A performance of hybrid biosorbent ‘M-Bios’ of Pb(II) and Cu(II) in aqueous solutions

‘M-bios’ biosorbent is a hybrid of mangrove wasted bark from charcoal industry at Perak, Malaysia and green algae from Sabah to remove heavy metals. This biosorbent is subjected to FTIR and ICP-MS. ‘M-Bios’ contain N – H (3421.89 cm-1, 3465.90 cm-1), C = O (1728.72 cm-1) and – OH (3531.37 cm-1, 3722.01 cm-1, 3768.36 cm-1) functional groups (weak groups) that that easily replaced by metal ions. The adsorption performances were fitted by pseudo-kinetic, Langmuir and Freundlich study. The plots obey both adsorption isotherm models, Langmuir and Freundlich by R2 values. A good agreement between experimental and theoretical qe for contact time data suggested that adsorption reaction happen in aqueous solution was a rate determination of chemisorption process(pseudo second-order kinetic)

Tuning the Redox Potential of Conducring Polymeric Films

Abstract Hybrid transition metal-containing conducting polymers represent a new class of advanced material that combine the electron transfer properties of transition metal ions embedded within a conducting polymer matrix. Attaching a thiophene residue (a precursor to the conducting polymer polythiophene) to a transition metal via a covalent bond to a ligand within the complex provides a route to novel hybrid polythiophene conducting polymers. In this project, a range of new tetraaza-macrocyclic ligands bearing appended thiophenyl groups have been prepared with a view to subsequent polymerization via an electrochemical synthesis (electropolymerisation) Two strategies were chosen to synthesize these new types of ligands. Copper-directed Mannich reactions have been used to produce ligands with pendent thiophene groups introduced via a thiophene containing nitro-substituted ‘carbon acid’. A number of new nitro, thiophene-substituted macrocyclic ligands were isolated and characterized as their Cu(II) complexes. Reduction of the nitro groups led to isolation of the amino analogues as their free ligands. Alternatively, thiophene substituents were introduced by a reductive alkylation process involving condensation between a suitable thiophene (or terpthiophene) aldehyde and the exocyclic primary amine of an existing tetraaza macrocycle. Redox active Co(III), Cu(II), Ni(II) and Mn(III) complexes of these ligands were prepared and fully characterized structurally, spectroscopically and electrochemically in their monomeric forms. Electropolymerisation of these complexes was attempted as well as with the metal free ligands. However, none of these thiophene-appended ligands or complexes proved suitable despite several variables being investigated including solvent, co-polymer, catalysts or types of electrode. However, terthiophene-appended macrocyclic ligands and complexes obtained from a similar reductive alkylation procedure were very effective precursors to polythiophene hybrid polymers. Electropolymerisation of the Co(III) complexes or free ligands yielded conducting polymeric films of good stability and morphology. Electrochemistry of the solid film adhered to an electrode showed that the Co centres within the polymer were redox active and could be cycled between their tri- and divalent oxidation states reversibly. Characterization of the films with X-ray photoelectron spectroscopy confirmed the presence of Co within the film. The elemental ratio of Co:S (1:3) within the polythiophene:Co polymer was the same as that within the monomer complex itself

Role of CA-EDTA on the Synthesizing Process of Cerate-Zirconate Ceramics Electrolyte

The role of a combination between citric acid (CA) and ethylenediaminetetra acetic acid (EDTA) as chelating agents in preparation of BaCe0.54Zr0.36Y0.1O2.95 powder by a modified sol-gel method is reported. The precursor solutions were prepared from metal nitrate salts (M+), chelating agents (C), and ethylene glycol (EG) at molar ratio of M+ : C : EG = 3 : 2 : 3. Chemical and phase transformation of samples during thermal decomposition were analyzed by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. TGA results show that the sample prepared by a combination of CA-EDTA exhibited the lowest thermal decomposition temperature, Ttd since there was no significant weight loss after 750°C. After calcined at 1100°C, the carbonates residue remained in the samples as proven by FTIR results. It was found that the used combination of CA-EDTA acts as a better combustion reagent to increase the reaction rate and influence the thermal decomposition behaviour compared to a single citric acid and EDTA, respectively. Apparently, calcination temperatures above 1100°C are needed to produce a pure perovskitic BaCe0.54Zr0.36Y0.1O2.95

Synthesis, characterization and antioxidant activity of 3-(2-Amino-1,3-Selenazol-4-yl)-2H-Chromen-2-Ones derivatives

Selenocompounds have been widely synthesized for their potential in pharmacology. Ebselen, a selenazole oxide, is a glutathione peroxidase mimic which is known to possess high antioxidant activity. Four derivatives of 3-(2-amino-1,3- selenazol-4-yl)-2H-chromen-2-ones were synthesized by reacting 3-(2-bromoacetyl)-chromen-2-one derivatives with selenourea through Hantzsch reaction using NaF as a catalyst in methanol-water (1:1) at room temperature. These reactions were completed in 30 min and purified using column chromatography eluted with n-hexane-ethyl acetate (7:3) to give 50-83% yields. All the compounds were successfully characterized using IR, 1H and 13C NMR as well as mass spectrometry. The synthesized compounds were tested with DPPH assay to determine the free radical scavenging activity and were compared to gallic and ascorbic acids as standard. Nonetheless, all compounds exhibited weak free radical scavenging activity with IC50 value ranging from 672.13 to 984.03 μM signifying that the derivatives may possess weak antioxidant activities

Macrocyclic thiophene-appended cyanido-bridged Co-III/Fe-II complexes: Precursors to mixed-valent poly-thiophene hybrid materials

The new cyanido-bridged mixed valent Fe/Co macrocyclic complexes [LCo(μ-NC)Fe (CN)] and trans-[LCo (μ-NC)Fe(CN)(-CN)Co L] have been prepared and characterized spectroscopically. The trinuclear complex trans-[LCo(μ-NC)Fe(CN) (-CN)CoL](ClO)11HO has been characterized crystallographically. The di- and trinuclear complexes exhibit metal-to-metal charge transfer transitions characteristic of Class II mixed valent chromophores and their redox and spectroscopic properties have been analyzed by Hush theory. The thiophene group attached to the macrocycle L in these complexes may serve as a precursor to conducting polythiophene-based hybrid materials incorporating redox active transition metal ions

Synthesis and variable coordination modes of a bis-thiophene-appended macrocycle in complex with cobalt(III)

The bis-thiophene appended cyclam derivative L (trans-6,13-dimethyl-6,13-bis(thiophene-3′-ylmethylamino)-1,4,8,11-tetraazacyclotetradecane) has been synthesised, characterised and complexed with Co. The crystal structure of the diprotonated ligand as its cyanoborohydride salt [HL][NCBH] is reported. Variable coordination modes to Co have been identified that find the ligand binding either as a tetradentate (cyclam-like) macrocycle in the structurally characterised complexes trans-[CoLCl]Cl and trans-[CoL(NCBH)(OH)]Cl or as a hexadentate in [CoL]Cl where both functionalised exocyclic amines coordinate in trans coordination sites. In this case, we have found that the structure of the hexadentate coordinated complex [CoL] is significantly tetragonally elongated due to steric effects of the thiophene rings and this also leads to a very large 500 mV anodic shift in the Co redox potential relative to the unsubstituted hexaamine complex of Co