Adsorption Studies of Radionuclides and Toxic Metal Ions on a Modified Mesoporous Lanthanum(III) Silicate

A new adsorbent, modified mesoporous lanthanum(III) silicate, has been prepared with various molar ratios of Si/La (10, 20, 40, 80) and cethyltrimethylammonium bromide (CTAB) as structure directing agent. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption of radionuclides and toxic metal ions have been studied. The results show that adsorption amount of some element such as Pb(II) and Th(IV) has been increased significantly by incorporation of lanthanum ions in the framework of adsorbent. Separation of Co(II)‐Th(IV), Co(II)‐U(VI) and Mo(VI)‐U(VI) has been developed on columns of this adsorbent.     

Adsorption Characteristics of Pb(II) and Cr(III) onto C‐4‐Methoxyphenylcalix[4]Resorcinarene in Batch and Fixed Bed Column Systems

A study on the adsorption characteristics of Pb(II) and Cr(III) cations onto C‐4‐methoxyphenylcalix‐[4]resorcinarene (CMPCR) in batch and fixed bed column systems has been conducted. CMPCR was produced by one step synthesis from resorcinol, 4‐methoxybenzaldehyde, and HCl. The synthesis was carried out at 78 °C for 24 hours and afforded the adsorbent in 85.7% as a 3:2 mixture of C_4ν:C_2ν isomer. Most parameters in batch and fixed bed column systems confirm that CMPCR is a good adsorbent for Pb(II) and Cr(III), though Pb(II) adsorption was more favorable than that of Cr(III). The adsorption kinetic of Pb(II) and Cr(III) adsorptions in batch and fixed bed column systems followed a pseudo 2ⁿ order kinetics model. The rate constant of Pb(II) was higher than that of Cr(III) in the batch system, but this result was contrary to the result obtained in a fixed bed column system. Desorption studies to recover the adsorbed Pb(II) and Cr(III) were performed sequentially with distilled water and HCl, and the results showed that the adsorption was dominated by chemisorption.     

An innovative SiO2-pyrazole nanocomposite for Zn(II) and Cr(III) ions effective adsorption and anti-sulfate-reducing bacteria from the produced oilfield water

Novel SiO₂-pyrazole (SiO₂-PYZ) nanocomposite was introduced for the elimination of Zn(II) and Cr(III) from oil reservoir water. Characterization analysis of prepared SiO₂-PYZ nanocomposite was investigated using SEM, FTIR, TGA, XRD, TEM, and BET. Studying the effects and optimization of the parameters such as retention time, pH, initial Cr(III) and Zn(II) ions concentrations, adsorbent dosage, and temperature were examined. For kinetics investigation, the pseudo-second-order (PSO) model matches the adsorption process effectively under different operating conditions. After applying two other isotherm models (Langmuir and Freundlich), the experimental data was adequately equipped with Langmuir, R² = 1. The thermodynamic results pointed that the adsorption of Zn(II) and Cr(III) ions was spontaneous, endothermic, and physisorption reaction. At pH 12, the influence of more than one ion, such as Ca(II) and Na(I), was checked, and the results revealed that this conjugate substance was highly selective to Cr(III). After washing with water in multiple cycles, the adsorbed material was regenerated with 0.1 M HCl and subsequently reused without deterioration in its case cavities. Interestingly, SiO₂-PYZ was highly effective against sulfate-reducing bacteria (SRB) in the petroleum field.     

Chemically modified silica gel with p-dimethylaminobenzaldehyde for selective solid-phase extraction and preconcentration of Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) by ICP-OES

Silica gel-bound amines phase modified with p-dimethylaminobenzaldehyde (p-DMABD) was prepared based on chemical immobilization technique. The product (SG-p-DMABD) was used as an adsorbent for the solid-phase extraction (SPE) Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The uptake behaviors of SG-p-DMABD for extracting these metal ions were studied using batch and column procedures. For the batch method, the optimum pH range for Cr(III) and Ni(II) extraction was ≥ 3, for Cu(II), Pb(II) and Zn(II) extraction it was ≥ 4. For simultaneous enrichment and determination of all the metals on the newly designed adsorbent, the pH value if 4.0 was selected. All the metal ions can be desorbed with 2.0 mL of 0.5 mol L^− 1 of HCl. The results indicate that SG-p-DMABD has rapid adsorption kinetics using the batch method. The adsorption capacity for these metal ions is in the range of 0.40-1.15 mmol g^− 1, with a high enrichment factor of 125. The presence of commonly coexisting ions does not affect the sorption capacities. The detection limits of the method were found to be 1.10, 0.69, 0.99, 1.10 and 6.50 μg L^− 1 for Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was 5.0% (n = 8) for all metal ions. The method was applied to the preconcentration of Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) from the certified reference material (GBW 08301, river sediment) and water samples with satisfactory results.     

