in solution significantly reduced the sensitivity of the electrode, for example there was an approximately 70 % and 90 % decrease in peak signals for lead(II) and cadmium(II), respectively, at a 10‐fold molar excess of copper(II). The decrease in sensitivity was ascribed to the competition between copper and bismuth or the metal ions for surface active sites. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) analysis suggested a large decrease in the amount of bismuth nanoparticles formed on the electrode surface in the presence of copper(II) occurred, validating the competition between copper and bismuth ions for surface active sites. Recovery of the stripping signal of lead(II) and cadmium(II) was obtained by adding ferrocyanide ion to the solution. Finally, the proposed method was successfully applied to determine lead(II) and cadmium(II) in water samples and the method was validated by ICP‐MS technique.     

Cu(II) retention on a humic substance

Humic substances (HS) are macromolecular products derived from a physical, chemical, and microbiological process called "humification." These substances play an important role in the mobility and bioavailability of nutrients and contaminants in the environment. Adsorption isotherms provide a macroscopic view of the retention phenomena. However, complementary techniques are needed in order to study the retention mechanism. The application of the classical models and some modern ones, based on humic substances chemistry, do not accurately describe these adsorption data. The aim of this paper is to model isotherms and combine adsorption data with spectroscopy and microscopy techniques to study the Cu(II) retention on a HS. The adsorption isotherms shape varies significantly with the solution pH from L-type (pH 2-6) to S-type (pH 8). FTIR shows that, when pH is 2 the retention of Cu(II), as [Cu(H(2)O)(6)](2+), is the preferred retention mechanism. The quantity of Cu(II) retained as [Cu(OH)(H(2)O)(6)](+) rises, as pH increases. At pH 4, Cu(II) begins to precipitate, which is the preferred mechanism at pH 8.02. The presence of HS has a great influence on the precipitation process of Cu(II), giving rise to amorphous precipitates. As it is shown by SEM-XRF, Cu(II) distributes heterogeneously on HS surface and accumulates on the humic phases. The presence of different anions (chloride and nitrate) slightly modifies the HS behavior as cation exchanger. When Cl(-) ions are present, part of the Cu(II) form [CuCl(4)](2-), which is stable in solution due to its negative charge; when the anion present is NO(3)(-) the formed complex, [CuNO(3)](+), is retained on the HS.     

Copper (II), Lead (II) and Cadmium (II) Complexes with the Antiinflammatory Drugs Piroxicam and Tenoxicam

Abstract

The chelating tendency of the antiinflammatory drugs piroxicam and tenoxicam towards copper (II), lead (II) and cadmium (II) ions has been investigated using both differential pulse polarography and cyclic voltammetry and the stability constants of the formed complexes have been compared. The effect of the nature of the supporting electrolyte, the pH and other parameters have also been considered.

Tenoxicam exhibits relatively stronger chelating properties than piroxicam towards each ion despite of their structural similarity.     

Anilinepropylsilica xerogel used as a selective Cu (II) adsorbent in aqueous solution

The metal ion adsorption properties of the microporous hybrid anilinepropylsilica xerogel were studied using divalent copper, zinc, and cadmium ions in aqueous solutions in concentrations ranging from 10(-4) up to 5x10(-3) moll(-1). At low concentrations the surface of the solid phase presents selectivity for Cu (II), even in competitive conditions. This preferential sorption ability for copper in relation to zinc and cadmium ions was interpreted by considering the xerogel morphology.     

Evaluation of copper(II)-binding ability of humic acids in peat using sulphopropyl-Sephadex C-25 cation exchanger

A method for the determination of copper(II) complexes with humic acids was developed by batch operation with the cation exchanger sulphopropyl-Sephadex C-25 (C-25). The copper-binding ability (conditional stability constants and copper-complexing capacities) of humic acids which were extracted from peat in Hokkaido was evaluated. A solution containing copper(II) ions and humic acids was shaken with the C-25 exchanger. The copper-humic acid complexes remained in the supernatant and the uncomplexed free copper ion was retained on the C-25. The copper-humic acid complexes were determined by flame atomic absorption spectrometry. The copper-binding ability of nitrilotriacetic acid (NTA) as a model ligand was similarly determined with a Scatchard plot. The conditional stability constant obtained at pH 4.5 was in good agreement with the reported value. The copper-binding abilities of the humic acids from peat were estimated using a Scatchard plot adopting a two-site model. The functional groups in the humic acids which contribute to the complexation with copper were investigated by conductimetric and pH titration, and the relationship between the copper-binding sites and functional groups in the humic acids was investigated.     

