Synthesis, characterisation and evaluation of polydithiocarbamate resin supported on macroreticular styrene-divinylbenzene copolymer for the removal of trace and heavy metal ions

A new chelating resin was synthesised by the modification of styrene-divinylbenzene (2%) copolymer and incorporation of dithiocarbamate groups. The polydithiocarbamate resin was characterised by elemental analysis, thermal studies and IR studies. The analytical characteristics of the sorbent were established and optimum sorption conditions for Cu, Ni, Pb, Fe, As and Mn determined. The total sorption capacity of the resin was 37 mg g⁻¹ for Ni(II), 35 mg g⁻¹ for Cu(II), 29 mg g⁻¹ for Fe(III) and 23 mg g⁻¹ for Pb(II). The optimum pH for the removal of metal ions was 3-5 for Ni(II), 5 for Cu(II), 4 for Fe(III) and 4-5 for Pb(II). High sorption capacity was observed when compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time t_1/2 values, indicating a better accessibility of the chelating sites.     

Extraction of metal ions by N-phenyl-, N-methyl-, and N-unsubstituted hydroxamic acid resins

Procedures are described for preparing macroreticular chelating resins with hydroxamic acid or N-methylhydroxamic acid functional groups. The chelating properties of the resins are compared with each other and with an N-phenylhydroxamic acid resin reported earlier. The extraction of 19 metal ions was studied as a function of pH for the N-methylhydroxamic acid resin. Several analytical applications of this resin have been demonstrated including the purification of chemical reagents, concentration of trace metal ions, and chromatographic separation of metal-ion mixtures.     

Study on the reactions of fluoroalkanesulfonyl azides with pyrazine and its derivatives

The thermal reactions of fluoroalkanesulfonyl azides R_fSO₂N₃ with pyrazine and its derivatives are studied in detail. All the reactions involved the fluoroalkanesulfonyl nitrene intermediates R_fSO₃N: which was captured by pyrazine to give the pyrazinium N-fluoroalkanesulfonyl ylides C₄NH₄N⁺-⁻NSO₂R_f and hydrogen abstraction product R_fSO₂NH₂, but no corresponding N-pyrazinyl fluoroalkanesulfonyl amide derivatives R_fSO₂NHC₄N₂H₃ were isolated. Excess azides did not afford the bisN-ylide product R_fSO₂N⁻-⁺NC₄H₄N⁺-⁻NSO₂R_f.     

Retention profile, kinetics and sequential determination of selenium(IV) and (VI) employing 4,4'-dichlorodithizone immobilized-polyurethane foams

Polyurethane foams (PUFs) loaded with the chromogenic reagent 4,4′-dichlorodithizone (Cl₂H₂D_Z) have been investigated for the quantitative retention, chemical speciation and sequential determination of traces of inorganic selenium(IV) and (VI) from aqueous media containing bromide ions. The retention profile of selenium(IV) onto the reagent loaded foam followed a dual-mode sorption mechanism involving both absorption related to “solvent extraction” and an added component for surface adsorption. The kinetics and thermodynamic characteristics of selenium(IV) uptake onto PUFs have been studied. The kinetics of selenium(IV) sorption onto PUFs was found fast, reached equilibrium in few minutes and followed a first-order rate constant in presence of bromide ions in the extraction media. The thermodynamic parameters, ΔH, ΔS and ΔG, indicated the exothermic and spontaneous nature of the sorption process. The sorption and the recovery percentages of inorganic selenium(IV) from fresh water by the proposed loaded foam columns were achieved quantitatively. The height equivalent to theoretical plate (HETP), the number of layers (N), breakthrough capacity and the critical capacity for selenium(IV) uptake onto Cl₂H₂D_Z loaded foams columns were found to be 1.3, 103, 8.6 and 7.2 mg/g, respectively. The method was successfully applied for the chemical speciation and sequential determination of inorganic selenium(IV) and/or (VI) species spiked to fresh and industrial wastewaters.     

Radiochemical studies of the sorption behavior of strontium and barium

The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.⁹⁰Sr (29.1 y) and¹³³Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratioR _d, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8–10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K⁺, Sr²⁺, Ca²⁺ and Al³⁺ ions, respectively, prior to sorption studies with Ba²⁺ ions. The results of Ca²⁺ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba²⁺ ion exchanges primarily with the Ca²⁺ ion on the clay minerals.     