Selective Adsorption and Determination of Hexavalent Chromium in Water Samples by Chemically Modified Activated Carbon with Tris(hydroxymethyl)aminomethane

This study introduces a sensitive and simple method for selective adsorption of hexavalent chromium, Cr(VI), from water samples prior to its determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The method utilized activated carbon modified with tris(hydroxymethyl)aminomethane (AC-TRIS) as an adsorbent. Surface properties of the new chemically modified AC-TRIS phase were confirmed by Fourier transform infrared (FTIR) spectroscopy. Seven metal ions, including Co(II), Cu(II), Ni(II), Pb(II), Cr(III), Cr(VI), and Fe(III) were evaluated and determined at different pH values (1.0–8.0), except for Fe(III) at pH values (1.0–4.0). Based on the results of the effect of pH on adsorption of these metal ions on AC-TRIS, Cr(VI) was selected for the study of other parameters controlling its maximum uptake on AC-TRIS under batch conditions and at the optimum pH value 1.0. The maximum static adsorption capacity of Cr(VI) onto the AC-TRIS was found to be 43.30 mg g^?1 at this pH and after 1 hour contact time. The adsorption data of Cr(VI) were modeled using both Langmuir and Freundlich classical adsorption isotherms. Results demonstrated that the adsorption of Cr(VI) onto AC-TRIS followed a pseudo second-order kinetic model. In addition, the efficiency of this methodology was confirmed by applying it to real environmental water samples.     

Study of the Complexation,Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric Conditions

The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two‐step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1 : 1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1 : 2 Cr(III)/DTPA complex. The electroreduction of the DTPA‐Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled.The Cr(III) ion, generated in‐situ from Cr(VI) at the mercury electrode at about ?50 mV (vs. Ag|AgCl) (3 mol L^?1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in‐situ built complex Cr(III) ion were found to adsorb on the mercury electrode.The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible.The proposed complex structures and an overall reaction scheme are shown.     

Ru(III), Cr(III), Fe(III) complexes of Schiff base ligands bearing phenoxy Groups: Application as catalysts in the synthesis of vitamin K3

Two polydentade Schiff base ligands and their Ru(III), Cr(III) and Fe(III) complexes were synthesized and characterized by elemental analysis (C, H, N), UV/Vis, FT IR, ¹H and ¹³C NMR, LC–MS/MS, molar conductivity and magnetic susceptibility techniques. The absorption bands in the electronic spectra and magnetic moment measurements verified an octahedral environment around the metal ions in the complexes. The thermal stabilities were investigated using TGA. The synthesized complexes were used in the catalytic oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1,4-naphthoquinone; vitamin K₃, menadione, 2MNQ; using hydrogen peroxide, acetic acid and sulfuric acid. L₁-Fe(III) complex showed very efficient catalytic activity with 58.54% selectivity in the conversions of 79.11%.     

Synthesis, structures and properties of hydrolytic Al(III) aggregates and Fe(III) analogues formed with iminodiacetate-based chelating ligands

Both Al(III) and Fe(III) display a rich hydrolytic chemistry which can lead to the formation of a variety of aggregated oxo and hydroxo-bridged aggregates. The formation, structures and properties of these species are important in defining the availability and reactivity of these species in aqueous environments such as are found in biological systems and the environment. Although there are many similarities in the behaviour of the Al³⁺ and Fe³⁺ ions there are also some important differences between these two metal ions which can lead to a divergence in their chemistries. These considerations are discussed and illustrated with reference to 16 Al(III) and Fe(III) compounds, which have been crystallographically characterised, and which form in aqueous environments in the presence of chelating ligands containing the iminodiacetate functionality.     

Adsorption Studies of Cr(III) & Cr(VI) on Lead Sulphide,Copper Sulphide & Zinc Sulphide-Determination Cr(III) in the Presence of Cr(VI)

Abstract

The adsorption studies of Cr(VI) in presence of Cr(III) on the sulphide of Lead, Zinc and Copper has been studied. It has been found that in case of lead sulphide 100% adsorption of Cr(VI) took place at pH 4.0 and of Cr(III) at pH 7.0. While in case of zinc sulphide the 100% adsorption of Cr(VI) took place at pH 4.5 and of Cr(III) at pH 6.5. In case of copper sulphide 100% adsorption of Cr(VI) took place at pH 5.0 and of Cr(III) at pH 7.0. This difference in adsorption at different pH values forms the basis for the determination of these ions. The method is accurate.     