Extraction of Copper(II) and Zinc(II) from Chloride Media with Mixed Extractants

Extraction of copper(II) and zinc(II) from acidic chloride solutions with mixtures of two extractants: a basic or solvating one and a chelating extractant was discussed. Processes for recovery and separation of Cu(II) from Zn(II) were proposed, which consist of the following steps: extraction from chloride media with the formation of metal chlorocomplex ion pair or solvate, scrubbing of chloride ions with an aqueous solution of appropriate pH with simultaneous transfer of the metal ion to the chelate, traditional stripping with sulphuric acid and conditioning of the basic extractant. Both effective recovery and separation of metal ions with simultaneous change of the system from the chloride to the sulphate state can be achieved. A bifunctional reagent, such as alkyl derivative of 8-hydroxyquinoline, can be also used instead of the extractant mixture.     

A new procedure for the speciation of mercury in water based on the transformation of mercury (II) and methylmercury (II) into stable acetylides followed by HPLC analysis

Conversion of mercury(II) and methylmercury(II) species dissolved in water into di(phenylethynyl)mercury and methyl(phenylethynyl) mercury takes place in satisfactory yield under alkaline conditions by stirring the aqueous solution with phenylacetylene at room temperature. Mercury speciation is simply obtained by HPLC analysis of the two organometallic species. The presence of heavy metals such as copper(II), zinc(II), cadmium(II) and lead(II) in concentrations 10000 times higher than mercury is tolerated, while little interference is displayed by humic acids and cysteine. Seawater samples can also be analysed following a properly adapted procedure.     

Comparative study of copper(II) and cadmium(II) salts as catalytic reagents in the determination of mercury by continuous-microflow cold vapour atomic absorption spectrometry

A continuous-microflow method with cold vapour atomic absorption spectrometric detection was used for the determination of mercury. A comparison of copper(II) and cadmium(II) salts as catalytic reagents is described in detail It was found that in the presence of at least 80 mg 1^?1 of copper(II) salt a similar signal was obtained for both inorganic mercury [mercury(II) chloride]and organic mercury [methylmercury(II) chloride]. With a cadmium(II) salt at least 100 mg 1^?1 were required.     

Analytical Separation of Copper(II), Cobalt(II) and Nickel(II) Using Polymer Bound Anthrantic Acid

Abstract

The preferential complexing tendency of different nietal ions towards chelating agents anchored on a polymer has been used for separation of transition metals. the anthranilic acid group was anchored on the polymeric cellulose back-bone by successive coupling with trifunctional reagent cyanuric chloride, in diozane medium, at pH 7 and 9–10, respectively. This polymer bound chelating agent was used to separate copper(II), nickel(II) and cobalt(II) in the concentration range 1.0–0.1 mmol/L. the separation of a mixture of two components was quantitative using column chromatography.     

Preconcentration of Trace Cadmium (II) and Copper (II) in Environmental Water Using a Column Packed with Modified Silica Gel-Chitosan Prior to Flame Atomic Absorption Spectrometry Determination

A new column loaded with modified silica gel-chitosan is proposed as a preconcentration system for adsorption of trace cadmium (II) and copper (II). The optimization steps were performed under dynamic conditions, involving pH, sample flow rate, eluent selection, concentration, volume, and flow rate. Trace Cd(II) and Cu(II) were quantitatively adsorbed by the modified silica gel-chitosan. The metal ions adsorbed on the separation column were eluted with 0.1 M HNO₃ and determined by flame atomic absorption spectrometry. Under the optimum conditions, this method allowed the determination of cadmium and copper with limits of detection (LOD) of 20 ng L^?1 and 38 ng L^?1, respectively. The relative standard deviation values (RSDs) for 1.0 mg L^?1 of cadmium and 1.0 mg L^?1 of copper were 2.62% and 2.85%, respectively.     