Equilibrium,kinetics and thermodynamics studies of Cd sorption onto a dithizone-impregnated Amberchrom CG-300m polymer resin

Amberchrom CG-300m, a styrene acrylic ester polymer resin, was studied for the first time as sorbent for metal ion sorption in a solid-phase extraction system. The polymer sorbent was modified via impregnation with dithizone to improve its efficiency. Efficiency of the modified sorbent improved by more than 47%. The loading capacity of the resin is 3.2 mg dithizone per gram of sorbent. The mechanisms of Cd(II) sorption from aqueous solutions are presented. Capacity of the modified resin for Cd(II) was investigated in batch experiments as a function of pH, initial metal ion concentration, temperature and time. Maximum capacity of 0.551 mg Cd(II) per gram of sorbent was achieved. The dimensionless separation factor, 0 < R_L < 1, associated with the Langmuir isotherm (at T = 294 K) signifies sorption of Cd(II) was favorable, as do negative values of free energy of sorption (ΔG) at temperatures exceeding 293 K. Sorption was endothermic (ΔH > 0) while ΔS > 0 reflects the affinity of the sorbent towards Cd(II). The pseudo-second order model proved to be the best fit model for Cd(II) sorption kinetics data. Particle-diffusion models suggest sorption follows film as well as pore diffusion mechanisms.     

Synthesis and structural characterization of a dichloro zinc complex of N,N′-bis-(2,6-dichloro-benzyl)-(R,R)-1,2-diaminocyclohexane: Application to ring opening polymerization of rac-lactide

A novel dichloro zinc complex (L¹)ZnCl₂, where L¹ is N,N′-bis-(2,6-dichloro-benzyl)-(R,R)-1,2-diaminocyclohexane, has been synthesized and characterized. The dimethyl derivatives, generated in situ from the well characterized dichloro zinc complexes (L¹)ZnCl₂ and (L²)ZnCl₂, where L² is N,N′-bis-(benzyl)-(R,R)-1,2-diaminocyclohexane, were employed as initiators for the ring opening polymerization (ROP) of rac-lactide (rac-LA). The complexes were found to be highly efficient initiators yielding the polylactide (PLA) with a narrow molecular weight distribution. The catalytic activity and heterotactic selectivity of the Zn(II) complexes were affected by the substituents on the phenyl groups of benzyl moieties in (R,R)-1,2-diaminocyclohexane. The dimethyl derivative of (L²)ZnCl₂ produced highly stereocontrolled PLA with P_r = 0.75 at −25 °C.     

Contribution to the atomic absorption spectrophotometry of calcium in the N2O-acetylene flame

Summary The use of the acetylene-nitrous oxide hot flame is not sufficient to remove all ion interferences in the atomic-absorption spectrophotometric determination of calcium. The most effective aid for that purpose is the addition of 500 ppm K⁺ (as chloride) as ionisation inhibitor and 0.04 M 5-sulphosalicylic acid as protector (up to 1000 ppm of ions), except of some ternary ion systems such as Ca²⁺/Al³⁺/PO₄ ^3–. The effects in two kinds of flames were compared, i.e. in N₂O-acetylene and air-acetylene.

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Zur atomabsorptionsspektrophotometrischen Bestimmung von Calcium in der N₂O-Acetylen-Flamme

Zusammenfassung Die Störung einer Reihe von Ionen bei der atomabsorptionsspektrophotometrischen Bestimmung von Calcium wird auch bei Anwendung der heißen N₂O-Acetylen-Flamme nicht aufgehoben. Dies gelingt aber in Anwesenheit von 500 ppm K⁺ als KCl und 0,04 M 5-Sulfosalicylsäure bis zu einem Ionengehalt von 1000 ppm. Man beobachtet dann nur Störungen in einigen ternären Systemen, wie z.B. Ca²⁺/Al³⁺/PO₄ ^3–. Die Einflüsse in der N₂O-Acetylen- und Luft-Acetylen-Flamme werden verglichen.