Kinetik und Mechanismus des Ligandentausches zwischen Thallium(III)oxinat und Eisen(III) in Propylencarbonat

The transfer of oxinate ions from thallium (III)oxinate to trivalent Fe(DMF) ₆ ³⁺ in propylenecarbonate takes place via rearrangements within a rapidly formed binuclear thallium(III)—iron(III) complex. In a last rapid step this rearranged complex reacts with excess reactants to the final products whose composition accordingly depends on the ratio of the reactant concentrations.

     

The use of Agrobacterium tumefacients immobilized on Amberlite XAD-4 as a new biosorbent for the column preconcentration of iron(III), cobalt(II), manganese(II) and chromium(III)

A microorganism Agrobacterium tumefacients as an immobilized cell on a solid support was presented as a new biosorbent for the enrichment of Fe(III), Co(II), Mn(II) and Cr(III) prior to flame atomic absorption spectrometric analysis. Amberlite XAD-4 was used as a support material for column preconcentration. Various parameters such as pH, amount of adsorbent, eluent type and volume, flow rate of sample solution, volume of sample solution and matrix interference effect on the retention of the metal ions have been studied. The optimum pH for the sorption of above mentioned metal ions were about 6, 8, 8 and 6, respectively. The loading capacity of adsorbent for Co(II) and Mn(II) were found to be 29 and 22 μmol g⁻¹, respectively. The recoveries of Fe(III), Co(II), Mn(II) and Cr(III), under the optimum conditions were found to be 99 ± 3, 99 ± 2, 98 ± 3 and 98 ± 3%, respectively, at the 95% confidence level. The limit of detection was 3.6, 3.0, 2.8 and 3.6 ng ml⁻¹ for Fe(III), Co(II), Mn(II) and Cr (III), respectively, by applying a preconcentration factor of 25. The proposed enrichment method was applied for metal ion determination from water samples, alloy samples, infant foods and certified samples such as whey powder (IAEA-155) and aluminum alloy (NBS SRM 85b). The analytes were determined with a relative error lower than 10% in all samples.     

Preparation and characterization of L-glutamic acid-functionalized graphene oxide for adsorption of Pb(II)

An efficient adsorbent (L-Glu/GO) was successfully synthesized by the reaction between L-glutamic acid (L-Glu) and graphene oxide (GO). The structure and morphology of this adsorbent were characterized by FTIR, SEM, XRD, and TGA. The SEM result indicated that the adsorbent was a nanomaterial with a size of about 50–400 nm. The adsorption experiments of various heavy ions on L-Glu/GO demonstrated that the adsorption performance of Pb(II) was better than others. Various variables affecting the adsorption of L-Glu/GO for Pb(II) were systematically explored. The experimental results indicated that the maximum adsorption capacity and equilibrium time of Pb(II) on L-Glu/GO were 513.4 mg g^?1 and 40 minute, respectively. The sorption kinetics and isotherm fitted well with the pseudo-second-order model and Langmuir model, respectively. The sorption mainly was a chemical process. Thermodynamic studies revealed that the adsorption was a spontaneous and exothermic process. The adsorbent could be regenerated with HCl solution. Hence, it was suggested that the L-Glu/GO could be applied in the removal of Pb(II) from wastewaters.     

Kalman filter deconvolution after cubic splines background removal in the HPLC determination of Cr(III) and Al(III) as 8-hydroxyquinolines

Summary A procedure for the simultaneous quantitation of Al(III) and Cr(III) ions by reversed-phase HPLC, after pre-column complexation with 8-hydroxyquinoline, is described. The deconvolution of the partially overlapped peaks was by the Kalman filter method which yielded accurate and precise results. Background removal from the chromatograms was by a new approach employing cubic splines as interpolators between the peak valleys. Finally, it is shown that the Kalman filter deconvolution, after subtraction of the background by cubic spline interpolation, allowed quantitation of Al(III) and Cr(III) down to 25 ppb for each metal. These concentrations were not detectable by conventional integration methods due to a very low signal-to-noise ratio.     

