New silica-immobilized hydroxypyrimidinone as sorbent of hard metal ions from aqueous fluids

Fabrication and covalent modification of highly chelated hybrid material based on silica-bipyridine framework for efficient adsorption of heavy metals: isotherms, kinetics and thermodynamics studies

Adsorbent materials are essential in clean-up processes.

3-Hydroxypyridinone derivatives as metal-sequestering agents for therapeutic use

Although iron is one of the most important metal ions for living organisms, it becomes toxic when in excess or misplaced. This review presents a glance at representative examples of hydroxypyridinone-based chelators, which have been recently developed as potential clinically useful drugs for metal overload diseases, mostly associated with excess of iron but also other hard metal-ions. It also includes a detailed discussion on the factors assisting chelator design strategy toward fulfillment of the most relevant biochemical properties of hydroxypyridinone chelators, highlighting structure-activity relationships and a variety of potential clinical applications, beyond chelatotherapy. This study appears as a response to the growing interest on metal chelation therapy and opens new perspectives of possible applications in future medicine.

Structural and Thermodynamic Analysis of the First Mononuclear Aqueous Aluminum Citrate Complex Using DFT Calculations

Structural and thermodynamic properties of the mononuclear Al/citrate complexes have been theoretically investigated aiming to understand the coordination mechanism at an atomic level. GGA-DFT/PCM calculations have been performed for the different conformations and tautomers arising from the Al(3+) and citric acid (H3L) interaction in aqueous solution. The Gibbs reaction energies were estimated based on the reaction of the trigonal planar Al(OH)3 and H3L to form different Al-citrate complexes. The estimated Gibbs free reaction energies for the [AlL], [AlHL](+), and [Al(OH)L](-) species are in good agreement with the experimental values. In these species, the Al(3+) center is coordinated by two carboxylic and the tertiary hydroxyl groups of the citrate. Conversely to what has been proposed based on the experiments, the present theoretical calculations indicate that the citric acid hydroxyl group remains protonated upon the coordination of Al(3+). In fact, our model turns out to be more consistent with the relative pKa values of citrate protonation groups and with the hydrolysis constant of the H2O bound to Al(3+) leading to better agreement with the available experimental data.

New hydroxypyridinone-functionalized sepharoses as sorbing agents for hard metal ions

Two new polymeric matrices functionalized with 3-hydroxy-4-pyridinone chelating units (HP-NH-SEPH and HP-C=NH-SEPH) have been prepared and studied for their chelating ability towards a set of metal ions (e.g. Fe(III), Al(III), and Th(IV)). Both matrices demonstrated excellent ability to complex these metal ions, but HP-NH-SEPH evidenced higher chelating capacity than HP-C=NH-SEPH. The corresponding metal-complex gels presented high stability in the pH range 3-7, and their chelating capacity followed the order, Fe(III)≈Th(IV)>Al(III), in agreement with previously reported thermodynamics of the corresponding monomeric ligand-metal complexes in aqueous solution. These functionalized supports also showed capacity to be regenerated and reused. Thus, there are good perspectives for potential environmental and medical applications of these new metal sorbents.

Immobilization of oxime derivative on silica gel for the preparation of new adsorbent

A new silica gel compound modified 4,4'-oxy-bis(chlorophenylglyoxime) (CPGO) was synthesized and characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The sorption capacity of such a matrix towards Co(II), Ni(II) and Cu(II) from aqueous solutions was studied. The optimum pH values for the separation of these divalent cations on the sorbent were 5.0, 6.0 and 6.0 for Cu, Co and Ni, respectively. The process of metal separation was followed by batch method, and fitted to a Langmuir and Freundlich sorption isotherms. The maximum sorption capacities (0.055, 0.042, and 0.034 mmol g(-1)) were found from the Langmuir equation and the enthalpies of binding were 44.96, 71.63, and 68.14 kJ mol(-1) for Cu, Co and Ni, respectively. The other thermodynamic parameters calculated from the adsorption results were used to explain the mechanism of the adsorption. For example, the Gibbs free energies of binding agree with the spontaneity of the proposed reaction between cations and basic centers.

Removal of heavy metals from artificial metals contaminated water samples based on micelle-templated silica modified with pyoverdin I

The micelle-templated silica (MTS) was firstly chemically modified with 3-glycidoxypropyl-trimethoxysilane (GPTMS) before immobilized with pyoverdin I. The characteristics of pyoverdin I-anchored onto the modified MTS were investigated using fluorescence, infrared spectra and scanning electron microscopy. The specific surface area of all materials was calculated by Brunauer, Emmett and Teller (BET) method using nitrogen isotherm adsorption data. As the results, the surface area of commercial silica gel decreased from 609.2 to 405.4 m2/g, it indicated that the pyoverdin I could be immobilized onto the surface of silica solid support. This adsorbent was used for extraction of Fe(III), Cu(II), Zn(II), and Pb(II) in artificial metals contaminated water. Experimental conditions for effective adsorption of trace levels of metal ions were optimized with respect to different experimental parameters using batch procedure. The optimum pH value for the removal of metal ions simultaneously on this adsorbent was 4.0. Complete desorption of the adsorbed metal ions from the adsorbent was carried out using 0.25 mol/L of EDTA. The effect of different cations and anions on the adsorption of these metals on adsorbent was studied and the results showed that the proposed adsorbent could be applied to the highly saline samples and the sample which contains some transition metals.