Synthesis and Chelating Properties of Polystyrene Supported Schiff Base (N,N′-disalicylidenepropylenetriamine) Resin Toward Some Divalent Metal Ions

A new polystyrene-supported Schiff base resin, N,N-bis(salicylidenepropylenetriamine)- aminomethyl polystyrene, has been synthesized through a reaction between the commercially available 4-chloromethyl polystyrene polymer and the Schiff base, N,N′-disalicylidenepropylenetriamine. The chelation behavior of this resin toward the divalent metal ions Cu^{2 +}, Ni^{2 +}, Zn^{2 +}, and Pb^{2 +} in aqueous solutions was investigated. Batch equilibration experiments were carried out as a function of contact time, pH, amount of metal-ion, polymer mass, and temperature. The amount of metal-ion uptake of the polymers was determined by using atomic absorption spectrometry (AAS). Results of the study revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Cu^{2 +} and that the metal-ion uptake follows the order: Cu^{2 +} > Zn ^{2 +} > Ni^{2 +} > Pb²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed.     

Chelation ion-exchange properties of salicylic acid-urea-formaldehyde copolymers

Chelation ion-exchange properties of copolymers prepared from salicylic acid, urea and formaldehyde by condensation in presence of acid catalyst were studied for Cu²⁺, Fe³⁺, UO²⁺, Mn²⁺,Zn²⁺ and Co²⁺ ions. A batch equilibration method was adopted to study the selectivity of metal ion uptake. This method involved the measurement of distribution of a given metal between the copolymer sample and a solution containing the metal ions. The study was carried out over a wide pH range and in media of various ionic strengths. The copolymer showed a higher selectivity for UO₂ ²⁺, Cu²⁺ and Fe³⁺ ions than Mn²⁺, Co²⁺ and Zn²⁺ ions.     

Transition Metal Ions or Acid-induced Suppression of Photoinduced Proton Transfer and Electron Transfer Reaction in 5-(4-Fluorophenyl)-2-hydroxypyridine: A Molecule of Dual Mode Fluorosensitivity

The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) at different pH and its fluorescence response toward different transition metal ions have been studied by steady-state absorption and emission spectroscopy in combination with quantum chemical calculations. Although keto-enol tautomerization is observed in the excited state, the molecule is weakly fluorescent due to the presence of electron-rich nitrogen atom and relatively electron-deficient fluorine atom, which may lead to photoinduced electron transfer process. In the presence of the transition metal ions, such as Zn²⁺, Cd²⁺, Hg²⁺, etc., the studied molecule exhibits changes in its absorption and emission properties. The present system shows fluorescence enhancement instead of usual quenching in presence of the transition metal ions, such as Fe²⁺ and Cu²⁺. Spectral observation leads to the interpretation that this structurally simple molecule can be effectively utilized as a chelation-enhanced fluorescence-based chemosensor for the detection of transition metal ions. The experimental findings corroborate well with theoretical calculations at Hartree–Fock level using 6-31G** and lanl2dz basis sets.     

Study of some metallic silicates as ion-exchangers

The extraction of ammine complexes of Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Zn²⁺ by synthesised manganese, nickel and zinc silicates has been studied at different pH and ionic concentrations in the external solution. It has been found that the uptake of the metal ion Co²⁺, Cu²⁺ and Zn²⁺ increases with increase in pH of the external solution, attains a maximum and then decreases. However, the uptake for Cd²⁺ and Ni²⁺ increases continuously. The q_A values of all the silicates increases with the increase in the concentration of the exchanging ion and its order for the investigated metal ions is Ni²⁺ < Co²⁺ < Cd²⁺ < Zn²⁺ < Cu²⁺.     

Effect of pH on the adsorption of Ce3+, Sm3+, Eu3+ and Gd3+ ions on activated charcoal

The adsorption of metal ions such as Ce³⁺, Sm³⁺, Eu³⁺ and Gd³⁺ ions on activated charcoal has been studied as a function of pH. The adsorption mechanism of these ions is discussed in terms of hydrolyzed species formed in aqueous solution at different pH.     