Structural studies and quantum chemical calculations of Cr(III), Fe(III) and Ru(III) bromazepam complexes

The reaction of bromazepam (7‐bromo‐1,3‐dihydro‐5‐(2‐pyridyl)‐2H ‐1,4‐benzodiazepin‐2‐one, BZM) with Cr(III) ( 1 ), Fe(III) ( 2 ) and Ru(III) ( 3 ) salts gives complexes of the type [M(BZM)₃]⋅3X (X = Cl or NO₃). Structural characterization was extensively carried out using various analytical and spectral tools such as infrared, ¹H NMR and UV–visible spectroscopies and magnetic, conductance, elemental and thermal analyses. BZM is a bidentate ligand and interacts with the metal ions via the pyridine and benzodiazepin‐2‐one nitrogen atoms. The magnetic and electronic properties of 2 and 3 are consistent with low‐spin octahedral complexes. The three BZM molecules are non‐isoenergetically coordinated to the metal ions and this is reflected in the values of the second‐order interaction energy. The antibacterial activity was studied using Staphylococcus aureus and Escherichia coli . Coordination of BZM to Cr(III) or Ru(III) ions leads to a marked increase in toxicity with respect to the inactive Fe(III) complex 2 .     

Chemical modification of expanded glass aggregate with N-Benzoyl-N′-(4-methylphenyl) thiourea (TTU) for the adsorptive removal of Cr(III) ion

In this study, the silylant agent 3-aminopropyl trimethoxysilane (APTES) was anchored on expanded glass aggregate (GA) to prepare a new adsorbent. N-Benzoyl-N′-(4-methylphenyl) thiourea (TTU) bonded to amino-functionalized GA adsorbent with reflux. Developed adsorbent (GA-APTES-TTU) was characterized using thermal analysis (TGA) and scanning electron microscopy (SEM). TGA and SEM studies indicated that modification of the glass aggregate (GA) surfaces was successfully performed. The adsorption studies exhibited that the GA-APTES-TTU could be efficiently used for the removal of Cr(III) from aqueous solutions. The effects of pH, adsorbent dosage, ion concentration, time, and temperature were investigated as adsorption parameters. The maximum removal of Cr(III) was observed at pH 4. The adsorption equilibrium was achieved in 120 min and adsorption of Cr(III) followed the Langmuir isotherm model. The maximum adsorption capacity for Cr(III) was 0.4305 mmol/g with GA-APTES-TTU. Thermodynamic parameters such as the standard free energy (ΔG^o), enthalpy change (ΔH°) and entropy change (ΔS°) were calculated in order to explain the mechanism of adsorption process. The thermodynamic data showed that Cr(III) adsorption was spontaneous, endothermic, and a physisorption reaction. In addition, the adsorption kinetic data fitted to the pseudo-second order model.     

Phosphoprotein electrophoresis in the presence of Fe(III) ions

Preparation of affinity polyacrylamide gels containing immobilized Fe(III) ions for the separation of proteins exhibiting metal ion binding properties is described. The presented method enables uniform distribution of immobilized metal ions in the affinity part of the polyacrylamide separating gel. Affinity gels prepared by this way are suitable to follow the effect of different concentrations of metal ions immobilized in polyacrylamide gel on a protein electrophoretic behavior. Polyacrylamide gels containing immobilized Fe(III) ions were used to study the electrophoretic behavior of two model proteins differing in their phosphate group content: chicken ovalbumin and bovine α‐casein. For the electrophoretic separation, both the native and the denaturating conditions were used.     

Speciation,adsorption and determination of chromium(III) and chromium(VI) on a mesoporous surface imprinted polymer adsorbent by combining inductively coupled plasma atomic emission spectrometry and UV spectrophotometry

In the present study, a Cr(III)‐imprinted polymer (Cr(III)‐IIP) was prepared by an easy one‐step sol–gel reaction with a surface imprinting technique on the support of silica mesoporous material. A new SPE method for the speciation, separation, preconcentration, and determination of Cr(III) and Cr(VI) by inductively coupled plasma atomic emission spectrometry and UV on the mesoporous‐imprinted polymer adsorbent was developed. The structure of the imprinted polymer was characterized by Fourier transform infrared spectroscopy, X‐ray powder diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherms. The adsorption kinetics, thermodynamics behavior, and recognition ability toward Cr(III) on Cr(III)‐IIP and nonimprinted polymer were compared. The results showed that Cr(III)‐IIP had higher selectivity and nearly a two times larger Langmuir adsorption capacity (38.50 mg/g) than that of NIP. The proposed method has been successfully applied in the determination and speciation of chromium in natural water samples with satisfactory results.     