Trace metal analysis by anodic-stripping voltammetry Effect of surface-active substances

The presence of cationic, anionic, and neutral surfactants and humic substances is shown to affect the peak heights of copper, lead and cadmium in synthetic sea-water analysed by differential pulse anodic-stripping voltammetry. At surfactant concentrations below 0.1 mg/l. the effect is insignificant, but at higher concentrations the peak heights usually decrease, although for copper an increase in the peak height was also observed. The peak heights do not depend to any great extent on the pH of the solution, except in alkaline solution and in the presence of humic substances. Adsorption and complex formation may account for the observed dependences.     

Comparative study of copper(II) interactions with monomeric ligands and synthetic or natural organic materials from potentiometric data

Potentiometric measurements were used to characterize the complexing properties of (a) a mixture of five monomeric ligands, (b) a synthetic humic-like substance and (c) fulvic acids extracted from soils, with copper (II). In order to compare the binding strengths involved, the same mathematical treatments of the data were used for all measurements. Calculations of the total ligand concentration with the Gran function give underestimated values for the multiligand mixture because of the known presence in the mixture of functional groups with pK^H ; 11 which > cannot be titrated and are revealed only by complexation phenomena. The acid-base properties of the humic substances are better described with a continuous model than with the descrete Henderson-Hasselbach model, because of the inability to distinguish properly between equivalent and independent types of functional groups. In the presence of copper (II), the formation functions show that a mixture of different kinds of complexes with different stability constants is probably formed. Extra protons released during the titration of the various copper (II) systems with alkali are attributed to untitrated functional groups with extremely low protonation constants in the case of the multiligand mixture, but ambiguity remains with the humic substances because their chemical structure is not known. Comparison of binding strengths can be made in terms of global conditional stability constants, by taking into account the three parameters, pH, concentrations of metal and of ligand. It is shown that the mechanisms of complexation are different for monomers and for polymers.     

Flame Atomic Absorption Spectrometric Determination of Cu(II), Co(II), Cd(II), Fe(III) and Mn(II) in Ammonium Salts and Industrial Fertilizers after PrEconcentration/Separation on Diaion HP-20

A sensitive and simple separation-enrichment technique for the determination of trace amounts of Cu(II), Co(II), Cd(II), Fe(III) and Mn(II) was described. Metal ions were complexed with 1-nitroso-2-naphthol at pH 9. Following solid-phase extraction on Diaion HP-20 resin, metals were determined by flame atomic absorption spectrometry. The effect of the matrix ions were investigated. The recoveries of metal ions were greater than 95%. The detection limits of the analyte ions ( k = 3, N = 21) were varying 0.18 µg/l for Cd(II) to 0.44 µg/l for Fe(III). The method was applied to a stream sediment standard reference material (GBW7309), some ammonium salts and industrial fertilizer samples for the determination of copper, cobalt, cadmium, iron and manganese. The relative standard deviations (RSD) of the determinations for analyte ions at µg/g levels varied from 1 to 10%.     

The ELECTRICAL INTERFACIAL LAYER at theTiO2 (ANATASE)/ELECTROLYTE INTERFACE - ADSORPTION of Zn(II) and Cd(II) IONS

Mechanism of adsorption of Zn(II) and Cd(II) ions at the TiO₂ (anatase)/electrolyte interface has been studied by different experimental techniques (potentiometric titration, microelectrophoresis and adsorption measurements of zinc and cadmium species). It was found that the point of zero charge (pzc) of anatase (pH =5.8) was shifted to the lower pH values with increasing concentrations of Zn(II) or Cd(Il) ions. The surface charge of anatase in the presence of Zn(II) and Cd(II) for pH > pH_pzc was higher than that observed for original sample in NaClO₄ solutions only. Due to low coverage of anatase surface with Zn(II) or Cd(II) species almost no shift of the isoelectric point (iep) or charge reversal were observed. Adsorption density vs. pH plots for both Zn(Il) or Cd(II) showed, typical for multivalent ions, presence of “adsorption edge.”     

