Anchoring of Copper(II)-Schiff Base Complex in SBA-15 Matrix as Efficient Oxidation and Biomimetic Catalyst

A new mononuclear Cu(II) complex [Cu(L2)(H2O)2], where L is the Schiff base 2-[2-(3-bromopropoxy)benzylideneamino] benzoic acid, was synthesized and covalently anchored onto an amino-functionalized SBA-15 mesoporous silica in order to obtain an efficient heterogeneous catalyst. The elemental, structural, textural and morphological characterization confirmed the coordination of the central Cu(II) ion with two ligands and two H2O molecules in the synthesized complex and its successful immobilization into the inner pore surface of the NH2-functionalized support without the loss of the mesoporous structure. The catalytic activity of the free or immobilized Cu(II) complex was tested in the oxidation of cyclohexene with H2O2 under an air atmosphere and the dismutation reaction of the superoxide radical anions with very good results. In addition, catalyst reuse tests claim its suitability in alkene oxidation processes or as a biomimetic catalyst.

Cu(II) and Mn(II) Anchored on Functionalized Mesoporous Silica with Schiff Bases: Effects of Supports and Metal-Ligand Interactions on Catalytic Activity

New series of Cu(II) and Mn(II) complexes with Schiff base ligands derived from 2-furylmethylketone (Met), 2-furaldehyde (Fur), and 2-hydroxyacetopheneone (Hyd) have been synthesized in situ on SBA-15-NH₂, MCM-48-NH₂, and MCM-41-NH₂ functionalized supports. The hybrid materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, SEM and TEM microscopy, TG analysis, and AAS, FTIR, EPR, and XPS spectroscopies. Catalytic performances were tested in oxidation with the hydrogen peroxide of cyclohexene and of different aromatic and aliphatic alcohols (benzyl alcohol, 2-methylpropan-1-ol, and 1-buten-3-ol). The catalytic activity was correlated with the type of mesoporous silica support, ligand, and metal-ligand interactions. The best catalytic activity of all tested hybrid materials was obtained in the oxidation of cyclohexene on SBA-15-NH₂-MetMn as a heterogeneous catalyst. No leaching was evidenced for Cu and Mn complexes, and the Cu catalysts were more stable due to a more covalent interaction of the metallic ions with the immobilized ligands.

Fe-Ce/Layered Double Hydroxide Heterostructures and Their Derived Oxides: Electrochemical Characterization and Light-Driven Catalysis for the Degradation of Phenol from Water

Fe-Ce/layered double hydroxides (LDHs) were synthesized via a facile route by exploiting the "structural memory" of the LDH when the calcined MgAlLDH and ZnAlLDH were reconstructed in the aqueous solutions of FeSO₄/Ce(SO₄)₂. XRD analysis shows the formation of heterostructured catalysts that entangle the structural characteristics of the LDHs with those of Fe₂O₃ and CeO₂. Furthermore, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, TG/DTG, SEM/EDX and TEM results reveal a complex morphology defined by the large nano/microplates of the reconstructed LDHs that are tightly covered with nanoparticles of Fe₂O₃ and CeO₂. Calcination at 850 °C promoted the formation of highly crystallized mixed oxides of Fe₂O₃/CeO₂/ZnO and spinels. The photo-electrochemical behavior of Fe-Ce/LDHs and their derived oxides was studied in a three-electrode photo-electrochemical cell, using linear sweep voltammetry (LSV), Mott-Schottky (M-S) analysis and photo-electrochemical impedance spectroscopy (PEIS) measurements, in dark or under illumination. When tested as novel catalysts for the degradation of phenol from aqueous solutions, the light-driven catalytic heterojunctions of Fe-Ce/LDH and their derived oxides reveal their capabilities to efficiently remove phenol from water, under both UV and solar irradiation.

Behavior of Cd Accumulation in Sinapis alba L. in the Presence of Essential Elements (Ca, Mg, Fe, Zn, Mn, Cu, Ni)

Heavy metal toxicity in plants is well known due to their severe phytotoxic effects and also because of their capability to accumulate in vegetables. The use of aromatic plants in remediation techniques has increased in the context of environmental pollution issues, including metal soil contamination. Cadmium is knowed as a toxic and bio accumulative element provided by natural or anthropic sources. In this context, the paper presents a laboratory experimental study aiming to evaluate the accumulating and transfer behavior of Cd in the plant organs of Sinapis alba L. (white mustard) and in the presence of essential elements (Ca, Mg, Fe, Zn, Mn, Cu, Ni). The study involves a comparison between white mustard cultivated in unpolluted soil and in two Cd polluted soils at values above the alert (2.8 mg/Kg), respectively intervention threshold for soils with sensitive use (5.6 mg/kg) according to the legislation in force in Romania. While Cd accumulated predominantly in roots (TC values 1.46 and 2.22), its transfer to the stem and leaves was observed too, the TF values for the aerial part of the plant being greater than 1. Moreover, the study showed that certain elements (Zn, Ca, Mg, Mn) were found in higher concentrations in plants subjected to Cd pollution than in the control sample indicating antagonistic effects and Cd toxicity limiting. Other essential metals, such as Cu, Fe and Ni were found in lower concentrations in intoxicated plants compared to control plants. Their translocation from soil in plant organs could be reduced by the Cd toxicity. Contrariwise, the mobility of these elements from roots to leaves could support the tolerance effect of plants to Cd stress. The study allows us to consider that Sinapis alba L. aromatic plants are suitable for soil phytoremediation technologies used in Cd decontamination.