Removal of Chromium(III) and Cadmium(II) Heavy Metal Ions from Aqueous Solutions Using Treated Date Seeds: An Eco-Friendly Method

The aim of the research was to prepare low-cost adsorbents, including raw date pits and chemically treated date pits, and to apply these materials to investigate the adsorption behavior of Cr(III) and Cd(II) ions from wastewater. The prepared materials were characterized using SEM, FT-IR and BET surface analysis techniques for investigating the surface morphology, particle size, pore size and surface functionalities of the materials. A series of adsorption processes was conducted in a batch system and optimized by investigating various parameters such as solution pH, contact time, initial metal concentrations and adsorbent dosage. The optimum pH for achieving maximum adsorption capacity was found to be approximately 7.8. The determination of metal ions was conducted using atomic adsorption spectrometry. The experimental results were fitted using isotherm Langmuir and Freundlich equations, and maximum monolayer adsorption capacities for Cr(III) and Cd(II) at 323 K were 1428.5 and 1302.0 mg/g (treated majdool date pits adsorbent) and 1228.5 and 1182.0 mg/g (treated sagai date pits adsorbent), respectively. It was found that the adsorption capacity of H₂O₂-treated date pits was higher than that of untreated DP. Recovery studies showed maximal metal elution with 0.1 M HCl for all the adsorbents. An 83.3–88.2% and 81.8–86.8% drop in Cr(III) and Cd(II) adsorption, respectively, were found after the five regeneration cycles. The results showed that the Langmuir model gave slightly better results than the Freundlich model for the untreated and treated date pits. Hence, the results demonstrated that the prepared materials could be a low-cost and eco-friendly choice for the remediation of Cr(III) and Cd(II) contaminants from an aqueous solution.     

Organically modified silica gel and flame atomic absorption spectrometry: employment for separation and preconcentration of nine trace heavy metals for their determination in natural aqueous systems

A 5-formyl-3-(1′-carboxyphenylazo) salicylic acid-bonded silica gel (FCPASASG) chelating adsorbent was synthesized according to a very simple and rapid one step reaction between aminopropyl silica gel (APSG) and 5-formyl-3-(1′-carboxyphenylazo) salicylic acid (FCPASA) and its adsorption characteristics were studied in details. Nine trace metals viz.: Cd(II), Zn(II), Fe(III), Cu(II), Pb(II), Mn(II), Cr(III), Co(II) and Ni(II) can be quantitatively adsorbed by the adsorbent from natural aqueous systems at pH 7.0–8.0. The adsorbed metal ions can be readily desorbed with 1 M HNO₃ or 0.05 M Na₂EDTA. The distribution coefficient, K_d and the percentage concentration of the investigated metal ions on the adsorbent at equilibrium, C_M,_eqm % (Recovery, R%) were studied as a function of experimental parameters. The logarithmic values of the distribution coefficient, logK_d, are 3.7–6.4. Some foreign ions caused little interference in the preconcentration and determination of the investigated nine metals by flame atomic absorption spectrometry (AAS).The adsorption capacity of FCPASASG was 0.32–0.43 meq g⁻¹. C and N elemental analyses of the adsorbent (FCPASASG) allowed us to calculate a surface converge of 0.82 mmol g⁻¹. This value compares well with the best values reported for the azo compounds. The adsorbent and its formed metal chelates were characterized by IR (absorbance and/or reflectance) and UV spectrometry, potentiometric titrations and thermogravimetric analysis (TGA and DTG). The mode of chelation between the FCPASASG adsorbent and the investigated metal ions is proposed to be due to reaction of those metal ions with the salicylic and/or the carboxyphenylazo chelation centers of the FCPASASG adsorbent. Nanogram concentrations (0.07–0.14 ng ml⁻¹) of Cd(II), Zn(II), Fe(III), Pb(II), Cr(III), Mn(II), Cu(II), Co(II) and Ni(II) can be determined reliably with a preconcentration factor of 100.     

Solid-phase extraction of iron(III) with an ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A new Fe(III)-imprinted amino-functionalized silica gel sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Fe(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Fe(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Fe(III) was 25.21 and 5.10 mg g⁻¹, respectively. The largest selectivity coefficient of the Fe(III)-imprinted sorbent for Fe(III) in the presence of Cr(III) was over 450. The relatively selective factor (α_r) values of Fe(III)/Cr(III) were 49.9 and 42.4, which were greater than 1. The distribution ratio (D) values of Fe(III)-imprinted polymers for Fe(III) were greatly larger than that for Cr(III). The detection limit (3σ) was 0.34 μg L⁻¹. The relative standard deviation of the method was 1.50% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08301 and GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace iron in plants and water samples with satisfactory results.