     

Identification of selective ion-exchange resin for fluoride sorption

The defluoridation capacity (DC) of a chelating resin, namely Indion FR 10 (IND), and Ceralite IRA 400 (CER), an anion-exchange resin, were compared under various equilibrating conditions for the identification of selective sorbent. The results showed that chelating resin is more selective than an anion-exchange resin for fluoride removal. The fluoride sorption was reasonably explained using Freundlich and Langmuir isotherms. The surface morphology of resins before and after fluoride sorption was observed using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used for the determination of functional groups responsible for fluoride sorption. Various thermodynamic parameters such as DeltaG0, DeltaH0, DeltaS0, and Ea have been calculated to understand the nature of sorption. The sorption kinetic mechanism was studied with reaction-based and diffusion-based models. The sorption process was found to be controlled by pseudo-second-order and particle diffusion models. The performance of the resins studied has been tested with field samples collected from a fluoride-endemic area.     

非水体系中磺酸铜型树脂对有机碱的配位吸附

研究了磺酸铜型树脂在乙醇、乙酸乙酯和正己烷中对苯胺、N 甲基苯胺和N ,N 二甲基苯胺的吸附规律 ,并与水中的结果相对照 .树脂在正己烷中对苯胺等的吸附量最大 ,在乙醇、乙酸乙脂和水中依次减小 .在4种不同的介质中 ,树脂对苯胺的吸附均表现出相同的吸附选择性 ,即对苯胺的吸附亲合性最大 ,N ,N 二甲基苯胺最小 .在不同的介质中 ,树脂对苯胺的吸附基本符合Freundlich吸附方程 ,并计算了在不同介质中对苯胺吸附的吸附焓 .在水中 ,吸附速率最高 ,在乙醇、乙酸乙酯和正己烷中 ,吸附速率依次降低     

Synthesis, characterization and application of a novel sorbent, glucamine-modified MCM-41, for the removal/preconcentration of boron from waters

A novel sorbent was prepared by the functionalization of an inorganic support material, MCM-41, with N-methylglucamine for the uptake of boron from aqueous solutions prior to its determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Characterization of the newly synthesized material was performed using BET, XRD, TEM, SEM and DRIFTS techniques, in addition to its C and N elemental content. Sorption behavior of the novel sorbent for boron was also investigated and found to obey Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The maximum amount of B (as H₃BO₃) that can be sorbed by the sorbent was calculated from the D-R isotherm and was found to be 0.8 mmol B g⁻¹ of sorbent. The applicability of the new sorbent for the removal/preconcentration of boron from aqueous samples was examined by batch method. It was found that the sorbent can take up 85% of boron in 5 min whereas quantitative sorption is obtained in 30 min. Any pH greater than 6 can be used for sorption. Desorption from the sorbent was carried out using 1.0 M HNO₃. The sorption efficiency of the new sorbent was also compared to that of Amberlite IRA 743, a commercial resin with N-methylglucamine functional groups. Within the experimental conditions employed, the new sorbent was found to have higher sorption efficiency than the commercial resin. For method validation, spike recovery tests were performed at various concentration levels in different water types and were found to be between 83-95 and 75-92% for ultra pure water and geothermal water, respectively.     

The calorimetric investigation of phosphoric acid-N,N-dimethylformamide system

Solution and mixing enthalpies for the orthophosphoric acid (H₃PO₄)-N,N-dimethylformamide (DMF) system were measured over the whole concentration range at 25 °C. The standard value of solution enthalpy of phosphoric acid in DMF and the standard transference enthalpy of H₃PO₄ from water to DMF were calculated. The mixing enthalpy concentration dependence permitted making assumptions on complex formation in the system under investigation.     

Removal of Trace Contaminants from Water Using New Chelating Resins

Abstract

The modification of cross‐linked polyacrylamide (CPAAm) and incorporation of methyl thiourea (MeTU) or phenyl thiourea (PhTU) group were utilized in the preparation of two new chelating resins CPAAm‐EDA‐MeTU (resin I) and CPAAM‐EDA‐PhTU (resin II), [EDA=ethylenediamine]. The prepared resins were characterized by elemental analysis and IR spectroscopy. The sorption behaviors of Cd(II), Pb(II), and Zn(II) ions on the prepared resins were studied and the optimum sorption conditions for the tested metal ions were determined. The optimum pH value for the sorption of Cd(II) and Zn(II) ions on both resins I and II was ranged between 7–8. The prepared new resins show very little affinity towards Pb(II) ion. The maximum experimental sorption capacities of resin I towards Cd(II) and Zn(II) ions were 3.2 and 0.6 mmol g^?1, respectively, and that of resin II were and 0.6 mmol g^?1 in the same prescribed order. Langmuir and Freundlich isotherm constants and correlation coefficients for the present system were calculated and compared. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) for cadmium and zinc sorption on the prepared resins were also determined from the temperature dependence.     

