Syntheses, spectroscopic and AFM characterization of some manganese porphyrins and their hybrid silica nanomaterials.

The present work is concerned with the manganese complexes of 5,10,15,20-tetraphenylporphyrin and of 5,10,15,20-tetra(3-hydroxyphenyl)porphyrin, which were prepared by metallation of the corresponding porphyrin ligands, and the study of their spectroscopic and photophysical behavior under strongly acidic and alkaline conditions. The second objective was to obtain and study some new hybrid materials, with special optoelectronic and surface properties, by impregnation of silica gels obtained by one step acid and by two steps acid-base catalysis with these Mn-porphyrins. The resulting nanomaterials exhibited interesting bathochromic and hyperchromic effects of their second band in the emission spectra in comparison with the Mn-porphyrins and also they have distinct orientation of the aggregates on surfaces, as shown by AFM images, making them useful for applications in medicine, formulation of sensors and for environmental-friendly catalysts for photodegradation of organic compounds.

Sustaining the efficiency of the Fe(0)/H2O system for Cr(VI) removal by MnO2 amendment.

This study aims to provide new knowledge regarding the effect of MnO2 co-presence on efficiency of Cr(VI) removal with Fe(0). Non-disturbed batch experiments (≤40 days) were conducted using two types of Fe(0) (milli- and micro-sized), two Cr(VI) concentrations (5 and 100 mg/L), in three different systems ("Fe(0) only", "MnO2 only", and "Fe(0) + MnO2"), at an initial pH value of 6.9. Compared to "Fe(0) only" system, the efficiency and rate of Cr(VI) removal were highly promoted in "Fe(0) + MnO2" system; moreover, while for the "Fe(0) only" system removal of Cr(VI) was severely hindered by increasing Cr(VI) concentration, in "Fe(0) + MnO2" system comparable high efficacies were noticed both at low and high concentration. Recycling experiments indicated that total Cr(VI) removal capacity of "Fe(0) + MnO2" system was up to 48.1 times greater than of the "Fe(0) only" system. Enhanced removal of Cr(VI) with Fe(0) was achieved at low doses of MnO2, with an optimal mass ratio Fe(0):MnO2 of 4:1. The favorable synergistic effect observed in "Fe(0) + MnO2" system was ascribed to capacity of MnO2 to accelerate Fe(0) oxidative dissolution, and to generate supplementary amounts of secondary adsorbents/reductants with removal ability towards Cr(VI). This study provides compelling evidence that "Fe(0) + MnO2" system could represent a highly efficient and cost-effective alternative for the abatement of Cr(VI) aqueous pollution.

Determination of (+)-3,3',5,5'-Tetraiodo-L-thyronine (L-T4) in Serum and pharmaceutical formulations using a sequential injection analysis/immunosensor system.

A sequential injection analysis/immunosensor system is proposed for the analysis of thyroxine (L-T4) in serum and in pharmaceutical formulations with a rate of 75 samples/hour. The immunosensor design is based on the physical immobilization of anti-L-T4 in carbon paste. The working concentration range of the immunosensor in the sequential injection analysis system is between 36 and 1080 ng/mL with a limit of detection of 24.6 ng/mL. The system is very reliable and very easy to design and operate.

Removal of Cr(VI) from aqueous solutions by adsorption on MnO2.

Adsorption of Cr(VI) on MnO2 was investigated with respect to effect of pH, temperature, ionic strength, initial Cr(VI) concentration, co-presence of different anions (HCO3(-), SO4(2-), H2PO4(-), NO3(-) and Cl(-)) and of low molecular weight natural organic materials (LMWNOM) (acetate, oxalate and citrate). The process was rapid during the first 3-5min, reaching equilibrium after one hour. Adsorption decreased with increasing pH, temperature and Cr(VI) initial concentration, and increased with increasing ionic strength. Co-presence of phosphate, sulfate, bicarbonate, citrate and oxalate hindered Cr(VI) adsorption, whereas nitrate, chloride and acetate did not exert any notable influence. The overall order of Cr(VI) adsorption suppression due to co-presence of anions and LMWNOM was H2PO4(-)>HCO3(-)>SO4(2-), and oxalate>citrate, respectively. Highest experimental equilibrium sorption capacity (0.83mgg(-1)) was obtained at 20°C and pH 5.9, while lowest (0.18mgg(-1)) was noticed in the co-presence of H2PO4(-), at 20°C and pH 6.9. Adsorption kinetics was successfully fitted by pseudo-second-order model. Mechanisms for both specific and non-specific adsorption are likely to be involved, while rate-controlling step involved both intra-particle and film diffusion processes. Cr(VI) was strongly bound to MnO2, which makes risks of its subsequent liberation into the environment to be low.

Simultaneous determination of L- and D-T4 using a sequential injection analysis/sensors system.

A sequential injection analysis system was selected for the simultaneous determination of L- and D-T4 in raw material and pharmaceutical products, because of the highest precision and accuracy, the lower consumption of sample and buffer, and the flexibility of selecting different buffers accordingly with the type of sensors utilized as detectors. An amperometric biosensor based on D-amino acid oxidase was used as detector for D-T4 and an immunosensor based on anti-L-T4 was used as detector for L-T4. The SIA/biosensors system can be used reliably on-line in synthesis process control, for the simultaneous assay of L- and D- T4 with a frequency of more than 30 samples per hour.