A family of solar light responsive photocatalysts obtained using Zn2+ Me3+ (Me = Al/Ga) LDHs doped with Ga2O3 and In2O3 and their derived mixed oxides: a case study of phenol/4-nitrophenol decomposition

Decomposition of dangerous organic contaminants under irradiation with sunlight by Zn²⁺ Me³⁺ (Me = Al/Ga) LDHs doped with Ga₂O₃ and In₂O₃ and their derived mixtures of mixed oxides.

Mesoporous silica functionalized with 1-furoyl thiourea urea for Hg(II) adsorption from aqueous media

New organic-inorganic hybrid materials were prepared by covalently anchoring 1-furoyl thiourea on mesoporous silica (SBA-15). By means of various characterization techniques (X-ray diffraction, nitrogen adsorption-desorption, thermogravimetric analysis, and FTIR spectroscopy) it has been established that the organic groups were successfully anchored on the SBA-15 surfaces and the ordering of the inorganic support was preserved during the chemical modifications. The hybrid sorbents exhibited good ability to remove Hg(II) from aqueous solution. Thus, at pH 6, the adsorption capacity of mercury ions reached 0.61 mmol g(-1).

Modified SBA-15 mesoporous silica for heavy metal ions remediation

N-Propylsalicylaldimino-functionalized SBA-15 mesoporous silica was prepared, characterized and used as an adsorbent for heavy metal ions. The organic-inorganic hybrid material was obtained using successive grafting procedures of SBA-15 silica with 3-aminopropyl-triethoxysilane and salicylaldehyde, respectively. For comparison an amorphous silica gel was functionalized using the same procedure. The structure and physicochemical properties of the materials were characterized by means of elemental analysis, X-ray diffraction (XRD), nitrogen adsorption-desorption, thermogravimetric analysis and FTIR spectroscopy. The organic functional groups were successfully grafted on the SBA-15 surfaces and the ordering of the support was not affected by the chemical modification. The behavior of the grafted solids for the adsorption of heavy metals ions from aqueous solutions was investigated. The hybrid materials showed high adsorption capacity and high selectivity for copper ions. Other ions, such as nickel, zinc, and cobalt were adsorbed by the modified SBA-15 material. The adsorbent can be regenerated by acid treatment without altering its properties.

Spectrophotometric Determination of Copper (II) with 5-Hydroxy-6-Mercapto-Benzo [a] Phenazine

5-Hydroxy-6-mercapto-benzo [a] phenazine (HMBP) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper (II). Copper reacts with HMBP to give a dark red complex which is soluble in chloroform. The composition of the CuII � HMBP complex is established as 1:2 by Job�s continuous variation method and molar ratio method. The instability constant of the complex calculated by Job�s relation for nonisomolar series is 4.65 . 10-9, at room temperature. The CuII-HMBP complex in chlorophorm shows a maximum absorbance at 495 nm, with molar absorptivity and Sandell�s sensitivity values of 7.39 . 103dm3 mol-1 cm-1 and 0.012 mg cm-2, respectively. Beer�s law is obeyed in the concentration range 0.67 - 26.90 mg mL-1 and the detection limit is 0.59 mg mL-1. A repetition of the method is checked by finding the relative standard deviation (RSD) at 1.00 mg mL-1 CuII of 0.6%. The method is successfully employed for the determination of copper (II) in environmental samples. The reliability of the method is assured by analysing the standard alloys and by inter-comparison of experimental values, using an atomic absorption spectrometer.

A new mesoporous micelle-templated silica route for enzyme encapsulation

A new mesoporous micelle-templated silica (MTS) route for enzyme encapsulation is presented. The pore structure is given by a new association oflecithin (double chain surfactant) and dodecylamine as cosurfactant. To enhance and to well protect the enzyme activity, lactose was loaded in the synthesis. The mixed-micelles give after the addition of tetraethyl orthosilicate a well-ordered mesoporous material with a spongelike rigid structure stable after calcination at 550 degrees C. The size of the pores lies between 30 and 40 A, matching well with the size of the lipases. The activity of this heterogeneous catalyst was tested in the hydrolysis of the ethylthiodecanoate. These new biocatalysts were very active, more than hydrophobic sol-gel materials and commercially available sol-gel encapsulated lipase. This new MTS synthesis route allows one to encapsulate in one-step various enzymes, even those that are very fragile.