Synthesis and characterization of novel indole-containing half-crowns as new emissive metal probes

Two new indole derivatives have been synthesized by a one-pot procedure and their potential as fluorescence probes for metal ions was investigated. The sensor capability of 1 and 2 toward cations such as Ag⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Hg²⁻ was studied in dichloromethane solution by absorption, fluorescence emission, and ¹H NMR titrations. Both probes showed selectivity for Ag⁺ and Hg²⁺ ions. The results suggest that these compounds may serve as promising models for future design of novel and more potent sensors.     

Epoxy-based polymer bearing 1-naphthylamine units: highly selective fluorescent chemosensor for ferric ion

A simple epoxy-based polymer 1 bearing 1-naphthylamine units has been synthesized and its recognition behaviors toward various metal ions have been investigated in THF-water (8:2, v/v) solution. The designed polymer 1 was found to exhibit selective ON-OFF-type fluorosensing behavior toward Fe³⁺ ions over other representative metal ions such as Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺, and Hg²⁺ ions.     

Sulfonic cation exchangers based on immobilized cis-Calix[4]resorcinolarenes

New sulfonic cation exchangers based on immobilized calix[4]resorcinolarenes were prepared. Their ion-exchange properties toward Na⁺, Cu²⁺, [Pd(NH₃)₄]²⁺, In³⁺, and Sn⁴⁺ ions were studied in a wide pH range, and their chemical stability was examined.     

The effects of biologically important divalent and trivalent metal cations on the cyclization step of dopamine autoxidation reaction: A quantum chemical study

Dopamine is the most essential monoaminergic neurotransmitter involved in the pathophysiology of neurodegenerative disorders, and its autoxidation has been recognized as one of the potential trigger factors for dopaminergic neuron loss. The cyclization of dopamine o-quinone was shown to be the irreversible and rate-limiting step of the autoxidation reaction at physiologic pH values. Furthermore, various metal ions such as Al³⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Mn²⁺ have been clinically associated with neurodegeneration, especially Parkinsonism and dementia. It has been proposed that these metal ions could increase the rate of the dopamine autoxidation reaction; however, the exact mechanism has not yet been fully understood. Using advanced quantum chemical calculations with the inclusion of solvent effects we showed that except for Mn²⁺, the studied metal cations could form complexes with dopamine o-quinone and significantly increase the dopamine o-quinone cyclization rate in aqueous solution; first, by enabling the cyclization to proceed spontaneously without the attack of the unprotonated amino group by hydroxide ion; second, by decreasing the intrinsic activation energy; and third, by decreasing the free energy of protonated amino group deprotonation. The latter also decreases the protective effect of acidic pH on dopamine autoxidation found in synaptic vesicles. The results are fully consistent with experimental data and provide deeper understanding of the effects of metal cations on the dopamine autoxidation reaction at physiologic pH values.     

Sol-gel synthesis of carbonate-containing zirconium(IV) hydroxide and its sorption properties toward alkaline-earth elements

Carbonate-containing zirconium hydroxide with a CO₂ content of up to 0.5 mol per mole of ZrO₂ was prepared by the sol-gel procedure. The sorption power of the carbonate-containing zirconium(IV) hydroxide toward Sr²⁺, Ca²⁺, and Mg²⁺ ions was studied. The effect of pH and electrolyte concentration on the sorption power was examined.     