Sorptive potential of sunflower stem for Cr(III) ions from aqueous solutions and its kinetic and thermodynamic profile

The sorptive potential of sunflower stem (180-300 μm) for Cr(III) ions has been investigated in detail. The maximum sorption (≥85%) of Cr(III) ions (70.2 μM) has been accomplished using 30 mg of high density sunflower stem in 10 min from 0.001 M nitric and 0.0001 M hydrochloric acid solutions. The accumulation of Cr(III) ions on the sorbent follows Dubinin-Radushkevich (D-R), Freundlich and Langmuir isotherms. The isotherm yields D-R saturation capacity X_m = 1.60 ± 0.23 mmol g⁻¹, β = −0.00654 ± 0.00017 kJ² mol⁻², mean free energy E = 8.74 ± 0.12 kJ mol⁻¹, Freundlich sorption capacity K_F = 0.24 ± 0.11 mol g⁻¹, 1/n = 0.90 ± 0.04 and of Langmuir constant K_L = 6800 ± 600 dm³ mol⁻¹ and C_m = 120 ± 18 μmol g⁻¹. The variation of sorption with temperature (283-323 K) gives ΔH = −23.3 ± 0.8 kJ mol⁻¹, ΔS = −64.0 ± 2.7 J mol⁻¹ K⁻¹ and ΔG_298k = −4.04 ± 0.09 kJ mol⁻¹. The negative enthalpy and free energy envisage exothermic and spontaneous nature of sorption, respectively. Bisulphate, Fe(III), molybdate, citrate, Fe(II), Y(III) suppress the sorption significantly. The selectivity studies indicate that Cr(III), Eu(III) and Tb(III) ions can be separated from Tc(VII) and I(I). Sunflower stem can be used for the preconcentration and removal of Cr(III) ions from aqueous medium. This cheaper and novel sorbent has potential applications in analytical and environmental chemistry, in water decontamination, industrial waste treatment and in pollution abatement. A possible mechanism of biosorption of Cr(III) ions onto the sunflower stem has been proposed.     

Synthesis of cross-linked chitosan possessing N-methyl-d-glucamine moiety (CCTS-NMDG) for adsorption/concentration of boron in water samples and its accurate measurement by ICP-MS and ICP-AES

A chitosan resin derivatized with N-methyl-d-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-d-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61 mmol ml⁻¹ (= 2.1 mmol g⁻¹). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1 ml resin; (5) complete elution of boron with 1 mol l⁻¹ nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8 μg l⁻¹. The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07 μg l⁻¹ and the limit of quantification (LOQ) was 0.14 μg l⁻¹ when the volume of each sample and eluent was 10 ml.     

Photodegradation and weathering effects on timber surface moisture profiles as studied using dynamic vapour sorption

The moisture sorption kinetic profiles of Scots pine (Pinus sylvestris) earlywood and latewood were studied using a Dynamic Vapour Sorption apparatus and the equilibrium isotherms determined. The samples were chosen to give an insight to the effects that photodegradation and weathering have on the moisture behaviour of the surface layers of timber. Samples were subjected to indoor and outdoor exposure regimes. Significant differences were found between the sorption isotherms of exposed and unexposed wood, as well as with the sorption kinetics profiles. The reasons for these differences are discussed.     

Separation and determination of some metal ions on new chelating resins containing N, N donor sets

Two new stable chelating resins have been synthesized incorporating the imidazolylazobenzene and 1,4-bis(imidazolylazo)benzene as functional group into Merrifield polymer through CN covalent bond and characterized by elemental analyses, IR and thermal study. A comparison of sorption capacity of newly formed resins towards the cations Ag(I), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) as a function of pH has been studied. Kinetic studies show the time for the completeness of metal ion saturation with the resin phase. Cd(II) in trace quantities has been successfully separated and determined in different biological samples and Zn(II) in medicinal samples. It is also found that Cd(II) can be removed from water at usual pH of natural water. Both the resins can be employed for water purification as the resins reveal sorption ability towards toxic metal ions and exhibit no affinity to alkali or alkaline earth metal ions.     