On the behaviour of cysteine as ligand of cadmium(II)

The ability of cysteine to form complexes with cadmium(II) in aqueous solutions has been investigated at 25 degrees C and in constant ionic medium NaCl at two different concentrations, 1.00 and 3.00 mol l(-1). The presence of chloride ions was necessary to avoid the precipitation of cadmium(II). Two kinds of measurements were carried out. The electromotive force of galvanic cells containing glass and cadmium amalgam electrodes was measured as a function of cadmium and hydrogen ion concentrations in acid or moderately alkaline solutions in order to obtain the free concentration of cadmium(II) and hydrogen ions. The experimental data obtained in 1.00 mol l(-1) NaCl were explained by assuming the presence of CdHL and CdH(2)L(2), while those obtained in 3.00 mol l(-1) NaCl were accounted for with the formation of CdHL, CdH(2)L(2), CdH(3)L(3) and CdH(2)L(3). Moreover, polarographic measurements were carried out under the same experimental conditions but in alkaline solutions, and the formation of CdL(2) and CdL(3) was assumed from the shift of E(1/2) of cadmium(II) with an excess of cysteine. The stability constants of the assumed species were determined. Protonation constants of cysteine in 1.00 and 3.00 mol l(-1) NaCl have been also determined. A comparison with the behaviour of serine and alpha-aminopropanoate towards cadmium(II) is proposed.     

Adsorption of copper(II), cadmium(II), nickel(II) and lead(II) from aqueous solution using biosorbents

Three types of agricultural waste, citrus maxima peel (CM), passion fruit shell (PF) and sugarcane bagasse (SB), were used to produce biosorbents for removing the heavy metal ions of copper(II), cadmium(II), nickel(II) and lead(II) from a pH 5.0 solution. The properties of biosorbents were characterized using scanning electron microscopy (SEM), zeta potential analyzer, Fourier transform infrared (FTIR) spectroscopy, elemental analyzer and tests of cation exchange capacity (CEC). The result indicated that the selected biosorbents possess rich carboxyl (COOH) and hydroxyl (OH) groups to produce a complexation with the heavy metals. Moreover, the negative surface charge of the biosorbent might adsorb the metal ions through the ion exchange. All of the adsorption isotherms indicated that L-type characters represented complexation and ion exchanges that were the adsorption mechanisms of biosorbents toward heavy metals. Biosorbents with higher oxygen content might generate high adsorption capacities. The adsorption capacities of CM and PF, estimated from the fitting to the Langmuir isotherm, are similar to those reported by others regarding biosorbents.     

Adsorption of Copper (II) Ions onto Surfactant-Modified Oil Palm Leaf Powder

Il palm leaf powder (OPLP), an agricultural solid waste was used as adsorbent for the removal of copper (II) ions after modification with an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), CH₃(CH₂)₁₁C₆H₄SO₃Na. The copper (II) ions adsorption is highly dependent on pH and maximum removal was observed at pH 6, above which copper (II) started to precipitate. The equilibrium adsorption data were fitted into the Langmuir and Freundlich isotherms. The Freundlich isotherm model fitted well to data with 0.989 regression coefficient (R²). The kinetics of the adsorption of copper (II) ions onto the surfactant-modified OPLP was best described by a pseudo-second-order model. Comparison of this SDBS-modified-OPLP to previously investigated adsorbents showed comparably good result, offering this material as a promising adsorbent for the treatment of waste waters containing lower concentrations of copper (II) ions.     

Extractive photometric simultaneous determination of iron(II) and copper(II) with syn-phenyl-alpha-pyridyl ketoxime and analysis of ferrites

A rapid method of simultaneous spectrophotometric determination of up to 4 ppm of iron(II) and 20 ppm of copper(II) in a mixture by chloroform extraction of the syn-phenyl-alpha-pyridyl ketoxime complexes at pH 10.0, is developed. Measurements are made at 550 and 475 nm. Two simultaneous equations are solved to obtain the concentrations of the two ions. Analysis of five synthetic mixtures in triplicate gave relative standard deviations of 0.7% for Fe(II) and 1.1% for Cu(II).