A Schiff base‐grafted nanoporous silica material as a reversible optical probe for Hg2+ ion in water

A novel organic–inorganic silica‐based fluorescent probe was designed, synthesized and characterized by different techniques such as XRD, BET, TGA, and FT‐IR. The fluorescence properties of the probe were studied in the presence of a variety of metal‐ions in water. The results revealed that various metal‐ions negligibly vary the emission intensity of the probe except for Hg²⁺, which quenched the intensity dramatically. The selectivity of the probe toward Hg²⁺ ion was further investigated in the presence of common competing metal‐ions and the results demonstrated the high selectivity of the probe toward Hg²⁺ ion. The fluorescence emission of the probe was also studied as a function of the concentration of Hg²⁺ ion. A nanomolar limit of detection was estimated for Hg²⁺, indicating a high sensitivity. Furthermore, the probe showed INHIBIT‐type logic behavior with Hg²⁺ and H⁺ as inputs. Also, the optimum pH range was studied in addition to reversibility and real world applicability of the probe.     

Uptake of Divalent Metal Ions (Cu2+, Zn2+ and Cd2+) by Polysiloxane Immobilized Glycinate Ligand System

ABSTRACT

Porous solid siloxane polymer carrying glycinate functional group of formula –(CH₂)₃NHCH₂COOH has been prepared by the sol-gel process. Treatment of aqueous solutions of divalent metal ions with the polysiloxane glycinate ligand system demonstrates that this material exhibits high potential for preconcentration of metal ions (Cu²⁺, Zn²⁺ and Cd²⁺). The ligand system chemisorbs these divalent metal ions, at optimum conditions, in the order: Cd²⁺ < Zn²⁺ < Cu²⁺. The uptake of copper ions is concentration dependent but it is independent on the presence of other competing ions. Treatment of the glycinate ligand system with acidic solution results in leaching of bound ligands. The highest leaching occurs in presence of copper ions at low pH     

Thermal and ion-exchange studies on chelating terpolymer resins derived from o cresol urea formaldehyde

Terpolymers prepared by condensation of o cresol and urea with formaldehyde in presence of acid catalyst (2 M HCl) proved to be selective chelating ion exchange resins for certain metal ions. The molecular weights of the synthesised terpolymers were determined by GPC Technique. TGA analysis was employed to study the thermal stability and the kinetic data like activation energy of the terpolymer resins. Chelation ion exchange properties of these terpolymers were studied for Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. A batch equilibrium method was employed in the study of the selectivity of metal ion uptake involving the measurements of distribution of a given metal ion between the polymer samples. The study was carried out over a wide pH range and in media of various ionic strengths.     

Uptake of Divalent Metal Ions (Cu2+, Zn2+ and Cd2+) by Polysiloxane Immobilized Monoamine Ligand System

ABSTRACT

Porous solid siloxane polymers carrying a monoamine functional group of formula P-(CH₂)₃NH₂ (Where P- represents a siloxane framework silica like ) has been prepared by polycondensation of Si(OEt)₄ and (MeO)₃Si(CH₂)₃-NH₂. Treatment of aqueous solutions of divalent metal ions with the polysiloxane monoamine ligand system demonstrates that this material has high potential for preconcentration of metal ions (Cu²⁺, Zn²⁺ and Cd²⁺). The tendency of these divalent metal ions to chemisorb by the monoamine ligand system at the optimum conditions increases in the order: Cd²⁺ <Zn²⁺ <Cu²⁺. The optimum pH is 5.5 for copper and 6-7 for zinc and cadmium. The ammonia/ ammonium chloride buffer solution gave maximum uptake for all metal ions. It is also found that the uptake of copper ions is concentration dependent and is independent of the presence of other competing ions. The monoamine ligand system suffers from leaching of ligand containing groups upon treatment with acidic solutions. The highest leaching occurs at low pH.     

Thin layer chromatography of 57 metal ions on an inorganic ion-exchanger in mixed solvent systems

Summary Thin layers of stannic arsenate have been used to study the chromatographic behaviour of 57 metal ions in different mixed solvents. Au³⁺, Hg²⁺, UO ₂ ²⁺ , Be²⁺ and Al³⁺ and others can be easily separated from numerous metal ions. Fast quaternary, ternary and binary separations have been also achieved. Important separations are discussed. The effect of pH, duration of heating of ionexchanger plates and layer thickness on the R_f values has been studied and discussed. It is shown that Lederer's equation is also obeyed by thin layers of stannic arsenate, if instead of concentration of Na⁺ ion its activity is taken into consideration.     