Synthesis, X-ray crystal structure and vibrational spectroscopy of the acidic pyrophosphate KMg0.5H2P2O7·H2O

The hydrated potassium hemimagnesium dihydrogen pyrophosphate KMg_0.5H₂P₂O₇·H₂O was synthesized. It crystallizes in the triclinic system, space group (n. 2), Z=2, with the following unit-cell parameters: a=6.8565(2) Å, b=7.3621(3) Å, c=7.6202(3) Å, α=81.044(2)°, β=72.248(2)°, γ=83.314(3)°, V=360.90(2) Å³. The structure was obtained by single-crystal X-ray diffractometry, and a full-matrix least-squares refinement based on F² gave a final R index of =0.0368 (wR=0.0975), utilizing 1446 observed reflections with I>2σ(I). The crystal packing consists in a three-dimensional network made by layers parallel to ab plane of PO₄ double tetrahedra and MgO₆ octahedra, linked by hydrogen bonds, while K atoms form complex coordination within cavities between tetrahedra and octahedra. The dihydro-pyrophosphate anion (H₂P₂O₇)²⁻ shows bent eclipsed conformation and the Mg²⁺ ion lies on inversion center. No coincidences observed between most of infrared and Raman spectral bands confirmed the centrosymmetric structure of the title compound; the vibrational spectra point to a bent POP bridge angle.     

Non-random cation distribution in hexagonal Al0.5Ga0.5PO4

Based on powder X-ray diffraction and ³¹P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) investigations of mixed phosphate Al_0.5Ga_0.5PO₄, prepared by co-precipitation method followed by annealing at 900 °C for 24 h, it is shown that Al_0.5Ga_0.5PO₄ phase crystallizes in hexagonal form with lattice parameter a=0.491(2) and c=1.106(4) nm. This hexagonal phase of Al_0.5Ga_0.5PO₄ is similar to that of pure GaPO₄. The ³¹P MAS NMR spectrum of the mixed phosphate sample consists of five peaks with systematic variation of their chemical shift values and is arising due to existence of P structural units having varying number of the Al³⁺/Ga³⁺ cations as the next nearest neighbors in the solid solution. Based on the intensity analysis of the component NMR spectra of Al_0.5Ga_0.5PO₄, it is inferred that the distribution of Al³⁺ and Ga³⁺ cations is non-random for the hexagonal Al_0.5Ga_0.5PO₄ sample although XRD patterns showed a well-defined solid solution formation.     

Sorption—desorption studies of anionic dyes on alumina pretreated with acids

Sorption—desorption behaviour of the anionic dyes naphthol blue-black (NB) and lissamine green ‘BN’ (LG) on chromatographic alumina, pretreated with mineral acids, is described. Alumina samples of surface-phase pH 1.0–8.0 were prepared and studied for their sorption behaviour. The sorption was found to vary with surface pH of the substrate and acid used for pretreatment. Quantitative sorption was shown at pH ⩽ 4.0 (NB) and pH ⩽ 3.5 (LG) on Al₂O₃ treated with HNO₃ [Al₂O₃(n)], and maximum sorption occurred at pH 5.0 (NB) and pH 5.5 (LG) on Al₂O₃ treated with H₂SO₄ [Al₂O₃(s)] and pH 2.5 (NB) and pH 3.0 (LG) on Al₂O₃ treated with H₃PO₄ [Al₂O₃(p)]. Variation in sorption with time (10 min-72, h), temperature (30–60°C) and regeneration of the substrates with aqueous electrolytes is also reported. Desorption efficacy of anions was in the order: PO³⁻₄ > SO²⁻₄ > NO⁻₃. The acid-treatment, and hence the specifically adsorbed anions (NO⁻₃, SO²⁻₄, PO³⁻₄), appears to modify the sorption properties of alumina significantly. It appears that the controlling force for adsorption is predominantly ion exchange. A few synthetic mixtures of the dyes were separated by column chromatography, using inorganic electrolytes as eluents.