Synthesis and fluorescent properties of novel chiral 1,2-diaminocyclohexane substituted ligands and their complexes

A series of novel chiral 1,2-diaminocyclohexane derivatives bearing heterocyclic units were synthesized via improved methods under ultrasonic irradiation. The photophysical properties of compounds were studied in ethanol, methanol, and chloroform. The sensitivity of these amines toward Cu²⁺, Cd²⁺, and Ni²⁺ was studied by the UV–vis and fluorescent methods. The π-electron structure of thiophene and bithiophene containing sensors is the most active toward all above mentioned metal ions and is highly selective for Ni²⁺ and Cd²⁺.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Preconcentration and recovery of uranium and thorium from Indian monazite sand by using a modified fly ash bed

Adsorption of uranium, as UO₂ ²⁺, and thorium, as Th⁴⁺, has been studied using a modified fly ash bed. Effects of pH and various ions like La³⁺, Fe³⁺, Ce⁴⁺, SiO₃ ^2- etc., have been examined. Synthetic mixtures of UO₂ ²⁺ and Th⁴⁺ in different concentrations were passed through the bed and eluted separately with various selective reagents viz. ammonium carbonate, sodium carbonate and acetic acid-sodium hydroxide buffer. Separations of these elements at ppm level are shown to be very effective. The separation of uranium and thorium in the presence of lanthanides in monazite sand has been studied successfully. In the analysis of monazite sand, the oxalate precipitation has been avoided. The method is simple and of very low cost. The modified fly ash bed can also be used to remove uranium from contaminated water.     

Novel nanostructured dendrimer based on 1,3-bis(4,6-dichloro-1,3,5-triazine-2-yl)urea as an excellent adsorbent for Pb2+, Ni2+, Co2+ and Zn2+ metal ions

Human health is seriously harmed by the consumption of poor-quality water. Due to high toxicity and water solubility, heavy metals are present in wastewater discharged from numerous industries. In the environmental realm, metal-containing water must be treated before being released. A dendrimer is a superior adsorbent for the removal of heavy metal ions due to its nanostructure and hydrophilic end group. In this work, a novel triazine-based hydroxy-terminated dendrimer up to generation three is designed employing a carbamide core. The dendrimer's structure was explored using FT-IR and ¹H NMR studies. Full generation dendrimers UG1.0, UG2.0, and UG3.0 were utilized as an adsorbent for Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ion removal from water in a series of tests. The ability of dendrimers to uptake Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions was investigated under various pH, time interval and dendrimer generation parameters. The presence of metal in the dendrimer was confirmed by FT-IR studies of dendrimer-metal complexes. The overall results show that Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions uptake increases with the generation, time, and pH.     

Aminoquinoline based highly sensitive fluorescent sensor for lead(II) and aluminum(III) and its application in live cell imaging

We have synthesized a new probe 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ) based on anthracene platform. The probe was tested for its sensing behavior toward heavy metal ions Hg²⁺, Pb²⁺, light metal Al³⁺ ion, alkali, alkaline earth, and transition metal ions by UV–visible and fluorescent techniques in ACN/H₂O mixture buffered with HEPES (pH 7.4). It shows high selectivity toward sensing Pb²⁺/Al³⁺ metal ions. Importantly, 10-fold and 5- fold fluorescence enhancement at 429 nm was observed for probe upon complexation with Pb²⁺ and Al³⁺ ions, respectively. This fluorescence enhancement is attributable to the prevention of photoinduced electron transfer. The photonic studies indicate that the probe can be adopted as a sensitive fluorescent chemosensor for Pb²⁺ and Al³⁺ ions.